Natural Sciences2nd YearTerm 2

Phases of Matter

Metals & Non-metals Processing materials

Name and Surname: ________________________________________Year group: ____________________

Introduction: MatterDate:___________________

In the past you have often heard us talk about matter. The word matter refers to

everything that has mass and occupies space. Literally all of the things that you can

observe around you are forms of matter. The furniture in a room, the objects on the

table or on the floor, the flowers outside, the birds and animals, water and all the

other liquids; yes, everything is matter.

Furniture Table with objects. Flowers in a garden.

Birds and animals. Water such as a river. A cup of tea.

But now you must remember that there are also certain forms of matter that you

cannot see. Just think of the gases in the air which you have already learned about.

They are not visible but, because they also occupy space and have mass, we must

regard them as examples of matter.

To summarise we can thus say that matter is the material from which things around us are made of.

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So what is matter made of? All matter is made of atoms. Atoms are the smallest

particle of matter. They are so small that you cannot see them with your eyes or

even with a standard microscope.

Atoms Microscope

Let us look at a few concepts first:

Solid

Solids are objects that are firm and stable. They hold their shape and they

could be hard, soft, big or small. E.g. a chair, when you move a chair to

another place, it will still have the same shape.

Liquid

Liquids flow and take on the shape of the container they are in. Therefore we can

say that it has no fixed shape. E.g. bottled water.

Gas

Do you remember in the first term when we spoke about breathing as one of the

seven life processes of living things? When we breathe, we are taking in and giving

out gases. But we cannot see the gas. Gases are everywhere around us. They are

free-flowing and one can easily put your hand through them. E.g. the air you

breathe.

Gases are a bit more difficult to understand as we usually cannot see gases. We

can see places where gases are used and the containers that gas is kept in.

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Cooking using a gas stove. A patient with an oxygen mask.

Balloons filled with helium or air. A scuba diver with oxygen in his back.

Evaporation

This process takes place when heat is added to the liquid. It means

the water changes from a liquid state to a gas state. Think about

hanging your clothes out to dry in the sun. They dry as the water

evaporates.

Condensation

The steam that comes from a boiling kettle or pot is extremely hot and you cannot

see it. The steam quickly cools down and form tiny droplets in the air. These tiny

droplets are visible and form the ‘cloud’ that you see. When these tiny droplets hit

the mirror they cool more and form the bigger droplets which you can see. We say

steam condensed to form water. The change of state is from gas to liquid.

Freezing / Solidifying

This process takes place when a liquid forms a solid when cooled down. E.g. ice

lollies are made from a liquid. The liquid is poured into the shape of an ice lolly

and then cooled, as heat is removed they freeze.

Melting

This process takes place when a solid turns into a liquid when heat is added. E.g.

when ice lollies are left in the sun.

Activity 1

1. Name the following objects.

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___________________ ______________________

2. _______________ are objects that are firm, stable and they hold their shape.

3. The process that takes place when a liquid turns into a gas when heat is

added is known as _______________________.

4. ______________ are everywhere around us. They are free-

_____________________.

5. The process that takes place when a solid turns into a liquid when heat is

added is known as _______________________.

6. The process that takes place when a gas cools down and forms a liquid is

known as _______________________.

7. __________________ flows and take on the shape of the container they are

in.

8. The process that takes place when a liquid forms a solid when cooled down is

known as ______________________.

Phases of MatterDate:___________________

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“Tom did you know…? A water molecule is formed when two atoms

of hydrogen join with one atom of oxygen…”

We’ve seen that matter usually exists in one of three states or phases: solid, liquid,

or gas. The chair you are sitting on is a solid, the water you drink is liquid, and the air

you breathe is a gas. Matter changes state when more energy gets added to it.

Energy is often added in the form of heat or pressure.

During the previous period we said that solids are objects that are firm and stable.

They hold their shape and room temperature; and they could be hard, soft, big or

small. This is matter that is composed of atoms packed tightly together. You cannot

walk through a solid wall. The matter is packed so tightly that it prevents you from

moving through it. Think about this; the pencil that you left on the desk at school will

still be the same shape when you return tomorrow. Examples of solids: table, chair,

door, wall, window, car, flower, tree, house, stationery, garbage bin etc.

Liquids flow and take on the shape of the container they are in. They do not hold

their shape at room temperature. There is space between the atoms of a liquid and

they move slightly all of the time. This allows you to stick your finger into water and

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“What is meant by room temperature?It refers to the air temperature not being

specifically heated or cooled.”

pull it back out, letting the water fill back in where your finger once was. But when

walking through the water in a swimming pool, you have to push the water out of the

way – this means that you feel the heaviness of the water. Liquids cannot be

handed to another person without a container. Imagine going into a

restaurant and asking for lemonade. What if the waiter just put the

lemonade into your hands – no glass or cup? Could you lay the lemonade

on the table to drink in a few minutes? Even water in a river or lake has a

container – the banks, the bottom, the shore – they form the container.

Examples of liquids: water, ocean, tea, coffee, juice, sodas, rain, milk,

medicine syrups etc.

Gases are everywhere around us. They are free-flowing (always moving) and one

can easily put your hand through them. They don’t hold their shape at room

temperature and don’t stay put. There is so much space between the atoms in gas

that you can move around in them easily. When you walk from one

side of the room to the other, you have walked through a bunch of

gases that make up our air. You barely even know they are there.

Examples of gas: oxygen, nitrogen, water-vapour, clouds, steam etc.

Activity 2

1. Look at the pictures below. Decide if they are a ‘solid’, ‘liquid’ or a ‘gas’?

__________________ ___________________ ___________________

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__________________ ___________________ ___________________

__________________ ___________________ ___________________

Matter: Changing from PhaseDate:___________________

Before we look at matter changing from phase, let’s just study the summary below.

Solid Liquid GasHas a definite shape. Has no definite shape. Has no definite shape.

Takes up a definite space. Takes up a definite space. Takes up any/all the space

available.

Do not flow. Can flow. Can flow.

During the introduction of matter we’ve seen that matter can change from one phase

to another. E.g. when ice melts; a solid changes into a liquid.

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Think about the following:

If you place tap water into an ice tray and put this in the freezer, what will

happen to the water?

If you take ice cubes and place them in the sun, what happens to the ice

cubes?

The difference between the freezer and the sun outside is that one is hot and the

other is cold. So if we place the water in a place that is cold enough, it freezes. If

we place the ice cubes in a hot place, they melt.

Study the illustration below about the phase changes of matter.

Notice when gas condenses (small drops of water) it is turned into liquid and

when liquid evaporates (changes into steam) it is turned into gas.

Notice when a solid melts (add heat) it is turned into liquid and when a liquid

freezes (extreme low temperature) it is turned into solids.

Some substances melt very easily, while others need to be heated for a while.

Each substance starts melting at a certain temperature. This is called the

melting point of a substance. Temperature is measured in degrees Celsius (ºC),

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with an instrument called a thermometer.

Here is a summary of the different phase changes:

Change of phase ‘Heating’ or ‘Cooling’ Process is called…..Solid to a liquid Heating Melting

Liquid to a gas Heating Evaporation

Gas to a liquid Cooling Condensation

Liquid to a solid Cooling Freezing

Activity 3

Read the following story and answer the questions that follow.

Giovanni’s Lesson

Giovanni Blaauw is a boy in Grade 1 at a primary school in a small village which gets very hot during the summer. He loves to play soccer. After school he often goes over to The Thunderbolt School of Learning to play with the Thunderbolt Kids. They really like having Giovanni there to play with them, even though he is a few years younger, because he is very talented and also fun and caring. Giovanni especially likes Johnique and they play well together as a team.

One day after school, Giovanni thought he would do something nice for his friends, the Thunderbolt Kids and surprise them with ice lollies, when they were done playing. Giovanni bought 5 ice lollies, one for himself and one for each of the Thunderbolt Kids. He put the ice lollies in a bowl and placed some ice blocks around them to keep them cool. Giovanni then ran off to join the others playing soccer.

After the game, Giovanni ran back to the bowl to get the ice lollies. But he got such a shock when he got there. They were all gone! He was so upset and started to cry. The Thunderbolt Kids saw that Giovanni was upset and ran over to see what was wrong.

"Hey Giovanni, what's wrong? Did you hurt yourself while playing?" Johnique asked.

"No, I didn't. I bought some ice lollies for all of you as a surprise and when I came back now to get them they were all gone! I think someone stole and ate them and just left the sticks! Look!" Giovanni cried out.

"Oh no, don't cry Giovanni! It's not your fault, and no one stole them or ate them either," Wharick said while rubbing Giovanni on the back.

"Yes, Giovanni, actually we learnt in class today about what happened to your ice lollies," said Devon, "and I can explain it to you too. Do you see that your bowl is actually not empty? There is a liquid in it. It also has a red colour, which was the colour of your ice lollies."

"Yes, I see that," answered Giovanni, "but then how did that happen?"

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Denise then answered, "Your ice lollies melted from the heat from the air around us. Even if the sun was not so hot, they would have melted! For something to stay frozen it needs to be at a very cold temperature, like in a freezer."

"Yes, melting is when heat causes the solid ice lollies to change into a liquid," Devon replied, "So no one stole the ice lollies, they just melted."

"Oh ok, I see," said Giovanni, "I must be really silly not to know that!"

"No, not at all Giovanni! We only learned about it today in class and we are in Grade 4!" laughed Wharick.

"I know what we should do!" shouted Johnique, "Let's go to the tuck-shop right now. I have some extra change and we can buy some more frozen ice lollies!"

They all really liked this idea, especially Giovanni who was now laughing. So off they all went, the Thunderbolt Kids and Giovanni, and bought some more ice lollies and sat under the tree to eat them.

QUESTIONS:

1. What is the name of the main character in the story?

__________________________________

2. What grade is he in?

______________________

3. What grade are the Thunderbolt Kids in?

______________________

4. What game are the children playing together after school?

______________________

5. When the ice lollies are frozen, are they a solid, liquid or a gas?

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______________________

6. Explain in your own words what happened to the ice and the ice lollies while

they were left in the sun.

______________________________________________________________

______________________________________________________________

7. What is the name of this process?

__________________________

8. Do you think you can reverse the process of melting? How?

______________________________________________________________

9. What is your favourite type of ice cream or ice lolly?

___________________________

10. If you wanted to do something nice for your friends, what would you do?

______________________________________________________________

______________________________________________________________

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