Lesson video

Hello scientists, my name is Mr. Wilshire and in this lesson we're going to be looking at evaporation and condensation in the water cycle.

The outcome of this lesson is I can identify the part played by evaporation and condensation in the water cycle.

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

The first is evaporation.

Next, water vapor.

Then it's water cycle.

After that, condensation and finally precipitation.

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

The definitions are on the screen for you now.

So if you need to, you can pause the video here and have a quick recap.

The first part of this lesson is called water travels from the land to the atmosphere.

Jun and Sophia have been learning about evaporation.

Take a moment here to have a think.

Can you explain to a partner what evaporation means? Pause the video and have a go.

Restart when you've done that.

How did you get on? What does evaporation mean? Well, evaporation is the change of state from the liquid to a gas.

They can see a cup with some water on it being changed into a gas.

So Jun says, when water evaporates, what happens to all the water vapor in the air? I wonder, does it, does it go to space? Sophia says, well, wouldn't we eventually just run out of water if all the water vapor is lost into space? Do you know what happens to water vapor in the air? Does it go to space? Have a think.

Restart the video when you've done that.

So does all the water vapor go to space or does something else happen? Let's find out more.

Well, water doesn't leave earth's atmosphere.

Here you can see earth and an image of its atmosphere.

So you can see there that the atmosphere around the earth is made of different layers, made of different pressures and different temperatures as well.

So it's actually quite a long time until we get out into space.

The atmosphere is the layer of gases that surrounds the earth.

That's what it's known for.

Water moves around between earth's surface and its atmosphere in what is called the water cycle.

The water cycle is the name of the journey that water takes as it moves from the oceans, the rivers, the lakes, or land to the atmosphere and back again.

Sophia says, where does the water cycle start, though? Hmm, that's a good question.

I wonder if you know.

Can you discuss this and restart the video when you've done that? So where does the water cycle start? Does it start in space or does it start underneath our feet? Jun says the water cycle doesn't really have a beginning or an end.

It's just a cycle.

We can begin to understand the cycle by first thinking of water on land.

So this is a good place to start, but it doesn't mean that this is the start of water or where the water comes from.

Here you can see an image of the land, sea, and sky.

And we've highlighted the land there because this is where we're going to start talking all about the water cycle.

So where can you find water on land? Have a think.

Do you find water in just cups or does it come out the taps, or is it anywhere else? So where can you find water on land? Let's find out more.

So on land, water can be found in ponds, lakes, streams, rivers, seas, and oceans among other places as well.

Sophia says, how does water get from the land or see into the atmosphere though? Hmm, I wonder, do you know? Have a quick discussion and restart when you've done that.

So how does water get from the land or sea into the atmosphere? Well water from lakes, rivers, and seas on the earth's surface evaporates to form water vapor in the atmosphere.

Here you can see an example of liquid water evaporating from earth's surface.

So there's liquid water on the land and that evaporates and moves up into the atmosphere in the form of water vapor.

Now the children are discussing this and the water cycle in general.

Jun says there is no water cycle on cold days because evaporation only happens in the sun.

Sophia says the water cycle occurs all year and in all weathers.

Andeep says there's no water cycle in winter because it's too cold.

Who do you agree with here and why? Have a quick discussion and restart when you've done that.

How did you get on? Were you able to discuss and who did you agree with and why? Well, Sophia is correct.

The water cycle occurs all year and it occurs in all weathers as well.

It doesn't matter about the temperature, but the temperature might affect how quickly this might happen.

The water cycle occurs all year, and in all weathers.

Even though evaporation happens more quickly at higher temperatures, it takes place in all weathers.

Let's stop and think.

By what process does water move from the land to the atmosphere? Is it by melting, freezing evaporation, or condensation? The correct answer here is through the process of evaporation.

Here's task A.

Are these statements always, sometimes, or never true? Have a read of each of those statements there and decide.

Put a tick into each box.

The first statement is water doesn't leave earth's atmosphere.

What do you think? Is that always true, sometimes true or never true? Next, the water cycle begins with water on earth's surface.

Then there is no water cycle in winter because it is too cold.

Next, evaporation is the change of state from a liquid to a gas.

And finally, water in gas state is called gas vapor.

You need to read each of those statements.

Have a think, is it always true, sometimes true or never true? Best of luck with your task.

Restart when you've done that.

How did you get on? So what did you agree with here? The first one said, water doesn't leave earth's atmosphere.

That is always true.

The next one says, the water cycle begins with water on earth's surface.

That's sometimes true.

That's where we like to think it starts, but remember, it's a cycle.

It's continuously ongoing.

The next one down there says there is no water cycle in winter because it's too cold.

That's never true.

Remember, evaporation can happen at any temperature.

Evaporation is a change of state from a liquid to a gas.

This is always true.

And water in gas state is called gas vapor.

That is never true.

Hopefully you've been able to show off some of the things that you know, and don't forget if you've got some of these wrong, that's okay because now you're going to know the answer, aren't you? And move forward knowing more.

The next part of this lesson is called water travels from the atmosphere to the land.

Sophia says, if the water in the atmosphere doesn't rise into space, what does happen to it? Well, do you know how the water returns to the earth's surface? It's always rising up.

Do the astronauts send it back down to earth? I don't think that's right.

Pause the video here and discuss.

Restart when you've done that.

So how does the water return to the earth's surface? Well, water can return to the earth as rain, snow, hail, or even sleet.

There you can see two different images of that exact thing happening.

Hail is small pellets of ice or frozen rain.

Sleet is rain, which contains some snow.

So as it moves through the water cycle, water can be in the liquid state, gas state, which is water vapor or solid state, which is ice.

Depending on which state it's going to be in, will give you the different type of thing that will fall to the ground.

Could be rain, could be sleet, could be hail, could be snow.

Let's stop and think.

True or false, water can only be in the liquid or gas state as it moves through the water cycle.

The correct answer there is false As it moves through the cycle, water can be in the liquid state, gas state, which is water vapor or solid state, which is ice.

So as water vapor rises in the atmosphere, it begins to cool down.

Remember, it can get very cold out towards space.

So as things are rising up off of the ground, it can then start to rapidly cool down.

So Sophia says, what happens when water vapor cools down? Do you know? Have a quick discussion and restart the video when you've done that.

Jun says, I know that as water vapor in my bathroom touches the cold tiles, it can condenses back into liquid water.

Have you ever noticed this? If you are in the bathroom or maybe even in the kitchen, if you've been cooking and it's got very hot, you can see there are water droplets on a cold tile.

So the water vapor in the atmosphere begins to cool.

It then condenses to form masses of tiny water droplets and water condenses here to form clouds.

So it's held in the atmosphere as a cloud, and the clouds can then be moved around by the wind.

So tiny water droplets as clouds move around as our water vapor cools and condenses.

Let's stop and think.

What happens to water vapor as it rises in the atmosphere? Does it warm and evaporate more? Does it cool and condense? Or does it travel into space? The correct answer here is it cools and condenses.

What happens to make clouds form? Does water vapor condense? Does liquid water evaporate? Or does liquid water freeze? The correct answer here is water vapor condenses.

Now the droplets of water in the clouds get larger.

They then get heavier and eventually they fall as rain, snow, hail or sleet.

There you can see an image of a cloud and rain falling from that cloud.

Jun says, why don't all the water drop? Its fall as rain? Do you know? Have a quick discussion.

Restart when you've done that.

So did you get it right? When air in the atmosphere is very cold, the water droplets freeze and change into solid state water, which is snow or ice.

That can then give us very different types of weather, can't it? Rain, snow, and sleet are known as precipitation.

Here you can see an image of precipitation as hail.

Precipitation is water in the solid or the liquid state, which falls from the atmosphere to earth's surface.

Sophia said, I heard the word precipitation on a weather report.

You may have done that as well.

Remember, all of this water is evaporating.

It's rising up into the atmosphere, and when it's there, it can then begin to cool, which then helps it to fall back down to earth as rain, hail, snow, or even sleet.

So once back on the earth's surface, the water cycle begins again.

So evaporation from the rivers and from the seas rises into the atmosphere.

That water vapor then begins to cool and condensation happens.

That creates clouds.

This rains precipitates onto the land, and then liquid water begins to evaporate all over again.

So I wonder which part does come first? Because it is just a cycle, isn't it? It goes on and on and on.

Remember as well, that rain, snow, hail or sleet will fall onto the land and then form eventually into the rivers.

Those rivers will then flow into lakes or ponds or even into the sea.

Evaporation can happen in all of those areas.

Stop and think.

True or false, precipitation is water in the liquid state, which falls from the atmosphere to Earth's surface.

The answer here is false.

Precipitation is water in the solid or liquid state, which falls from the atmosphere to the earth's surface.

You need to remember that it's not just water in the liquid state that falls.

Rain isn't the only type of things that falls from clouds.

It could be hail, snow, or even sleet.

Here's task B.

Make a model water cycle.

Using a recycled clear bag, you can add some arrows to represent the water cycle and labels in suitable places, including evaporation, condensation, and precipitation.

Then if you add a little bit of water into the bottom of the bag, you can then create your very own water cycle and make some observations after a few hours.

Have a little go at this task.

Restart the video when you've done that.

So here is an example of what could have happened to yours that may be similar.

The bag had gone misty or foggy, showing that some of the liquid water had evaporated and risen.

When we pressed lightly on the surface of the bag, some of the water vapor condensed and could be seen as droplets of liquid water.

So this is showing exactly what happens in the water cycle.

There you've created your very own model.

Well done.

Let's summarize our lesson.

Water doesn't leave earth's atmosphere.

It moves around in what is called the water cycle.

Water evaporates from sources such as seas and rivers, as well as from the earth's surface.

As it moves through the water cycle it can be in the liquid state, the gas state, which is vapor, or the solid state, which is ice.

Water vapor rises into the atmosphere, then cools and condenses into clouds.

Well done for completing that lesson.

Hopefully you've got a better understanding of the water cycle and how it can create the rivers, how it can create clouds, rain, snow, sleet, and even hail.

I'd be Mr. Wilshire.

Thank you very much for listening.