Required Practicals-Paper 1

Question 1

What is the aim of the osmosis practical?

Answer 1

To investigate the range of concentrations of salt or sugar solutions on the mass of plant tissue

Question 2

What is the independent variable of the osmosis practical?

Answer 2

the concentration of salt or sucrose in mol/dm^3

Question 3

What is the dependent variable of the osmosis practical?

Answer 3

the mass and the length of each potato cylinder before and after it has been submerged in solution-then calculate percentage change in length and mass

Question 4

What are the control variables of the osmosis practical?

Answer 4

One of the boiling tubes should have distilled water, temperature, time, volume of solute in solution

Question 5

What are some improvements that could be made to the osmosis practical?

Question 6

What are the steps to the osmosis practical?

Answer 6

1)use a cork borer to cut 5 potato cylinders of the same diameter
2)use a scalpel and ruler to trim each potato cylinder so they’re all the same length-measure this length and record
3)measure the mass of each potato cylinder and record in a table of results
4)measure 10cm^3 of sugar or salt solution and pour into each boiling tube-label the tubes carefully
5)add one potato cylinder to each boiling tube and leave for a specified time
6)remove the potatoes blot and dry and record the final mass and length of each

Question 7

What does a positive percentage change in mass mean(osmosis)?

Answer 7

A positive percentage change in mass indicates that the potato has gained water by osmosis (net movement of water from the solution into the potato) meaning the solution is more dilute,(negative percentage change is opposite)

Question 8

What is the aim of the enzyme practical?

Answer 8

To investigate the effect of pH on the rate of reaction of amylase

Question 9

What does amylase do?

Answer 9

Digests starch into maltose(starch can be tested for using iodine)

Question 10

What are the steps to the enzyme experiment?

Answer 10

1)add iodine to a spotting tile
2)add amylse+buffer to a test tube and mix, then add starch solution and start the stopwatch
3)start the time
4)after 10 seconds, add a drop of solution to iodine in the spotting tile
5)repeat every 10 seconds until the iodine doesn’t change colour
6)repeat steps 1-5 using buffer solutions of different pH

Question 11

What are some improvements to the enzyme method?

Answer 11

Use at water bath at 35 degrees to control temp, a colorimeter can be used to measure the progress of the reaction more accurately, all solutions that need to be used should be places in a water bath and allowed to reach the temperature before being used

Question 12

What is the independent variable of the enzyme experiment?

Question 13

What is the dependent variable of the enzyme experiment?

Answer 13

pH of the solution

Question 14

What are some control variables in the enzyme experiment?

Answer 14

Temperature of the solution??, concentration of starch solution?

Question 15

What is the aim of the transpiration experiment?

Answer 15

To investigate the role of environmental factors in determining the rate of transpiration from a leafy shoot

Question 16

What are the steps to the transpiration practical?

Answer 16

1)cut a shoot underwater to prevent air entering the xylem and place in tube
2) set up the environment factor you’re investigating
3)allow the plant to adapt to the new environement for 5 minutes
4)record the distance of air bubble at the start of the experiment
5) allow the plant to adapt to the new environment for 5 minutes
6)leave for a set period of time eg 1 hour
7)record the end location of the air bubble and calculate the distance travelled
8)repeat the experiment after changing factor being investigated(eg light intensity)
9)reset the air bubble using a tap of reservoir if needed

Question 17

What are some control variables in the transpiration practical?

Answer 17

Make sure the leaves of the shoot are dry, …

Question 18

What is the independent variable in the transpiration practical?

Answer 18

The environmental factor affecting transpiration eg humidity, light intensity, temperature

Question 19

What is the dependent variable in the transpiration practical?

Answer 19

The distance travelled by the air bubble

Question 20

Which environmental factors can be investigated in the transpiration practical?

Answer 20

Airflow(set up a fan), humidity(spray water in a plastic bag and wrap around plant), light intensity(change distance of light source from the plant), temperature(cold room/warm room)

Question 21

What is the aim of the photosynthesis practical?

Answer 21

To investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism like pondweed

Question 22

What is the independent variable in the photosynthesis practical?

Answer 22

The distance of the lamp from the plant

Question 23

What is the dependent variable of the photosynthesis practical?

Answer 23

The oxygen bubbles produced per minute as photosynthesis occurs

Question 24

What are some control variables in the photosynthesis practical?

Answer 24

Temperature(use thermometer), the same photosynthesising aquatic plant, the concentration of sodium hydrogencarbonate

Question 25

What is the method of the photosynthesis practical?

Answer 25

1)Place a piece of pondweed into a beaker with 45cm^3 of sodium hydrogencarbonate inside and allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form
2)Cut a piece of the pondweed 8cm long
3)use forcepts to place the pondweed in the boiling tube carefully
4)position the boiling tube so the pondweed is 10cm from the light source and allow the tube to stand for 5 minutes
5)count the number of bubbles emerging from the cut end of the stems in 1 minute-repeat the count 5 times and record results
6)calculate the average no. of bubbles produced per minute, repeat the experiement at different distances from the light source

Question 26

How could the photosynthesis practical be improved?

Answer 26

By using a gas syringe, by using a datalogger, use an LED bulb to make sure heat isn’t affecting the rate

Question 27

What is the aim of the aseptic practical?

Answer 27

To investigate the effect of antiseptics on bacterial growth using agar plates and measuring zones of inhibition

Question 28

What are the steps for the aseptic practical?

Answer 28

1)glass Petri dishes and agar gel must be sterilised before use
2)pour the sterile agar plates and allow to set fully
3)sterilise the inoculating loop by heating it in the Bunsen burner flame
4)dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate
5)replace the lid as soon as possible and secure with tape. Label and invert the plate and store upside down
6)incubate at a max temp of 25 degrees in schools/colleges

Question 29

What are the reasons for all the steps in the aseptic practical?

Answer 29

1)to kill any bacteria present in solution or on Petri dishes
2)this provides the selected bacterium with all the nutrients needed to grow
3)kills any bacteria present on the loop
4)to allow bacteria to spread out and grow in individual colonies on the agar plate-a lawn of bacteria can be produced using a sterile spreader to evenly spread the bacteria across the whole plate
5)stops more unwanted bacteria in the air contaminating the plate-don’t fully seal lid bc this stops oxygen reaching bacterium and this could encourage harmful anaerobic bacteria to grow
6)reduces the chance of growing harmful pathogens