A Level Biology Paper 5 Notes 2021

CO2:  Usually, most of the CO2 absorbants are with -OH eg: NaOH or KOH  Sources of CO2 are usually those with the -CO3 eg: CaCO3, H2CO3  a non-chemical source: gas cylinder  the gas is supplied through a bubbler.  to measure CO2 concentration: use probe with meter Temperature:  method of controlling: use an electronic water-bath (a beaker of boiling water)-depends on the experiment  use an electronic thermostat  heat screen*/ heat filter *for uniform distribution of heat.  incubator  digital/mercury thermometer  for food tests, such as Benedict's test, the temp must be above 80'C. Time: Always mention: - the method of timing (stopwatch/ wall clock) -precise time -mention the time according to the need (Teacher's advice: Don't be vague when mentioning the time period; be sensible, realistic and precise! ) Sample Size:  the larger the sample size, the more reliable the results.  When making concentrations, the minimum number you should make is 3. Ideally, the number of conc you're going to make must be 5.  mass must be the same when comparing two samples. Measuring:  use mm calipers  a ruler- calibrated to cm or mm  measuring cylinders  syringe, pipette  weighing scale/ electronic balance  digital/mercury thermometer  MEASURING PLANT LENGTH1. use ruler 2. use a thread (remind me to explain what this means if i didn't by the end of this post please)  MOVEMENT AND TIME 1. measure distance moved at a certain time (