Paper 2 Practicals Flashcards
(16 cards)
What is the method for the reaction time pracitcal?
1) sit down on a chair and place your arm on the table with your hand hanging over the edge
2) have a partner hold a ruler with the bottom end between your index finger and thumb
3) the 0 mark should be in level with the top of your thumb
4) your partner should drop the ruler without telling you and you should catch the ruler by pinching it between your thumb and index finger as quickly as you can
5) record the number from the top of your thumb
6) repeat the test at least 5 times
What are some sources of error in the reaction time practical?
participant may have different experiences in performing similar task previously
sample size may be too small to make a valid conclusion
What is the aim of the plant growth practical?
investigate the effects of light on the growth of newly germinated seedlings
What is the method for the plant growth practical?
1)pour a fixed volume of water into 3 petri dishes and add cotton wool
2) place 10 mustard seeds in each petri dish
3) place the petri dishes in a warm location e.g. incubator
4) allow time for the seeds to germinate, if necessary, add more water to the petri dishes (same volume for each dish)
5) if not all seeds germinated into seedlings, remove excess ones so that there is the same number in each petri dish
6) place one petri dish in full sunlight by a window, one in partial sunlight, and one in darkness
7) use a ruler to measure the height of each seedling every day for at least a week
8) find the mean height of seedlings in each petri dish every day
What are some sources of error in the plant growth practical?
seedlings in the same petri dish may not receive the same exposure to sunlight
sample size for each environmental condition may be too small
temperature may affect plant growth as well
What are the 2 parts of the sampling practical?
1) use random sampling to estimate the population size of a plant species
2) use continuous sampling with a transect line to investigate the effect of variation in a factor on the distribution of a plant species
How do you estimate the population size of a plant species?
1) create a grid measuring 10m x 10m using 2 tape measure
2) use a random number generator to obtain 2 numbers, which are to be used as coordinates to find the location on the 2 tape measure set up
3) count and record the number of the required plant species in the quadrat (1m x 1m)
4) take a total of 10 samples
5) to estimate total population size do total area/area sampled * total number of plants counted
How do you investigate the effects of variation in a factor on the distribution of a plant species?
1) lay down a tape measure from the base of a tree to an open area of ground
2) place the quadrat along the 0 end of the tape measure with one corner touching the 0
3) count the number of plants and record it
4) place the quadrat 5m up the tape measure and repeat step 4
5) repeat step 4 at 5m intervals until you reach the end of the transect line
What is a source of error in the sampling practical?
without repetitions, the results from only one transect may be anomalous and not reliable
What determines the size of a quadrat in a field investigation?
size of the plants being studied
What is the purpose of using a random sampling method in a field investigation?
to avoid bias in sample selection
What is the purpose of analysing the data in an investigation on the effect of light intensity on plant distribution?
to determine the correlation between light intensity and plant distribution
What are the independent and dependent variables in the decay practical?
independent - temperature of milk
dependent - time take for the pH of the milk to change
What are the control variables in the decay practical?
type of milk
volume of milk
What is the method for the decay practical?
1) fill half a beaker with 60 degree water from the kettle for a water bath
2) use a syringe to transfer 5cm^3 of lipase solution into a boiling tube and label as ‘lipase’
3) add 5 drops of cresol red into another boiling tube and label as ‘milk’
4) use a pipette to transfer 5cm^3 milk into the ‘milk’ tube
5) use another pipette to transfer 7cm^3 sodium carbonate solution to the ‘milk’ tube, which should make the solution purple
6) place a thermometer into the ‘milk’ tube
7) place both boiling tube into the water bath and allow time for the temperatures to reach that of the water
8) use another pipette to transfer 1cm^3 lipase from the ‘lipase’ tube into the ‘milk’ tube and start timing immediately
9) record the time for the colour change to yellow
10) repeat experiment with different temperature and repeat it 3 times for each temperature
What is a source of error in the decay practical?
colour change at the end point may be difficult to judge
