Lesson video

Hello, I am Mrs. Adcock, and welcome to today's lesson on atmospheric carbon.

Today, we are going to be thinking about: What causes carbon dioxide levels in the atmosphere to increase, and how are these increasing levels of carbon dioxide leading to global warming? Today's lesson outcome is: I can describe how too much carbon dioxide affects Earth's atmosphere and is leading to global warming.

Some of the key words we will be using in today's lesson include carbon dioxide, atmosphere, greenhouse gas, and global warming.

Here, you can see those keywords written in a sentence.

You might like to pause the video here and read through those sentences.

It would be a good idea, too, to make some notes so that you can refer back to them later in the lesson if needed.

Today's lesson on atmospheric carbon is split into two parts.

We are firstly going to focus on combustion of fuels, and then we're going to move on to look at a greenhouse gas.

Let's get started on the first part of our lesson on combustion of fuels.

Natural gas, coal, and crude oil are all fossil fuels.

Fossil fuels are non-renewable because they are being used at a faster rate than they are produced.

It takes millions of years to produce fossil fuels.

Fossil fuels contain hydrocarbons, and hydrocarbons are molecules made of hydrogen and carbon atoms only.

Some examples of hydrocarbons include methane, and methane has the molecular formula CH4, so it contains carbon and hydrogen atoms only.

So it's a hydrocarbon.

Ethane is another example of a hydrocarbon.

It has the molecular formula C2H6, so it's two carbon atoms and six hydrogen atoms in a molecule of ethane.

And propane has the molecular formula C3H8.

It's three carbon atoms and eight hydrogen atoms, and they are all chemically bonded together.

So we can see three examples of hydrocarbons there.

There are many different hydrocarbons that exist, but they all contain only hydrogen and carbon atoms and you find these hydrocarbons in fossil fuels.

Which of the following are hydrocarbons? Is it A, methane, that has the molecular formula CH4; B, ethane, which is C2H6; C, propanol, which is C3H7OH; or D, butene, which is C4H8? Now, there may be some molecules here which are unfamiliar to you.

You are just trying to identify any that are hydrocarbons.

There may be more than one answer, so choose any that you think are correct.

The correct answer is A, methane; B, ethane; and D, butene.

These all are hydrocarbons because they only contain hydrogen and carbon atoms. Propanol is not a hydrocarbon because that contains an atom of oxygen.

So, well done if you were able to identify the hydrocarbons there.

Humans burn fossil fuels to provide energy.

Some examples of where we burn fossil fuels include in cars, we are burning petrol and diesel.

And by burning, we mean we are reacting them with oxygen.

And in this reaction, energy is released.

We also burn fossil fuels when we burn gas to cook our food, and also in some power stations when we generate electricity.

Can you think of any other examples of where we burn fossil fuels? You may have thought of some other examples, such as when we burn fossil fuels in other vehicles, like lorries, aeroplanes , and ships, but also we burn fossil fuels for heating.

Burning is scientifically known as combustion.

And combustion requires three things, and these are shown in the fire triangle below.

So we need a fuel.

This will react in a supply of oxygen, and to get this reaction going, we need a heat source.

So heat, fuel, and oxygen are all required for combustion.

Time for a question.

What three things are required for combustion? Is it A, fuel, heat, and oxygen; B, fuel, heat, and carbon dioxide; or C, fuel, water, and oxygen? The correct answer is A.

The three things needed for combustion are fuel, heat, and oxygen.

So well done if you choose A and got that question correct.

What happens when a fuel combusts? We can see in our diagram there we've got a hydrocarbon, and that's reacting with oxygen to produce carbon dioxide and water.

So the carbon and hydrogen atoms from our fuel, which is a hydrocarbon, they react with oxygen atoms from the air.

So we have O2 present in our air, and this reacts with our hydrocarbon in a combustion reaction.

Carbon dioxide and water are produced, and the formula for carbon dioxide is CO2.

So carbon atoms from the fuel combine with oxygen atoms from the air to make carbon dioxide, and hydrogen atoms from the fuel react with and combine with oxygen atoms from the air to produce water that has the formula H2O.

The general equation for the combustion of a fuel is fuel plus oxygen react together to produce carbon dioxide and water.

The things we start with in our reaction are known as the reactants, and our reactants in combustion are fuel and oxygen, and the things that we produce in our reaction are called the products, and the products of combustion are carbon dioxide and water.

The products of combustion, water and carbon dioxide, are both compounds, and a compound is a substance that contains two or more different elements chemically joined together.

We've got a model there of carbon dioxide, and the formula of carbon dioxide is CO2, and that's because carbon dioxide is made from one carbon atom and two oxygen atoms. Water is also a compound.

It's made of two different elements, hydrogen and oxygen.

It has the molecular formula H2O, and it's made from two hydrogen atoms and one oxygen atom.

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

What you need to do here is firstly label the fire triangle showing the three things needed for combustion, and then secondly, complete the equation to show the products of combustion.

If you pause the video now, have a go at Question 1 and 2, and then we will move on to the next part of this task.

For the final part of this task, you need to complete the table stating the number of atoms of each element present in the compounds.

The compounds are C2H6, CH4, H2O, and CO2.

The first row has been completed for you as an example.

So the compound is C2H6, and you have to say the number of atoms of each element.

So C2H6 has two carbon atoms and six hydrogen atoms. See if you can complete the table for the other compounds.

Pause the video now, have a go at completing this task, come back when you're ready to go over the answers to this first task.

Question 1, label the fire triangle showing the three things needed for combustion.

You should have had oxygen, heat, and fuel.

And it doesn't matter where you've written those on your triangle, so long as you've included the three things needed for combustion and complete the equation to show the products of combustion.

So we have fuel and oxygen.

They are our reactants, and they react together to produce carbon dioxide and water.

And again, it doesn't matter if you've written those the other way around.

You might have written water plus carbon dioxide, so long as you have correctly identified the two products of combustion.

Question 3, complete the table stating the number of atoms of each element present in the compounds.

CH4 has one carbon atom and four hydrogen atoms, H2O has two hydrogen atoms and one oxygen atom, and CO2 has one carbon atom and two oxygen atoms, so well done if you got those correct.

We have looked at the combustion of fuels and seen that carbon dioxide is one of the products when we combust fuels.

We're now going to move on to have a look at a greenhouse gas.

The combustion of fossil fuels by humans has led to increased levels of carbon dioxide in the atmosphere.

And atmosphere is one of our keywords from today's lesson.

So the atmosphere is the layer of gas that surrounds the planet.

Carbon dioxide levels are 50% higher than they were before the Industrial Revolution.

We can see here we've got an image of an industry, and it says, "Carbon dioxide produced by industries burning fossil fuels." And the current levels of carbon dioxide in the atmosphere are about 0.

04%.

What is the percentage of carbon dioxide in the atmosphere? Is it A, 20%; B, 1%; or C, 0.

04%? The correct answer is C.

There is 0.

04% carbon dioxide in the atmosphere, so well done if you identified that one correctly.

A is 20%.

There is 20% oxygen in our atmosphere.

And B, 1%, there's 1% argon in the atmosphere.

Carbon dioxide, which has the molecular formula CO2, exists naturally in the atmosphere, but as the graph shows, its levels have increased in recent years.

We can see as the years have gone by, the amount of carbon dioxide, which is measured in parts per million, in the atmosphere have increased.

And this is since records began in 1958.

Carbon dioxide is a greenhouse gas.

What do greenhouse gases in the atmosphere do? Greenhouse gases absorb infrared radiation, and we're gonna have a look at the impact this has now.

We've got a diagram and we can see the Sun, and the Sun is emitting infrared radiation.

And at the bottom of the diagram, we've got the Earth.

And around the Earth is the Earth's atmosphere, and in the atmosphere is the greenhouse gases.

Infrared radiation from the Sun is absorbed at the Earth's surface and then radiated from the Earth's surface.

And when it's radiated from the Earth's surface, the infrared radiation is of a different wavelength.

This infrared radiation that has been radiated from the Earth's surface is absorbed by greenhouse gases, preventing it from escaping into space.

What do greenhouse gases do? Do they A, absorb infrared radiation? And we shortened infrared to IR.

Do they B, produce carbon dioxide? Or do greenhouse gases, C, emit ultraviolet radiation? And ultraviolet has been shortened to UV.

What do greenhouse gases do? Greenhouse gases absorb infrared radiation that has been radiated from the Earth's surface.

Well done if you chose option A.

Infrared radiation emitted from Earth is trapped by those greenhouse gases in the atmosphere.

And increased levels of greenhouse gases, such as carbon dioxide, which has been produced from the combustion of fossil fuels, means that more radiation is being trapped.

This leads to an increase in global temperatures.

This is known as global warming.

And the Earth's average global temperatures have risen by about 0.

2 degrees Celsius every 10 years since 1980.

So as we have increased the combustion of fossil fuels, we have produced more carbon dioxide, and that increased carbon dioxide means more infrared radiation is trapped, and therefore global temperatures are increasing.

This data collected by NASA shows that global temperatures are increasing, and we can see here we've got the year and temperature anomaly in degrees Celsius.

Now, temperature anomaly is the difference between current data and an average of the previous 30 years.

So if we look where it says 0 on the temperature anomaly scale, that's the average temperature for the previous 30 years.

For the last 45 years, global temperatures have been increasing.

Time for a question to check for our understanding.

What impact does increasing levels of greenhouse gases have on global temperatures? Is it A, global temperatures decrease; B, global temperatures stay the same; or C, global temperatures increase? So as we increase the level of greenhouse gases, such as carbon dioxide, what impact does this have on global temperatures? The correct answer is C.

So as we have increased levels of greenhouse gases, such as carbon dioxide, then we have more infrared radiation being trapped, and global temperatures increase.

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

First of all, you need to describe what the graph shows.

The graph is showing us the year on the x-axis, and we can see the amount of carbon dioxide in the atmosphere measured in parts per million on the y-axis.

And you need to describe what this graph is showing.

When you describe a graph, you will often mention whether there has been an increase, decrease, or whether something has stayed the same.

So look carefully at that graph and have a look what is happening to the amount of carbon dioxide in parts per million over the years.

Pause the video now and have a go at answering Question 1.

Question 1, describe what the graph shows.

The graph shows that since 1960, the amount of carbon dioxide measured in parts per million in the atmosphere has steadily increased.

For the second part of this task, you need to rearrange the statements to explain how greenhouse gases cause global warming.

So pause the video now, read through those statements, then rearrange them so they're in the correct order to explain how greenhouse gases cause global warming.

Come back when you're ready to go over the answer.

These statements have now been moved into the correct order.

So you should have infrared radiation from the Sun passes through Earth's atmosphere.

Infrared radiation is absorbed at Earth's surface.

Infrared radiation is then emitted from Earth's surface.

Greenhouse gases absorb the infrared radiation and prevent it from escaping to space.

The trapped infrared radiation leads to global warming.

Well done if you are able to rearrange those statements into the correct order.

You've clearly got a good understanding of how the greenhouse gases cause global warming.

We have now reached the end of today's lesson, but we are going to summarise some of the key points that we have covered in our lesson on atmospheric carbon.

When fuels containing carbon are burned, it is common for carbon dioxide to be made.

Carbon dioxide is a compound with molecules that each contain one carbon atom and two oxygen atoms. So carbon dioxide has the molecular formula CO2.

Less than 1% of Earth's atmosphere is carbon dioxide.

So we saw today that it's about 0.

04%.

Carbon dioxide is a greenhouse gas, and greenhouse gases absorb infrared radiation that has been radiated from Earth's surface.

In the atmosphere, some gases are greenhouse gases and have properties that enable its temperature to rise over time.

So we discussed how the greenhouse gases trap that infrared radiation and stop it from escaping into space, and this leads to rises in global temperatures known as global warming.

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

I've really enjoyed the lesson.

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