Chemistry 1b

Question 1

What is cracking?

Answer 1

The splitting up of long-chain hydrocarbons into smaller ones.

Question 2

Give an example of a substance that is cracked, and the products you get from it.

Answer 2

Diesel is cracked to give petrol, paraffin and ethene for plastics

Question 3

What kind of carbon-carbon bonds do alkenes have?

Answer 3

Double bonds

Question 4

What is the general formula for alkenes?

Answer 4

C (2) H (2n)

Question 5

What are polymers? What kind of substances can form polymers?

Answer 5

Polymers are the lots of small alkene molecules (monomers) joined together to form very large molecules. Alkenes form polymers.

Question 6

Give three factors which affect the physical properties of a polymer.

Answer 6

1. What it is made from
2. The temperature used to make it
3. The number of atmospheres used to make it

Question 7

List four uses of polymers.

Answer 7

1. LDPE used to make plastic bags
2. Waterproof coatings for fabrics
3. Biodegradable packaging materials made from polymers and cornstarch
4. Memory foam matresses

Question 8

Why might polymers become more expensive in the futurw

Answer 8

They are made of crude oil, a fossil fuel that is running out, which will become more expensive as resources run out. Therefore, polymers will become more expensive.

Question 9

Why are polymers distilled after they have been extracted?

Answer 9

It refines the oil, removes water, solvents and impurities

Question 10

List two advantages of using vegetable oils in food.

Answer 10

1. They provide a lot of energy because they have a high energy content.
2. They contain essential fatty acids, which the body needs for many metabolic processes

Question 11

Apart from food, give one use of vegetable oils.

Answer 11

They can be used to produce fuels

Question 12

What kind of carbon-carbon bond do unsaturated oils contain?

Answer 12

Double bonds

Question 13

What happens when you react unsaturated oils with hydrogen?

Answer 13

The hydrogen reacts with the double-bonded carbons and opens out the double bonds. This causes the vegetable oils to be hardened

Question 14

Why do some foods contain partially hydrogenated vegetable oils instead of butter?

Answer 14

1. Turning all the double bonds to single bonds would make margarine too hard and difficult to spread
2. The oils are a lot cheaper and they keep longer

Question 15

Give an example of an emulsion.

Answer 15

Oil-in-water OR water-in-oil emulsions

Question 16

How do emulsifiers keep emulsions stable?

Answer 16

1. Emulsifiers have a part attracted to water (hydrophilic) and a part that is attracted to oil (hydrophobic)
2. The hydrophilic end of the emulsifier latches onto the water molecules
3. The hydrophobic end of the emulsifier latches onto the oil molecules
4. Hydrophilic part faces outwards and repels oil droplets so the emulsion will not separate out.

Question 17

Suggest one problem of adding emulsifiers to food?

Answer 17

People are allergic to certain emulsifiers.

Question 18

What are emulsions?

Answer 18

They are made up if droplets of one liquid suspended in another liquid.

Question 19

What evidence did Wegener use to support his continental drift theory?

Answer 19

1. He found fossils on opposite sides of the Atlantic that were similar to each other
2. Countries and continents looked like the once fitted together.

Question 20

What can be found beneath the Earth’s crust?

Answer 20

The mantle and the core.

Question 21

Name the two main gases that make up the Earth’s atmosphere today?

Answer 21

78% nitrogen and 21% oxygen

Question 22

Explain why today’s atmosphere is different from the Earth’s early atmosphere.

Answer 22

1. The Earth’s surface use to be molten
2. When it cooled, a thin crust formed
3. Volcanoes kept erupting, which let out lots of gas, forming oceans and the atmosphere
4. Green plants and algae evolved and liked the CO2 atmosphere
5. CO2 dissolved into oceans and green plants and algae used it up during photosynthesis, releasing oxygen.
6. The build-up of oxygen killed off some early organisms but allowed more complex organisms to evolve
7. The oxygen also created the ozone layer which blocked harmful rays from the Sun and enable more complex organisms to evolve, including us
8. Virtually no CO2 left now

Question 23

What is meant by the term ‘primordial soup’?

Answer 23

It is a theory that states that billions of years ago, the Earth’s atmosphere was rich in nitrogen, hydrogen, ammonia and methane. Lightning struck, causing a chemical reaction between the gases, resulting in the formation of amino acids. The amino acids gradually combined to produce organic matter which eventually evolved into simple living organisms

Question 24

Why do we fractionally distil air?

Answer 24

To get a variety of products used in industry.

Question 25

The burning of fossil fuels is causing a rise in the level of carbon dioxide in the atmosphere. How is this affecting the oceans and the climate?

Answer 25

Oceans are a natural store of CO2, however, we are releasing too much CO2 causing them to become acidic. This means that the environment is becoming toxic for coral and shellfish and means that, in the future, they won’t be able to absorb any more carbon dioxide.