# Lesson video

In progress...

Hello again, it's lovely to see you.

Today, I'm going to be teaching you science.

In our lesson today, we are going to be learning about changes of state.

I am really excited about today's lesson as we're going to be learning lots of new scientific vocabulary so we can speak like scientists.

Right, let's get started.

In today's lesson, we're going to start by recapping our previous knowledge, then we will look at state changes that happen during heating and cooling, and finally, we will look at some examples and identify the state change that is taking place.

In this lesson, you will need: An exercise book or paper and a pencil.

If you don't have one of these items, pause the video now and go and get them.

Let's start by recapping our previous knowledge.

Can you remember the three states of matter? The three states of matter are solid, liquid and gas.

Pause the video and write down an example of a solid, a liquid and the gas.

Can you remember the properties of solids? Pause the video and write down three properties of solids.

Solids cannot be compressed, they do not flow and they have a fixed shape.

Can you remember the properties of liquids? Pause the video and write down three properties of liquids.

Liquids cannot be compressed, they can flow and they can take the shape of the bottom of their container.

Can you remember the properties of gases? Pause the video and write down three properties of gases.

Gases can be compressed, they can flow and they can fill the shape of their container.

Which of these diagrams shows a solid? How did you know? The diagram on the left shows a solid, oh, sorry.

The diagram on the right shows a solid because the particles are arranged in ordered rows.

Which diagram shows a gas? The diagram in the middle shows a gas because the particles are far apart? Which diagram shows a liquid? The diagram on the left shows a liquid because the particles are touching, but they're arranged in a random order.

What is the between particles in a solid and particles in a liquid? Particles in a solid are arranged in an ordered rows whereas particles in a liquid are arranged in a random order.

Pause the video and match the description to the correct state of matter.

Solid particles are touching and in ordered rows.

Liquid particles are touching and in a random arrangement.

Gas particles are far apart from each other.

Pause the video and draw lines to match to the description to the correct state of matter.

Solid particles cannot move, but vibrate on the spot.

Liquid particles can slide past each other, and gas particles are moving constantly in all directions.

Particles in a solid are vibrating on the spot, in a liquid, they're sliding past each other, and in a gas, they're moving fast in all directions.

As a substance is heated, the temperature increases, when the temperature increases, the particles have more energy and move around more.

This means that the substance expands.

Pause the video and complete the sentence at the bottom.

Increasing the temperature means particles have more energy and the substance expands.

As substances are cooled, the temperature decreases, this means the particles have less energy and the substance contracts.

Pause the video and complete the sentence at the bottom of the slide.

Decreasing the temperature means particles have less energy and the substance contracts.

What happens when we heat the particles in a solid? when we heat the particles in a solid, they vibrate more.

If we heat the particles enough, they will vibrate so much that the bonds between the particles break and the particles can slide over each other, they have become a liquid.

Imagine we had some ice on the table, what would happen to that ice cube? The ice cube would melt and become a liquid water.

When the ice cube melts, we have heated up the particles enough so that they vibrate so much the bonds between the particles break, and the particles can slide over each other.

When the particles can slide over each other, it has become a liquid.

If we heat a liquid, the particles move around faster.

Eventually, if we heat the liquid enough, all the bonds holding the particles together will break, and the particles will no longer touch, they have become a gas.

What is broken when the temperature increases and a change of state happens? When the temperature increases and a change of state happens, bonds between the particles are broken.

Scientists call this a change of state, and each change of state has a different name.

When a solid becomes a liquid, it is called melting.

Which change of state is called melting? Melting is when a solid becomes a liquid.

When a liquid becomes a gas, it is called boiling.

What happens during boiling? Boiling is when a liquid becomes a gas.

Pause the video and complete these sentences.

When solids are heated strongly, the bonds between some of the particles, which means they can now, each other.

It has become a.

When liquids are heated strongly, any bonds that are left over between the particles now, which means they can now, from each other.

It has become a.

Pause the video to complete the sentences, press play when you're ready to continue.

When a solid is heated strongly, the bonds between some of the particles break, which means they can now slide over each other.

It has become a liquid.

When liquids are heated strongly, any bonds that are left over between particles break, which means they can now move far apart from each other.

It has become a gas.

Press play when you're ready to continue.

Now let's think about what happens during cooling.

When we call particles, those bonds that were broken reform, forming a liquid or a solid.

When a gas becomes a liquid, it is called condensing.

Which change of state is involved in condensing? Condensing is when a gas becomes a liquid.

When a liquid becomes a solid, it is called freezing.

Which change of state is called freezing? Freezing is when a liquid becomes a solid.

You are going to complete these sentences, I'm going to read them to you and then give you time to pause the video to write them down.

When liquids are cooled down, the particles move more, and become strongly, together again.

They are now in a, and have become a.

When gases are cooled down, the particles move more, and they become, together again.

They are stuck together, but they can still, each other, and move so they have become a.

Pause the video and complete those two sentences.

When liquids are cooled down, the particles move more slowly and become strongly bonded together again.

They are now in a fixed position and have become a solid.

When gases are cooled down, the particles moved more slowly, they become bonded together again.

They are stuck together, but can still slide past each other and move so they have become a liquid.

Pause the video and write down the change of state that each arrow represents.

When a select becomes a liquid, it is called melting.

When a liquid becomes a gas, it is called boiling.

When a gas becomes a liquid, it's called condensing.

When a liquid becomes a solid, it's called freezing.

Press play when you're ready to continue.

Which states changes in both particles gaining energy? Option one, melting, option two, boiling, option three, condensing, option four, freezing.

What do you think? Changes of state that involve particles gaining energy are melting and boiling.

Melting is when a solid turns into a liquid, and boiling is when a liquid turns into a gas.

Which state changes in both particles losing energy? Option one, melting, option two, boiling, option three, condensing, or option four, freezing.

What do you think? Condensing and freezing involve particles losing energy.

Condensing is when a gas turns into a liquid, and freezing is when a liquid turns into a solid.

Let's have a look at some examples.

Here are examples of state changes, you need to identify the state change and then explain how you know.

For example, if I was thinking about the steam produced from a kettle, I know that a liquid is turning into a gas, which state change is that? That is boiling.

How did I know? I know it was boiling because a liquid turned into a gas.

Pause the video to copy and complete the table.

A puddle turning into water vapour in hot weather is boiling because liquid water is becoming a gas.

Rain turning into snow is freezing because liquid water is becoming solid.

An ice cream on a hot day is melting because solid ice cream is becoming a liquid.

Water falling on the buffer mirror is condensing because steam which is gaseous water is becoming a liquid.

Press play when you're ready to continue.

What happens to the particles in chocolate if you hold it for too long? Pause the video, write down your thoughts.

When you hold chocolate in your hand for a long time, it starts to melt.

What happens to particles when a solid melts? The particles gain energy and vibrate more.

The bonds between the particles break and they're able to slide over each other, meaning that chocolate has become a liquid.

You have worked so hard today learning about different changes of state, I'm really looking forward to seeing all of your excellent work in the quiz.

See you next time, bye.