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• Y YOUR OUR HE HEAL ALT AL TH: TH: He eat Cra amps, mps, 6 • EA ART RTH TR TRU USTEE: US TE EE: The e Gre rea at P at Pac a ifi fic G Gar arba bage ba ge Pat atcch,, 7 • HO HOW W DO OES E IT WO WORK RK K?: ?: A Green en Bui uild ild ding, g, 1 10 0 • CO C MP MPUT U E UT ER RAC A Y: Virtu tuall K Keyybo boar ards d , 11 ds 1 • IN INTE TERE TE REST RE ST AC ACTI TIVI VIT TY: Bui u ld d a Gal alax axxy! y , 14 1 The Science and Technology Magazine of Student’s Student s Digest Publications Vol. XIII • No. 6 • January – February 2009 • ISSN 0118 0118-3575 3575



Changing Climate CONCEP EPT T MA MAP: P: Plate Tectonics • 8-9 9 C NC CO NCEP EPT EP T AR RTI T CL C E:: Th he Mi Milk lkyy Way • 12 2-1 -13

Intense summer heat, heavier rains, stronger typhoons — these are just some weather changes that we are experiencing now. Are these effects of a climate change?

values corner




Who’s to blame? Karla P. Abulencia

First exoplanets

pictures captured

For the first time, photographs of planets outside our solar system were captured! They include an image of three exoplanets circling the star HD 8799 and a picture of another one orbiting the star Fomalhaut. HD 8799 is found in the constellation Pegasus. It is about 130 light-years away. The exoplanets revolving around it are seven to ten times larger than Jupiter. The fourth planet, named Fomalhaut 2, is one of the smallest exoplanets ever found. It is believed to be about the same size as Jupiter. The planet goes around Fomalhautt in the constellation Piscis Austrinus. At 25 light-years away, Fomalhaut is one of the brightest stars in the sky.

Are humans to blame for ? Many theories and speculations about climate change have been circulating. However, we really don’t have a clue on which ones are true and which ones are nott. In discussing climate change, there arre re real ally ly many factors to consider. Most theories blamee hu huma man n ac acti tivi ti v ti vi ties e. es However, there are re act ctua uallllllyy ot ua othe herr fa he fact ctor o s that cause clim mat atee ch han ange gee, an and d mo most st of them are out of o our ur con ontr trrol o , su such ch as solar radiation. Beca Be caus ca u e of ttec us echn h ological advancements, m ny h ma hum uman an activities now rely too much on foss fo ssilil fuels which emit dangerous particles into the air. These activities do contribute to climate change. And in recent years, they have greatly increased. But are we solely to blame? Even if the answer is no, human activities are still the only factors within our control. Thus, by always being aware and responsible in everything we do, we can still help prevent climate change.


Nilaa V. Mata Mata,, Publ Publishe isherr • L Lililia ia M. Ra Raba bago go,, Ph.D h.D., ., Scien Science Education Con o sultant • Carmelita C. Corone el & Ce Celiini niaa J. D Dic icen en,, • Antonette Yap–Castillo, Supervising Editor • Karla P. Abu b le l ncia i , Ez Ezek ekie i l T. Man a alaysay l & Jenilee A. Abenes, Stafff Wr Staf Writer iterss • F Fra ranc ncis isco co D DC C. M Men endo doza za, Art & Design Design Sup Supervi ervisor sor • P Pau aull Da Davi vidd D. A Aro rocs cs,, Grap Graphic/ hic/Layo Layout ut Artis Artistt • N Noe oell L. P Per erez ez,, Area Editors

Imagesetting & Stripping Supervisor

S&T Digest Grade 5 Edition is published each semester of the school year by SD Publications, Inc. with business and d edito editoria i l offi offices at Vib Vibal al Pub Publis lishin hingg Hous H ousee , Inc Inc., G. Ara Aranet netaa A Ave. ve cor. cor Ma Ma. Clara Clara St., St Que Quezon zon Ci City ty • Tels Tels.:.: 712 712-27 2722 22 loc loc. 319/ 712-9156 to 59. E-mail: d Member: Philippine Educational Publishers Association



Twinkle, twinkle green and purple stars... Observe the stars at night. Can you see any ggreeen or purple star? Why not? There are actually green an nd purple stars. In fact, our sun is yellow-green in color. Butt why w do we only see mostly white and yellow stars? The answer lies in the way our eyes perceive co colo ors. Green is found in the middle of the visible spectrum m. When W we look at a green star, most of its radiation will peak ak at the middle of the spectrum. Green will mix with the other colors of the spectrum, so we will see the star as white. The same goes with purple stars. Purple stars are actually the hottest. Because they peak toward ultraviolet light, we only see the blue portion of these stars.

Extraterrestrial clouds Clouds are not unique to Earth. Any planet or mo with an atmosphere also has clouds. Clouds moon in Venus Ven are composed entirely of sulfuric acid droplets. lets Mars has clouds composed of water ice. Jupiterr and a Saturn have clouds made of ammonia crystals a and possibly ammonia hydrosulfide. Uranus and Neptune pt have methane clouds. Clouds in Saturn’s ’s moon, Titan, are believed to be composed of droplets opl of liquid methane.

SDMAGS.NET Weighing a cloud Technically, clouds cannot be weighed. Earth’s clouds are made up of a small amount of water vapor and mostly of air. Clouds float because moist air weighs less than dry air. A cloud’s weight depends on the size and type of cloud, but a 1 km x 1 km x 1km cumulus cloud can weigh more than 907 million kilograms!




Changing Climate Ω Alfred R. Sanchez


ollywood paints a bleak picture of the future. There are dozens of postapocalyptic movies depicting a world that was destroyed. In most of these movies, the destruction was brought about by a drastic change in climate. This phenomenon is usually blamed on man’s activities. We often ask, “Are we altering the climate due to what we are emitting in the air? How much carbon dioxide (CO2) and other greenhouse gases are we emitting? Are these emissions causing changes to the climate that might be detrimental to our existence?” We may not know the answers to all these questions, but one thing is definitely clear: The recent increase in the amount of CO2 in the atmosphere is due to human activities.

can be taken to mean changes over all timescales and in all the components of climate, including precipitation, clouds and temperature. Climate changes can be caused both by natural forces and by human activities. However, in recent usage, it refers more specifically to changes being studied at present, including an increase in the average temperature of Earth’s surface and oceans or global warming. Today, all nations are seriously considering the effects of climate change. In international conventions, climate change usually connotes a change brought about by humans while climate variability refers to a change not caused by humans. Sometimes, the term anthropogenic climate change is used to indicate human involvement.

What is climate change? The term climate change is used to refer to any long-term significant change in the average climate of a region. In the most general sense, it

Climate change factors Climate changes can be due to internall and externall factors. Internal factors are those due to interactions within Earth’s climate system.



External factors, called climate forcings, are divided into naturall factors, such as variations in solar radiation, and anthropogenic factors (those attributed to human activities). One major anthropogenic factor is the increase in CO2 levels due to emission from fossil fuels combustion. This began on a large scale during the Industrial Revolution, and most of which was emitted beginning 1945. Other factors include forest alterations, and agricultural or other changes that affect Earth’s albedo, the carbon cycle and methane production. The main anthropogenic factors are emissions of greenhouse gases, changes in land use and emission of aerosols such as sulfates. Greenhouse gases trap the sun’s heat in Earth’s atmosphere and prevent it from being radiated back to space. They include water vapor, CO2, methane, nitrous oxide and tropospheric ozone. Since 1750, CO2 concentration has increased by 31%, methane by 151%, nitrous oxide by 17% and tropospheric ozone by 36%. Majority of the anthropogenic CO2 is produced by the combustion of fossil fuels. Methane is produced by cattle, energy and rice productions in similar amounts — each emitting about 66% of the amount produced by major natural sources (wetlands).

challenged and there are claims that ancient forest clearance and rice paddies increased CO2 and methane levels starting 8000 years ago. Other scientists disagree, saying that there is no need for a significant anthropogenic influence on the methane record. As you can see, there’s a healthy controversy in the scientific community on climate change. For all of us, there’s no harm in reducing greenhouse gas emissions. After all, this reduces pollution and may even stabilize our climate!


Different conclusions Anthropogenic factors are presumed to be negligibly small for climate change before, say, 1750. However, this has recently been

Science Words albedo – the amount of radiation reflected by Earth tropospheric ozone – ozone in the lowest portion of Earth’s atmosphere wetland – an area of land that is covered often intermittently with shallow water or has soil saturated with moisture, e.g., marsh, swamp, bog

Guide Questions 1. 2. 3.

What factors cause climate change g ? Has man altered Earth’s climate? in what ways? What can man do to help prevent climate chan ch ange ge??



Heat Cramps t was a sunny Saturday morning. You decided to run around your village. You put on your running shoes and got out of your house. You started slow, jogged a little, then you were running in no time. Halfway through, you felt thirsty. Alas! You forgot to bring your bottle of sports drink. You were drenched in sweat but you decided to continue running. The sun’s heat was already intense during that time. You were almost finished with your lap when you felt your leg muscles gave an involuntary jerk. Then, pain tore through your leg and you almost fell on the ground. Your leg muscles twitched once more and stopped. Then, they jerked again. This lasted for a few minutes but eventually stopped. What just happened?

such ass sso sodi dium ium, m, ca calc l iu i m an and d po p ta tass ssiu ium m, are m, known ass ele elect ctro roly lyte tess. When you ou u exercise exe exerc rcis isee or do do other oth ot ther her strenuous sttre ren nuous ous activities, your body dy loses water wa r and salt. salt Sweat contains a large amount of sodium. The lost minerals can be replaced by drinking fluids that contain electrolytes. That is why athletes take sports drinks. They replenish electrolytes, carbohydrates and other nutrients lost after sweating a lot. The muscles that are most commonly affected by heat cramps include those found in the calves, arms, shoulders, thighs, legs, abdomen, abdominal wall, back and other muscles involved in an exercise. Muscle spasms are usually painful, involuntary, intermittent but brief. They also go away on their own. You are at risk of experiencing heat cramps when you do strenuous activities in a hot environment, sweat a lot and drink large amounts of water or other fluids without electrolyte content.

SDMAGS.NET Muscle spasms You just had heaat cramps. Heat cramps are painful, in nvoluntary muscle sp pasms that occur du uring or after a strrenuous exercise in hot environments. Docctors still do not know thee exact cause of heat cramps bu ut it is mainly associated with h electrolyte problems. Min nerals in our body,



First aid When you start to feel heat cramps, the following can help: • Rest briefly and cool down. • Find a cool place to rest and drink clear juice or sports drink. • Gently massage the affected area. You will feel fine after a few minutes. • If the cramps don’t go away after an hour of resting and restoring fluids and electrolytes, seek medical attention.

The Great Pacific Garbage Patch Ω Myren G. Manalaysay

aste disposal is one of the biggest environmental problems in our society today. Landfills have taken up much space in many communities around the world. But do you know that the biggest garbage accumulation in the world is not found on a landfill? The largest garbage buildup on Earth is in the Pacific Ocean. It is known as the Great Pacific Garbage Patch or the Pacific Gyre. It floats on a remote area of the Pacific Ocean that sailors avoid because there is not enough wind in order to sail. Fishermen also do not pass through this “oceanic desert” where only tiny phytoplankton and very few big fishes and animals are found. Much of the garbage that people throw away are made of plastics and other nonbiodegradable materials. Most of these waste materials are dumped in seas and other bodies of water where they accumulate. The rotational direction of ocean currents and the continuous pollution of the ocean have resulted to the accumulation of waste in this particular spot over the years. Anything that floats within the rim of the Pacific, no matter where it comes from, ends up in this area. Even after drifting for 12 years or more, a waste may still end up here. Although the name refers to this spot as a “patch”, the garbage accumulation is about the size of a continent and still continues to grow. The area of affected regions is estimated to range between 700 000 to 15 million km2. The garbage patch branches into two large masses of gathered trash — the Western and

Eastern Pacific Garbage Patches. The former is found on the east of Japan and west of Hawaii. The latter floats between Hawaii and California. The patches are connected by a thin 9656-kilometer current called the Subtropical Convergence Zone. Garbage accumulation is hazardous to marine life. It also threatens the fishing industry and the ecosystem. Floating garbage can be eaten by marine animals such as birds, sea turtles and dolphins. When this happens, animals may die due to poisoning or choking. Many animals also get caught and are trapped in the swirling garbage. Meanwhile, floating debris also absorb toxic pollutants disposed of in the water. Some efforts can be done to help lessen the threats brought about by the Great Pacific Garbage Patch. Recycling garbage is one. Many communities and even some small countries have also eliminated the use of plastic bags. We all need to be responsible if we do not want the world to swim in one big ocean of garbage.




concept map

PLATE TECTONICS is a theory that states that att

is made up of


Earth’s lithosphere

upper mantle is broken into o


tectonic plates

mo ove v in rela re ela l tion n to o one n anotther at

can be

continental carry the


oceanic carry the

ocean basins




volcanic activities mountain building

occur along g

oceanic trench formation

SDMAGS.NET plate boundaries c n be ca b

convergent (collision) divergent (spreading) transform

The plate tectonics theory embraces the older concepts of continental driftt and seafloor spreading. According to this theory, tectonic plates move around causing changes in Earth’s crust. Tectonic plates can move away from each other, toward each other or slide past one another.

ACRO AC ACROS OS FFu Fukuoka uk ka building bui d ngg in in JJa Japan apa ap pa

The Ballard The B ll l rd Li LLibrary ibr ry

A perfect pe f ctt eexample pe ple pl le of of a ggreen r enn hhome re me

Green Buildings Ju e a

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placement are employed. Renewable energy ook around you. I’m sure you will be able such as solar power, wind power, hydropower to give many examples of green objects and biomass are used to heat, cool and light the but can you point to an example of a building. This helps reduce the use of ozonegreen buildingg in your neighborhood or depleting compounds found in refrigeration and community? fire suppression systems. Some green buildings A green building is not a structure that is also have cooling towers that replace hot air inside green in color. Instead, it refers to the practice the building with cool air from the outside. of planning, designing, constructing, operating, To reduce waste generated by the occupants, maintaining, renovating and deconstructing green buildings provide on-site solutions such buildings and other structures while taking into as compost bins. They also have wastewater utmost consideration their present and future treatment systems. For example, wastewater from impacts to the environment. washing dishes and clothes is used to flush toilets A green building is also known as a and d wash h cars. susttainabl i ble builildi ding, a high-perf h formance build ildiing In the Philippines, there are companies or an environmental building. At present, many that belong to a group called the Philippine architects and engineers, specially in North Green Building Council (PhilGBC). It is a America and Europe, are involved in designing nonstock, nonprofit organization that promotes and constructing green buildings. envi en viro ronm nmen enta tallllyy se sens nsit itiv ivee pr prac acti tice cess in tthe he d des esig ign, n, Gree Gr een n bu builildi ding ngss ha have ve ccom ommo mon n fe feat atur ures es. Fi Firs rstt, construction and management of buildings they use natural, environment-friendly building to ensure a sustainable environment for the materials that are free from harmful synthetic Philippines. chemicals. Examples are bamboo, straw, lumber Young people like you can also make a from sustainably managed forests, recycled stones difference. Do “green” practices to help save our and metals, and other nontoxic, renewable and home planet. Act now before it’s too late! recyclable products. These materials should also come from the area where the structure is being constructed. The newly constructed mansion of Hollywood superstar Julia For energy conservation, Roberts in Malibu, California is eco-friendly! It used wood efficient insulation and windows


harvested from sustainable forests and recycled tiles. It has solar panels and a range of other energy conservation features.



Virtual Keyboards Ω Karla P. Abulencia

few strokes on the keyboard and words appear on your computer screen. A few more strokes and you have saved your file and opened another program. All these actions happen just by pressing some keys!

However, it can be controlled by a mouse, a trackball, through a touch screen or other pointing devices. Most virtual keyboards are displayed on the computer screen. The user just needs to point and click on the image of a key to enter a character. Some cell phones and personal digital assistants (PDA) require a stylus (a pen-shaped pointing device used for entering data) to input characters on a virtual keyboard built into the operating system of the device. There are also virtual keyboards that are touch sensitive. By simply touching a virtual key, the gadget will sense the motion as a command. A new type of virtual keyboard available in the market today is the projection keyboard. This can be projected and used on any flat surface such as tables and walls. It can be used with cell phones, PDAs and laptops. Here’s a simple description of how it works: 1. A laser projects a holographic keyboard on any nonreflective, opaque flat surface. 2. A sensor or camera picks up hand and finger movements and interprets these movements as keystrokes in the attached device.


A computer keyboard A keyboard is a computer input device with buttons or keys, engraved or printed with characters. It distinguishes each key from the others and reports all strokes to the controlling software, which then interprets the command. Keyboards are used to type letters, numbers and other characters in word processing programs and other applications. Simultaneously pressing several keys can also produce various computer actions. However, the need to physically press a key on the keyboard can be a hindrance to people suffering from certain disabilities that prevent them from typing on a physical keyboard. This is when a virtual keyboard comes in handy. A virtual keyboard A virtual keyboard is a software and/or hardware that allows users to enter characters. Basically, it works like an ordinary keyboard.



The Milky Way SDMAGS.NET

Ω M. C. Cano & K. P. Abulencia

ave you seen a band of light across the sky on a very clear, dark night? This could be the Milky Way — our very own galaxy! Our sun and all the visible stars in the sky belong to the Milky Way Galaxy. It got its name because it looked like a trail of milk spilled in the sky by a goddess who was nursing her baby. Astronomers estimates that the Milky Way has been around for 13 billion years or so. It measures 100 000 light-years in diameter and is home to about 200 to 400 billion stars. The Milky Way’s mass is believed to be about 5.8 x 1011 solar masses.

Picturing our galaxy Since Earth is bound to the sun, which is located in the Milky Way, we cannot take a picture of our own galaxy from the outside. Astronomers use photographs of nearby galaxies to help us picture how the Milky Way may look like.



We know that the Milky Way is a flat system of stars because on the dark night sky, it can be seen as narrow band across the sky. From studies of other galaxies, astronomers found that galaxies that appear flat are the spiral type (like a pinwheel) with several arms. If you could see the Milky Way from its side, it would look like a thin, shiny disk that swells at the center. Astronomers have conducted intensive studies on our galaxy for more than 50 years. Yet, they still do not know the exact shape of the Milky Way in terms of how many arms it actually has. We may never know completely just how our galaxy looks like. For now, we can at least trace a few of the major and minor arm segments nearest to the sun with a fair amount of confidence. Rotating like a pinwheel Like Earth, the Milky Way also rotates like a pinwheel. Its rotation was discovered by Bertil Lindblad in 1926. Jocobus Kapteyn discovered

A view vviiew w of of the thhe the the M th Milky ky Way's y's core y' c rre co e

that the proper motions of nearby stars were not random but moved along a stream toward the constellation Lyra. Lindblad showed that this could be explained if the Milky Way is rotating. Our own galaxy is constantly eating up small galaxies. It has a black hole lurking at its center. So far, the Milky Way has not yet “digested” enough galaxies. But in three billion years or so, our galaxy may become a full-fledged “active galaxy”, ejecting powerful pieces of matter and energy as the Andromeda galaxy collides with it.

is estimated to be 13.2 billion years old. This is almost as old as the universe itself (which is believed to be between 13.5 and 14 billion years). As you can see, even in our own galaxy, there are still a lot of questions yet unanswered, a lot of things to research on, and this means a lot of learning opportunities for you. This year, different nations around the world will celebrate the International Year of Astronomy. You can take this opportunity to learn more about our planet and our place in the universe. Who knows? You may end up knowing more about our galaxy. Be involved this year!


Defining features Like other spiral galaxies, the Milky Way has three distinguishing features: a central bulge, a disk and a halo. The central bulge, or the core of the Milky Way, is a high-density region where old stars are found. It is believed to be 12 000 light-years in diameter. Our sun lies about 26 000 light-years from the bulge. Protruding from the central bulge are the spiral arms. These arms are collectively known as the galactic disk. Here, active star formation takes place. The galactic disk is filled with gas, dust and blue young stars between one to 10 billion years old. The sun is found within a smaller spiral arm, the Locall or Orion Arm, which connects the more massive Sagittarius and Perseus Arms. Surrounding the disk is the halo. This is a diffused region of old stars and globular clusters. It is believed to be composed mainly of dark matterr which extends well beyond the edge of the disk. The oldest known star in the Milky Way

Science Words solar mass – the mass of the sun used as a unit to express the mass of other celestial objects; equal to about 2 X 1030 kilograms globular cluster – a spherical collection of stars that orbits a galactic core as a satellite dark matter – a hypothetical matter that does not interact with electromagnetic forces but its presence can be inferred from its gravitational effects on visible matter

Guid Gu idee Qu Ques esti tion onss 1. 2. 3.

Describe the Milky Way galaxy. Doo al D alll ga gala laxi xies es hhav avee a bl blac ackk ho hole le aatt th thei eirr ce cent nter er? ? Whyy do yyou Wh ou tthi hink nk sso? o? Wha W hatt do yyou ou tthi hink nk w wou ould ld hhap appe penn wh when en tthe he Milk Mi lkyy Wa Wayy co collllid ides es w witithh th thee An Andr drom omed edaa ga gala laxy xy??



Build a Galaxy! SDMAGS.NET Ω Karla P. Abulencia

alaxies come in different shapes and sizes. Our own Milky Way is a spiral galaxy — a galaxy that looks like a pinwheel and is composed of young and old stars, dust and gas. In this activity, you will make a model of the Milky Way. Each centimeter will represent 3300 light-years! You will need: glue pencil bag of cotton balls black cartolina red, blue, gold and silver glitter You will: 1. Fold the black cartolina in half. Trace a circle about 30 cm wide on it. 2. Cut out the circle. You should end up with two circles. 3. Glue the circles together. 4. Build a dome of cotton balls on the center of the circle. Apply lots of glue to hold them together. The dome should be about 8 cm across and 4 cm high. Repeat the procedure on the other side of the circle.



5. Gently pull out some cotton ball into streams. Glue them in a spiral around the cotton ball dome. These will be your Milky Way’s “spiral arms”. 6. Dribble glue on the spiral arms. Sprinkle blue and silver glitter on the glue. These will represent newly forming stars. 7. Dribble glue all over the circle and cotton ball dome. Sprinkle some gold and red glitter to represent older stars. 8. Repeat steps 5-7 on the other side of your Milky Way. Answer these: 1. Using the scale model of the Milky Way, where do you think is our solar system located? 2. Why did you place only blue and silver glitter on the spiral arms of your model?

DIRECTIONS: Read each questions carefully, then blacken the circle beside the letter that corresponds to the best answer. Check your answers with your teacher afterwards.

1. When a sedimentary rock like limestone is heated, it changes into marble. What kind of rock is marble? ❍ a. igneous ❍ b. metamorphic ❍ c. sedimentary ❍ d. volcanic 2. ❍ ❍ ❍ ❍

Where does a tropical cyclone get its energy? a. From the sun’s heat b. From air pressure c. From the ocean d. From the winds

3. ❍ ❍ ❍ ❍

Which two processes make up the water cycle? a. Heating and cooling of the air b. Heating and cooling of the soil c. Cooling of water and heating it under the sun d. Heating of water to become water vapor and cooling of water vapor

6. A comet’s tail is directed away from the sun because the _____________________________. ❍ a. gases pushed out of the comet’s head by solar energy form a tail ❍ b. comet’s head is attracted to the sun ❍ c. comet’s head is heavier than its tail ❍ d. comet is moving toward the sun 7. What do you call the pathway of planets that revolve around the sun? ❍ a. axis ❍ b. pole ❍ c. orbit ❍ d. equator


4. What holds the solar system together? ❍ a. The temperature at different parts of the solar system ❍ b. The sun’s gravitational pull ❍ c. The orbit of each planet ❍ d. Earth’s gravity 5. Which of the following factors affects the surface temperature of planets with the exception of Venus? ❍ a. size ❍ b. distance from the sun ❍ c. presence of atmosphere ❍ d. magnetic pull of the planet

8. What would happen if the sun’s gravitational pull on the planets lessens? ❍ a. The planets would collide with each other. ❍ b. The sun would stop shining. ❍ c. The planets would explode. ❍ d. The sun would explode. 9. ❍ ❍ ❍ ❍

Which pair is composed of metamorphic rocks? a. shale and schist b. marble and schist c. sandstone and shale d. dolomite and limestone

10. Which of the following causes the ocurrence of tides? ❍ a. The combined gravity of the sun and the moon ❍ b. The surface temperature of Earth ❍ c. Earth’s rotation and revolution ❍ d. Both 1 and 2



Anagram mix-up Ί Karla P. Abulencia

As you have learned from the cover story, climate change is caused by different factors. These factors can either be internall or external. Included in the external factors are human activities. Listed below are anagrams related to climate change. Choose which of them can be turned into the concepts/phrases found in the box at the bottom. Have fun!

SDMAGS.NET chemical agent

ball going warm

foul, poisonous, alert untold evils to ruin air huge trees offence greenhouse gases climate change anthropogenic climate change industrial revolution global warming

greenhouse emission pollution of our seas carbon dioxide greenhouse effect climate forcings

(The correct answers are in the Teacher’s Edition.)

S&T Grade5#6  

S&T Grade5 Issue 6