Core Practicals in Paper 1

Question 1

What will you have to decide when doing the food tests

Answer 1

What test to use for each substance

Question 2

Explain the using a microscope practical

Answer 2

Collect a small specimen of cells, stain them and record the name of the stain. Use a toothpick to slowly cover the slide with the coverslip. Examine the specimen under the microscope starting with the lowest magnification. Draw what you see and annotat

Question 3

What will you have to do prior to the testing foods experiment

Answer 3

Decide what test you will do, how said tests will show positive results including the use of control samples, identify hazards and how to avoid them and wear eye protection.

Question 4

What does quantitive results mean

Answer 4

It will give you an exact value

Question 5

What does qualitative results mean

Answer 5

Results that show whether it is present or not

Question 6

What test can be semi-quantitive

Answer 6

Biuret test, as it shows if it has lots or little but not exact values

Question 7

Explain the pH and enzymes practical

Answer 7

Set up heating apparatus with a large beaker half filled with water. Heat the water to 40 degrees and then use the collar on the Bunsen burner to keep it at this temperature. Check that the temp is being kept constant for a few minutes before continuing. Place a drop of iodine solution into each depression of the well tray. Measure 2cm cubed of amylase solution into a test tube. Add 1cm cubed of a pH solution into the same tube. Add 2cm cubed of a starch solution to the tube and place in a water bath. Start stop clock and stir mixture. Every 20 seconds, take a small bit of the solution and drop it into each depression. Do this until the iodine stops changing colour. Repeat with different pH solutions

Question 8

Explain the osmosis of a potato skin practical

Answer 8

Label separate boiling tubes with the sucrose concentration of each solution and place in a rack. Cut similar sized potato pieces, blot dry and record mass. Place in the tubes and cover with appropriate solution. After 15 minutes take potato out, blot dry and record final mass.

Question 9

Explain stage 1 of the antibiotics practical

Answer 9

Use aseptic technique to pour an agar plate. Make sure the base is covered and the top is even and smooth. Once the agar has set, take a packaged pipette out and do not put it down. With your left hand pick up the bacterial culture bottle. Pass the neck of the bottle through a Bunsen burner and insert the pipette to collect a small amount of culture. Pass the neck back through and place the lid back on. Lift lid a little bit, place culture inside and put lid back on quickly. Place pipette in disinfectant, and unwrap sterile spreader. Spread culture around, replace lid and place spreader in disinfectant.

Question 10

Explain stage 2 of the antibiotics practical

Answer 10

Mark the bottom of the dish with quarters, and label one with control and 3 with the concentration of antibiotics you will use. Sterilise forceps and place a circle of sterile filter paper on the control section. Resterilise the forceps and place the discs of antibiotics in the other sections, making sure you sterilise the forceps and place the lid back on between each one. Tape the lid on each side and place upside down. Incubate dish and wash hands.

Question 11

Explain stage 3 of the antibiotics practical

Answer 11

Measure the diameter of clear space around each disc. Work out radius and use this to work out it’s area. Plot graph showing cross sectional area against concentration of antibiotic