Lesson video

Hi, I'm Miss Mia and I'm really looking forward to teaching you this lesson today.

In this lesson, you'll be able to describe and explain what happens when a substance changes state and how evaporation occurs.

Your key words are on the screen now and you can write them down if you'd like to.

Energy, evaporation, evaporation rate, alcohol.

Great.

Let's find out what these keywords mean.

Particles gain or lose energy when a substance changes state.

Evaporation is when a particle of a substance in the liquid state at the surface has enough energy to change to the gas state and mix with air.

The evaporation rate is a measure of how quickly a substance evaporates.

Ethanol is a type of alcohol that has a higher evaporation rate than water.

We have three lesson cycles today and our first lesson cycle is to do with energy and changing state.

We're then going to be looking at evaporation and lastly, evaporation rates.

I'm super excited about this lesson.

I hope you're too.

Let's begin.

Here, we can see different states of matter have different amounts of energy.

What do you notice about these diagrams?

On the left, we have solid state, liquid state.

And then lastly, a gas state.

Over to you.

Which state of matter has the greatest energy?

Is it A, solid state, B, liquid state, or C gas state?

What do you think?

You can pause the video here and click play when you've got the answer.

So what did you get?

If you got C, you are correct.

The gas state has the greatest amount of energy.

When particles gain energy, they move more as they have more energy.

In the solid state, the particles can only vibrate on the spot because the forces of attraction are very strong.

Once the particles gain enough energy, they can overcome forces of attraction holding them in a fixed position and move past each other changing into the liquid state.

This is called melting.

Over to you.

True or false?

When a substance melts, the particles gain energy.

If this true or is this false?

You can pause the video here and click play once you've completed answering the first part of this check for understanding.

So what did you get?

If you got true that's correct, I'd like you to justify why.

Is it because A, the particles gain energy and can overcome the forces of attraction to move over and pass each other or be the particles gain energy and vibrate more in a fixed position?

What do you think?

You can pause the video here and click play when you've got the answer.

So what did you get?

If you got A, you are correct.

When a substance melts, the particles gain energy and can overcome the forces of attraction to move over and past each other.

Well done.

Let's move on.

In the liquid state, the particles can move past each other, but are still held together by forces of attraction.

We can see this highlighted here in these diagrams.

If the particles gain enough energy to completely overcome these forces of attraction, they can move freely in all directions.

This is called boiling and the substance is now in the gas state.

Over to you.

Once the particles gain enough energy, they can completely overcome forces of attraction holding them together and move freely in all directions.

The substance then becomes in the, is it A, solid state, B, liquid state or C gas state?

What do you think?

You can pause the video here and click play when you've got the answer.

So what did you get?

If you got C gas state, you are correct.

The substance becomes a gas state because the particles have gained enough energy to completely overcome the forces of attraction that were once holding them together.

And now they can move freely in all directions.

Super.

Let's move on.

So now we know that in the gas state, the particles can move freely in all directions.

Have a look at this diagram.

What do you think is happening here?

Now if the particles lose energy, they move less.

So the forces of attraction between them increase and they come together moving in the liquid state.

This is known as condensing.

Over to you.

A substance in the gas state condenses.

Which information matches the description of condensing?

Is it A, gas state to liquid state loses energy, particles move less?

Is it B, gas state to liquid state gains energy, particles move more or is it c, gas state to liquid state loses energy, particles move more.

What do you think?

You can pause the video here and click play once you've got the answer.

So what did you get?

If you got a, you are correct.

When during condensation, we go from gas state to liquid state.

So the particles lose energy and so there's a loss of energy and the particles move less.

Well done if you got that correct.

Let's move on.

In the liquid state, particles touch and move over and around each other.

Have a look at these diagrams here.

What do you think is happening?

If the Substance loses energy, then the particles are no longer able to overcome the forces of attraction between particles and the particles can only vibrate in a fixed position.

Over to you.

Select two correct endings for the following statement.

When particles in the liquid state lose energy and change to a solid state, A, they're no longer able to overcome the forces of attraction between particles.

B, they're able to overcome the forces of attraction between particles.

C, they can no longer move over and around each other or D, they can move over and around each other.

What do you think?

You can pause the video here and click play once you've got the answer.

So what did you get?

If you got a, you're correct.

When particles in the liquid state lose energy and change to a solid state, they are no longer able to overcome the forces of attraction between particles.

If you've got C as well, you are correct, they can no longer move over and around each other.

This forces them into a solid state.

Well done if you got that correct.

Let's move on.

Task A: I'd like you to complete the missing information in this diagram.

You can pause the video here and click play once you've completed this task.

So how did it go?

Well, you should have got this, moving from a liquid state to a solid state, we are freezing.

To go from a solid state to a liquid state, we enter melting point.

That's when the solid turns to liquid.

When particles go from a gas state to a liquid state, this happens during the condensing point.

And the last diagram here is showing the gas state.

Two: I'd like you to complete the table using the information below.

Two have completed for you.

So we've energy of particles, movement of particles, and then, we've got the states across the table top.

So we've got the solid state, liquid state and gas state.

You can pause the video here and click play once you've completed this table.

So what did you get?

Well, for solid state the energy of particles, they have the lowest energy.

For the gas state, they've got the highest energy.

In terms of movement of particles during liquid state, they can move over and around each other and lastly for gas state, they can move randomly in all directions.

Well done if you've managed to get that correct.

Let's move on.

Evaporation.

On the left, we have a puddle of water.

Now we know that water boils at a hundred degrees Celsius.

The puddle of water does not reach this temperature but will disappear when all the water evaporates and changes from the liquid state to the gas state.

Evaporation of a puddle of water.

All particles have enough energy to be in the liquid state.

Most particles are in the liquid state.

Some particles have enough energy to be in the gas state.

The particles with enough energy at the surface can leave the puddle and mix with the air as water in the gas state.

So here we have a table.

At the top it says enough energy to be in the liquid state or in the liquid state.

And lastly have enough energy to be in the gas state.

So for this, the first one, all particles have enough energy to be in the liquid state.

Most particles are in the liquid state and some particles have enough energy to be in the gas state.

So only some particles at the surface can leave the puddle and mix with the air as water in the gas state.

And we can see this happening here as well.

Over to you.

A liquid is added to a beaker, the beaker is left.

Where does evaporation take place?

Is it A, the surface only?

B, inside the liquid only or C?

Everywhere in the liquid.

What do you think?

You can pause the video here and click play once you've got the answer.

So what did you get?

If you got A, the surface only, you're correct.

Only some particles are able to evaporate.

Let's move on.

Back to you, select two answers, particles of water in a puddle.

.

.

A, all have the same energy.

B, have some with more energy than others.

C, can leave the puddle at the surface and mix with the air.

Or D, always stay in the puddle unless the puddle boils.

What do you think?

You can pause the video here and click play once you've got the answer.

So what did you get?

If you've got B and C, you are correct.

Particles of water in a puddle have some more energy than others and can leave the puddle at the surface and mix with the air.

Well done if you've managed to get that correct.

Let's move on.

Differences between evaporation and boiling.

So on the left, we've got evaporation and then we've got boiling on the right.

Evaporation can happen at any temperature between the melting and boiling point.

Boiling specific temperature for substances.

Example, water at a hundred degrees Celsius.

Evaporation.

No bubbles are formed.

Particles only leave from surface.

Boiling bubbles of the substance in the gas state produced within the liquid.

Back to you.

During evaporation, particles leave the liquid and mix with the air particles.

The diagram shows the location and energy of four particles.

Which particles is or are most likely to leave?

Is it A, one and two, B three and four, C one and three or D one only?

What do you think?

You can pause the video here and click play when you've got the answer.

So what did you get?

If you got D, one only that's correct.

That's because these particles are more closer to the surface and have more energy to mix with the air.

Well done.

Let's move on.

Back to you.

I'd like you to decide if these statements are right or wrong.

A, evaporation takes place at a specific temperature.

B, boiling produces bubbles of the substance in the gas state.

C, during boiling, only the particles at the surface leave or D, during evaporation the particles mix with particles in the air.

What do you think?

You can pause the video here and click play once you've got the answers.

So what did you get?

Well for A, you should have got that that is incorrect.

B, this is correct.

Boiling produces bubbles of substance in the gas state.

C is also incorrect and D is correct.

During evaporation, the particles mix with the particles in the air.

Let's move on.

Task B, for each observation below, state whether the student is describing boiling or evaporation, explain how you decided.

Laura says a liquid is heated, the volume reduces, bubbles are formed.

Sam says a puddle of water dries on a cold day.

Sofia says some water is heated to a hundred degrees Celsius.

The volume of the water reduces.

Alex says, a liquid is heated, the volume reduces.

No bubbles are formed.

So what do you think?

Are these describing boiling or evaporation?

And how do you know?

You can pause the video here and click play once you've completed this task.

So what did you get?

Laura, "Boiling has taken place because bubbles are formed.

" Sam, "Evaporation because it's below the boiling point of water.

" Sofia, "Boiling takes place as a specific temperature is given.

" And lastly, Alex, "Evaporation takes place as no bubbles are formed.

" Well done if you manage to get those correct and explain why.

Let's move on.

Lesson cycle three, evaporation rates.

Let's begin.

All particles of a substance in the liquid state do not have the same amount of energy.

The higher the temperature, the higher the energy of the particles.

More of the particles will have enough energy to be in the gas state and evaporation will be faster.

So here we can see two diagrams.

On the left we've got lower temperature, so we've got less particles with higher energy.

And then on the right, we've got a higher temperature and we can see more particles with more energy.

In general, the higher the temperature, the faster the rate of evaporation.

Over to you.

The same volume of water at three different temperatures was added to three beakers.

The beakers were left in a room at 25 degrees Celsius for two weeks.

In which beaker or beakers do you expect the water to have evaporated?

Is it A, beakers two and three, B, beaker one only, C, beaker three only or D, beakers one, two, and three.

What do you think?

You can pause the video here and click play once you've got the answer.

So what did you get?

Well, you should have got beakers one, two, and three.

Some substances evaporate faster than others, need a different amount of energy than other substances to evaporate.

Ethanol is a type of alcohol.

It's used in hand gel.

It evaporates faster than water.

Acetone, which is a nail varnish remover, evaporates faster than alcohol and water.

Over to you.

The same volume of water and acetone are added to two beakers.

What do you predict will be observed after four hours in a warm room?

Is it A, B, C, or D?

What do you think?

You can pause the video here and click play once you've got the answer.

So what did you get?

If you got C, you are correct.

This is because acetone evaporates faster than water.

Let's move on.

Back to you again.

The same volume of water and alcohol are added to two beakers.

What do you predict will be observed after six weeks?

So we've got A, B, C, and D.

You can pause the video here and click play once you've got the answer.

So what did you get?

If you got B, you are correct.

Why do you think this is?

So both water and alcohol have evaporated here, even though they have different evaporation rates.

Task C: Only use the words temperature and energy to fill in the gaps to explain why the rate of evaporation is higher in beaker A.

Evaporation takes place from both beakers.

Particles with enough are able to escape from the liquid.

Beaker A is at a higher than beaker B.

This means the particles in beaker A have more.

.

.

In both beaker A and beaker B, some particles have more than others.

However, in beaker A more particles have enough to escape the liquid.

For this reason, evaporation takes place faster from beaker A.

In general, the higher the, the faster the rate of evaporation.

You can pause the video here and click play once you've completed this task.

So how did you do?

Let's go through this together.

So evaporation takes place from both beakers.

Particles with enough energy are able to escape from the liquid.

Beaker A is at a higher temperature than beaker B.

This means that on average the particles in beaker A have more energy.

In both beaker A and beaker B, some particles have more energy than others, however, in beaker A more particles have enough energy to escape the liquid.

For this reason, evaporation takes place faster from beaker A.

In general the higher the temperature, the faster the rate of evaporation.

Well done if you managed to get that correct.

You now understand that states of matter can have differing amounts of energy.

Solid states have the least energy.

Gas states have the most energy.

A substance in its liquid state can evaporate at temperatures below its boiling point.

And here we have a diagram to show all of those processes.

The hotter the water, the more quickly it evaporates.

And you now also know that water evaporates at temperatures that are lower than a 100 degrees Celsius.

Thank you so much for joining me in this lesson.

I hope you really enjoyed it.

Bye.