2: The Atmosphere

Question 1

What are natural resources?

Answer 1

Natural resources are useful materials that come from the Earth. Humans have found many ways to make use of the resources from the atmosphere, the ocean, and the crust of the Earth to meet their needs.

Question 2

List all layers of the atmosphere from low to high altitude.

Answer 2

Four layers: the troposphere, stratosphere, mesosphere, and thermosphere.

Question 3

What is the composition of gases in air in the atmosphere?

Answer 3

nitrogen (78%), oxygen (21%). The rest is mainly argon, with 0.03-0.04% carbon dioxide, small amounts of other noble gases, and varying amount of water vapour.

Question 4

What is an element?

Answer 4

An element is a pure substance that cannot be broken down into anything simpler by chemical methods.

Question 5

What are compounds?

Answer 5

A compound is a pure substance that consists of two or more elements chemically joined together.

Question 6

What are mixtures?

Answer 6

A mixture is made up of two or more substances (elements of compounds) that are not chemically joined together.

Question 7

How can we separate nitrogen and oxygen from air?

Answer 7

Fractional distillation: Dust, water, and carbon dioxide are removed from air. The purified air is compressed to a high pressure and becomes hot. The hot air is cooled down by water.
The cold, compressed air is passes into the expansion chamber. It expands rapidly and becomes colder during the process. This process is repeated until air reaches -200ºC where it becomes a liquid.
Liquid oxygen is collected at the bottom of the fractionating column, while gaseous nitrogen is collected at the top.