Investigating Respiration

Question 1

germinating peas experiment

Answer 1

• as the peas start to grow they respire, releasing heat
• the thermos flask is insulated, so heat is not transferred to the surroundings and we can measure the change in temperature
• we only see a temperature rise in thermos A, as the peas in thermos B are dead (they have been boiled)
• in both thermos flasks the peas are soaked in Milton solution (bleach)
• this kills any bacteria - bacteria would also respire so this would affect results
• we could also use gas delivery tubes to collect any gas produced
• the gas can then be bubbled through limewater - the gas from flask A only would turn the limewater cloudy - this shows that carbon dioxide is produced

Question 2

hydrogen carbonate indicator and insects experiment

Answer 2

• the indicator is red, but turns yellow when the carbon dioxide concentration increases
• carbon dioxide reacts with water to form a weak acid

Question 3

investigating anaerobic respiration in yeast

Answer 3

• this equipment can be used to investigate the effect of changing a single variable on the rate of anaerobic respiration in yeast
• dependent variable could be the time taken for the limewater to turn cloudy
• you could also connect the delivery tube to a gas syringe, to measure the volume of carbon dioxide produced

Question 4

what do you do when an examiner asks you to describe experimental data?

Answer 4

say what the results are

Question 5

what do you do when an examiner asks you to explain what the results are?

Answer 5

say why the results occur