Physics and Chemistry 2 Student Book Sample

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Building

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your book

Reading and listening

ch unit

f ea The opening pages o

Speaking

5

We read and listen about the topic of the unit, learning about key concepts and developments in technology.

We speak about the different issues relating to the unit and the UN Sustainable Development Goals.

Speaking Describing an image

Chemical reactions Reading and listening

Modern agriculture

first thing “pollution” the hearing the term to the Normally, when greenhouse gases r, minds is releasing that comes to our and oceans. Howeve fluids in rivers, seas atmosphere or toxic soil pollution. we rarely think of on models (to on ongoing producti based a re, Modern agricultu less cost), has become less time and at use of fertilizers produce more in broad and the invention on vicious cycle. Since th agriculture focused 19 century, global and on intensive by the end of the than polycrop farming, monocrop rather tion. e exploita year, rather than extensiv that, year after ral trend has meant ater This new agricultu and in groundw levels in the soil es, and higher pollution fertilizers, herbicid The overuse of ve farming soils, are measured. rise to less producti ral sector on the pesticides has given nce of the agricultu increasing the depende y. industrial chemistr to ce importan more ? think that we give than soil pollution 1 Why do you or toxic fluids rather greenhouse gases crops in less time? to produce more 2 Why do we want

. hly what you observe and describe thoroug Look at the picture different levels. the lights and the Describe the pipes, is it?

What kind of place picture? the in ng g crops What else is happeni and cons of producin rs what are the pros by using the quantifie In pairs, discuss questions and answers in this way. Create much. how many and how Example: can you count?

How many levels need? do these systems How much water

Writing

ns ral Asking questio for the current agricultu to be the solution needs of our Vertical farming seems to the productive time, farming adapts problem. Vertical more crops in less it allows us to produce the need for pesticides society because without much space and without using too without or herbicides. crops grow is to vertical farming can be The basic idea behind a problem, this system where light is not sunlight, soil. In countries s with a lack of uses. In countrie installed within greenho it. re. Ask LED lights can replace this type of agricultu is moving towards te to achieving Nowadays Europe that can contribu farming vertical questions about and 15.5.

SDGs targets 15.4

s?

3 What are fertilizer come from? water that you drink 4 Where does the es e between herbicid think is the differenc 5 What do you and pesticides?

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Writing 102

The audios of each unit’s content are available at www.anayaeducacion.es

SDG. Reflection on and analysis of SDGs, such as gender equality, climate action, reducing inequalities, etc.

We write a variety of different styles and types of text relating to the unit topic, sometimes relating them to the UN Sustainable Development Goals. By practising different styles of writing, we improve our writing skills we need.

content development ä 6.3 The destruction of the ozone layer

ä 6.1 Anomalous greenhouse effect

For the shield effect to work, there must be enough ozone to absorb the radiation.

The temperature of our planet is kept within limits that are suitable for life thanks to the atmosphere, which behaves like a greenhouse: it retains part of the thermal energy emitted by the Earth and lets the rest pass through.

This phenomenon is called the greenhouse effect.

Understand, think, search… Activities to strengthen learning and relate knowledge. with Working Develop . s picture acity for your cap on and observati tion. interpreta

Unit

Knowing the causes of environmental problems allows us to start solving them, as we have seen in the previous section. Here we look at three environmental problems that affect our planet’s atmosphere globally.

One of the main gases responsible for this effect is carbon dioxide. As its amount in the atmosphere has increased in recent decades due to the use of fossil fuels, an unwanted increase in the amount of energy retained is occurring. This is known as the anomalous greenhouse effect.

If CO2 emissions are not reduced, the increase in the Earth’s average temperature will continue to rise, and the global warming our planet is currently experiencing will have catastrophic consequences.

Substances such as nitrogen oxides and compounds known as CFC (which includes chlorine) in the atmosphere cause chemical reactions that destroy ozone.

Formation and destruction of the ozone layer

3

Natural process of formation of O3 O2

1

+

UV radiation

CHARACTERISTICS 2 2 + OFO CHEMICAL O REACTIONS 3 3

4 O2 O3

O

1 UV rays attack the O2 molecule

andsome split important it into two oxygen This year we will focus Chemical reactions have properties. atoms. on two laws: one related to the masses of the reactants and products, and Each of thesereaction. oxygen atoms 2 of the other to the rate a chemical

+

O2

O2

ä 3.1 Law of 3conservation mass Each ozone moleculeof combines

O3

O

with another oxygen atom, 3 If we mix sand and salt, the mass of the mixture is equal to the sum of the giving two O2 molecules as masses of its components.

That is, the mass is conserved. What if, instead products. of a mixture, two substances undergo a chemical change and produce 4 The cycle is closed by the new substances? Will reaction, the massagain, be conserved? of O with UV or 2

O2

as a reactant of the Othis French chemist A. Lavoisier answered question in 1789, when he 2 reaction.

In the stratosphere, UV radiation separates oxygen molecules intodiscovered atoms. Eachand stated the law of conservation of mass.

Consequences of the greenhouse effect and acid rain

atom combines with separate oxygen molecules, forming a molecule of ozone.

This reaction requires a lot of energy and high temperatures.

Acid rain

In a chemical reaction, matter is neither created nor destroyed, only transformed. Therefore, the sum of the masses of the reactants is equal to the sum of the masses of the products of the reaction.

Destruction of O3 by chlorine

O3

1

CFC

+

+

Cl

2

We highlight two aspects and the circumstances in which it was stated:

1 UV rays attack CFCs and cause • The statement of this law is based onbe multiple experiments in which the a chlorine atom to released.

mass of the reactants the products of different chemical reactions chlorine atom attacks the 2 Theand were measured. It is therefore a law drawn from experience; it is an ozone molecule. empirical law. 3 Two products are formed:

Rayos UV

+

4 O

O2

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The icons included with some activities indicate the keys to the project.

Fossil fuels often contain sulphur impurities. When burned in air, which contains oxygen and nitrogen, they produce sulphur dioxide and nitrogen oxides.

+ ClO

+

5

The melting of continental ice, a consequence of global warming, affects not only sea levels but also the global climate, altering the humidity of the atmosphere.

combines with an O2 molecule to produce ozone, O3.

4

O2

O

O2

Greenhouse effect

What global solutions have been proposed to reduce the destruction of the ozone layer?

In which products was CFC present? Which products have replaced CFCs? Discuss with the rest of the class the need for global agreements.

The reactions release chlorine when they reach the stratosphere, where ozone normally forms and degrades in an equilibrium. The chlorine disrupts this balance, reducing the amount of ozone.

ä 6.2 Acid rain This is the name given to the polluting phenomenon whereby rainwater carries dissolved highly corrosive acids, such as sulphuric acid, H2SO4, and nitric acid, HNO3. These acids are formed when atmospheric emissions of sulphur dioxide, SO2, and nitrogen oxides, NO and NO2, react with water vapour. When this water precipitates as rain, it is called acid rain. Its consequences on the environment are the destruction of flora and fauna.

5

The ozone (O3) layer is in the stratosphere and shields everything below from harmful ultraviolet radiation from the sun.

3

the ClO involving a reactant or the O2ofmolecule • Experimental verification this law and in reactions molecule. a product in the gaseous state was technically complicated at the time, ClO molecule reacts with 4 The and represented an advance in the knowledge of the transformations of monoatomic oxygen. matter.

5 As a result, one oxygen molecule

Cl

release chlorine due to UV radiation, they break down ozone. Chlorine is one of the products of the reaction, so it continues destroying ozone.

Verification of the law of conservation of mass The mass of the reagents and the laboratory material is equal to the mass of the products obtained and the same material. In order to carry out the experiment, the container must have an adequate volume so that the CO2 produced does not cause the stopper to burst.

Vinegar (contains acetic acid)

Carbon 115 dioxide Aqueous sodium acetate solution

Sodium bicarbonate We bring the reagents into contact with each other

Water H2O

Acetic acid CH3COOH

Sodium bicarbonate NaHCO3

Unit

5

ä 3.2 Law of definite proportions With regard to mass, another law that a chemical reaction follows is the law of definite proportions.

In a chemical reaction, the masses of the reactants and the masses of the products are in constant proportion to each other.

This law is related to the fact that the elementary entities of each substance involved in a reaction have different masses, and always combine in the same numerical proportion. We will study this law in detail next year.

ä 3.3 Rate of a chemical reaction Some chemical reactions are extremely slow, such as the formation of minerals in the Earth’s crust, while others are very fast, such as an explosion or the combustion of methane that we have already studied. There are several factors on which the rate of a chemical change depends. The following are the most important ones: • Temperature. Generally speaking, it can be seen that as temperature increases, the rate of a chemical reaction increases.

• Concentration of the reactants. The higher the concentration of the reactants, the faster the rate of the reaction.

O2

This empirical law wasand laterone explained the atomic theory proposed by chlorinebyatom are CFCs are compounds that remain in the atmosphere for a long time.

Whenbetween they Dalton 1803 released and 1808. into the atmosphere.

There is a resource on the effects of carbon dioxide on anayaeducacion.es.

The problems solved allow the learning of reasoning processes and problem-solving strategies.

Working with images

Two types of activities:

6 CHEMICAL REACTIONS AND THE ENVIRONMENT

Sodium acetate CH3COONa

Carbon dioxide CO2

At the microscopic level, we observe that the atoms that form the reactants rearrange themselves to form the new substances, the products, which is why the mass does not change during a chemical reaction.

Problem solved

Understand, think, investigate…

1 When 30 g of nitrogen react with hydrogen, 170 g

10 Find information about the chemical reaction

To calculate the mass of hydrogen that has reacted, we apply the law of conservation of mass:

a) What are the reactants and products of this reaction?

of ammonia are obtained. What mass of hydrogen has reacted? What mass of ammonia would be obtained if 90 g of nitrogen react?

between vinegar and sodium bicarbonate described above to test the law of conservation of mass, and answer these questions:

mass of reactants = mass of products

b) Is vinegar a pure substance?

Thus, the mass of hydrogen will be the difference between the mass of ammonia and the mass of nitrogen:

c) Why is the result of the reaction an aqueous solution?

mass of hydrogen = 170 g – 30 g = 140 g

d)

We can calculate the mass of ammonia obtained from the law of definite proportions; thus, from 90 g of nitrogen we obtain: 30 g nitrogen 90 g nitrogen = x 170 g ammonia

11 If 224 g of iron reacts with oxygen to form 320 g of

90 $ 170 x= = 510 g ammonia 30 We can represent this reaction as:

iron oxide, how much iron oxide will be formed from 112 g of iron?

12 Why do you think most cooking techniques involve

3 H2

raising the food’s temperature?

+ N2

Think and share in pairs. Explain why this experience proves that gases have mass.

e) Explain, using the KTM, what would happen if we did the experiment at a temperature much higher than room temperature.

2 NH3

13

Explain why storing food in refrigerators conserves it.

You can find the solutions to all the numerical activities at anayaeducacion.es.

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KEYS

PROJECT

SDG SDG Commitment Discover the Sustainable Development Goals and be an active part of our commitment to make a more equal and liveable world.

Developing thinking Work on strategies for thinking: reflect on the content you are learning, generate ideas, organise them, debate them, explain them…

Cooperative learning Get involved in your learning and participate in the group’s learning; you will find that cooperating improves performance and harmony in the class.

Emotional education Get to know yourself; identify the situations that bring up complicated emotions and manage them with constructive, self-affirming experiences.

Science workshop A research project in each unit to implement the application of the scientific method and encourage the acquisition of skills and attitudes necessary for scientific work.

SCIENCE WORKSHO

Unit

P

research project homemade glue

PRACTICAL WORK chemical reactions

INTRODUCTION As we have studied, if mixing several substances causes the appearance of new substances, we say that a chemical change has occurred.

In the experiment proposed, a series of chemical reactions take place which cause the appearance of new substances. Among these is the appearance of a solid substance and the release of a gas. To speed up the process, we will use a heat source.

• Vinegar.

• Chemical yeast (baking soda).

• A tablespoon.

• A wooden spoon.

• Pour back into the pan, add a tablespoon of baking powder and a little water. Heat and stir the mixture. You will notice some bubbles at first.

Continue heating and stirring until the mixture boils.

• A cup.

• Remove the mixture from the heat source and continue stirring.

• A sieve.

• Finally, transfer it to a container and cover it. You can use it as a glue when it is cold. It will last up to two days before it spoils.

• A mixing container.

• A source of heat.

The experiences of the Practical Work section to remember and apply what was studied in the initial unit of the book and, at the same time, work on the contents developed in the unit.

When chemical yeast (sodium bicarbonate) and water are added to the rennet, a gas is released. This is carbon dioxide, which is the result of the chemical reaction between vinegar and bicarbonate; in this way, we eliminate the excess acid (vinegar), since it is used in the chemical reaction. In this reaction, other products are obtained, such as sodium acetate, which has multiple industrial applications.

THINK When you add the vinegar to the milk, you separated the casein, the rennet, from the whey, the rest of the milk. When the rennet, proteins and fats are formed, they solidify and agglomerate under the action of an acid (in this case, vinegar), resulting in lumps that are separated with a strainer. The properties of casein as a glue have been known since ancient times. Nowadays, it is used in the manufacture of glues and adhesives.

Responsibility

OUR PROPOSAL We will carry out two experiments: • Experiment A: we will test the chemical reaction that takes place between metals and hydrochloric acid.

• Experiment B: we will use a glow stick to test how temperature affects the reaction rate.

• Separate the rennet obtained from the remaining liquid by straining your mixture.

• A frying pan.

Creativity

STATEMENT OF THE PROBLEM. OBJECTIVE The objective of this practice is to have evidence of a chemical change, and to observe how the temperature and concentration of the reactants affect the rate of reaction.

PRELIMINARY STEPS Make a plan to detect chemical changes, and to observe how the temperature and concentration of the reactants affect the rate of chemical change.

EXPERIMENT • Pour one and a half cups of milk and three tablespoons of vinegar into a frying pan. With the help of an adult, heat the mixture a little while stirring with a wooden spoon. You will notice some lumps forming; this is the rennet in the milk.

YOU NEED • Milk.

5

PRECAUTIONS Hydrochloric acid is a very corrosive liquid. Follow the safety rules to avoid accidents.

MATERIALS • Glow sticks • Beaker • Ice • Water • Salt • Metal filings • Dilute hydrochloric acid solution • Slightly more concentrated hydrochloric acid solution.

Motivation

GUIDELINES FOR CARRYING OUT THE EXPERIMENT EXPERIMENT A • Pour some water into a beaker and add the metal filings.

EXPERIMENT B • Prepare one beaker with hot water, and another with a mixture of water, ice and salt.

• Repeat the previous experiment, now using the dilute hydrochloric acid solution instead of the water.

• Bend two glow sticks to trigger the chemical reaction inside them.

• Again, repeat the previous experiment, this time using the slightly more concentrated hydrochloric acid solution.

• Put one of them in the glass with hot water, and the other in the glass with the mixture of ice, water and salt.

• Observe and note what happens in the three cases.

• Write down the differences you observe in each case.

Planning tasks

Draw conclusions…

1 How do you explain the differences observed in the first

4 Find information on how glow sticks work and their

2 What chemical reaction occurs when a metal is mixed

5 Explain the differences observed between the stick

step and the third step of experiment A?

with hydrochloric acid? Why does it generate bubbles?

3 How do you explain the differences observed between

the last two steps of experiment A? What factor is influencing the reaction rate?

Team-building

applications.

placed in hot water and the stick placed in the beaker with ice. Which factor influences the reaction rate?

6 Find information on why salt is added to ice water. What applications does it have in everyday life?

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Review resources from to choose .

Remember for your portfolio this unit to

Unit

REVIEW

ORGANISing MY IDEAS

Visual organizer of the content

Hierarchical concept map

1 Copy the diagram in your notebook and include: a) The name of the scientist who stated the law of conservation of mass. b) A new branch with the law of definite proportions.

are

are identified by

are represented by

physical evidence

chemical equations

which can be

composed of

chemical changes in which occurs a

Systemic diagram, etc.

rearrangement of atoms

change of colour

light

bubbling

causing a transformation of reactants

into

1 Write down three examples of chemical changes and three examples of non-chemical changes. What type are the latter?

3 Classify the changes as physical or chemical: a) Piece of fruit rotting.

Trust in your skills and knowledge, develop creativity, adapt to changing situations and have a proactive and responsible attitude.

stoichiometric coefficients

Chemical reactions

2 Are there any chemical changes in the distillation of a mixture of alcohol and water? Explain your answer.

4

What makes you say that? Indicate whether the following statements are true or false, and explain why: a) The products of a chemical reaction are always artificial in origin. b) The number of substances in the reactants is always equal to the number of substances in the products. c) Chemical changes are represented by an arrow.

b) Boiling water. c) Melting a piece of butter in a hot frying pan. d) Cooking a grilled steak. e) Effervescence of a medicine when it is placed into water. f) Sweetening an infusion with saccharin.

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chemical formulae

products

Changes in material systems

Questions on the essential aspects of the unit so that you may make your own summary.

energy in the form of heat

comply with the law of conservation of mass

d) The number of atoms of each chemical element present in the reactants is equal to the number of these atoms in the products. e) In a chemical reaction, different atoms are obtained in the products. f) In a chemical reaction, there is always a product obtained in gaseous state.

Solutions to all the numerical activities at anayaeducacion.es.

6 Indicate whether the following statements are true or false, and justify your answer: a) The mass of the reactants is destroyed in a chemical reaction. b) In a chemical reaction, atoms are rearranged; therefore, the sum of the masses of the reactants and the masses of the products is equal. c) The atoms that form the products of the reaction are generated from the atoms present in the reactants.

7 If 306 g of one substance reacts completely with 72 g of another, what will be the sum of the masses of the products of the reaction? Which law have you applied?

8 We have a 224 g piece of iron that combines completely with oxygen to form iron oxide. Are the following statements true or false? Justify your answer. a) The mass of iron oxide formed will be the sum of 224 g plus the oxygen that has combined with the iron. b) The mass of the iron oxide will be less than that of the iron at the start. c) The mass of the iron oxide will be the same as the mass of iron.

9

Let’s check. 8 g of hydrogen react with 64 g of oxygen to form 72 g of water. a) Check that the law of conservation of mass is fulfilled. b) Calculate the mass of water that will be formed if 20 g of hydrogen react completely.

Products of artificial and natural origin 10 Classify the following products according to their origin, natural or artificial: a) Unrefined sugar e) Flax b) Saccharin f) Cotton c) Wood g) Nylon d) Formica h) Acrylic anayaeducacion.es Check the ‘Let‘s study’ and ‘Learn by playing‘ sections in the resource bank.

5

Sustainable chemistry and SDG commitments 11 Search the Internet for the twelve principles of green or sustainable chemistry and make a presentation about them. Which SDG targets are they related to?

12

Characteristics of chemical reactions

Chemical reactions

Timeline

Enterprising culture

c) An example of a chemical equation indicating the formulae of the reactants, the formulae of the products, and the stoichiometric coefficients.

5 State the names of the reactants and products of these chemical reactions, and draw a picture representing them on an atomic scale: a) N2 + O2 8 2 NO. b) C + 2 H2 8 CH4.

C&R. In pairs, look for information about the SDG targets in anayaeducacion.es and on the Internet. Then, make a poster explaining the target you have chosen, why you think it is important, and how you could implement it in your classroom.

Chemical reactions and the environment 13

Shared interpretation. Indicate whether the following statement is true or false, and explain your answer: ‘Carbon dioxide emissions from the use of fossil fuels are creating a hole in the ozone layer, which is having an impact on global climate.‘

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en to strength Activities d ie d u st n bee w h at h a s rk o ferent w using dif strategies.

Mirror. How are the anomalous greenhouse effect and ozone depletion similar and different?

15 Find information on substances that cause the destruction of the ozone layer.

16 Gases that do not destroy the ozone layer are currently used in pressure vessels, but can cause harm to the user if certain precautionary measures are not taken. Which gases are involved? What is the risk to be taken into account when handling these vessels?

17 Climate change, caused by the anomalous greenhouse effect, is an undeniable fact. Find information on the climate summits that have taken place in recent years, and on the measures that have been agreed upon.

18 The effects of acid rain are felt at a great distance from the place where the emission of corrosive gases occurs. During the nineteen-seventies and -eighties, this effect was observed in European forests. What solutions have been proposed to mitigate these effects and to repopulate these affected areas?

19

Roundtable. Massive logging of forests and jungles, as in the case of the Amazon. How can it harm us in the short and long term?

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Images to observe and interpret.

Academic and professional

ICT

orientation

Evaluation

Linguistic Plan

Learn how to obtain information, select it and apply it; to plan, manage and work on projects; to collaborate online in an ethical and safe manner.

Evaluate your personal skills, discover and awaken your calling, train yourself to make decisions and learn to choose between different options.

Discover different strategies to analyse what you have learnt and how you learnt it; train yourself to take responsibility or overcome difficulties.

Use your communication skills in the different types of text that you will see.

Language is always present, communicate!

RESOURCE

BANK

Register at www.anayaeducacion.es to access your resource bank or download your digital book. You just need an email address, the code from the inside cover of this book and permission from your parent or legal guardian.

www.anayaeducacion.es

DIGITAL BOOK RESOURCE BANK

A digital version of your book to be used online or offline. It offers access to your digital resources which are grouped by type or linked to unit content.

A space with resources, techniques and activities, designed to strengthen your knowledge.

More about the keys

Resources related to THE PROJECT KEYS

SDG

SDG Commitment with short videos that will help you understand the targets for reaching the Sustainable Development Goals worked on in this project.

Linguistic Plan with infographics that will give you models to work with the four linguistic skills, using different text types (descriptive, narrative, explanatory, etc.).

Cooperative learning Preparing for the task In small groups, of four or five members: 1 All the members of the team will review how the assigned task can be accomplished.

2 To do this, the steps can be shared out to each team member who then in turn will explain how each part of the process can be done to the others. The others listen and participate if they think they can contribute something.

Authorship / adaptation : Variant of the Educational Innovation Laboratory of the colegio Ártica - David and Roger Johnson.

Developing thinking with explanations on how to apply the different thinking techniques proposed in the project.

3 Once everyone is in agreement on how to do each part, you will all complete the tasks and, finally, verify, among everyone, that you have solved it correctly.

Cooperative learning which includes the descriptions of the cooperative learning techniques proposed in the project.

Thinking techniques

Emotional education with resources to help you overcome any worries that may arise in different situations at school (beginning of the school year, taking a test, etc.).

Logic Wheel This thinking technique will help you to establish phases when analysing specific content that you have to study.

Identify What is it? What is it like? Are there different types?

By following a logical sequence (the logic wheel), and by asking yourself a series of questions in each phase, you can:

1

• Identify content by asking yourself: What is it? What is it like?

Are there different types?

• Compare the content by formulating questions such as: In what way is it similar to ...? In what way is it different from ...?

• Establish cause-effect relationships by asking yourself questions such as: Why? What impact does it have ...?

• Argue, assess and ask yourself questions such as: What conclusions can be drawn after the analysis? What can be assessed or scored about it?

Doing a data dump of these questions into a graphic organiser will help you.

Compare

Argue, assess What can we conclude?

4

Logic wheel

2

In what way is it similar to ...?

In what way is it different from ...?

3 Establish cause-effect relationships Why? What impact does it have ...?

Authorship: Hernández, P., and García, L. A.; adapted by Escamilla, A.

ICT resources to help you use information and communication technology in a healthy, correct and safe way.

Academic and professional orientation with information on different professions linked to the subject content.

0:40/1:33

Assessment which includes resources for your portfolio, as well as rubrics and targets that will help with your self-assessment.

resources

SUBJECT KEY CONCEPTS What you should know To study Learn by playing Virtual laboratories and simulations Self-assessments Solutions

Resources classified by unit

All the resources are classified by unit so that you can find them more easily.

Course Contents The scientific activity

Page 8

The scientific method and a hypothesis ........................

1. Scientific knowledge ..........................................................

2. Physical and chemical changes ......................................

3. Physical quantities. Units and measurement ............

4. Scientific language ..............................................................

5. Laboratory equipment. Safety guidelines ..................

6. Science, technology and society ...................................

8 10 11 12 16 18 22

Science workshop.

Scientific report. The snowman ........................................... 24 Practical work. Measurement errors ................................. 25 Review .......................................................................................... 26

1

Matter

Page 28

3

Atom

Page 66

Defining matter ......................................................................... 28 1. The properties of matter .................................................. 30 2. Pure and mixed substances ............................................. 34 3. Liquid solutions ........................................................................ 36 4. Methods for separating mixtures .................................. 38 5. Suspensions and colloids .................................................. 40

The atom: a journey to discover its structure .............. 66 1. Matter is composed of atoms ......................................... 68 2. The characteristics of atoms ........................................... 70 3. Atomic number and atomic mass ................................. 72 4. Ions ............................................................................................ 74 5. Can we see atoms? ............................................................. 76

Science workshop. Solid or viscose liquid? ................... 42

Science workshop. Constructing atoms ......................... 78

Practical work. Which type of mixture is It? .................. 43

Practical work. Discontinuity of matter ........................... 79

Review .......................................................................................... 44

Review .......................................................................................... 80

2

The states of aggregation

Page 46

Global warming: A human challenge .............................. 46 1. The properties of the states of matter ........................ 48 2. he kinetic theory of matter .............................................. 50 3. Pressure and temperature ................................................ 52 4. Laws of gases ........................................................................ 54 5. Phase changes ...................................................................... 58 6. Phase change diagrams .................................................... 60

4

Chemical substances

Page 82

Naming chemical substances ............................................. 82 1. The periodic table of chemical elements ................... 84 2. Simple substances and compounds ............................. 86 3. Molecules and crystals ....................................................... 88 4. Molecular mass and chemical formulas ...................... 90 5. The application of chemical elements ......................... 92

Science workshop. Oil cubes ............................................... 62

Science workshop.

Memorizing the chemical elements ................................... 98

Practical work. Boiling a mixture ....................................... 63

Practical work. Discontinuity in matter II ........................ 99

Review .......................................................................................... 64

Review .......................................................................................... 100

5

Chemical reactions

Page 102

7

Energy. Mechanical energy

Page 142

Modern agriculture .................................................................. 102 1. Changes in material systems ........................................... 104 2. Chemical reactions .............................................................. 106 3. Characteristics of chemical reactions .......................... 108 4. Chemicals of natural and artifical origin ..................... 110 5. Sustainable chemistry and commitments .................. 112 6. Chemical reactions and the environment .................. 114

Earthquakes: Natural catastrophe or divine punishment? ............................................................................... 142 1. Energy ...................................................................................... 144 2. Manifestations of energy .................................................. 146 3. Energy exchange ................................................................. 150 4. Mechanical waves ................................................................ 152 5. Sound ....................................................................................... 154

Science workshop. Homemade glue ................................ 116

Science workshop. String phone ....................................... 156

Practical work. Chemical reactions ................................... 117

Practical work. What does mechanical energy depend on? ................................................................................. 157

Review .......................................................................................... 118

6

Forces and motion

Page 120

Review .......................................................................................... 158

8

Thermal energy

Page 160

Fascinated by the Universe ................................................. 120 1. Forces ....................................................................................... 122 2. Studying motion .................................................................. 126 3. Elastic deformation. Hooke’s Law ................................. 131 4. Simple machines .................................................................. 132 5. Everday forces ...................................................................... 134 6. Universal gravitation ........................................................... 136

When lightbulbs block the stars ....................................... 160 1. Thermal energy and temperature ................................. 162 2. Heat: energy in transit ....................................................... 164 3. Effects of heat ....................................................................... 166 4. Heat propagation ................................................................ 168 5. Electromagnetic waves (EM waves) ............................. 170 6. Light .......................................................................................... 172

Science workshop. The time factor in force .................. 138

Science workshop. Newton’s disc ..................................... 176

Practical work. Elastic deformation. Hooke’s Law........ 139

Practical work. Heat propagation ...................................... 177

Review .......................................................................................... 140

Review .......................................................................................... 178

5

Chemical reactions Reading and listening

Modern agriculture Normally, when hearing the term “pollution” the first thing that comes to our minds is releasing greenhouse gases to the atmosphere or toxic fluids in rivers, seas and oceans. However, we rarely think of soil pollution.

Modern agriculture, based on ongoing production models (to produce more in less time and at less cost), has become a vicious cycle. Since the invention and broad use of fertilizers by the end of the 19th century, global agriculture focused on monocrop rather than polycrop farming, and on intensive rather than extensive exploitation.

This new agricultural trend has meant that, year after year, higher pollution levels in the soil and in groundwater are measured. The overuse of fertilizers, herbicides, and pesticides has given rise to less productive farming soils, increasing the dependence of the agricultural sector on the industrial chemistry.

1 Why do you think that we give more importance to greenhouse gases or toxic fluids rather than soil pollution?

2 Why do we want to produce more crops in less time?

3 What are fertilizers?

4 Where does the water that you drink come from?

5 What do you think is the difference between herbicides and pesticides?

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Speaking Describing an image

Look at the picture and describe thoroughly what you observe.

Describe the pipes, the lights and the different levels.

What kind of place is it?

What else is happening in the picture?

In pairs, discuss what are the pros and cons of producing crops in this way. Create questions and answers by using the quantifiers how many and how much.

Example: How many levels can you count?

How much water do these systems need?

Writing Asking questions Vertical farming seems to be the solution for the current agricultural problem. Vertical farming adapts to the productive needs of our society because it allows us to produce more crops in less time, without using too much space and without the need for pesticides or herbicides.

The basic idea behind vertical farming is to grow crops without soil. In countries where light is not a problem, this system can be installed within greenhouses. In countries with a lack of sunlight, LED lights can replace it.

Nowadays Europe is moving towards this type of agriculture. Ask questions about vertical farming that can contribute to achieving SDGs targets 15.4 and 15.5.

NK E BANK A B E G A ANGU LANGUAG L ANK ANK GE BANK B B E E G G A A U U GUA K LANG ANG N L A L AN GE BANK 103 ANK GE BANK B B E E G G A A U U G A LAN LANG LANGUA LANGU

1 CHANGES IN MATERIAL SYSTEMS

ää 1.1 Changes in matter A chemical change produces new substances that did not exist before the change.

As you have studied previously, change where new substances do not appear are called physical change. For example: • A phase change is not a chemical change. In a phase change, the substance is the same before and after the process. For example, when water melts, the water molecules become more mobile than in their solid state, but they remain water molecules.

• Dissolving one substance in another is not a chemical change. It is a homogeneous mixture of the two substances. No new substance appears.

ää 1.2 How do we identify a chemical change?

To identify whether new substances appear from a chemical change, we must analyse the composition of the matter after the change. This is not always possible, so sometimes we must use other physical evidence (see photos on the next page).

• Gas release. Gases may not be visible. Sometimes we identify them via bubbles in a liquid.

• Colour change. New substances from a chemical reaction may have a different colour.

• Thermal energy exchange. All chemical changes involve energy exchanges. In thermal energy, the surrounding temperature will change.

• Energy released as light. Some chemical reactions generate light. One well-known case is combustion, which produces flames. There are also other natural reactions that generate light without combustion.

Physical changes Dissolution

Changes of state

In the process of salt dissolution, the crystals, consisting of cations and anions, and the water molecules do not form different bonds at the atomic level.

In a change of state, the interactions between the elementary entities of the substance may be stronger or weaker, but they do not change, they are still water molecules.

There is a resource on chemical changes on anayaeducacion.es.

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5

Possible evidence of a chemical change Release of a gas

Colour change

Appearance of a bubbling on the surface as a result of the chemical change between vinegar and sodium bicarbonate.

The rust on a piece of iron is a chemical process; iron oxide is formed, which is orange in colour.

Thermal energy exchange

Light

Cold packs are an example of a chemical change that causes a decrease in the temperature of the environment.

Fireflies emit light due to a chemical change involving a substance called luciferin.

Understand, think, investigate…

1 Indicate whether a chemical change occurs in the

following everyday phenomena. Justify your answer according to whether new substances appear or not:

3 When food is digested, it is transformed into nutrients.

Is this change physical or chemical, and do you know of any other such changes that occur in our bodies?

Explain your answers.

a) Clouds forming. b) Dissolving sugar in water.

4 Explain what elementary entities are shown in the image on the previous page.

c) Rust forming on a piece of iron. d) Caramelisation of sugar during cooking.

5

Make an attribute wheel with the evidence that allows us to identify a chemical change. Add examples other than those shown on this page and explain why you have chosen them as evidence of a chemical change.

6

Research the Maillard reaction. What are the reactants and what evidence of a chemical change is observed?

e) Blending vegetables to make a cream or puree. f) Fruit oxidizing by air.

2 Statues made of bronze (an alloy of copper and tin) that

adorn some town squares acquire a greenish hue over time, which is not the original colour of the bronze. Find information on the chemical change they undergo.

There is a resource on the evidence of chemical change on anayaeducacion.es.

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2 CHEMICAL REACTIONS

ää 2.1 Chemical reactions Most chemical changes in our environment are complex, as physical changes also occur at the same time. In addition, many chemical changes are interrelated.

However, it is possible to isolate a simple chemical change and analyse it; in this case, we can study and describe a chemical reaction.

A chemical reaction is the transformation of starting substances, which we call reactants, into new substances known as products.

Favourable conditions are necessary for the reactants to react, as two or more substances come into contact with each other will not always react.

For example, in the combination of iron with oxygen to form iron oxide, contact with water is necessary, or in the combination of oxygen with a fuel there is only a combustion reaction under certain energy circumstances (presence of a spark, high temperature, etc.).

ää 2.2 Chemical equations To represent a chemical reaction, we use the chemical equation. In it, the chemical formulae of the reactants are written on the left, and those of the products on the right, separated by an arrow, which marks the direction of the reaction. If there is more than one reactant or product, the “+” sign is written between them.

Stoichiometric coefficients These are the numbers preceding each chemical formula in a chemical reaction.

They indicate the number of elementary entities of each substance involved in that particular reaction. If the value of this number is one, it is not written.

In addition, we write the number of elementary entities of reactants and products involved in the reaction, choosing the values of the stoichiometric coefficients.

A chemical equation contains all the relevant information about a chemical reaction.

Determining the value of the stoichiometric coefficients is called balancing the chemical equation, as shown below.

A popular chemical reaction Vinegar (contains acetic acid)

Sodium bicarbonate

Carbon dioxide

Sodium acetate

is sodium resulting sodium carbon combined and and water bicarbonate in acetate dioxide with CH3COOH NaHCO3 + 8 CH3COONa + CO2 + H2O Acetic acid

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The image shows the chemical reaction that takes place when vinegar (a mixture in which one of its components is acetic acid, which is the one that reacts) is put in contact with sodium bicarbonate, to obtain sodium acetate, carbon dioxide and water. The form in which this chemical reaction is expressed is its chemical equation.

Unit

5

ää 2.3 Interpretation of a chemical reaction In a chemical reaction, the appearance of new substances is the result of the rearrangement of the atoms that make up the reactants to form the products.

As the chemical formulae representing the substances cannot change, the number of crystals or molecules of reactants and products involved in the reaction must be such that the number of atoms of each chemical element is the same on the reactant side as on the product side. Consider for example the combustion of methane. The reaction is represented molecularly as follows: O2

H2O

Reaction CH4 (methane)

+

(combustion) O2

CO2 (carbon dioxide)

H2O

The dashed arrows show the rearrangement of the atoms. Notice that each molecule of methane, CH4, reacts with two molecules of oxygen, O2, to form two molecules of water, H2O, and one molecule of carbon dioxide, CO2.

The balanced chemical equation is CH4 + 2 O2 8

CHEMICAL FORMULAE OF SOME COMMON SUBSTANCES

CO2 + 2 H2O

Check that the number of atoms of each chemical element does not change: No. of atoms in reagents

1 · 1 6 Carbon, C

8 1 ·1

2 · 2 6 Oxygen, O

8 1 ·2+ 2 ·1

1 · 4 6 Hydrogen, H 8 2 · 2

No. of atoms in products

The number of atoms of each chemical element before and after the chemical change, that is before and after the substances are rearranged, is the same, since matter is neither created nor destroyed in a chemical reaction.

Water

H2O

Oxygen

O2

Hydrogen

H2

Methane

CH4

Ammonia

NH3

Sodium chloride

NaCl

Hydrochloric acid

HCl

Nitrogen

N2

Carbon dioxide

CO2

Nitrogen monoxide

NO

Understand, think, investigate…

7 Using the formulae in the table on this page, write the

chemical equation for these reactions: a) Three hydrogen molecules combine with one nitrogen molecule to form two ammonia molecules. b) Two hydrogen molecules combine with one oxygen molecule to form two water molecules. c) Two sodium atoms combine with two molecules of hydrochloric acid to form two molecules of NaCl and one molecule of hydrogen.

8

Make a diagram like the one on this page with all the information contained in this chemical equation: 4 NH3 + 5 O2 8 4 NO + 6 H2O

9 Indicate which are the reactants and which are the

products in the following chemical reactions. With the help of your teacher and in pairs, find the chemical formulae of the substances named and write the chemical equation for each reaction: a) Iron combines with oxygen in the atmosphere to produce iron oxide. b) Limestone breaks down under the action of heat into calcium oxide and carbon dioxide. c) Water, under the effect of an electric current, breaks down into molecular hydrogen and molecular oxygen.

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3 CHARACTERISTICS OF CHEMICAL REACTIONS

Chemical reactions have some important properties. This year we will focus on two laws: one related to the masses of the reactants and products, and the other to the rate of a chemical reaction.

ää 3.1 Law of conservation of mass If we mix sand and salt, the mass of the mixture is equal to the sum of the masses of its components. That is, the mass is conserved. What if, instead of a mixture, two substances undergo a chemical change and produce new substances? Will the mass be conserved?

French chemist A. Lavoisier answered this question in 1789, when he discovered and stated the law of conservation of mass.

In a chemical reaction, matter is neither created nor destroyed, only transformed. Therefore, the sum of the masses of the reactants is equal to the sum of the masses of the products of the reaction.

We highlight two aspects and the circumstances in which it was stated: • The statement of this law is based on multiple experiments in which the mass of the reactants and the products of different chemical reactions were measured. It is therefore a law drawn from experience; it is an empirical law.

• Experimental verification of this law in reactions involving a reactant or a product in the gaseous state was technically complicated at the time, and represented an advance in the knowledge of the transformations of matter.

This empirical law was later explained by the atomic theory proposed by Dalton between 1803 and 1808.

Verification of the law of conservation of mass The mass of the reagents and the laboratory material is equal to the mass of the products obtained and the same material. In order to carry out the experiment, the container must have an adequate volume so that the CO2 produced does not cause the stopper to burst.

Vinegar (contains acetic acid)

Aqueous sodium acetate solution

Sodium bicarbonate We bring the reagents into contact with each other

Water H2O

Acetic acid CH3COOH

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Sodium bicarbonate NaHCO3

Carbon dioxide

Sodium acetate CH3COONa

Carbon dioxide CO2

At the microscopic level, we observe that the atoms that form the reactants rearrange themselves to form the new substances, the products, which is why the mass does not change during a chemical reaction.

Unit

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ää 3.2 Law of definite proportions With regard to mass, another law that a chemical reaction follows is the law of definite proportions.

In a chemical reaction, the masses of the reactants and the masses of the products are in constant proportion to each other.

This law is related to the fact that the elementary entities of each substance involved in a reaction have different masses, and always combine in the same numerical proportion. We will study this law in detail next year.

ää 3.3 Rate of a chemical reaction Some chemical reactions are extremely slow, such as the formation of minerals in the Earth’s crust, while others are very fast, such as an explosion or the combustion of methane that we have already studied. There are several factors on which the rate of a chemical change depends. The following are the most important ones: • Temperature. Generally speaking, it can be seen that as temperature increases, the rate of a chemical reaction increases.

• Concentration of the reactants. The higher the concentration of the reactants, the faster the rate of the reaction.

Problem solved

Understand, think, investigate…

1 When 30 g of nitrogen react with hydrogen, 170 g

10 Find information about the chemical reaction

To calculate the mass of hydrogen that has reacted, we apply the law of conservation of mass:

a) What are the reactants and products of this reaction?

of ammonia are obtained. What mass of hydrogen has reacted? What mass of ammonia would be obtained if 90 g of nitrogen react?

between vinegar and sodium bicarbonate described above to test the law of conservation of mass, and answer these questions:

mass of reactants = mass of products

b) Is vinegar a pure substance?

Thus, the mass of hydrogen will be the difference between the mass of ammonia and the mass of nitrogen:

c) Why is the result of the reaction an aqueous solution?

mass of hydrogen = 170 g – 30 g = 140 g

d)

We can calculate the mass of ammonia obtained from the law of definite proportions; thus, from 90 g of nitrogen we obtain: 30 g nitrogen 90 g nitrogen = x 170 g ammonia

e) Explain, using the KTM, what would happen if we did the experiment at a temperature much higher than room temperature.

11 If 224 g of iron reacts with oxygen to form 320 g of

90 $ 170 = 510 g ammonia 30 We can represent this reaction as: x=

iron oxide, how much iron oxide will be formed from 112 g of iron?

12 Why do you think most cooking techniques involve

3 H2

raising the food’s temperature?

+ N2

Think and share in pairs. Explain why this experience proves that gases have mass.

2 NH3

13

Explain why storing food in refrigerators conserves it.

You can find the solutions to all the numerical activities at anayaeducacion.es.

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4 CHEMICALS OF NATURAL AND ARTIFICIAL ORIGIN

ää 4.1 Development of chemical industry Since the discovery of fire, mankind has carried out chemical transformations to improve quality of life. Knowledge of these reactions is often limited to necessity and experience. Examples include obtaining quicklime from limestone, synthesising soap from fats and fermenting milk to make cheese, among many others.

Since the Industrial Revolution, and with the development of modern chemistry, we have increased our knowledge about the factors that influence the reactions that aim to improve our quality of life, obtaining products through what is known as synthesis reactions. This has led to the development of the chemical industry.

A synthesis reaction is a reaction aimed at obtaining, or manufacturing, a substance.

These reactions range from those that take place in our bodies to those that occur on a large industrial scale.

ää 4.2 Products of natural and artificial origin Synthesis reactions exist in nature and can also be performed in the laboratory. They are distinguished by the products obtained, which are natural in the first case and man-made in the second.

We sometimes hear the claim that something, because it is natural, is less harmful to health. But it is not always the case that the natural or artificial (also called synthetic) origin of a product is related to its benefit to society and the environment.

Products of natural and artificial origin Acetylsalicylic acid

Recyclable bags

Artificial flavours

Salicylic acid is obtained from willow bark.

It was traditionally used as an analgesic and antipyretic, but caused stomach irritation. Its artificial modification to acetylsalicylic acid is the active ingredient in aspirin.

Plastic bags are a problem for the environment. Nowadays bags that can decompose can be made from potato starch. Their origin is natural, but they are processed industrially.

The flavour of vanilla is due to a substance called vanillin, which is present in vanilla pods. It is expensive to extract, so it is synthesised from lignin, which is a substance found in wood.

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ää 4.3 Sectors of the modern chemical industry The main objective of the chemical industry is to obtain substances that are necessary for society. These substances are very varied and have many different applications. The most important of these are:

Chemical industry Pharmaceuticals

Petrochemicals

Other products

Drugs can be classified according to their action (antipyretics, analgesics, antibiotics, etc.). This industry invests heavily in research to formulate and develop processes for the synthesis of new medicines.

In addition to its use as a fuel source, oil is a raw material for the manufacture of other products. These include synthetic polymers (plastics), some synthetic fibres (nylon or polyester), glycerine, and some solvents.

In addition to the two previous groups, there are a myriad of products obtained in the chemical industry, all of which are necessary in our daily lives, such as fertilisers, acids, additives for construction, and food additives.

Understand, think, investigate…

14 Copy the composition of some clothes you have at home and classify the fibres they are made of as natural or synthetic. What type of fibres are there more of?

Why do you think this is?

15 Look up information on formica and answer: a) Is it a natural or synthetic product? b) What are its main applications?

16

I think, I’m interested, I investigate. Look for information on the types of plastic bags that exist on the market and on the meaning of: biodegradable, compostable, reusable and recyclable. From the above information, indicate what use should be made of each type of plastic bag in order to minimise the pollution caused by these products.

17 Find the formula for vanillin and explain whether it

matters if this substance is obtained from the vanilla pod or it has a synthetic origin from lignin.

18

Search the Internet for the formula of salicylic acid and acetylsalicylic acid. In view of the properties of each of these substances: a) Discuss the contribution of chemistry in this case. b) Was the modification of salicylic acid beneficial?

Explain your answer. c) Is the geographical location of the white willow tree relevant to the artificial development of salicylic acid? Explain your answer.

19 Why are artificial products also called synthetic products?

20 Make a list of chemical products that help to improve our lives. Classify them into categories according to their use and the industry they come from.

21 Are there synthesis reactions in the natural world?

Justify your answer.

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5 SUSTAINABLE CHEMISTRY AND COMMITMENTS

ää 5.1 Pollution by the chemical industry Since the Industrial Revolution, and with the development of the chemical industry, we have caused alterations to the material systems that surround us (the atmosphere, soil and water). As a result, in the last few decades problems have arisen such as: • Atmospheric pollution, due to the emission of substances that affect the composition of the atmosphere and the reactions that take place in it, as we will see in the following section; • Pollution of inland waters, affecting the quality of drinking water, which will contain dissolved substances harmful to health; • Soil pollution, by releasing toxic substances or an excessive use of fertilisers, leading to problems related to soil impoverishment and excess organic matter, thus modifying ecosystems.

ää 5.2 Sustainable chemistry and environmental chemistry What is sustainable development?

According to the 1987 Brundtland Report, sustainable development is “development that meets the needs of the present without compromising the ability of future generations to meet their own needs”.

These and other problems have had consequences on the health of the planet and all the species that inhabit it. This has led to the emergence of sustainable development as a response to this situation. This concept has been taken into account in both industry and research, resulting in the development of sustainable chemistry and environmental chemistry: • Environmental chemistry is mainly concerned with identifying what pollutants are in the environment, where they were emitted, in what chemical reactions they have been produced, and how they have reached the place where they were detected.

• Sustainable chemistry is concerned with the design of environmentally friendly processes and products in order to reduce the production of pollutants. Industries that emitted pollutants without control have been progressively replaced by others that try to avoid waste production (see figures below), analyse the consequences on the environment, study the life cycle of the products they manufacture, and use energy efficiently.

Developments in the chemical industry

The chemical industry has evolved from the economic optimisation of manufacturing a product to sustainable

112

chemistry. Here, the emission of pollutants is minimised and future consequences are foreseen in order to avoid them.

Unit

5

ää 5.3 Sustainable Development Goals Chemical knowledge contributes significantly to the achievement of several of the targets of the Sustainable Development Goals.

The most relevant is related to chemical transformations that occur in the environment as a result of products that have been released over decades and have caused pollution problems.

The diagram shows the relationship between chemistry and the SDGs.

Chemistry and the SDG targets SUSTAINABLE CHEMISTRY

UNDERWATER LIFE

TARGET 14.3

acts on HARMFUL CHEMICAL CHANGES

AIR

CLEAN WATER AND SANITATION

TARGET 6.3

WATER

TARGET 11.6 SUSTAINABLE CITIES AND COMMUNITIES

SOIL

TARGET 3.9 HEALTH AND WELL-BEING

TARGET 12.4 RESPONSIBLE PRODUCTION AND CONSUMPTION

Several of the SDG targets refer to problems caused by the release of substances into the natural environment. This alters the chemical reactions that take place in the environment and affects the balance of the ecosystem and the health of the beings that inhabit it, potentially causing irreparable damage.

Understand, think, investigate…

22 Analyse the pictures on the previous page. Do you think that factories like the one on the left still exist?

23

Conduct an analysis of your household waste and draw up an action plan. You can use these guidelines to help you: a) Make a list of the types of domestic waste in your household for one month. b) Classify each waste according to whether it has been separated and deposited in the appropriate container, whether it is a waste that can be reduced, or whether it is hazardous waste (cleaning product or medicine).

24 Find information about the targets referenced in

the diagram above and relate them to the following situations: a) Development of air quality monitors. b) Development of packaging made of materials other than plastic and that are biodegradable. c) Reuse of plastics in the manufacture of outdoor furniture. d) Studies of how pH affects underwater life.

c) Calculate your household’s water consumption from your utility bill.

e) Collection of garbage and household waste for treatment.

other

hazardous

d) With the above information, draw up an action plan based on specific objectives and share it with the members of your household.

f) Raising public awareness through an information plan on how our actions have consequences for the environment.

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6 CHEMICAL REACTIONS AND THE ENVIRONMENT

Knowing the causes of environmental problems allows us to start solving them, as we have seen in the previous section. Here we look at three environmental problems that affect our planet’s atmosphere globally.

ää 6.1 Anomalous greenhouse effect The temperature of our planet is kept within limits that are suitable for life thanks to the atmosphere, which behaves like a greenhouse: it retains part of the thermal energy emitted by the Earth and lets the rest pass through.

This phenomenon is called the greenhouse effect.

One of the main gases responsible for this effect is carbon dioxide. As its amount in the atmosphere has increased in recent decades due to the use of fossil fuels, an unwanted increase in the amount of energy retained is occurring. This is known as the anomalous greenhouse effect.

If CO2 emissions are not reduced, the increase in the Earth’s average temperature will continue to rise, and the global warming our planet is currently experiencing will have catastrophic consequences.

ää 6.2 Acid rain This is the name given to the polluting phenomenon whereby rainwater carries dissolved highly corrosive acids, such as sulphuric acid, H2SO4, and nitric acid, HNO3. These acids are formed when atmospheric emissions of sulphur dioxide, SO2, and nitrogen oxides, NO and NO2, react with water vapour. When this water precipitates as rain, it is called acid rain. Its consequences on the environment are the destruction of flora and fauna.

Consequences of the greenhouse effect and acid rain Greenhouse effect

Acid rain

The melting of continental ice, a consequence of global warming, affects not only sea levels but also the global climate, altering the humidity of the atmosphere.

Fossil fuels often contain sulphur impurities. When burned in air, which contains oxygen and nitrogen, they produce sulphur dioxide and nitrogen oxides.

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There is a resource on the effects of carbon dioxide on anayaeducacion.es.

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5

ää 6.3 The destruction of the ozone layer The ozone (O3) layer is in the stratosphere and shields everything below from harmful ultraviolet radiation from the sun.

Substances such as nitrogen oxides and compounds known as CFC (which includes chlorine) in the atmosphere cause chemical reactions that destroy ozone.

The reactions release chlorine when they reach the stratosphere, where ozone normally forms and degrades in an equilibrium. The chlorine disrupts this balance, reducing the amount of ozone.

Formation and destruction of the ozone layer

What global solutions have been proposed to reduce the destruction of the ozone layer?

In which products was CFC present? Which products have replaced CFCs? Discuss with the rest of the class the need for global agreements.

Natural process of formation of O3 1

O2

UV radiation

2

+ 4 O2

+

2

O

3

O3

1 UV rays attack the O2 molecule and split it into two oxygen atoms.

+

3

O3

O

2 Each of these oxygen atoms combines with an O2 molecule to produce ozone, O3.

4

O2

O

O3

O

O2

O2

O2

Working with images

For the shield effect to work, there must be enough ozone to absorb the radiation.

3 Each ozone molecule combines with another oxygen atom, giving two O2 molecules as products.

4 The cycle is closed by the reaction, again, of O2 with UV or as a reactant of the O2 reaction.

O2

In the stratosphere, UV radiation separates oxygen molecules into atoms. Each atom combines with separate oxygen molecules, forming a molecule of ozone.

This reaction requires a lot of energy and high temperatures.

Destruction of O3 by chlorine O3

1

CFC

+

+

Cl

2

1 UV rays attack CFCs and cause a chlorine atom to be released.

2 The chlorine atom attacks the ozone molecule.

Rayos UV

+

4 O

+ ClO

3

O2

4 The ClO molecule reacts with monoatomic oxygen.

+

5 O2

Two products are formed: 3 the O2 molecule and the ClO molecule.

Cl

CFCs are compounds that remain in the atmosphere for a long time. When they release chlorine due to UV radiation, they break down ozone. Chlorine is one of the products of the reaction, so it continues destroying ozone.

5 As a result, one oxygen molecule and one chlorine atom are released into the atmosphere.

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SHOP SCIENCE WORK

research project homemade glue

INTRODUCTION As we have studied, if mixing several substances causes the appearance of new substances, we say that a chemical change has occurred.

In the experiment proposed, a series of chemical reactions take place which cause the appearance of new substances. Among these is the appearance of a solid substance and the release of a gas. To speed up the process, we will use a heat source.

YOU NEED • Milk.

• Vinegar.

•C hemical yeast (baking soda).

• A frying pan.

• A tablespoon.

EXPERIMENT • Pour one and a half cups of milk and three tablespoons of vinegar into a frying pan. With the help of an adult, heat the mixture a little while stirring with a wooden spoon. You will notice some lumps forming; this is the rennet in the milk.

• Separate the rennet obtained from the remaining liquid by straining your mixture.

• A wooden spoon.

• Pour back into the pan, add a tablespoon of baking powder and a little water. Heat and stir the mixture. You will notice some bubbles at first.

Continue heating and stirring until the mixture boils.

• A cup.

• Remove the mixture from the heat source and continue stirring.

• A sieve.

• Finally, transfer it to a container and cover it. You can use it as a glue when it is cold. It will last up to two days before it spoils.

• A mixing container.

• A source of heat.

THINK When you add the vinegar to the milk, you separated the casein, the rennet, from the whey, the rest of the milk. When the rennet, proteins and fats are formed, they solidify and agglomerate under the action of an acid (in this case, vinegar), resulting in lumps that are separated with a strainer. The properties of casein as a glue have been known since ancient times. Nowadays, it is used in the manufacture of glues and adhesives.

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When chemical yeast (sodium bicarbonate) and water are added to the rennet, a gas is released. This is carbon dioxide, which is the result of the chemical reaction between vinegar and bicarbonate; in this way, we eliminate the excess acid (vinegar), since it is used in the chemical reaction. In this reaction, other products are obtained, such as sodium acetate, which has multiple industrial applications.

Unit

5

PRACTICAL WORK chemical reactions

STATEMENT OF THE PROBLEM. OBJECTIVE The objective of this practice is to have evidence of a chemical change, and to observe how the temperature and concentration of the reactants affect the rate of reaction.

PRELIMINARY STEPS Make a plan to detect chemical changes, and to observe how the temperature and concentration of the reactants affect the rate of chemical change.

OUR PROPOSAL We will carry out two experiments: • Experiment A: we will test the chemical reaction that takes place between metals and hydrochloric acid.

• Experiment B: we will use a glow stick to test how temperature affects the reaction rate.

PRECAUTIONS Hydrochloric acid is a very corrosive liquid. Follow the safety rules to avoid accidents.

MATERIALS • Glow sticks • Beaker • Ice • Water • Salt • Metal filings • Dilute hydrochloric acid solution • Slightly more concentrated hydrochloric acid solution.

GUIDELINES FOR CARRYING OUT THE EXPERIMENT EXPERIMENT A • Pour some water into a beaker and add the metal filings.

EXPERIMENT B • Prepare one beaker with hot water, and another with a mixture of water, ice and salt.

• Repeat the previous experiment, now using the dilute hydrochloric acid solution instead of the water.

• Bend two glow sticks to trigger the chemical reaction inside them.

• Again, repeat the previous experiment, this time using the slightly more concentrated hydrochloric acid solution.

• Put one of them in the glass with hot water, and the other in the glass with the mixture of ice, water and salt.

• Observe and note what happens in the three cases.

• Write down the differences you observe in each case.

Draw conclusions…

1 How do you explain the differences observed in the first

4 Find information on how glow sticks work and their

2 What chemical reaction occurs when a metal is mixed

5 Explain the differences observed between the stick

step and the third step of experiment A?

with hydrochloric acid? Why does it generate bubbles?

3 How do you explain the differences observed between

the last two steps of experiment A? What factor is influencing the reaction rate?

applications.

placed in hot water and the stick placed in the beaker with ice. Which factor influences the reaction rate?

6 Find information on why salt is added to ice water. What applications does it have in everyday life?

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m resources fro r to choose Remembe lio. fo rt po ur for yo this unit to

REVIEW

ORGANISing MY IDEAS

Hierarchical concept map

1 Copy the diagram in your notebook and include: a) The name of the scientist who stated the law of conservation of mass. b) A new branch with the law of definite proportions.

c) An example of a chemical equation indicating the formulae of the reactants, the formulae of the products, and the stoichiometric coefficients.

Chemical reactions

are

are identified by

are represented by

physical evidence

chemical equations

which can be

composed of

chemical changes in which occurs a rearrangement of atoms

change of colour

light

bubbling

causing a transformation of reactants

into

chemical formulae

the law of conservation of mass

stoichiometric coefficients

products

Changes in material systems 1 Write down three examples of chemical changes and three examples of non-chemical changes. What type are the latter?

2 Are there any chemical changes in the distillation of a mixture of alcohol and water? Explain your answer.

3 Classify the changes as physical or chemical: a) Piece of fruit rotting. b) Boiling water. c) Melting a piece of butter in a hot frying pan. d) Cooking a grilled steak. e) Effervescence of a medicine when it is placed into water. f) Sweetening an infusion with saccharin.

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energy in the form of heat

comply with

Chemical reactions 4

What makes you say that? Indicate whether the following statements are true or false, and explain why: a) The products of a chemical reaction are always artificial in origin. b) The number of substances in the reactants is always equal to the number of substances in the products. c) Chemical changes are represented by an arrow. d) The number of atoms of each chemical element present in the reactants is equal to the number of these atoms in the products. e) In a chemical reaction, different atoms are obtained in the products. f) In a chemical reaction, there is always a product obtained in gaseous state.

Solutions to all the numerical activities at anayaeducacion.es.

Unit

5 State the names of the reactants and products of these chemical reactions, and draw a picture representing them on an atomic scale: a) N2 + O2 8 2 NO. b) C + 2 H2 8 CH4.

Characteristics of chemical reactions 6 Indicate whether the following statements are true or false, and justify your answer: a) The mass of the reactants is destroyed in a chemical reaction. b) In a chemical reaction, atoms are rearranged; therefore, the sum of the masses of the reactants and the masses of the products is equal. c) The atoms that form the products of the reaction are generated from the atoms present in the reactants.

7 If 306 g of one substance reacts completely with 72 g of another, what will be the sum of the masses of the products of the reaction? Which law have you applied?

8 We have a 224 g piece of iron that combines completely with oxygen to form iron oxide. Are the following statements true or false? Justify your answer. a) The mass of iron oxide formed will be the sum of 224 g plus the oxygen that has combined with the iron. b) The mass of the iron oxide will be less than that of the iron at the start. c) The mass of the iron oxide will be the same as the mass of iron.

9

Let’s check. 8 g of hydrogen react with 64 g of oxygen to form 72 g of water. a) Check that the law of conservation of mass is fulfilled. b) Calculate the mass of water that will be formed if 20 g of hydrogen react completely.

Products of artificial and natural origin 10 Classify the following products according to their origin, natural or artificial: a) Unrefined sugar e) Flax b) Saccharin f) Cotton c) Wood g) Nylon d) Formica h) Acrylic anayaeducacion.es Check the ‘Let‘s study’ and ‘Learn by playing‘ sections in the resource bank.

5

Sustainable chemistry and SDG commitments 11 Search the Internet for the twelve principles of green or sustainable chemistry and make a presentation about them. Which SDG targets are they related to?

12

C&R. In pairs, look for information about the SDG targets in anayaeducacion.es and on the Internet. Then, make a poster explaining the target you have chosen, why you think it is important, and how you could implement it in your classroom.

Chemical reactions and the environment 13

Shared interpretation. Indicate whether the following statement is true or false, and explain your answer: ‘Carbon dioxide emissions from the use of fossil fuels are creating a hole in the ozone layer, which is having an impact on global climate.‘

14

Mirror. How are the anomalous greenhouse effect and ozone depletion similar and different?

15 Find information on substances that cause the destruction of the ozone layer.

16 Gases that do not destroy the ozone layer are currently used in pressure vessels, but can cause harm to the user if certain precautionary measures are not taken. Which gases are involved? What is the risk to be taken into account when handling these vessels?

17 Climate change, caused by the anomalous greenhouse effect, is an undeniable fact. Find information on the climate summits that have taken place in recent years, and on the measures that have been agreed upon.

18 The effects of acid rain are felt at a great distance from the place where the emission of corrosive gases occurs. During the nineteen-seventies and -eighties, this effect was observed in European forests. What solutions have been proposed to mitigate these effects and to repopulate these affected areas?

19

Roundtable. Massive logging of forests and jungles, as in the case of the Amazon. How can it harm us in the short and long term?

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