Biology A

Question 1

Give one reason for using 25 degrees as a maximum temperature to incubate agar plates in a school laboratory

Answer 1

Reduces the Risk of growth of pathogens

Question 2

In industrial laboratories higher temperatures are used to incubate agar plates.
Give one reason why?

Answer 2

Microorganisms grow faster

Question 3

Describe how crude oil is separated into fractions by fractional distillation

Answer 3

Crude oil is heated
Crude oil evaporates
Vapour condenses
At different temperatures

Question 4

Some properties of hydrocarbons change as the size of the molecules increases.
Describe the trends in boiling point and viscosity as the number of carbon atoms in the molecule increases

Answer 4

As the number of carbon atoms increases
Boiling point increases
Viscosity increases

Question 5

Burning fuels releases energy.

Name two products formed when LPG is burnt

Answer 5

Any two from:
•carbon dioxide
•water

• carbon monoxide
• carbon

Question 6

Some cars are now designed to use LPG as a fuel. LPG is about 50p per litre cheaper than petrol.
Suggest one reason why most car owners use cars designed to use petrol and not LPG dad a fuel.

Answer 6

Any one from:
•lack of availability of LPG
•cars need to be modified

Question 7

A lithium atom has an atomic number of 3 and a mass number of 7.
describe the atomic structure of lithium.
Include in your answer:
•the number of each type of particle
• where in the atom each particle is found.

Answer 7

Any four from:
•3 protons 
•4 neutrons
•3 electrons 
•nucleus contains protons and neutrons 
•electrons in energy levels/shells

Question 8

Name one other element with similar chemical properties to lithium.

Answer 8

Any one from: 
•sodium 
•potassium 
•rubidium 
•caesium
•Francium

Question 9

Why are lithium and sodium classed as different elements?

Answer 9

Contains different number of protons

Question 10

Compare solids, liquids and gases in term of their particles.

Answer 10

Solids:
•arranger in a regular pattern
•particles vibrate about fixed points
•particles have low energy

Liquids:
•pattern is irregular
•particles are not fixed in place/can move freely
•particles have more energy than solids and/or less energy than gases

Gases:
•particles are in a random pattern
•particles move freely/randomly
•particles have high energy

Question 11

The mirror changed from being dry to being covered with small drops of water.
name the process causing this Change on the mirror.

Answer 11

Condensation

Question 12

The towel will dry faster if it is hung from the unheated towel rail instead of the towel ring
Explain why.

Answer 12

•Larger (exposed) surface area
So
•water can evaporate faster
•more water can escape

Question 13

One advantage of calculating a mean

Answer 13

Reduces random errors

Question 14

Why are antibiotics not effective against viral infections?

Answer 14

Viruses live / reproduce inside cells

(So) the drug cannot reach the virus

Question 15

What must be done to make sure we will be able to treat bacterial infections in the future?

Answer 15

Developed new antibiotics

Not prescribe antibiotics for viral infections

Question 16

What is the junction between neurones called?

Answer 16

Synapse

Question 17

How does information cross the junction between neurones

Answer 17

Chemical

Question 18

Describe main stages of IVF

Answer 18

Any 4 from
•women is given FSH/LH
•(FSH/LH hormones) to stimulate egg maturation/ release/ production
•eggs and sperm are collected/ mixed
Fertilisation happens
•embryos inserted into the woman’s uterus/ womb

Question 19

Suggest reasons for and against women in their 50s and 60s having IVF treatment to have children

Answer 19

Three arguments given from-
For: 
• more money/time to support child 
•may make better parents 
•allows women who have late marriage to have a family

Against :
•mother may die before child has grown up
•baby may not be as healthy
•mother may have more problems during birth
•mother may have less energy

Question 20

Limestone is used to make cement.

What is added to limestone to make cement?

Answer 20

Clay

Question 21

Suggest why the total amount of carbon dioxide produced by the manufacturing process is high

Answer 21

Burning of (fossil) fuels (to provide energy)

Question 22

Why is gold found in the earths crust as the element

Answer 22

Gold is Unreactive

Question 23

Scientists were not able to extract aluminium until the 11th century.
Explain why.

Answer 23

Aluminium is high on the reactivity series
Or
Aluminium is more reactive than carbon.

(So) cannot be extracted with carbon
Or
(So) requires electrolysis