P1 Required practical's (will come up)

Question 1

How to prepare a slide for an onion cell (5 steps)

Req Prac 1

Answer 1

Add a drop of water to the middle of a clean slide

2. Cut an onion and separate it into layers, using tweezers peel off some epidermal tissue from the bottom of a layer
3. With tweezers place the epidermal tissue into the water on the slide
4. Add a drop of iodine stain to see the structures
5. Place a cover slip on top by standing the cover slip upright next to the water droplet (onion tissue) and carefully tilt and lower it so it covers the specimen

Question 2

How to set up and use a light microscope (6 steps)

Req Prac 1

Answer 2

1. Clip the prepared slide onto the stage
2. Select the lowest powered objective lens
3. Use the coarse adjustment knob to move the stage up to just below the lens
4. Look down the eyepiece and use the coarse adjustment knob to move the stage down until its roughly in focus
5. Adjust the focus with the fine adjustment knob until the image is clear
6. Swap to a higher powered objective lens if you want to see the slide with a greater magnification

Question 3

How to investigate the effect of sugar solutions on plant cells (6 steps)
Req prac 3

Answer 3

1. Using a cork borer create 5 potato cylinders and using a ruler and a knife make them approximately the same lengths
2. Measure their masses using a balance
3. Get beakers and fill them with different sugar solutions with concentrations between 0.2 mol/dm^3 to 1mol/dm^3, fill one beaker with distilled water, make sure there is the same volume of each
4. Place one potato cylinder in each beaker for 30 minutes using a timer
5. Take the potatoes out, dry them with a paper towel and measure their masses again with a balance
6. Record the mass of each potato cylinder in a results table

Question 4

How to work out a change in mass for req prac 3

Answer 4

Take away the initial mass from the final mass

Question 5

What are the risks of req prac 3 and how to prevent injury

Answer 5

A sharp knife
Cut away from yourself
The blade should be sharp and clean

Question 6

Dependent variable of req prac 3

Answer 6

Potato cylinder mass

Question 7

Independent variable of req prac 3

Answer 7

Conc of sugar solution

Question 8

Control variables of req prac 3

Answer 8

Volume of solution
Temperature
Time cylinders left in solution
Type of sugar used

Question 9

How can you reduce the effect of errors in req prac 3

Answer 9

Repeat the experiment and calculate a mean percentage change at each conc

Question 10

Errors that may occur in req prac 3

Answer 10

If some potato cylinders weren’t fully dried the excess water would give them a higher mass
If water evaporated from the beakers the concs of the solutions would change

Question 11

How to work out percentage change in mass req prac 3

Answer 11

change in mass / initial mass x 100

Question 12

What does it mean if the potato has increased in mass req prac 3
(the potato gets bigger)

Answer 12

Water has moved into the potato by osmosis
The sugar solution has a lower solute concentration than inside of the potato cells

There was a higher conc of water molecules in the solution so they moved into the cells

Question 13

What does it mean if the potato has decreased in mass req prac 3
(the potato gets smaller)

Answer 13

Water has moved out the potato by osmosis

The sugar solution has a higher solute conc than inside the potato