Hello, I'm Mrs. Adcock, and welcome to today's lesson on gases in the atmosphere.

Today we are going to be thinking about which gases make up our atmosphere and what are some uses of these gases.

Today's lesson outcome is, I can name the main gases in the atmosphere and describe the test and some uses for each one.

Some of the key words we are going to be using in today's lesson include atmosphere, mixture, respiration, and precipitate.

Here you can see each of those keywords written in a sentence.

You might like to pause the video here and read through those sentences, or perhaps pause the video and make a note of those keywords in those sentences so that you can refer back to them later in the lesson if needed.

Today's lesson on gases in the atmosphere is split into three parts.

The first part we're going to be looking at Earth's atmosphere and thinking about what is the atmosphere and what's the atmosphere made up of.

Then we're going to move on to look at some of the uses of gases that are found in our atmosphere.

And finally, we're going to look at tests for gases.

Right, let's get started on Earth's atmosphere.

The atmosphere is a layer of gas that surrounds a planet, so it's not just Earth that will have an atmosphere.

Other planets can have an atmosphere too.

The atmosphere may contain a small amount of solid and liquid particles, and in the image there we can see Earth, and those rings around Earth represent the atmosphere.

And Earth's atmosphere is split into little subsections known as the exosphere, thermosphere, mesosphere, stratosphere, and troposphere.

And if you look at the image, you can see some of the objects that are found in each of those spheres.

So in the thermosphere, that's where we might find the Northern Lights or satellites.

In the mesosphere, we've got meteors.

In the stratosphere, there's weather balloons, and sometimes aeroplanes may pass up into the lower stratosphere.

And then in the troposphere, that's where we find hot air balloons.

So what's the atmosphere made up of? Well, the atmosphere comprises about 79% nitrogen, about 20% oxygen, about 1 argon, and argon is a noble gas.

And then there are trace gases, including 0.

04% carbon dioxide.

So by trace gases we mean that there are some other gases that are found in really low amounts, such as carbon dioxide there, which we can see is about 0.

04% of our atmosphere.

Now this data here is represented on the pie chart, and the blue colour on the pie chart is nitrogen.

So nitrogen makes it about 79% of our atmosphere, so it makes up a huge proportion of our atmosphere.

And then the pink section is oxygen, and we can see oxygen is about 20%.

And then there's just a low percentage of lots of other gases in our atmosphere.

Time for a check for understanding.

What is the percentage of nitrogen in Earth's atmosphere? Is it A, 79%, B, 20%, C, 1%, or D, 0.

04%? So just think carefully.

Which one of those is nitrogen? The percentage of nitrogen in Earth's atmosphere is about 79%.

So well done if you chose option A.

Another question now.

What is the percentage of oxygen in Earth's atmosphere? Is it A, 79% B, 20%, C, 1%, or D, 0.

04%? The correct answer is B, 20%.

So 20% of Earth's atmosphere is oxygen.

Well done if you got that correct.

A, 79%, we already know from the previous question is the percentage of nitrogen in Earth's atmosphere.

There's about 1% argon and 0.

04% carbon dioxide.

The atmosphere is a mixture.

And just to remind ourselves, a mixture is a material that contains two or more different substances which can be physically separated.

We can see in the box there we've got a model of air in our atmosphere, and the blue represents nitrogen, and nitrogen has the molecular formula N2.

Those red atoms represent oxygen, and oxygen has the formula O2, so it's travelling in pairs.

So we've got two oxygen atoms there joined together to make an oxygen molecule.

Argon is 1% of our atmosphere, and argon is a noble gas, and the symbol for argonne is Ar.

We've got carbon dioxide in our atmosphere.

Carbon dioxide is a compound made of two different elements that are chemically joined together.

So we've got carbon and oxygen atoms that join together to make carbon dioxide.

And also we've got water vapour in our atmosphere, and water is also a compound.

It's made of hydrogen and oxygen atoms that are chemically joined together.

So air is a mixture made of compounds, such as water vapour and carbon dioxide, and elements, such as nitrogen, oxygen, and argon.

So they are elements because elements are made up of just one type of atom.

We can see that these compounds and elements are all mixed together, but they are not chemically joined, so they can be physically separated from each other.

Earth's atmosphere is a, A, compound, B, solution, or C, mixture.

Earth's atmosphere is a mixture.

It's a mixture made up of different elements and compounds.

Well done if you chose C, mixture.

The atmosphere is really important for us on Earth.

The atmosphere helps maintain a stable temperature and it blocks harmful radiation from the sun.

And we can see in this diagram here we've got the sun and we've got some harmful radiation coming from the sun.

And then we've got the Earth at the bottom.

One part of our atmosphere contains lots of a molecule called ozone.

So we call this area of our atmosphere the ozone layer, and the ozone layer helps block harmful UV radiation from the sum.

So we've got different types of UV radiation.

We've got harmful UV-C radiation, which we can see there is absorbed by the ozone layer, which helps protect us on Earth from that harmful radiation.

The atmosphere allows some ultraviolet UV radiation to pass through, but absorbs some harmful UV radiation, preventing it from reaching Earth's surface.

So we can see the yellow.

That's a type of UV radiation that can reach the Earth's surface, but we can see that there's parts of the atmosphere that protect Earth and absorb some of that harmful radiation.

The atmosphere is also essential for supporting life on Earth, such as providing oxygen gas that is needed for respiration.

All plants and animals respire, and when they respire, they release energy that's needed for life processes, and the equation for respiration is shown below.

So this is something that we've said all plants and animals do.

So they take in oxygen from the atmosphere and they react that with glucose, and that produces carbon dioxide and water, and in the process energy is released.

Why is the atmosphere on Earth important? Is it important because, A, it maintains a stable temperature, B, it blocks some harmful radiation from the sun, or C, it provides oxygen needed for respiration? Now choose any options that you think are correct.

Well done if you chose A, B, and C.

So all of these are reasons why the atmosphere on Earth is important.

It maintains a stable temperature, it blocks some harmful radiation from the sun, and it provides oxygen needed for respiration.

Another question here to have a go at.

Oxygen is required for humans and plants to respire.

What is the correct equation for respiration? Is it A, glucose and oxygen react together to produce carbon oxide and water, B, carbon dioxide and water react together to produce glucose and oxygen, or C, oxygen and water react together to produce carbon dioxide and glucose? So just pause for a minute and think about what is it that humans need to respire.

Think about which gas we take in from the atmosphere and use this to help you select your answer.

The correct equation for respiration is A, so humans take in oxygen from the atmosphere, this reacts with glucose to produce carbon dioxide and water.

Time for first practise task of today's lesson.

What you need to do here is answer these two questions.

Question one, what is the atmosphere? So you're going to define the atmosphere.

Question two, complete the table below to show the percentage composition of different gases in Earth's atmosphere.

Think about which gases are in Earth's atmosphere and what percentage they are of Earth's atmosphere.

Pause the video now, have a go at those two questions, and then come back when you're ready to go over the answers.

Welcome back.

Question one, what is the atmosphere? The atmosphere is a layer of gas that surrounds a planet.

So well done if you correctly defined what the atmosphere is.

You may have mentioned that it can contain solid and liquid particles too.

Question two, complete the table below with the percentage composition.

Nitrogen is 78% of Earth's atmosphere, 20% is oxygen, argon is 1%, and 0.

04% is carbon dioxide.

We've looked at what Earth's atmosphere is and the gases that make up Earth's atmosphere.

Now we're going to move on to have a look at some of the uses of those gases.

Nitrogen gas, which is found in Earth's atmosphere and makes up about 79% of Earth's atmosphere, has the molecular formula N2.

So it's two nitrogen atoms joined together.

It is a colourless, odourless, so that means we can't smell it, gas which is very unreactive.

Nitrogen gas has many uses, such as in the production of fertilisers, which are obviously essential for crop production.

And also nitrogen is used to provide an unreactive atmosphere in food packaging.

A packet of crisps contains your crisps, but also nitrogen gas because it's unreactive, so it will not react with the crisps, so it'll keep them fresh, ready for when you want to eat them.

Oxygen gas, which makes up about 20% of our atmosphere, has the molecular formula O2.

So it's two oxygen atoms combined together.

It is a colourless and odourless gas, so like nitrogen, it's colourless and odourless.

Oxygen gas, we've already seen, is essential for respiration and also it's needed for the combustion of fuels.

And combustion is when we burn a fuel.

So when we burn our fuel, it reacts with oxygen, but oxygen has many other uses as well, such as in the production of steel and also in the manufacture of chemicals.

Carbon dioxide, which makes up about 0.

04% of our atmosphere, is also, like nitrogen and oxygen, a colourless and odourless gas.

It has the molecular formula CO2.

So it's a compound made up of two different elements.

It's carbon and oxygen atoms chemically bonded together.

Carbon dioxide has many uses, such as enabling plants to photosynthesize.

So plants take in carbon dioxide from the atmosphere.

They react to that with water to produce oxygen and glucose.

Carbon dioxide is also found in carbonated drinks.

So in your fizzy drinks there is carbon dioxide.

And also, carbon dioxide is found in some fire extinguishers.

Time to check we've understood what we've learned about uses of gases.

Which of the following gases are colourless and odourless? A, nitrogen, B, oxygen, C, methane, D, carbon oxide.

Now choose any options that you think are correct.

Well done if you chose nitrogen, oxygen, and carbon oxide, so A, B, and D, they are all colourless and odourless gases.

For our practise task of this section of the lesson, what you need to do is answer these two questions.

Question one, what is the molecular formula of nitrogen, oxygen, and carbon dioxide? And for question two, you've got to state a use of nitrogen, oxygen, and carbon dioxide.

You might like to use a periodic table to help you when doing the molecular formula to look at the symbols of nitrogen, oxygen, and carbon if you can't remember those.

And also be careful to use capital letters if required.

Pause the video now, have a go at those two questions, and then come back when you're ready to go over the answers.

Let's look at question one.

What is the molecular formula of nitrogen, oxygen, and carbon dioxide? Nitrogen is N2, oxygen is O2, and the molecular formula of carbon dioxide is CO2.

So they have all got capital letters and the little twos should be subscript.

Question two, state a use of nitrogen, oxygen, and carbon dioxide.

Possible answers include nitrogen is used in the production of fertilisers and in food packaging, oxygen is used for respiration, combustion of fuels, production of steel, and the manufacture of chemicals, and C, carbon dioxide is used for photosynthesis, in carbonated drinks, and in some fire extinguishers.

So well done if you were able to remember some of the uses of nitrogen, oxygen, and carbon dioxide.

Time for us to move onto the final part of our lesson, which is on tests for gases.

We can test for the presence of oxygen gas by firstly lighting a splint, allowing it to burn for a few seconds, and then extinguish the splint to leave a glowing splint.

So when we test for oxygen gas, the first thing we need to do is get a glowing splint.

So here we can see in the image we've got a glowing splint.

So we light it, leave it to burn, and then extinguish it and we'll have a glowing splint.

Then place the glowing splint in the presence of oxygen gas and the glowing splint will relight.

And there we can see a picture of a lit splint.

So we take a glowing splint, put it in the presence of oxygen gas, and it will relight.

That's our test for oxygen gas, and we can watch a little clip here to see this in action.

We can test for the presence of carbon dioxide gas by firstly bubbling carbon dioxide gas through limewater.

And when we do this, a white precipitate is formed.

Now precipitate, that's one of our key words, is an insoluble solid.

So we will get a white precipitate that's formed and this makes that colourless limewater turn milky.

You can see in the diagram below, we have a reaction happening, and that's producing carbon dioxide.

Then the carbon dioxide gas can escape out the top and travel down the delivery tube and into the limewater, and the colourless limewater, when the carbon dioxide is bubbled through it, will form a white precipitate, which will make the limewater turn milky.

And we can watch a little clip of this happening.

Let's check we've understood the tests for oxygen and carbon dioxide gas.

So what is a positive test for oxygen gas? Is it A, it will relight a glowing splint, B, it will make a squeaky pop sound, or C, it will turn limewater cloudy? Oxygen gas will relight a glowing splint.

Another question here, what is a positive test for carbon dioxide gas? Is it A, it will relight a glowing splint, B, it will make a squeaky pop sound, or C, it will turn limewater cloudy? Well done if you chose C, the test for carbon dioxide is it will turn limewater cloudy.

A, we know relighting a glowing splint is a test for oxygen, and B we haven't looked at in today's lesson, but this is a positive test for hydrogen gas.

For our final practise task of today's lesson, there are two methods for you to follow to prepare and test firstly for oxygen gas, and then to prepare and test for carbon dioxide gas.

What you need to do in this first method is add five centimetres cubed of hydrogen peroxide to a boiling tube.

Add one small spatula of manganese dioxide.

Hold the boiling tube with tongs at a 45-degree angle.

Light a splint, leave it to burn for a couple of seconds, then extinguish the flame so that you've got a glowing splint.

Move the glowing splint to the end of the boiling tube and the splint will relight due to the presence of oxygen gas.

For the second part of this task, you're gonna prepare and test for carbon dioxide gas.

And to do this, we're going to place 20 centimetres cubed of limewater in a boiling tube, then add five centimetres cubed of hydrochloric acid to a different boiling tube, and to this acid you're going to add a few marble chips.

Immediately place a bung with an attached delivery tube over the end of the boiling tube that contains the acid and marble chips.

Ensure the other end of the delivery tube is in the limewater.

The acid and marble chips will react together to produce carbon dioxide.

The carbon dioxide bubbles will travel through the delivery tube, turning the limewater milky.

If you're not able to complete both of those tasks, then don't worry.

We have already watched a little video clip seeing what happens when we test for oxygen and carbon dioxide gas.

You can, however, still have a go at questions three and four.

Question three is, how can we test for the presence of oxygen gas? And question four, how can we test for the presence of carbon oxide gas? So pause the video now, have a go at those questions, and come back when you're ready to go over the answers.

Question three, how can we test for the presence of oxygen gas? We light a splint, extinguish the splint to leave a glowing splint, then we place the glowing splint in oxygen gas and it will relight.

How can we test for the presence of carbon dioxide gas? We bubble the carbon dioxide gas through limewater and a white precipitate will form which makes the limewater appear milky.

Well done if you used that key word precipitate and you were able to explain how we can test for the presence of oxygen and carbon dioxide gas.

We have come to the end of today's lesson on gases in the atmosphere.

So let's just summarise some of the key points that we've learnt in today's lesson.

About 79% of the atmosphere is nitrogen gas, and this is a very unreactive gas.

Nitrogen gas is often used to fill food packaging to provide an unreactive atmosphere.

About 20% of the atmosphere is oxygen, and the test for oxygen gas is that it relights a glowing splint.

The test for carbon dioxide gas is that it forms a white precipitate that turns limewater milky.

Well done.

You've worked really hard in today's lesson.

I really enjoyed it.

I hope that you have too, and I hope that you're able to join me for another lesson soon.