Biology - Controlled Assessment P1

Question 1

What’s the background to the experiment?

Answer 1

Most fossil fuels contain sulphur as an impurity which burns and oxidises to form sulphur dioxide.

This gas dissolves in rain water and reacts with oxygen in the air to form sulphuric acid. This contributes to acid rain.

This can affect the pH of the soil which can cause plants to grow differently.

pH of the soil can affect the enzymes in a plant by altering the pH from the optimum. This causes chemical reactions to slow down which slows or stops growth altogether.

Question 2

What sources did you use? Comment on the usefulness of both.

Answer 2

Source 2 was useful as it provided a small list of equipment, a method and some safety points.

However, I found source 1 more useful as it gave a more detailed equipment list, a detailed and step by step method, a risk assessment and a table with various concentrations to use.

Question 3

What are the different variables?

Answer 3

Independent:
Concentration of acid in the water mol/dm3

Dependent:
Number of seeds which germinated

Control:
Temperature
Number of seeds
Type of acid
Light
Material
Time
Total volume

Question 4

In this investigation you will need to control some variables.
Write down one variable you’ll need to control.
Describe briefly how a preliminary investigation could help find a suitable value for the control variable

Answer 4

Type of acid

I would carry out the experiment using 3 different types of acid and compare the results.
I would use the acid that gave the best germination results.
Sulphuric acid germinates best so I would use this to obtain the best results.

Question 5

How do you answer a preliminary investigation question?

Answer 5

State a suitable control variable

Mention testing a range of this C.V

Say how you will measure the D.V

Explain how you’ll use these results

Question 6

What’s the hypothesis and the explanation to the hypothesis?

Answer 6

As the acidity of the water increases, the rate of germination decreases.

This is due to how, as the concentration of sulphuric acid in the water increases, the pH in the soil is affected which results in the enzymes of the plant being altered.
This results in chemical reactions slowing down growth or stopping the growth altogether.