How Science Works

Question 1

Explain how choosing volunteers of a similar age improved an investigation.

Answer 1

Age affects the risk of disease

also it is a control variable

Question 2

Describe how the student would show that reducing sugars were present in a
solution.

Answer 2

1. Add Benedict’s;
2. Heat;
3. Red shows reducing sugar present;

Question 3

how many variables/ conditions need to be studied before a conclusion can be made?

Answer 3

more than 2

Question 4

How does severe diarrhoea (watery faeces) occur?

Answer 4

Lower water potential of
intestine;
Osmosis down a WP
gradient;
Less water reabsorbed

Question 5

Explain how standard deviations of these

mean values would help you to interpret the data

Answer 5

1. Standard deviation gives a measure of
   spread/variation;
2. More standard deviations overlap, the less likely it is
   that differences are

Question 6

Explain how the standard deviation helps in the interpretation of data

Answer 6

1. see spread of data
2. Overlap = no difference and not significant;
3. Low SD means results more reliable /
   repeatable;

Question 7

Why would experiments be repeated?

Answer 7

1. to get concordant results

2. makes mean more reliable

Question 8

Describe how you would use a 1.0 mol dm–3 solution of sucrose to produce 30 cm3 of a 0.15 mol dm–3 solution of sucrose.

Answer 8

Add 4.5 cm3 of 1.0 mol dm–3 solution to 25.5 cm3
(distilled) water;
0.15dm-3 x 100 = 15cm3
15% of 30 = 4.5

Question 9

Suggest three reasons why the percentage of people vaccinated decreased between

Answer 9

1. fewer cases of disease
2. fear of side effects
3. insufficient vaccine available

Question 10

The percentage of the population vaccinated does not need to be 100% to be effective in preventing the spread of a disease. Suggest why

Answer 10

1. more people immune o pathogen

2. so unvaccinated people are less likely to contact infected people

Question 11

Explain why taking repeated readings increases the reliability of the results

Answer 11

1. Allows for anomalies to be identified
2. Allows a mean to be calculated
3. Effect of variation in data to be minimised

Question 12

Why would taking more readings improve the graph of the results?

Answer 12

1. Line of best fit is more reliable
2. Intercept of line is more reliable

Or..

1. Can plot standard deviation bars
2. To show the variance of the results