Skills Flashcards
practical and mathematical
1
Q
formula for magnification
A
observed / actual size
2
Q
formula for rate of diffusion
A
rate = distance travelled / time
3
Q
apparatus needed for investigating osmosis with a partially permeable membrane
A
- capillary tube
2.water - dialysis tube
- ^ containing sugar solution with red dye
4
Q
why/ how does investigating osmosis with a partially permeable membrane work
A
- tubing allows small molecules and ions to pass through but prevents movement of larger molecules
- after apparatus is left for 30 mins the dialysis tubing will swell.
-pressure forces colored solution up the capillary tube. because water enters tubing by osmosis
5
Q
formula calculating percentage change
A
change in size/ size at start x 100
6
Q
dependant vs independent variable
A
The independent variable is the variable being controlled in the problem, and the dependent variable is the variable that changes because of this control.
7
Q
where to plot independant and dependant variable on a graph
A
independant - x
dependant - y
8
Q
steps of testing a leaf for starch
A
- boil the leaf in water
- boil the lead in ethanol
- rinse the leaf in water
- spread the leaf out on a white tile
- add iodine solution to the leaf
9
Q
reasons for each step in testing a leaf for starch
A
- boil the leaf in water - to kill the leaf and make it permeable
- boil the lead in ethanol - to decolourise the leaf, chlorophyll dissolves in ethanol
- rinse the leaf in water - boiling the leaf in ethanol makes it brittle , water softens it
- spread the leaf out on a white tile - makes results easy to see
- add iodine solution to the leaf - to test for the presence of starch
10
Q
hazards when testing a leaf for starch
A
- boiling leaf in water - danger or scalding
- boiling lead in ethanol - no naked flames because ethanol is highly flammable
- adding iodine - avoid skin contact with iodine solution
