REQUIRED PRACTICALS

Question 1

microscopy required practical preparation

Answer 1

• add a drop of water to the middle of a clean slide
• separate onion into layers; peel off epidermal tissue using tweezers
• place epidermal tissue into the water on the slide
• add a drop of iodine solution - a stain that highlights the subcellular structures
• place a cover slip on top and make sure there are no air bubbles

Question 2

microscopy required practical

Answer 2

• clip slide onto stage
• select objective lens with lowest magnification
• use coarse adjustment knob to move the stage up to just below the lens
• look down eyepiece
• adjust focus with fine adjustment knob until the image is clear

Question 3

effect of osmosis on plant tissue (9)

Answer 3

• peel the potato
• use a cork borer to produce three cylinders of potato
• use a scalpel to make sure all cylinders are the same length
• measure the mass of the potato cylinders then leave one cylinder in a beaker with pure water and the other in a beaker with very concentrated solution
• leave for 24 hours
• take the cylinders out and let them dry on a paper towel
• measure their masses again
• if their mass has increased, they have drawn water in by osmosis
• if their mass has decreased, the water has been drawn out

Question 4

food tests practical preparation (4)

Answer 4

• break up a piece of food using a pestle and mortar
• transfer to a beaker and add some distilled water
• stir with glass rod to dissolve some of the food
• filter solution to get rid of the solid bits of food

Question 5

what does biuret reagant test for?

Answer 5

protein

Question 6

biuret reagant test (4)

Answer 6

• transfer 2 cm cubed of food sample into a test tube
• add 2 cm cubed of biuret solution
• shake gently

will go purple if protein is present

Question 7

what does ethanol test for?

Answer 7

lipids

Question 8

ethanol test (3)

Answer 8

• food sample is mixed with 2 cm cubed of ethanol
• add an equal volume of distilled water

will go cloudy if lipids are present

Question 9

what does benedict’s solution test for?

Answer 9

sugar

Question 10

benedict’s solution (5)

Answer 10

• transfer 5 cm cubed of food sample to a test tube
• prepare water bath at 75 degrees
• add about 10 drops of benedict’s solution to the test tube using a pipette
• place tube in water bath and leave for five minutes

will go brick-red if sugar is present

Question 11

what does iodine test for?

Answer 11

starch

Question 12

iodine test (4)

Answer 12

• transfer 5 cm cubed of food sample to test tube
• add a few drops of iodine solution
• shake gently

will go blue-black if starch is present

Question 13

photosynthesis practical (6)

Answer 13

• place a boiling tube 10 cm away from an LED light source
• fill the boiling tube with sodium hydrogen carbonate solution
• place a piece of pondweed into the boiling tube with the cut end at the top
• leave for five minutes
• start a stop watch and count the number of bubbles produced in a minute
• repeat the experiment with the boiling tube at different distances