A student studied how temperature affected the rate of respiration in yeast cells.
The apparatus used is shown in Fig. 2.1.
Fig. 2.1 labels: yeast suspension, water-bath, clamp, measuring cylinder, water.
The student carried out this procedure:
• Transfer 25 cm$^3$ of yeast suspension into a test-tube.
• Place the test-tube in a water-bath and add water at 10^{\circ}C to the water-bath.
• Allow the apparatus to stand for five minutes before continuing.
• Begin a stop-clock and count how many bubbles are given off by the respiring yeast cells in three minutes.
• Repeat the procedure with a water-bath kept at different temperatures.
(a(i))[2]
State two variables that were controlled during this investigation.
(a(ii))[2]
State one possible source of error when the dependent variable is measured and suggest one improvement to this measuring method. error ... improvement ...
(b(i))[2]
Calculate the rate of bubble production at 30^{\circ}C. Give your answer rounded to an appropriate number of significant figures.
(b(ii))[4]
Plot the values in Table 2.1 on the grid to illustrate how temperature affects the rate of bubble production.
(b(iii))[2]
Describe what the results of this investigation show.
(c)[2]
Describe how the student could show that the gas produced is carbon dioxide.
Worked solution & mark scheme
This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: “volume of the yeast suspension” …