Lesson video

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Hello again.

How are you today? Are you excited for our lesson? I am really excited as today we're going to be learning about physical changes.

And we will be having a go at an investigation into a physical change ourselves.

In today's lesson, we will start by recapping our previous knowledge.

Then we will look at what a physical change is and some examples.

Finally, we'll be investigating a physical change.

In today's lesson, you will need an exercise book or paper and a pencil.

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

Press play when you're ready to continue.

If you would like to have a go at our experiment, you will need a bar of chocolate and a lamp like the one I have here.

Let's get started by recapping our previous knowledge.

Can you remember the properties of solids, liquids and gases? Pause the video now and complete the table.

Pause the video and complete the diagram in your notes.

What do the particles look like in solids, liquids and gases? Press play when you're ready to check your answer.

Particles in solids are touching and in ordered rows.

In liquids, they are touching and arranged randomly.

And in gases, they're far apart, not touching and moving very fast.

As you increase the temperature, particles have more energy.

What state change happens when a solid becomes a liquid? When a solid becomes a liquid, it is called melting.

What is it called when a liquid becomes a gas? When a liquid becomes a gas, it is called boiling.

What is it called when a gas becomes a liquid? It is called condensing.

What is it called when a liquid becomes a solid? It is called freezing.

Today we're going to think about physical changes.

A physical change is a change in the form or arrangement of a substance.

For example, an ice cream melting, paper tearing, or glass smashing.

What happens when I tear this piece of paper? It is still paper.

Yes, it is still paper.

So the particles are still paper particles, however, the arrangement or form has changed.

I now have two smaller pieces of paper rather than one big piece.

The form or arrangement of the substance has changed, but the substance itself has stayed the same.

In all of these examples, ice cream melting, paper tearing, and glass smashing, the form or arrangement of the substance has changed, but the type of particle has stayed the same.

Pause the video and write down three examples of physical changes.

Press play when you're ready to continue.

What is a physical change? A physical change is a change in the form or arrangement of a substance.

Three examples of physical changes are ice cream melting, paper tearing and glass smashing.

What is the same before and after the physical change? The type of substance or particle is the same before and after the physical change.

Remember, when we are identifying a physical change, it is when the form or arrangement has changed, but the type of substance has stayed the same.

Is this a physical change? Water boiling in a saucepan.

What particles are present at the start? What particles are present in the end.

Has the arrangement of the particles changed? Is this a physical change? What do you think? This is a physical change because the water particles are changing arrangement from a liquid to a gas, but the substance or type of particles remains the same.

It is still water just in a different form.

Is this a physical change? Ice melting in my drink.

What particles are present at the start? What particles are present at the end? Has the arrangement of the particles changed? Is this a physical reaction? What do you think? This is a physical reaction.

This is a physical change because the water particles are changing arrangement from a solid to a liquid, but the substance or type of particle remains the same.

It is still water just in a different form.

Is this a physical change? A bonfire burning.

What particles are present at the start? What particles are present at the end? Has the arrangement of the particles changed? Is this a physical change? What do you think? This is not a physical change because when the wood burns, it produces ash.

This is a different type of substance, rather than a different form of the same substance.

So it's not a physical change.

Is this a physical change? Soap dissolving in water.

What particles are present at the start? What particles are present at the end? Has the arrangement of particles changed? Is this a physical reaction? Sorry, is this a physical change? What do you think? This is a physical change because the salt and water particles are changing arrangement from a solid and a liquid to a solution, but the substance or types of particle remain the same.

It is still water and salt.

They are just in a different form.

We are going to investigate what happens when chocolate melts.

Let's start by thinking about the particles in chocolate.

Pause the video and complete the diagram.

What do the particles of chocolate look like when they're a solid and when they're a liquid? The particles of a solid are arranged in ordered rows, whereas the particles in the liquid are arranged randomly.

What will happen to the energy of the particles when they melt? The particles will have more energy.

To do our experiment, we're going to place one square of chocolate on a plate.

We're going to place the lamp directly facing the chocolate and turn the lamp on.

We're going to watch what happens to the chocolate for three minutes before turning the lamp off.

If you'd like to have a go at this experiment, you need to get yourself a lamp, some chocolate and an adult to help you.

If you prefer to watch me do the experiment, you can watch me do it now.

I am going to place a few squares of chocolate into my glass.

And I'm going to place the lamp at the top of the chocolate so that I can heat it up.

I've turned my lamp on.

The lamp is going to get hot.

Make sure that you don't touch the lamp.

Watch carefully to see what happens to the chocolate.

We're going to heat the chocolate for three minutes to see what happens.

You may need to leave your experiment a little bit longer than three minutes before you start seeing the chocolate melt.

Make sure that you don't touch the lamp, which will get very hot during this time.

Have a look at my chocolate.

Can you see that the solid is turning into a liquid? It is starting to lose its shape.

What has happened to the particles during melting? The particles have gained energy and they're now able to move past each other.

How do I know that this is a physical change? I know that this is a physical change because the particles are still chocolate particles, they're just arranged in a different way.

What has happened to the chocolate when we placed it under the lamp? What happened to the energy of the particles during this process? Draw a particle diagram to represent the particles at the end of the investigation.

Is this a physical change? How do you know? Pause the video and complete the questions in full sentences.

Question one, the chocolate melted when it was placed under the lamp.

During the melting process, the chocolate particles gained energy.

The particles in a liquid are touching and not arranged in ordered rows.

They are arranged randomly.

This is a physical change because when the chocolate is melting, the arrangement of particles changes, but the actual type of particle does not.

Thank you for all your hard work in our lesson today.

I can see that you have been working really hard.

Have a go at the quiz to recap your knowledge.

See you next time.

Bye.