the three states of matter...the three states of matter matter is anything that has weight and takes...

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P3/4 science

the three States of Matter

Matteris anything that has weight and takes up space.

LiQUiD• has a definite volume

The plunger cannot be pushed further into the syringe because the water inside the syringe has adefinitevolumeandcannotbe compressed.

• has no definite shape

Water takes the shape of the container it is in. The water in each part of the communicating vessel above takes the shape of the container but the water level remains the same throughout.

• has weight / massWecanfindouthowheavya liquid is by weighingthe empty container on anelectronic balance or beambalance before weighing thecontainerfilledwithliquid.

The difference in the tworeadings is the weight of theliquid only.

SoLiD• has a definite shape

The shape of a solidwill not change unlesswe do something to it,e.g. moulding a ballof plasticine, folding apiece of paper etc.

• has a definite volumeItoccupiesafixedamount of space andcannot be compressed.

• has weight / massWecanfindouthowheavy an object isby weighing it on anelectronic balance orbeam balance.

Matter exists in three different states.

GaS• has no definite volume

The plunger can be pushed further into the syringe because the air inside the syringehasnodefinitevolume and can be compressed.

• has no definite shape

The air inside the three balloons takes the shape of the balloons.

• has weight / mass

When the balloon on one side bursts, the rod tilts because the balloonthatisstillfilledwithair is heavier. This shows that gases have weight.

plunger

water air

Taken from ScieNce PartNer: a complete Guide to Lower Block Science

The Three States of Matter

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P3/4 science

Matter can change from one state to another by heating or cooling it.

The table below gives a clear picture about the characteristics of the three states of matter.

StateProperty Solid Liquid Gas

Has mass? Yes Yes Yes

Takes up space? Yes Yes Yes

Hasafixedvolume? Yes Yes No

Hasafixedshape? Yes No No

Examples

paper, book, clothes, sugar, plants, glass, car etc.

water, oil, blood, petrol, milk, fizzydrinks,cough syrup etc.

water vapour, carbon dioxide,nitrogen, oxygen etc.

Comparing the three states of matter

Matter and changes of state

Gain heat

condensation

evaporationmelting

freezing

sublimation

Lose heat (cooling)

solid liquid gas


The Three States of Matter

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P3/4 science

energy

Energy is the ability to do work.

In science, when we say that work has been done, we mean that a force has been exerted to cause an object to move a distance.

Hence, energy is required to make things move.

There are many forms of energy. The common forms of energy are: • heat energy,• light energy,• sound energy,• electrical energy etc.

The sun is our primary (main) source of heat and light energy.

In this chapter, we are going to learn about light energy and how shadows are produced.

All living things depend directly or indirectly on the sun’s energy.

Plants make use of light energy from the sun to make food during photosynthesis.

Light energy from the sun brightens up the surroundings in the day so we can see things easily.

Our wet clothes are able to dry because the heat energy from the sun causes evaporation to take place.

Heat energy from the sun is used to keep the earth warm so living things can survive.

Heat energy from the sun causes evaporation of water from rivers etc. so that the water cycle can continue.

Plant-eaters indirectly get the sun’s energy when they feed on plants.

Animal-eaters indirectly get the sun’s energy when they feed on the plant-eaters.


Light And Shadows

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P3/4 science

Light

Light is a form of energy.

Things that give out their own light are known as light sources.

As mentioned earlier, the sun is our main source of light energy. The sun gives out its own light to brighten our surroundings. In this way, we are able to see things around us more easily.

However, we cannot rely only on the sun to provide us with light to see things. The sun does not shine at night. It also does not shine in enclosed spaces with no windows, such as inside some rooms in your house. In these cases, we have to rely on other light sources.

Luminous objects

Light sources give out their own light so we can see them directly.

These are some examples of light sources.

Light sources are also called luminous objects. Luminous objects give out their own light.

The brighter (or the greater the intensity of) the light source, the easier it is to see.

Themostcommonman-madesourcesoflightarelightbulbsandfluorescenttubes.Ifyouareinyour classroom right now, look above you. The ceiling in your classroom may have some long fluorescent tubeswhichproduce lightwhentheyareswitchedon.This isknownasartificial lighting.Werelyheavilyonartificiallightingtolightupourhomes,schools,roadsandotherpublic places.

sun star light bulbburning

candleflame

pictures on a TV screen

afirefly afluorescenttube


Light And Shadows

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P3/4 science

Artificiallightingisalsousedfordecorativepurposes.TakeawalkalongGeylangSeraiduringthe Hari Raya Puasa period, Little India during the Deepavali season, Chinatown during the Lunar New Year and Orchard Road during the Christmas season. The streets and buildings are adorned with thousands of colourful fairy lights to create a spectacular sight.

Inorder for artificial lighting towork, electrical energy isneeded.AsSingaporehas limitednatural resources, we should try our best to conserve (save) energy wherever possible. Here are somewaysofsavingenergyonartificiallighting.

• Switch off all lights when they are not in use.

• Do not turn on all the lights in a room when you do not need such bright lights. Dependingon the number of people in the room or the activity you are going to do in the room, fewerlights may be needed.

• Useenergy-savingbulbs.

• Do not sleep with the lights on.

• Try to make use of natural lighting wherever possible. For example, open the windows tolet in the sunlight instead of switching on the lights.

Light given out by luminous sources travels in straight lines. They are called rays.

Non-luminous objects

Non-luminous objects do not give out their own light. A book, table, water bottle and even the moon and earth are examples of non-luminous objects.

Wecan seenon-luminousobjectsbecause they reflect light from light sources intooureyes.When light bounces off from something, we say that it is reflected.

Inatotallydarkroom,therearenolightsourcestocastlightontheobjectstoreflectintooureyes. As a result, we are unable to see anything in a dark room.

However,mostroomsarenottotallydark.Alittlelightfromsomewhereoutsidemayfilterin.As a result, we may be able to see some objects faintly once our eyes become accustomed to the darkness.

Each ray of light travels in a straight line, represented by an arrow shown in the picture.

Light rays radiate outwards from the source of light (bulb) in all directions.

Light travels in straight lines.


Light And Shadows

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P3/4 science

Some animals such as bats are born with excellent night-vision capabilities. They are able to see much more clearly in the dark than us. The simile ‘as blind as a bat’ is just based on the belief that a bat is blind. It is not!

A bat can see clearly in the dark.

The military has invented night vision goggles for soldiers to have a clearer view of their surroundings in the dark. This gives them an advantage of spotting enemy targets in the dark while avoiding being seen by the enemy.

A soldier uses night vision goggles to see in the dark.

how We See objects

The moon does not give out light of its own. We can see the moon because light rays from the sunwhichshineonthemoonarereflectedoffthesurfaceofthemoonintooureyes.

earth

moon

Light rays from the moon arereflectedintotheman’s eyes on earth.

sun

Light rays from the sun shine on the moon.


Light And Shadows

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P3/4 science

Inthesameway,aboyinadarkroomisabletoseetheflowerbecausethelightfromthetorchwhichshinesontheflowerisreflectedbytheflowerintohiseyes.

A boy has object M. When he shines a torch at object M, a bright spot is seen on the wall. This showsthatobjectMmusthavereflectedthelightthatwasshoneonitontothewall.ObjectMisa mirror.

Smooth,shinysurfacesareabletoreflectlightverywell.Whenyoulookintoamirror,youareabletoseeaclearimageofyourself.Themirrorreflectsalmostallthelightthatshinesonitbackinto your eyes in a regular manner.

BarryisbehindAndy.However,AndyisabletoseeBarry’sreflectioninthemirrorand know that he is there. This is because light from the sun falls onto Barry (Ray A) andisreflectedintothemirror(RayB).ThemirrorthenreflectsthelightintoAndy’seyes (Ray C).

Light rays from a torch shineontheflower.

Light rays from the flowerarereflectedintothe boy’s eyes so that he can see it.

Light rays from object M is reflectedontothewall.Itisseen as a bright patch.

Light rays from the torch shine on object M.

Object M

Andy

Barry

Ray C

Ray B

Ray A


Light And Shadows

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P3/4 science

Regular Reflection

Alltheraysoflightfallonthemirrorsurfaceinonedirection.Theraysarethenreflectedbythemirror in one direction.Thisisknownasregularreflection.Regularreflectionproducesa clear image which can be seen.

Regularreflectiononasmoothsurface

Apart from mirrors, shiny and polished surfaces such as tinted glass windows can produce regularreflections.Eventhecalmwatersurfaceofapondcanproduceaclearreflection.

Thereflectionofaswaninthepond

Diffused Reflection

A piece of paper may appear smooth to the naked eye. However, when you look at it from under a microscope, you will notice that the surface of the paper is actually quite bumpy. Light rays strike the surface of the paper in different directions.Hence,theyarereflectedindifferentdirections.Althoughweareabletoseethepieceofpaper,itcannotprovideusareflectionifwe look at it. It does not produce a clear and definite image. This scattering of light is known as diffusedreflection.

Diffusedreflectiononaroughsurface

Reflectorsaredesignedtoreflectlightandappearbrightatnight.

rough surface

mirror surface


Light And Shadows

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the three states of matter...the three states of matter matter is anything that has weight and takes...

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