Mock Exam Set 1 - Paper 3

[Maximum mark: 5]

An investigation was carried out into the effects of household detergents on aquatic habitats. Scientists tested the effect of different household detergents on the surface tension of water in order to better understand the impact they may have on organisms living on the surface.

A paper clip was folded slightly on one side and rested on the surface of the water, maintained at a constant temperature and contained within a water tank. Drops of detergent solution were slowly added to the water tank until the paperclip sank to the bottom. The volume of detergent solution taken to sink the paperclip was recorded.

Detergent solutions were made by adding 5 ml of detergent to 15 ml of water.

The results are shown in the table.

1. Describe the relationship between the volume of detergent solution added and the surface tension of water. [1]
   

2. For the Easy Clean detergent, calculate the mean number of drops of detergent needed to sink the paper clip. [1]
   

3. 1. Suggest one method that could be used to keep the water at a constant temperature. [1]
      

   2. Explain the importance of maintaining water at a constant temperature. [2]
      

[Maximum mark: 5]

The table shows the results from a study on the percentage of cholesterol found in the cell membrane of epithelial skin cells of different animals.

1. State one role of cholesterol in the cell membrane. [1]
   

2. Suggest why arctic foxes have a greater mean percentage of cholesterol in their cell membranes than kangaroos. [2]
   

3. Estimate, with a reason, the percentage of cholesterol that would be found in the cell membranes of polar bears. [1]
   

4. Suggest why the cells studied may contain a higher percentage of cholesterol than shown in the table. [1]
   

[Maximum mark: 5]

In an investigation into the effects of artery occlusion on blood pressure, students set up a simple experiment. A rigid, hard, plastic tube, representing an artery, was fixed to an electric water pump, and the end was sealed with a rubber stopper. A single hole was drilled into the plastic tube and the electric pump was turned on. Students measured the distance the water stream travelled.

In subsequent trials, students added increasing numbers of equally sized and shaped clay-like masses to the inside of the plastic tube and the distance the water stream travelled was measured again.

Results are shown below.

1. Outline the relationship between the number of clay-like masses and the distance travelled by the water stream. [1]
   

2. Explain how the results of this experiment can be used to understand artery occlusion. [2]
   

3. State a risk factor associated with coronary heart disease. [1]
   

4. Identify a limitation of using the plastic tube to represent an artery in this experiment. [1]