Lesson video

Hello, I'm Mrs. Adcock and welcome to today's lesson.

Today we are going to be looking at atmospheric pollutants.

So we are going to look at the pollutants that are in our atmosphere, how they are made, and the problems associated with these pollutants.

We're also then going to look at what can we do to reduce the levels of these pollutants in our atmosphere.

Let's have a look at what our outcome for today's lesson is.

I can describe how pollutants can be produced by impurities in fuels and by incomplete combustion.

Some of the key words that we are gonna cover in today's lesson include pollutant, carbon monoxide, soot, catalytic converter, and catalyst.

Here you can see those keywords written in a sentence, so you might like to pause the video here and just read through those statements, or you might like to make a note of them so that you can refer back to them later on in the lesson.

Today's lesson on atmospheric pollutants is split into four main parts.

So the first part of today's lesson is on pollutants in the atmosphere.

Then we're going to look at some of the problems associated with those pollutants.

Then we're going to look at catalytic converters, so what they are and how they help reduce pollutants in the atmosphere.

And our final part of today's lesson is on using hydrogen fuel as an alternative fuel.

Right, let's get started on pollutants in the atmosphere.

Often we consider pollution as the unwanted components of air that we can see, so such as car fumes, or smog-laden cities, and smoke.

So you can see images there where we can see the pollution.

So we can see the pollutants coming from car exhaust.

We can see Paris there that's covered in the layer of smog.

And we can see the smoke coming from an industrial chimney.

The air is polluted with many harmful particles that are not visible to the human eye, which we are inhaling all the time.

Pollutants can be from natural sources, so such as volcanoes, or manmade, such as from power stations.

And we can see images there.

The first one is of a volcano erupting and there will be pollutants such as ash being emitted into the atmosphere.

And in the second image of a power station, we can see that there are emissions coming from the chimneys into the atmosphere.

The World Health Organisation estimated in 2019 that 99% of the world's population is living in places where the World Health Organisation air quality guideline levels are not being met.

Let's just have a check for understanding.

Which statement about pollutants is false? Is it A, pollutants can be natural such as volcanic ash, B, pollutants can be manmade such as sulphur dioxide from power stations, or C, all pollutants are visible to the unaided human eye? Well done if you chose option C.

Not all pollutants are visible, so this statement is false.

A is correct because pollutants can be natural, and B is correct because pollutants can be manmade such as sulphur dioxide from power stations.

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

There's two questions here for you to answer.

Question one, state two manmade sources of atmospheric pollutants.

And question two, can you name a natural source of atmospheric pollutants? If you pause the video now, have a go at answering those two questions and I'll see you when you're ready to go over the answers.

Question one, state two manmade sources of atmospheric pollutants.

Your answer may have included car exhaust fumes or smoke from industrial plants or power station emissions.

And question two, name a natural source of atmospheric pollutants.

Your answer may have included volcanoes or you might have thought of forest fires as well, or maybe you've thought of something different.

So well done if you've answered both of those questions correctly.

Time for us to move on to the second part of our lesson, which is on the problems associated with pollutants.

Carbon dioxide, which has the molecular formula CO2, is a pollutant produced during complete combustion reactions.

So complete combustion reactions are when we burn a fuel in a plentiful supply of oxygen so the fuel burns fuller.

And carbon dioxide is a greenhouse gas which contributes to global warming.

There we can see the general formula for complete combustion.

So we have a fuel and we react to that with oxygen and that will produce carbon dioxide and water.

And as we've just seen, carbon dioxide is a pollutant that contributes to global warming.

Carbon monoxide, which has the molecular formula CO, and carbon particulates, which are unburnt particles of carbon, so that has the formula C, are pollutants produced during incomplete combustion reactions.

And incomplete combustion reactions are where our fuel burns in a limited supply of oxygen.

There is an example there of an incomplete combustion reaction where our fuel reacts with oxygen to produce carbon, so our carbon particulates, plus carbon monoxide and water.

What's wrong with producing carbon monoxide? Well, carbon monoxide is also a pollutant, and carbon monoxide is a colourless, odourless, toxic gas.

If there was carbon monoxide in the room with you now, you wouldn't know because it's colourless, so you wouldn't be able to see it.

It's odourless, so you wouldn't be able to smell it.

But if you inhale carbon monoxide, then it will diffuse from your lungs into your blood and there it will bind irreversibly to the haemoglobin in your red blood cells and therefore those red blood cells will not be able to carry as much oxygen around the body.

So if you inhale carbon monoxide, it can result in fainting, coma, and even death.

You may have seen these before.

This is a carbon monoxide alarm and carbon monoxide alarms save lives because they can detect if there's carbon monoxide in the room, which obviously we wouldn't know ourselves because it's colourless and an odourless gas.

Carbon particulates, which are produced during incomplete combustion reactions, and also known as soot because they are unburnt particles of carbon, can have a negative impact on human health.

So these are another type of pollutant.

Exposure to particulates has been linked with respiratory problems and heart disease.

There have been some recent studies that have shown that carbon particulates may even be linked with brain disease, but more research is needed on this.

Carbon particulates and unburnt hydrocarbons, which have been released into the atmosphere, also cause global dimming, and we can see an image there showing global dimming.

And this is where less sunlight reaches the Earth's surface.

Let's have a go at question.

What is the impact of increased levels of carbon dioxide in the atmosphere? Is it A, global warming, B, respiratory problems, C, global dimming, or D, death due to inhaling toxic gas? Well done if you chose option A.

Carbon dioxide is a greenhouse gas released during complete combustion reactions and it leads to global warming.

What is the impact of increased levels of carbon particulates, or soot, in the atmosphere? So do carbon particulates lead to A, global warming, B, respiratory problems, C, global dimming, D, death due to inhaling toxic gas? There may be more than one answer for the impact of carbon particulates.

The correct answers are B, respiratory problems, and C global dimming.

So well done if you were able to correctly identify both of those as problems associated with carbon particulates in the atmosphere.

Global warming is due to increased levels of carbon dioxide and hopefully you were able to identify that D, so death due to inhaling this toxic gas, is linked with carbon monoxide in the atmosphere.

We're going to look at a couple of other pollutants now and the problems associated with these.

So sulphur dioxide, which has the molecular formula SO2, so di means two, so two oxygens, so sulphur and two oxygens, is a pollutant produced from the combustion of fuels which contain sulphur impurities.

So if we are burning a hydrocarbon fuel but it is impure and contains some sulphur atoms, then these can react with oxygen in the atmosphere and we will produce this pollutant, sulphur dioxide.

Sulphur dioxide can react with oxygen and water in the atmosphere to produce acid rain, and there's an image there showing acid rain.

Oxygen and nitrogen are both present in Earth's atmosphere, so oxygen is present at about 21% and nitrogen at about 78%.

So these are making up a huge percentage of the Earth's atmosphere and they don't normally react together.

However, they do react together at high temperatures such as in a car engine to produce oxides of nitrogen.

So oxides of nitrogen might be nitrogen monoxide and nitrogen dioxide.

So nitrogen monoxide has the molecular formula NO, and nitrogen dioxide has the molecular formula NO2, and we refer to these as a whole as oxides of nitrogen, or nitrogen oxides.

We've got an example reaction there, where nitrogen and oxygen, both present in the atmosphere, can react together at high temperatures to produce nitrogen monoxide.

And these oxides of nitrogen, which we give the molecular formula, NOX, can cause respiratory problems in humans and react with oxygen and water to produce acid rain.

Time for another check.

Increased amounts of sulphur dioxide in the atmosphere causes A, respiratory problems, B, global dimming, C, acid rain, or D, global warming? So well done if you chose C, acid rain.

So sulphur dioxide is produced when we have impurities in fuels, so they contain sulphur, they react with the oxygen, and produce sulphur dioxide which can cause acid rain.

Increased amounts of oxides of nitrogen in the atmosphere may lead to A, respiratory problems, B, global dimming, C, acid rain, or D, global warming? So well done if you were able to identify that oxides of nitrogen may lead to respiratory problems as well as C, acid rain.

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

So you need to complete the table below.

In the first column, you're going to complete the pollutant names.

In the second column, you need to fill in the pollutant formulas.

And in the final column, the problem associated with each of those pollutants.

If you pause the video now, have a go at filling in the table and then come back when you're ready to go over the answers.

Well done for getting your table completed.

For the first row, you should have put carbon monoxide, and that has the pollutant formula CO.

A possible answer is that it's a toxic gas which can cause death.

In the second row you should have carbon dioxide, CO2, and that's a greenhouse gas which contributes to global warming.

Carbon particulates have the formula C, and the problem associated with this is respiratory problems and global dimming.

Sulphur dioxide has the formula SO2, and the problem with sulphur dioxide is it can cause acid rain.

And nitrogen oxides have the formula NOX, and these can cause acid rain and respiratory problems. Well done if you were able to complete the name of the pollutants, the formula of those pollutants, and the problems associated with each of those pollutants.

For the second part of this task, we need to complete the following question.

Car engines use fossil fuels, so such as petrol or diesel, which naturally contain carbon, hydrogen and sulphur atoms. The fuel combusts in a plentiful supply of oxygen at high temperatures inside the car engine.

Predict the atmospheric pollutants that may be produced and give equations for the pollutants produced.

Think about the atoms that were contained in that fuel.

Think about whether it combusts by incomplete or complete combustion.

And think about the impacts of the high temperature inside the car engine.

If you pause the video now, have a go at answering question two and come back when you're ready to go over the answer.

Let's go over the answer to question two.

Now you may have answered this in a different order, but hopefully you've got the key points in your answer.

Complete combustion of the fuel, because we had a plentiful supply of oxygen, will produce carbon dioxide.

The fuel contains some sulphur atoms which will react with oxygen to produce sulphur dioxide.

At high temperatures inside the car engine, nitrogen and oxygen may react to produce oxides of nitrogen.

If we have a look at the equations for the pollutants being produced, you may have given fuel plus oxygen will react to make carbon dioxide plus water.

The sulphur and oxygen atoms can react to produce sulphur dioxide, and nitrogen and oxygen in the atmosphere will react to produce nitrogen monoxide.

Well done if you were able to identify the pollutants that may be produced and write equations for those reactions.

We have looked at sources of pollutants in the atmosphere and problems associated with some pollutants.

What we're now going to do is move on to our third part of our lesson on catalytic converters.

Scientists are constantly working to reduce air pollution and most cars are now fitted with catalytic converters.

And there's an image there showing a catalytic converter which is fitted to the exhaust system of a car.

A catalytic converter is a device fitted to the car's exhaust, which reduces the amount of harmful pollutants entering the atmosphere.

Catalytic converters reduce the amount of carbon monoxide and oxides of nitrogen being released into the atmosphere, and they convert these pollutants into carbon dioxide and nitrogen.

We can have a look at those reactions there.

So carbon monoxide and nitrogen monoxide, which are produced in the car engine, can react in the catalytic converter to produce carbon dioxide and nitrogen.

And we've got a word and a balanced symbol equation for that reaction.

Now you might be thinking, well, we had carbon monoxide, which is a pollutant, and nitrogen monoxide, which is pollutant, and we react to those together, but we're still producing carbon dioxide, which as we've seen earlier in the lesson, is a greenhouse gas that can contribute to global warming.

However, carbon dioxide is less harmful to humans than toxic carbon monoxide and oxides of nitrogen.

Catalytic converters have a honeycomb structure which increases the surface area and this large surface area is covered in rhodium and platinum.

Rhodium and platinum are catalysts and they speed up the rate of reaction inside the hot catalytic converter without being used up themselves.

We've got an image there showing the honeycomb structure inside a catalytic converter, and like we've just seen, that would be covered in rhodium and platinum.

And then the gases will come from the engine, pass through our catalytic converter, where the nitrogen monoxide and carbon monoxide will react to produce carbon dioxide and nitrogen.

The rate of that reaction is increased by having those catalysts present.

We then have the gases released from the exhaust, which contain less pollutants than the gas that came from the engine that entered the catalytic converter.

Catalytic converters reduce the amount of which gases released from car exhausts? So which two gases enter the catalytic converter and have their levels reduced because they react together to form other products? So is it A, carbon monoxide, B, carbon dioxide, C, nitrogen monoxide, or D, nitrogen? So well done if you chose carbon monoxide and nitrogen monoxide.

these react together to produce carbon dioxide and nitrogen and it's the carbon dioxide and nitrogen that then leave the catalytic converter and enter the atmosphere.

For our third practise task, we've got a couple of questions.

Question one, rhodium and platinum are catalysts used in catalytic converters.

So what is a catalyst? Question two, complete the word equation to show what happens inside a catalytic converter.

If you pause the video here and then come back when you're ready to go over the answer.

Welcome back.

Hopefully you were able to define a catalyst as a chemical that speeds up the rate of reaction without itself being used up.

And to complete the word equation of what happens inside the catalytic inverter, we should have had carbon monoxide plus nitrogen monoxide and they react together to produce carbon dioxide plus nitrogen.

So well done if you got those correct.

We're going to move on to the final part of our lesson, which is looking at using hydrogen fuel as an alternative fuel to try and reduce the amount of pollutants in the atmosphere.

Hydrogen is an alternative fuel which can be used instead of petrol and diesel to reduce air pollution.

And the advantages of using hydrogen fuel instead of petrol are it releases more energy per kilogramme of fuel, and it only produces water when combusted.

We can see the reaction there.

Hydrogen, so that's our fuel, reacts with oxygen in the air to produce just water as the product.

Whereas when we combust petrol, we get carbon dioxide, which is a greenhouse gas.

Underneath, we can see the balanced symbol equation.

So two hydrogen molecules react with one oxygen molecule to produce two molecules of water.

The disadvantages of using hydrogen fuel instead of petrol are that the manufacture of hydrogen uses large amounts of energy and could release carbon dioxide into the atmosphere depending on how that hydrogen gas has been produced.

The storage of hydrogen gas also creates difficulties because it can be dangerous, as hydrogen needs to be stored in highly pressurised containers.

And these are some of the hazard symbols that you will see on hydrogen gas.

It's extremely flammable and the gas is stored under high pressure.

Which of the following is an advantage of using hydrogen fuel in cars? Is it A, the manufacture of hydrogen requires lots of energy, B, it only produces water when combusted, or C, it needs to be stored in highly pressurised containers? Well done if you chose option B, hydrogen fuel when combusted only produces water.

So this is an advantage of using hydrogen fuel.

A is a disadvantage because it requires lots of energy in the manufacture of hydrogen, and C is another disadvantage of using hydrogen fuel in that the difficulties of storing it in highly pressurised containers.

For the final practise task of today's lesson, you need to describe one advantage and one disadvantage of using hydrogen as an alternative fuel in cars.

Pause the video here, have a go at answering that question, and then come back when you're ready to go over the answer.

Your answer may include, for the advantages, it releases more energy per kilogramme of fuel and the only product is water.

And for the disadvantages, you may have written one of these answers.

It needs highly pressurised containers to store the fuel.

The manufacture of hydrogen uses large amounts of energy, and it can produce carbon dioxide, which obviously is a pollutant.

Time for us to summarise the key points that we have covered in today's lesson on atmospheric pollutants.

Carbon monoxide, which is produced during incomplete combustion reactions, is a toxic gas that's both odourless and colourless.

Carbon particulates, which are also produced during incomplete combustion reactions, they contribute to health issues and global dimming.

Sulphur dioxide, which is produced when a fuel contains impurities of sulphur, and nitrogen oxides, are formed through burning fuels and they can both form acids in water so they contribute to acid rain.

Catalytic converters help complete combustion reactions by turning that carbon monoxide into carbon dioxide and the removal of nitrogen monoxide from exhaust gases.

And hydrogen can be used to fuel in cars and that has both its advantages and disadvantages.

Well done for all your hard work in today's lesson on atmospheric pollutants.

I hope you've enjoyed the lesson and I look forward to seeing you again soon.