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Kinetic Par ticle T heor y (Kinetic M odel of M atter )


You ar e expected to… •

describe the three states of matter and explain their interconversion in terms of the kinetic particle theory.

show understanding that Brownian motion provides evidence for the kinetic molecular model of matter.

explain everyday effects of diffusion in terms of particles, e.g. the spread of perfumes and tea/ coffee grains in water.

describe qualitatively the molecular structure of solids, liquids and gases, relating their properties to the forces and distances between molecules and to the motion of the molecules.


Recall: What is M atter ? •

Objects that have mass and occupy space are called matter.


Question: Is this glass bottle empty?

No. It is filled with air!


Recall: H ow do w e classify matter ? • What are the three states of matter?

M atter

• Do you know that there are more than three states of matter? - Plasma - Bose-Einstein condensate

Solid

L iquid

Gas


Recall: Pr oper ties of each state of matter

Shape

Solids fixed shape

L iquids Gases no fixed shape no fixed shape

Volume

fixed volume

fixed volume

Ability to incompressibl be e compr essed

incompressibl e

no fixed volume compressible


What is matter made of? Let’s see what the philosophers have to tell us‌


D emocr itus “…if one were to break up matter into smaller and smaller piece, there would come a point when it could no longer be divided fur ther .” He called this smallest indivisible bit of matter ‘atom’ (from the Greek word atomos which means indivisible). Greek Philosopher (460 B.C. – 370 B.C.)


Ar istotle “ Matter has a continuous composition and that it can be br ok en dow n into smaller and smaller pieces for ever .� Aristotle was highly regarded and most people followed his school of thought about the nature of matter Philosopher (384 B.C. – 322 B.C.)


Who is right? Democritus or Aristotle? Let’s vote!

L et’s see w ho’s r ight…


Br ow nian M otion


Br ow nian M otion Think, Pair, Share • Describe the motion of pollen grains in water and the smoke particles in air. – Moving constantly in a random or irregular motion

• What caused these motions? – Pollen grains and smoke particles were bombarded by water molecules and air particles respectively which themselves were moving constantly and randomly.


Br ow nian M otion • The constant and random motion of small solid particles in fluids (liquids and gases) is called Br ow nian motion. • Brownian motion provided the evidence of molecular motion & proved the existence of particles that cannot be observed with a normal microscope. • Just for info: Brownian motion is first observed in 1827 by Robert Brown. Through the microscope, he observed the motion of pollen grains suspended in water. However, he was unable to provide an explanation for Brownian motion.


Par ticles that mak e up of matter • Using a scanning tunneling microscope (STM), scientists are now able to observes the particles that make up matter.

Gol d a toms


Par ticles that mak e up of matter

I r on on Copper


So, w ho’s r ight? In conclusion… Matter is made up of discrete (separate not continuous) particles which are in constant and random motion. In other words…

Democritus (460 B.C. – 370 B.C.)

Democritus’ proposal that matter is made up of tiny particles is right!


Kinetic M odel of M atter (Kinetic Par ticle T heor y) • Based on observations, a model (Kinetic Model of Matter) which explains the nature of matter was proposed. • The Kinetic M odel of M atter (Kinetic Par ticle T heor y) states that matter is made of tiny discr ete par ticles (atoms or molecules), w hich ar e in constant and r andom motion . • Energy due to movement = Kinetic energy


Remember ed this? Shape

Solids fixed shape

L iquids Gases no fixed shape no fixed shape

Volume

fixed volume

fixed volume

Ability to incompressibl be e compr essed

incompressibl e

no fixed volume compressible

Kinetic Model of Matter can be used to explain the properties for each state of matter


Kinetic M odel of M atter (Kinetic Par ticle T heor y)


Video: Things to look out for •Arrangement of particles •Motion of particles •Attractive forces between particles •Speed of particles (if any)


Par ticles in a Solid Ar r angem ent

Closely packed together in a fixed, regular pattern, occupying minimum space. This results in solids having high densities


Par ticles in a Solid M ovement Cannot move freely but vibrate about fixed positions. Held in position by very strong attractive forces This explains why solids have fixed volumes and shapes


Par ticles in a L iquid Ar r angeme Randomly arranged with the particles slightly nt further apart as compared to that of solids. This results in liquids having relatively high densities


Par ticles in a L iquid M ovement

Particles slide past one another Free to move about but confined within the vessel containing it. Have attractive forces between particles. This explains why liquids have fixed volume but will take the shape of vessels containing them.


Par ticles in a Gas Ar r angeme Very far apart. Particles are randomly arranged nt and will occupy any available space. This results in gases having relatively very low densities


Par ticles in a Gas M ovement

Particles have very little attraction between them and move about randomly at a very high speed.. This explains why gases have no fixed volume and shape, and why they are highly compressible.


T he states of matter • The relative strength of the intermolecular forces between the particles differ between the different states of matter


T he states of matter • The relative distances between the particles also differ between the different states of matter


A Summar y… • Matter is anything that has mass and occupies space • All matter can exist in 3 physical states, – Solid – Liquid – Gas

depending on the temperature and pressure of their surroundings


Solid Volume

Fixed

L iquid

Gas

Fixed

Takes the volume of its container

Takes the shape of the part of Takes the shape the container it of the container fills

Shape

Fixed

Density

High

Medium

Low

Expansion on heating

Little

Moderate

Large

Ease of compression

Difficult

Difficult

Easy


A Summar y‌ So why do solids, liquids and gases have such different properties?

Kinetic Par ticle T heor y


Kinetic Par ticle T heor y • All matter is made up of a large amount of tiny particles (cannot be seen by the naked eye) which are always in constant random motion • Energy due to movement = Kinetic energy


Evidence of Kinetic Par ticle T heor y? • Diffusion – par ticles moving r andomly fr om a r egion of high concentr ation to low er concentr ation • in gases • in liquids • in solids???


T hink ing Question: • Now that you know the arrangement / movement of particles in solids, liquids and gases, can you compare the rates of particle movement (diffusion) in solids, liquids and gases and explain why it is so?


T hink ing Question: • If a solid is usually more dense than a liquid, why does ice float on water?


Role play ď Š


M elting • When a solid is heated, the particles absorb heat ener gy. The particles gain k inetic ener gy and start to vibr ate faster and move fur ther apar t . At a certain temperature known as the melting point, the particles have enough k inetic ener gy to overcome the str ong for ces of attr action holding the particles together in the solid. The particles start to br eak aw ay fr om one another and the solid becomes a liquid. • At the liquid state, the particles start to r oll and slide over one another


F r eezing • When a liquid is cooled, the particles release heat ener gy. The particles lose k inetic ener gy and vibr ate slow er . At a certain temperature known as the fr eezing point , the particles no longer have enough k inetic ener gy to overcome the str ong for ces of attr action holding them together. The particles start to come together in a r egular ar r angement and the liquid becomes a solid.


Boiling • Particles in a liquid are held by str ong attr active for ces. • When a liquid is heated, the particles absorb heat ener gy. The particles gain k inetic ener gy and slide over each other mor e r apidly. • Eventually, the particles gain sufficient ener gy to over come the attr active for ces betw een the par ticles and move far apar t r apidly in all dir ections.


Summar y of today’s lesson • All matter is made up of a lar ge amount of par ticles in constant r andom motion • The particles in a solid, liquid and gas are arranged differently – so they have different properties • During change of state, the particles gain or lose energy, resulting in a change in the arrangement of the particles


T hink ing question • A liquid expands and changes into gas during boiling. Does it mean that the particles in a liquid become bigger and change their shape? • The liquid expands because the particles move farther apart, so the space between them is bigger. The particle remain the same in size and shape.

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Kinetic Model of Matter  

Kinetic Model of Matter

Kinetic Model of Matter  

Kinetic Model of Matter