Chemistry revision

Question 1

What changes might occur in a chemical reaction?

Answer 1

Colour, light emitted, gas release, temperature change

Question 2

What is always formed in a chemical reaction?

Answer 2

A new substance

Question 3

Examples of physical changes

Answer 3

Melting/freezing, boiling, chopping, breaking.

Question 4

Mean rate of reaction

Answer 4

Quantity of reactant used/ time taken or quantity of product formed/time taken

Question 5

Use the correct units for volume and don’t say amount

Answer 5

Units: cm^3

Question 6

Use the units for rate of reaction (it has to be related to time).

Answer 6

Units: e.g. g/s, cm^3/s

Question 7

What do you exclude when working out the mean?

Answer 7

Anomaly

Question 8

How do you calculate the mean?

Answer 8

All of the numbers added together and divided by the quantity of the individual numbers.

Question 9

Calculate the gradient of a graph

Answer 9

Revise

Question 10

How does the surface area affect the rate of reaction?

Answer 10

The higher the SA the higher the rate of reaction due to collision theory. This is when a chemical reaction takes place due to the particles colliding with on another.

Question 11

How does the concentration affect the rate of reaction?

Answer 11

Higher concentration (quantity) of particles meaning that they are more likely to collide and a bigger reaction due to collision theory.

Question 12

How does a higher pressure affect the rate of reaction?

Answer 12

The higher the pressure means that the particles have less space to move making the collide more and a bigger reaction due to collision theory.

Question 13

How does the temperature affect the rate of reaction?

Answer 13

The higher the temperature makes those particles more active. This means that they will collide more and due to collision theory the reaction will be greater.

Question 14

How does the presence of a catalyst affect the rate of reaction?

Answer 14

A catalyst provides an alternative lower energy route where there is a lower activation energy.

Question 15

Predict the effects of changing the temperature, concentration and pressure using collision theory

Answer 15

The higher the pressure, concentration or temperature the higher the rate of reaction because the particles will collide more often, making the reaction greater.

Question 16

Predict what will happen by changing the surface area to volume ratio.

Answer 16

The higher the surface area to volume ratio the higher the rate of reaction. This is due to there is more of an area for those particles to collide with. And using collision theory the reaction will be greater.

Question 17

Give examples of Earth’s resources and what they are used for.

Answer 17

Sand: glass, timber: furniture or construction, coal: energy.

Question 18

Define finite and sustainable resources and give examples.

Answer 18

Finite: a resource that can be used up before it is replaced, e.g. coal, metal ores, fossil fuels. Sustainable: a resource that cannot be used up before it is replaced, e.g. timber.

Question 19

State examples of natural products that are farmed or made synthetically in laboratories.

Answer 19

Plastic, medicine, new fuels.

Question 20

Explain what potable water is and why we need it to live.

Answer 20

Potable water is water that is suitable for human consumption. It hydrates humans and is used for cooking or boiling.

Question 21

Describe the steps in turning water from a lake into potable water.

Answer 21

1. screening - removes large solid items.
2. clarification - allows solids to settle to the bottom.
3. filtration. - this removes small particles that are suspended in the water.
4. chlorination. - kills any microorganisms in the water by adding chlorine.

Question 22

Describe the methods of sterilising water e.g. ozone, chlorine, UV light.

Answer 22

1. ozone is injected into water, and immediately starts oxidizing and eliminating contaminants, such as bacteria, viruses, and metals.
2. UV light: damaging the DNA of microorganisms, including bacteria, viruses, and protozoa, thus rendering them unable to reproduce and causing them to die.
3. Chlorine: it reacts with organic substances that occur naturally in the water by breaking the chemical bonds.

Question 23

Describe desalination by reverse osmosis. Why do we do it and what are the advantages and disadvantages of the process?

Answer 23

Reverse osmosis: water is blasted a high pressures at a permeable membrane to kill the nucleus. It removes dissolved or suspended chemical species as well as biological substances. We also use it to produce potable water. Flat Taste.
Good Mineral Removal.
High Waste Water Volume.
Slow Filtration Rate.
High Initial Cost.
High Maintenance Costs.
Acidic pH of Water.

Question 24

Describe desalination by distillation. Why do we do it and what are the advantages and disadvantages of the process?

Answer 24

Distillation involves boiling the solution and then condensing. the vapour. back into a liquid by cooling it down. It is used to separate liquids from nonvolatile solids and create potable water. Advantages: Produces very high quality water, does not use any chemicals or filters, it is a completely natural process. Disadvantages: Slow process, Expensive, particularly if you are distilling a compound that is not readily available.

Question 25

Describe what a life cycle assessment is and give examples.

Answer 25

A process of evaluating the effects that a product has on the environment over the entire period of its life thereby increasing resource-use efficiency and decreasing liabilities. Examples are the carbon footprint on steel and concrete.

Question 26

What are the three ‘Rs’

Answer 26

Reduce, reuse, recycle. Reduce: use things that have less or no plastic. Reuse: use reusable bags or plastic to keep instead of single use plastics. Recycle: put plastic and other single use material in the recycling bin.

Question 27

Explain what happens to metal and glass when it is recycled.

Answer 27

They both get crushed and shredded into smaller pieces so that they can be reused as other things.