RP9

Question 1

RP9

Independent variable

Answer 1

Temperature
[Could do type of sugar]

Question 2

RP9

Dependent variable

Answer 2

Time taken for meniscus to move 1cm – demonstrating oxygen being taken in to yeast
Or time taken for methylene blue to go colourless

Question 3

RP9

Controls

Answer 3

Volume and concentration of yeast suspension
Type
Volume and concentration glucose
Volume of methylene blue

Question 4

RP9

Why does the methylene blue decolourise?

Answer 4

Methylene Blue accepts e- and is reduced = colourless

Question 5

RP9

Why use a glass beaker as water bath rather than electric water bath?

Answer 5

Allows you to see colour change more easily, without removal from temperature

Question 6

RP9

How do you convert time taken to rate?

Answer 6

1/ time

Question 7

RP9

How could make your results more accurate?

Answer 7

Smaller intervals for temperature.
Repeat, remove anomalies
Calculate mean.

Question 8

RP9

Describe a control you could set up

Answer 8

Methylene blue with boiled yeast and glucose. This would show that glucose alone does not cause methylene blue to go colourless and the change is a result of respiration

Question 9

1 mark

Suggest one reason why it was important that the student left the apparatus for one
hour after the yeast culture reached a constant temperature.

Answer 9

So the oxygen is used/absorbed/respired