required practicals Flashcards
(7 cards)
Describe a practical to investigate the effect of a factor on reaction time.
effect of factor on reaction time:
1) person 1 sits on stool and places forearm of dominant arm across the table with hand overhanging the edge
2) person 2 holds the ruler vertically, with 0cm mark between P1’s thumb and finger
3) P2 tells P1 to prepare to catch the ruler
4) P2 drops ruler and P1 catches ruler with thumb and first finger ASAP
5) record measurement level with the top of the thumb
6) repeat and calculate a mean
- change the person being tested, the hand catching the ruler, the effects of chemicals, the effects of background activity and the effect of practice
- find reaction time through a conversion table online
Describe a practical to investigate the effect of light on the growth of new seedlings.
effect of light on plant growth:
1) place cotton wool in three petri dishes and soak with equal volumes of water
2) place ten mustard seeds in each dish
3) leave seeds in a warm place to allow germination
4) water everyday with the same volume of water
5) after 2-3 days, seeds germinate - make sure there is the same amount of plants in each
6) use a ruler to measure the height of each
7) place one dish in sunlight, one in partial light and one in darkness
8) measure the height everyday for at least 5 days
9) calculate the mean for each day
- the tallest should be in the dark, and be yellow
- the smallest should be in the light, and be bright green
Describe a practical to investigate the effect of gravity on the growth of new seedlings.
effect of gravity on plant growth:
1) place cotton wool in three petri dishes and soak with equal volumes of water
2) place ten mustard seeds in each dish
3) leave seeds in a warm place to allow germination
4) water everyday with the same volume of water
5) after 2-3 days, seeds germinate - make sure there is the same amount of plants in each
6) use a ruler to measure the height of each
7) place one dish upside down and the other upright
8) measure the height everyday for at least 5 days
9) calculate the mean for each day
Describe a practical to estimate the total population of daisies in a field.
estimating number of daisies:
1) place two tape measures at right angles, 20m x 20m
2) have two bags with numbers 1-20 in each
3) person 1 chooses number and goes that number of metres up the tape measure, person 2 for other axis
4) person 3 places a quadrat on ground, level with both
5) record the number of daisies in the first quadrat
6) repeat 9 more times for 10 samples
7) total pop = (total area / area sampled) x number of daisies sampled
Describe a practical to measure the effect of a factor on the distribution of a species.
(hint: light intensity on daisies)
effect of factor on population:
1) use a transect line to go along two different environments
2) use a quadrat to count the number of daisies at the start of the transect and record factor (if light intensity, light meter or app)
3) move quadrat 1m and repeat until you finish the transect
4) compare results along different factors
- other abiotic factors could be influencing
Describe a practical to investigate the effect of temperature on decay.
effect of temperature on decay:
- if milk is left at room temp, it goes sour after a few days as the bacteria in the milk starts decaying, and these bacteria use enzymes to produce acidic molecules
- decay is slow, so use enzyme lipase, so it isn’t strictly decay but it is very similar
1) label test tube ‘lipase’ and fill with 5cm^3 of lipase solution
2) label another test tube ‘milk’ and add 5 drops of Cresol red indicator
3) add 5cm^3 of milk and 7cm^3 of sodium alkaline to milk, and it should turn purple as Cresol red is purple in an alkali
4) place a thermometer in the milk, place both tubes in a beaker of water at the first chosen temperature
5) wait until the temp of the solutions is the same as the beaker
6) transfer 1cm^3 of lipase to milk and stir and start timer
- lipase will start to break down fat molecules in milk, which releases fatty acids, so acidic, so Cresol red should turn to yellow
7) once turns yellow, stop timer and record results
8) repeat at a range of temperatures
- clean test tubes for milk solution for each experiment as traces of lipase will trigger a reaction early
- as everyone sees colour differently, repeat and share data with other groups and calculate a mean
What colour does Cresol red indicator turn in acids and alkalis?
Cresol red indicator:
acids - yellow
alkalis - purple
