Lesson video

Hi, I'm Mrs. Adcock, and today we are going to be learning about Earth's atmosphere and thinking about what is the Earth's atmosphere made up of.

Today's learning outcome is I can describe the composition of Earth's atmosphere.

So we are looking at the Earth's atmosphere and thinking about what are the things that make up Earth's atmosphere.

Today, the keywords that we will cover in the lesson are atmosphere, composition, precipitation, altitude, and particulates.

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

So you can either pause the video here and read through those sentences, or you might want to pause and make some notes that you can refer back to so you can look up what those keywords mean later on in the lesson.

Today's lesson is split into two parts, so the first part is composition of the atmosphere, and the second part is how does the atmosphere change with altitude? So let's get started on composition of the atmosphere.

The atmosphere is a layer of gas that surrounds a planet, so other planets can have atmospheres too.

And although the atmosphere is largely made of gas, it may contain a small amount of solid and liquid particles too.

So we can see in the diagram there that we've got a picture of Earth and we've got the atmosphere that's surrounding Earth.

And the atmosphere is split into little subsections called the exosphere, thermosphere, mesosphere, stratosphere, and troposphere.

And we can see some of the things that you might find within those parts of the atmosphere.

So in the thermosphere we've got satellites and the Northern Lights.

In the mesosphere, we've got meteors.

We've got weather balloons in the stratosphere.

And then in the troposphere we've got hot air balloons and aeroplanes , although they do sometimes go up into the stratosphere.

And although we split the atmosphere into these different spheres, the atmosphere doesn't have a definite endpoint.

So the atmosphere extends from the surface of Earth, thousands of kilometres up, and there's not a definite point where the atmosphere ends and space begins.

Another interesting thing about the atmosphere is that 98% of the mass of the atmosphere is found really low down in the first 30 kilometres, or about 30 kilometres.

The atmosphere supports life on Earth in many ways, such as providing oxygen for respiration, helping maintain a stable temperature, and blocking harmful cosmic radiation from the sun.

Scientists believe that Earth was formed about 4.

6 billion years ago, so Earth is really, really old.

However, for approximately the last 200 million years, the proportion of different gases in Earth's atmosphere have been much the same as they are today.

And although 200 million years is a really big number, when we think about how old the Earth is, then this is quite a small proportion of time that the gases in the atmosphere have been as they are today.

So this is what the Earth was thought to look like 4.

6 billion years ago.

You can see that it is like an orange red burning hot Earth that was covered in volcanoes.

Then we can see the Earth has changed a lot over the years.

So 2.

3 billion years ago, the Earth was thought to be what we call snowball Earth, where it's covered in a layer of ice.

And then at the bottom we can see the Earth as we know the Earth today.

Time to just check for understanding, so we've got a question here.

For approximately how many years has the atmosphere on Earth contained the same proportion of different gases as it does today? So is it, A, 200 billion years? B, 2 billion years? Or C, 200 million years? And the correct answer is C, 200 million years, so well done if you put answer C.

So what is the atmosphere comprised of? Well, it's about 4/5, so about 80% of our atmosphere is nitrogen gas, with only 1/5, about 20% being oxygen gas.

And then small proportions of other gases, including carbon dioxide, water vapour, and noble gases such as argon.

So we can represent this data in a pie chart like we have below and you can see how much of our atmosphere is nitrogen.

So 80%, a huge percentage of our atmosphere is nitrogen.

And there's 20% there oxygen.

And then all the other gases that make up our atmosphere are only in a really small percentage there.

Life can exist on Earth because of the atmosphere, so the air that we breathe is a mixture of different gases, and we can see this in the diagram below.

So a mixture is something that contains elements or elements and compounds or lots of different compounds, and they are not chemically joined together.

So we can see this in air because we have nitrogen, which has the formula N2, oxygen, which has the formula O2, argon, which has the chemical symbol there Ar, carbon dioxide, which is CO2, and water vapour, so H2O.

So you can see that we've got elements and compounds in air and they are not chemically joined together, so air is a mixture of different gases.

Alright, time for another check.

So air is a mixture of gases.

Name the substance that makes up the largest percentage of air.

Well done if you put B, the correct answer is nitrogen.

What is the percentage of oxygen in Earth's atmosphere? Is it A, 80%? B, 20%? C, 1%? Or D, 0.

04%? So well done if you put B, 20%, so about 1/5 of Earth's atmosphere is oxygen.

Although the atmosphere largely contains gases, it does contain some liquids and solids.

So 99% of water in the atmosphere is water vapour, so we do find it in its gassier state, but the atmosphere does contain water in the liquid and solid states in clouds and precipitation.

So here we've got rain in the atmosphere, so we've got liquid water in the atmosphere.

Snow in the atmosphere.

And also we've got some hail in the atmosphere.

The atmosphere also contains a wide range of solid particulates.

So we've got volcanic ash, that's a particulate.

Salt, so sea water can spray salt.

As waves crash, they spray salt up into the atmosphere.

Pollen and also dust are just some examples of particulates which are found in the atmosphere.

So particulates are very small particles of solids and liquids that are suspended in air.

Human activity has led to increased levels of some particulates in the atmosphere, so burning fossil fuels in particular can produce carbon particulates, so little bit tiny particles of carbon which are released into the atmosphere, reducing the air quality.

So burning wood is an example of where we burn fuels and produce carbon particulates.

Power stations, so again, a place where we burn fossil fuels.

And in our fuels in vehicles.

So time for another check.

So true or false, the Earth's atmosphere is a mixture consisting of gases, liquids, and solids.

Well done if you put true, that is true.

So let's see now if you can choose between these answers to try and justify your answer.

So is it A, the Earth's atmosphere contains only gases, e.

g.

nitrogen, and liquids, e.

g.

water? Or B, the Earth's atmosphere contains gases such as nitrogen, liquids such as water, and solids such as dust? Okay, good job if you put B.

Okay, so the Earth's atmosphere does contain gases, liquids, and solids, and we've got some examples there.

Which of the following is not an example of a solid particulate found in the atmosphere? Okay, well done if you put C, nitrogen.

So nitrogen is found in its gas state in Earth's atmosphere, whereas soot, salt, and dust are all examples of particulates found in the atmosphere.

Right, time to have a go at a practise task.

So what you need to do here is first of all complete the table below to show the percentage composition of different gases in Earth's atmosphere.

Once you've done that, then see if you can work out the percentage of oxygen on Planet X.

Then we've got a couple more questions here, so see if you can describe the differences, so use your table to describe the differences between the composition of the atmosphere on Earth and Planet X.

And finally, Planet X is a hostile planet with no life forms, so give examples of solid particulates which are found on Earth that you do not think you will find on Planet X.

Right, pause the video and have a go at these questions and I'll see you when you're ready to go over the answers.

Well done having a go, let's see how you got on.

So the percentage of nitrogen in the atmosphere on Earth is about 78%.

You've then got oxygen, which is 21%, argon is 1%, and carbon dioxide was the gas that had 0.

04%.

So on Planet X, the atmosphere should, total percentage should be 100, so you should have got an answer of somewhere between 7 and 9%.

So well done if you got those correct.

So question three, describe the differences between the composition of the atmosphere on Earth and Planet X.

Hopefully your answer will include some of this.

So the nitrogen oxygen levels are much higher on Earth than Planet X.

The percentage composition of argon is the same, so that's 1% on both planets.

And the carbon dioxide levels are much lower on Earth, so there are about 0.

04% compared to 65% on Planet X.

And you could have gone one step further to have worked out the difference, so the atmosphere on Planet X contains 64.

96% more carbon dioxide.

And well done if you did actually do some manipulation of the numbers there.

Give examples of solid particulates which are found on Earth that you will not find on Planet X.

So pollen is a good example of a particulate which is formed obviously from living organisms, so we get pollen from plants.

So if Planet X has no life forms, then you're not likely to find any pollen on Planet X.

And humans burn fossil fuels which release carbon particulates into the atmosphere.

So well done if you got pollen or carbon.

Time to move on to the second part of our lesson, which is how does the atmosphere change with altitude? Altitude is the distance above sea level and people can suffer with altitude sickness if they travel to really high altitudes, so we class anything above 2,500 metres above sea level as a high altitude.

So we've got some examples here of where you could travel to a high altitude.

If you went to the top of Mount Everest in Nepal, then that would be a high altitude.

La Paz, which is a mountain in Bolivia, or Mount Kilimanjaro, which is in Tanzania.

Just so you can kind of compare, the highest mountain in the UK is Ben Nevis, and that has an altitude of about 1,345 metres.

So if you travel to the top of Ben Nevis, then you're not classed as being at a high altitude.

Mountain climbers are at risk of developing altitude sickness if they ascend to high altitude too quickly.

So what are some of the symptoms of altitude sickness? So we've got a list here of some of the main symptoms. Obviously there could be many more symptoms that people can suffer from, but the main symptoms include headache, dizziness, feeling sick and feeling exhausted.

And altitude sickness can be life-threatening.

People suffering with altitude sickness who are very unwell need to seek medical help immediately.

And this is why when people travel to high altitudes, they normally carry satellite phones with them, so even when there's no phone signal, they can communicate via satellite.

And if you're suffering from altitude sickness, you're very likely to be advised to travel to a lower altitude if possible and be given oxygen through a mask.

And we've got a picture here of someone receiving oxygen at a high altitude through a mask.

So what do you think causes altitude sickness? The composition of Earth's atmosphere remains the same even at high altitudes such as the top of Mount Everest.

So when you're at the top of Mount Everest, there is still going to be about 21% oxygen in the atmosphere.

However, as altitude increases, the atmosphere becomes less dense, which makes it harder for humans to breathe sufficient oxygen at these high altitudes.

So we've got a diagram here of a mountain, and this is just showing us that at low altitude we've got a high density of air particles and at a high altitude we've got a lower density of air particles.

So let's just check that we've understood that.

Which statements about the atmosphere at high altitudes are correct? Is it A, at the top of Mount Everest, the atmosphere will contain a lower percentage of oxygen than at sea level? B, at the top of Mount Everest, the atmosphere will contain the same percentage of oxygen as at sea level? C, as altitude increases, the atmosphere becomes less dense? Or D, as altitude increases, the atmosphere becomes more dense? And you might find that you choose more than one statement.

Okay, so the correct answers are B and C.

So at the top of Mount Everest, we've got the same percentage of oxygen.

However, the atmosphere becomes less dense.

So well done if you've got both of those correct.

And we have another check for understanding.

What will be the percentage of nitrogen in the air on the top of Mount Kilimanjaro? Will it be A, 80%? B, 65%? Or C, 20%? Well done if you put A.

So the percentage of nitrogen at the top of Mount Kilimanjaro, so at that high altitude, will still be about 80%.

At high altitudes, the air is thinner, which means there are fewer oxygen molecules per volume of air.

So as we've said, the air is less dense at higher altitudes.

So we've got a simulation there of a high altitude and we can see there are fewer oxygen molecules per volume of air.

So the little red balls represent oxygen molecules.

And then at low altitude, we can see that there are more oxygen molecules per volume of air, so the air is more dense.

So now that we understand this, why do you think some athletes train at high altitudes? When athletes train at high altitudes, their bodies need to produce more red blood cells to deliver oxygen to cells for respiration.

So when they're working and they're training and they're exercising, their bodies need more oxygen to be delivered to the cells.

But because the air's less dense, that's more difficult for them.

So how their body compensates is to produce more red blood cells so that the oxygen that's needed is delivered to those cells.

Then this is really good because once they compete back at a lower altitude, this increased number of red blood cells help the athletes to deliver more oxygen to their muscle cells.

Okay, time for another check.

What happens to the number of oxygen molecules per volume of air as the altitude increases? So does the number of oxygen molecules per volume of air increase, decrease, or stay the same? It decreases, so well done if you chose decreases.

Time for our final practise task of today's lesson.

So question one, what you need to do is read the statements below and decide who has correctly described changes in the atmosphere at high altitude.

And once you've decided who is correct, then can you make changes to improve any incorrect comments? If you pause the video now and have a go at that, and I'll see you in a moment to go over the answers.

So here we've got that Andeep and Lucas, both of their statements are correct, so let's see if we can improve Sophia and Laura's statements.

We could improve Sophia's statement by saying, "The percentage composition of gases in the atmosphere is the same at different altitudes." Whereas Sophia had incorrectly said that the percentage of oxygen at high altitudes would be less than 20%.

So Laura kind of got her high and low altitudes the wrong way round, so we could improve her statement by saying, "At higher altitudes, the air pressure decreases and the air is less dense." Well done if you managed to correct Sophia and Laura's statements.

Right, final question of this task is explain why mountaineers carry oxygen cylinders and masks with them when hiking to the top of Mount Everest.

And your answer must include the following keywords, so altitude, dense, oxygen, air, and volume.

Good luck, I'll see you in a moment to go through your answer.

So your answer may include the following.

"Mountaineers carry oxygen cylinders when climbing to the top of Mount Everest because as the altitude increases, the air becomes less dense.

This means there will be less oxygen molecules per volume of air and the mountaineers will not receive sufficient oxygen unless they use oxygen masks." Let's summarise what we've learned about in today's lesson.

The atmosphere comprises about 80% nitrogen and 20% oxygen and then it has small proportions of other gases including carbon dioxide, water vapour, and noble gases such as argon.

The atmosphere contains water mainly in its gas state, but in its liquid or solid states in clouds and precipitation.

The atmosphere also contains a wide range of solid particulates.

And the atmosphere thins out with height, which makes it harder for humans to breathe sufficient oxygen at high altitude.

Well done in today's lesson, you've worked really hard.

I've enjoyed learning with you and I look forward to seeing you again soon.