GCSE · Chemistry · AQA · Spec 8462

Properties and effects of atmospheric pollutants

Black smoke looks like the obvious villain, but one of the most dangerous pollutants has no colour and no smell. Which pollutant causes which problem?

What do you think?

Can you spot polluted air?

You walk into a room. There is no smoke, no haze and no smell.

Which of these is closest to what you think about the air in that room?

Air pollution is the smoke and smog you can see. If the air looks clear, it is clean.If a gas were harmful, I would smell it. No smell means it is safe.Many harmful pollutants are invisible gases. Carbon monoxide has no colour and no smell, and it is extremely toxic.

How sure are you?

I'm sureI think soI'm guessing

Air pollution is the smoke and smog you can see. If the air looks clear, it is clean.

This is a common misconception

Smoke and smog are only the visible kind of air pollution. Many harmful pollutants are invisible gases, so clear-looking air tells you very little.

If a gas were harmful, I would smell it. No smell means it is safe.

This is a common misconception

Your nose is not a pollution alarm. Carbon monoxide is colourless and odourless, and it is extremely toxic, so a harmful gas can be present with nothing to see or smell.

Many harmful pollutants are invisible gases. Carbon monoxide has no colour and no smell, and it is extremely toxic.

This matches the evidence

Spot on. That is why carbon monoxide is so hard to detect: nothing about it tells you it is there.

You cannot judge air by looking or sniffing. Carbon monoxide is colourless, odourless and extremely toxic, so it can harm you without any warning.

How carbon monoxide harms the body

Step through the route from the air in the room to the harm to the person.

Breathed inA person breathes in air containing carbon monoxide. It is colourless and odourless, so nothing warns them.
Diffuses into the bloodThe carbon monoxide diffuses into the blood.
Oxygen is not availableOxygen is no longer available to the respiring cells, so the cells are starved of oxygen.
Harm to the personThis can cause fainting, coma and death.

Predict, then check

Commit to an answer before you look. Soot is made of tiny particles in the air.

More soot particles are in the air above a city. What happens to the sunlight that reaches the ground below?

Now you explain

Acid rain in your own words

Burning fuels that contain sulfur releases sulfur dioxide, and engines release oxides of nitrogen. Explain how these gases can lead to acid rain, and why acid rain is a problem. [4 marks]

Your answer

0 words · your answer stays on this page and is not sent anywhere.

The mark scheme

The gases react with oxygen and water in the atmosphere to form acids. (1 mark)
The acids fall as acid rain. (1 mark)
Acid rain harms living organisms. (1 mark)
Acid rain reacts with limestone buildings and erodes them. (1 mark)

Model answer

Sulfur dioxide and oxides of nitrogen react with oxygen and water in the atmosphere to form acids. These acids fall as acid rain. Acid rain is a problem because it harms living organisms, and it reacts with limestone buildings and erodes them.

Two steps for the cause (react to form acids, then fall as rain) and two for the problem (living organisms, limestone). Four marks, four ideas.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Four pollutants, five big problems, and one gas that gives you no warning at all.

What you need to know

Carbon monoxide is colourless, odourless and extremely toxic. It is hard to detect and can cause death.
Soot can cause respiratory problems and heart disease, and it causes global dimming.
Sulfur dioxide and oxides of nitrogen both cause acid rain, and both can cause lung irritation and respiratory illness.
Acid rain harms living organisms and erodes limestone buildings.

The big picture

Carbon monoxide, soot, sulfur dioxide and oxides of nitrogen each cause particular problems, and some problems have more than one cause. Carbon monoxide takes oxygen's place on haemoglobin, soot causes global dimming, and sulfur dioxide and oxides of nitrogen make acid rain.

Key points

1Many harmful pollutants are invisible gases, so clear-looking air is not proof of clean air.

2Carbon monoxide binds with haemoglobin in red blood cells in place of oxygen, so cells are starved of oxygen.

3Soot absorbs light and reflects light back into space, so less sunlight reaches the surface: global dimming.

4Sulfur dioxide and oxides of nitrogen react with oxygen and water in the atmosphere to form acids, which fall as acid rain.

5Acid rain harms living organisms and reacts with limestone buildings, eroding them.

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Worked example

Problem

A safety leaflet describes a gas with no colour and no smell. It says that breathing it in can cause fainting, coma and even death. Which of the four pollutants is it, and why can people not simply notice it is there?

⚠ Watch out

Thinking air pollution is only the smoke and smog you can see. Many harmful pollutants are invisible gases, and carbon monoxide is colourless, odourless and extremely toxic.

🧠

Memory hook

Carbon monoxide is the silent seat-thief: colourless, odourless, and it steals oxygen's seat on haemoglobin. And soot is the sun-blocker: soot in the sky, less sun below.

✓

Check yourself

Without looking back: which two pollutants make acid rain, and which pollutant takes oxygen's place on haemoglobin?

Flashcards

(12)

Why can't you rely on your eyes and nose to spot dangerous air?

Many harmful pollutants are invisible gases. Carbon monoxide is colourless, odourless and extremely toxic, so it is hard to detect.

What does carbon monoxide do to the blood?

It diffuses into the blood and binds with haemoglobin in the red blood cells, in place of oxygen.

Why are cells starved of oxygen in carbon monoxide poisoning?

Because the haemoglobin is carrying carbon monoxide, oxygen is no longer available to the respiring cells.

What can carbon monoxide poisoning do to a person?

Cause fainting, coma and death.

Name the three problems soot can cause.

Respiratory problems, heart disease and global dimming.

What is global dimming, and how does soot cause it?

Less sunlight reaches the Earth's surface, because soot particles absorb light and reflect light back into space.

Which two pollutants cause acid rain?

Sulfur dioxide and oxides of nitrogen.

Apart from acid rain, what else do sulfur dioxide and oxides of nitrogen cause?

Lung irritation, which can lead to respiratory illness.

How do sulfur dioxide and oxides of nitrogen end up as acid rain?

They react with oxygen and water in the atmosphere to form acids, and the acids fall as acid rain.

How does acid rain affect living things?

It harms living organisms.

Why does acid rain damage limestone buildings?

It reacts with the limestone and erodes it.

Which problems have more than one pollutant behind them?

Acid rain (sulfur dioxide and oxides of nitrogen) and respiratory problems (soot, sulfur dioxide and oxides of nitrogen).

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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Properties and effects of atmospheric pollutants

Who causes what?

Can you spot polluted air?

Acid rain in your own words

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