Earth and atmosphere

Question 1

The atmosphere is a mixture of __ .

Answer 1

gases

Question 2

The atmosphere is mostly __ (approximately 80%) and __ (approximately 20%). The remaining gases are found in much smaller proportions, such as carbon dioxide and water vapour.

Answer 2

nitrogen

oxygen

Question 3

__ in the atmosphere is essential for all living things to stay alive, and for the combustion (burning) of fuels.

Answer 3

Oxygen

Question 4

What do the following substances have in common?

Nitrogen, carbon dioxide, hydrogen, oxygen, hydrogen, helium.

Answer 4

They are all gases.

Three of them are found in the Earth’s atmosphere in noticeable amounts – read on to find out which ones.

Question 5

Which two gases make up around 99% of the Earth’s atmosphere?

Answer 5

Nitrogen and oxygen.

The atmosphere is made up of 78% nitrogen (N₂) and 21% oxygen (O₂).

Question 6

Which gas makes up around 1% of the atmosphere?

Answer 6

Argon (Ar).

Question 7

All living things on Earth, including humans, use oxygen from the atmosphere for __ to stay alive.

Answer 7

respiration

Question 8

__ is the chemical process that occurs inside cells to release energy from glucose when it reacts with oxygen.

Answer 8

Respiration

Question 9

Word equation for respiration

Answer 9

Glucose + oxygen → carbon dioxide + water

Question 10

Plants and some bacteria use carbon dioxide from the atmosphere for __ .

Answer 10

photosynthesis

Question 11

Photosynthesis is the chemical process when carbon dioxide and water react together, in the presence of light and __ , to produce glucose and oxygen.

Answer 11

chlorophyll

Question 12

Word equation for photosynthesis

Answer 12

Carbon dioxide + water → glucose + oxygen

Question 13

What is the name of the process that takes place inside the cells of living things and releases energy from glucose in the presence of oxygen from the atmosphere?

Answer 13

Respiration.

Question 14

Combustion happens when a fuel is __ and reacts with oxygen to __ useful energy.

Answer 14

heated

release

Question 15

For combustion to occur, there needs to be a fuel, heat and oxygen. This is represented by the __.

Answer 15

fire triangle

Question 16

If one side of the fire triangle is removed, __ cannot happen.

Answer 16

combustion

Question 17

In most situations, the oxygen for combustion comes from the __ .

Answer 17

atmosphere

Question 18

Human activities - like burning fossil fuels - over the past 200 years have increased the amount of __ in the atmosphere, thickening the earth’s layer of __ . As a result, the earth has been getting hotter. This is known as __ .

Answer 18

carbon dioxide
greenhouse gases
global warming

Question 19

Which of the following is not a fuel?

Methane, carbon dioxide, wood, petrol.

Answer 19

Carbon dioxide is not a fuel. It is produced when many fuels burn.