RP- Respiration

• what is the aim of the respiration practical

  investigate effect of temperature on rate of reaction
• why does temp affect the rate of reaction

  as respiration is an enzyme catalysed reaction
• describe the method

  • add some soda lime granules to 2 test tubes
  • add ball of cotton wool in each tube
  • place 10 woodlice in weighing boat + record mass
  • place woodlice on top of wool in 1 tube
  • place glass beads of same mass into other tube = CV
  • insert bungs + capillary tubes
  • place tubes into a rack in water bath of 20°C
  • leave tubes for 5 mins so organism can adjust to new temp
  • add coloured liquid to capillary tubes
  • mark position of coloured liquid and time for 5 mins
  • mark position of coloured liquid AFTER 5 mins
  • repeat using different temps
• what's the control variable in the method

  • soda lime granules should be same mass
  • glass beads = CV for comparison
• why do you use glass beads for a CV

  • as they dont respire
  • so proving the bead will move due to RESPIRATION
• how can you improve the accuracy

  repeat to calculate a mean
• what is soda lime

  chemical that absorbs CO2
• why should u be careful when dealing with soda lime

  it's corrosive
• what should u do to keep yourself safe from soda lime

  • wear safety goggles
  • gloves
• how does the investigation work

  • soda lime absorbs CO2 produced in aerobic respiration by woodlice
  • oxygen in boiling tube used up by respiration by organisms -> pressure drops in tube so water droplet in the capillary tube moves
  • cotton wool ensures organisms dont touch the soda lime
• what is added to move the coloured liquid back to the start

  reservoir