Lesson video

Hello, scientists.

My name is Mr. Wilshire.

In this lesson, we're going to be looking at everyday examples of changing state, solids and liquids.

The outcome for this lesson is I can give everyday examples of solids and liquids changing state.

There are some key words for us to consider as we work our way through this lesson.

The first is solid, then changing state, after that temperature, then it's melting.

Finally, liquid.

Don't worry if you're not too sure some of these words mean.

You can pause the video here, have a read of the definitions, and remind yourself.

If you need to do that, pause the video now.

Restart when you're ready.

The first part of this lesson is called changes of state in real life: solids and liquids.

Now Laura here is rushing to eat her breakfast.

She says, "The butter has taken straight from the fridge.

It's far too hard to spread on my toast." Hmm, here you can see hard solid state butter.

I wonder, how could she make her butter softer to make it easier to spread? Have you ever had this problem before? I certainly have, especially if you've ever visited a hotel.

Sometimes they like to use hard butter like this, and it doesn't really spread very well.

So what could she do to make it softer? Pause the video and discuss.

Restart when you've done that.

So what kind of things did you think of? How is she going to be able to make this butter softer? Is there a process you might need to follow? Let's find out more.

Laura says, "If I put a lump of solid state butter on the warm toast, the butter begins to change state." Ah, excellent.

Why is this? What is it about the toast that's making the butter change state? Discuss.

So why is the butter changing state? Because of the toast? Well, it's because of heat.

The heat from the toast raises the temperature of the butter, and so it begins to melt.

This is an everyday example of a change of state.

This is also why we keep butter in the fridge.

If butter is left out on the side and even gets the room temperature, it can start to go a little bit slushy.

If it's rapidly heated up on something like on the toaster, it's going to go really melty really quickly.

Now butter in a solid state was heated.

It then began to melt.

It changed to butter in a liquid state.

So its still butter, but it's in a liquid state.

Now you can see an example, the solid state butter on top of the toast, and that then turns into melting butter in a liquid state.

This is an everyday example of melting.

I wonder if you can think of any other everyday examples here too.

Can you think of any other examples of melting? Pause a video and discuss.

Restart when you've done that.

What did you think of? Is there any other things that you can see that melt? Is there anything that you observe melting every day? Well, we could observe ice cream changing state from solid to liquid.

That needs to be very cool and cold in order for you to be able to eat it.

But if it starts melting, it does turn into a liquid form.

The temperature of air is usually a lot higher than inside of a freezer, which is where ice cream is stored.

So when you take ice cream out of the freezer, the warmer air causes the ice cream to melt.

Have you ever seen chocolate change state like this? You can see some chocolate buttons on a plate and chocolate buttons on a hand.

Has this ever happened to you before? I know it has happened to me.

On a cool plate, the chocolate is in its solid state.

But when placed in someone's hand, the higher temperature from their hand melts a chocolate into its liquid state.

That's why it's not a very good idea to hold chocolates on your hand for too long.

Let's stop and think.

There are lots of examples of solids and liquids changing, what? In real life.

Changing volume, changing size, changing state, or changing math.

The correct answer here is changing state.

There are lots of examples of solids and liquids changing state in real life.

Laura here says, "Can materials only change from their solid to their liquid state? Are there any examples of materials changing state from liquid to solid?" What do you think? Have a discussion about these two questions.

What answers do you come up with? Restart the video when you've done that.

Well, there are lots of examples of materials changing from liquid state to a solid state in real life.

I wonder if you mentioned any of these.

For example, making ice lollies.

What else did you think of? Was there anything else that change state? Andeep here says, "When a material changes from a solid state to a liquid state, is it possible for it to change back to a solid state again?" Well, a bar of chocolate can be heated up.

That then changes it from a solid state to a liquid state.

The chocolate in the liquid state can then be cooled to change back to a solid state.

Here you can see an example of that.

This is how they make really delicious puddings.

There you can see the solid chocolate in the wrapper, it turns into a liquid form by heating it up, and then you cool it down again to turn it into a solid.

Oh, that looks really yummy.

I'm starting to get hungry.

Laura says, here's an example too, "The shape of this candle has changed over time.

The wobbly wax down the side looks like a liquid, but it is in the solid state." So the wax has been heated up, and then it starts to fall down the side of the candle in a liquid form.

As it cools, it turns back into a solid.

Do you know what has happened here? How has this liquid turned to a solid? Well, I can see here that the wax has been heated up by lighting the wick on the candle.

This has then started in liquid form to melt and run down the side of the candle.

As it cools down again, this creates a little bit of a platform.

And then of course, that wax can start building up as it cools.

So as it drips down the side of the candle, it gets to where the rest of it is cools down instantly and forms the wax again.

It doesn't take wax very long to harden once it's been cooled.

Andeep says, "What about cheese on toast?" Here you can see an example of cheese on toast.

Oh, there's lots of examples of food here, aren't there? To make cheese on toast, solid cheese is placed on bread.

It's then heated under a grill or in a microwave.

The high temperature melts the cheese into its liquid state.

And once outta the grill, the temperature is lower so the cheese becomes solid again.

That's a little bit like the candle except a much yummier example.

Stop and think.

Everyday examples of materials, blank, can include butter, chocolate, and candle wax.

Is it everyday examples of materials: disappearing, melting, growing or moving? The correct answer here is melting.

Everyday examples of materials melting can include butter, chocolate, and candle wax.

Here is task A.

You need to explore changes between liquid and solid state with candle wax.

Look at the candle wax.

What state is it in? Now, how do you know this? You need to place one teaspoon of grated candle wax in a plastic bag and seal the bag.

Then, ask an adult to put the bag in a bowl or jug of hot water.

You need an adult to help you here because you don't want to burn yourself.

Then, after one minute, ask an adult to take the bag outta the hot water and observe the candle wax.

Then, place the bag on the side and observe it as it cools.

Then, you need to explain your observations at each stage.

So you really need to use your observing skills here to keep an eye on what's going on and explain or write down what you see.

Best of luck with your task.

Restart the video when you've done that.

So how did you get on? Were you able to explore the changes that were happening? Your observations may have been a bit like this.

The candle wax was hard at the beginning, so we know that it was a solid.

After being in the hot water, the wax was transparent.

It flowed in the bag so we know it was a liquid.

When it cooled, it became a hard lump, so we know it was a solid again.

You are then only able to get that wax back into the original form of a candle if you use the same kind of model or stencil for you to be able to pour the wax in in a liquid form for it to harden up in the correct shape again.

The final part of this lesson is called changes of state at work.

Many people use their understanding of changing state in their work.

Laura here says, "Chefs rely on cheese melting when they make a pizza." So here you can see some pizza with melted cheese on top.

They know that if they place solid cheese on pizza dough, the higher temperature in the oven will cause the cheese to melt.

Chocolatiers change solid chocolate to liquid chocolate to be able to pour it into appealing shapes.

Here you can see lots of melting chocolate.

Oh, very yummy.

Candle makers melt wax to make attractive candles.

So these are two examples of jobs which require you to melt something into a liquid form and then to fill a container or a mold to be able to turn it into a hard form again, and then you can sell it, eat it, or set it on fire.

Solid metal steel melts at high temperatures.

In industry, liquid steel is used to join metal parts together.

This is called welding.

And you see there that there's somebody welding some plates of metal together.

It can be poured into molds as well to create new shapes or a little bit like the chocolatier you saw.

You can cast with it in this way.

Casting in this way with liquid metal can be very useful for making tools.

For example, in the olden days, this is certainly how they would've made swords by heating up the metal into a liquid form and then putting it into a mold that could then help it to form that long shaft that becomes a sword.

Laura says, "My gran has a glass balloon decoration which she says was made by melting solid glass." Wow, glass blowing involves melting glass so that it can be shaped and then cooling it so it holds its new shape.

So glass balloons can be created here when they're heated up to extraordinary temperatures and blowing air into them.

The glass is melted over a very hot fire, and then the glass maker will blow through a tube to put some air inside it.

And then as that glass cools, it creates a beautiful shape.

Here you can see it at work.

Small amounts of the melted glass are collected on the end of a long metal pipe.

There you can see the liquid state glass.

I didn't even know that glass could be turned into a liquid state like this.

The glass blower can roll this liquid glass to shape it.

So rolling it around that pipe.

They then blow through the pipe inflating the glass a little bit like a balloon.

You can create lots of different shapes and animals like this if you are very skilled.

'Cause of solid glass can be melted in its liquid state, in industry, it can be molded using machines.

This allows us to create objects in various shapes and sizes for different purposes like glass containers that you can see here holding milk, a magnifying glass that will enable you to read things that are a little bit too small, and of course, a window.

All of these have been cut to size.

They've been molded using special machines.

So stop and think.

Which of these people may require knowledge of solids and liquids changing state? Is it a hairdresser, a glass blower, a carpenter or a chef? The correct answer here is a glass blower and a chef.

These are two jobs that require you to know how solids and liquids change state.

Volcanologists are scientists who study volcanoes.

So where might they see materials changing between liquid and solid states here? Have a think.

Restart the video when you've done that.

How do you get on and what did you think? Well, deep within the earth, the temperature is so high that the rocks are in their liquid state.

This is called magma.

When volcanoes erupt, the liquid magma is forced through vents in the earth's surface.

So when the magma breaks through the surface of the earth, it's called lava.

As soon as the lava breaks through the earth's surface, it begins to rapidly cool down.

Remember, it's a lot cooler up here on the surface than it is underneath the ground.

Over time, the lava changes state from liquid to solid rock.

Liquid lava calls really quickly at first, but it can take years for it to completely change into solid state rock.

Here you can see a picture of solid rock formed from called liquid lava.

This has flowed over the surface and created more rock.

Volcanologists can use their knowledge of this to help them predict where larva will flow during an eruption.

It can also give them information about what eruptions have taken place in the past.

Let's stop and think.

Many people use their understanding of solids and liquids changing, what? In their work.

State, position or pressure? The correct answer here is state.

Everyday examples of materials changing from liquid state to solid state include liquid, blank, changing to solid rock.

Is it honey, water, oil, or lava? The correct answer here is lava.

Liquid lava changing to solid rock.

Here's task B.

Describe how people working in these jobs would need an understanding of solids and liquids changing state.

How does a candle maker, an ice cream server and a glass blower need to know this information, and why? Have a think and discuss.

Record your ideas.

Restart the video when you've done that.

How did you get on? Your answers may have been similar to this.

First of all, a candle maker.

They need to know about melting solid wax into a liquid so it can be poured into molds.

That's gonna make it candle shaped.

How about an ice cream server? They would need to store the solid ice cream at the correct temperature to make sure it doesn't melt before the customer buys it.

Finally, a glass blower.

They would need to know how to use the furnace equipment to heat the solid glass into a liquid ready to be blown.

I wonder if you came up with some similar ideas there or if there are any other jobs that you can think of that might need to know about this information.

You could have a go describing the reasons why they would need to know that in their job as well.

Let's summarize our lesson.

There are lots of examples of solids and liquids changing state in real life.

Everyday examples of materials changing between solid state and liquid state include butter, chocolate and candle wax.

Many people use their understanding of solids and liquids changing state in their work.

Everyday examples of materials changing from liquid state to solid state include liquid lava changing to solid rock.

Wow, lots of information learned in this lesson all about how things can change state.

I wonder if that's interested you in any career path in the future.

I wonder what kind of job you might like to do where you get to change the state of things or where you need to understand why things change state.

I'm Mr. Wilshire.

Thank you very much for listening.