B1.4.2 - Photosynthesis Experiments

Question 1

What can testing for starch prove?

Answer 1

That light, chlorophyll and carbon dioxide are essential for photosynthesis

Question 2

What are the steps for testing for starch?

Answer 2

Get a leaf and use forceps to put it into a beaker of boiling water. Then, place the leaf, using forceps, into a boiling tube of boiling ethanol. Then, wash the leaf with water and spread it out on a white tile. Add a few drops of iodine solution, and the leaf will change colour if there is starch present

Question 3

Why should you use forceps yo place the leaf into the boiling liquids?

Answer 3

So you do not accidentally burn yourself

Question 4

Why do you need to place the leaf into the boiling water?

Answer 4

In order to kill it. Also, putting it into boiling water disrupts the cell membranes, softens the cell wall and allows the iodine solution to penetrate the cells and react with any starch

Question 5

Why do you need to place the leaf until the boiling ethanol?

Answer 5

So the chlorophyll is removed

Question 6

What does washing it do?

Answer 6

It removes the ethanol

Question 7

What is the iodine solution made of?

Answer 7

A mixture of iodine and potassium iodide

Question 8

What colour should the leaf turn if starch is present?

Answer 8

Blue/black

Question 9

What is a variegated leaf?

Answer 9

It is only coloured green in some areas

Question 10

How can you prove chlorophyll is needed for photosynthesis?

Answer 10

Place a de-starched variegated plant in sunlight for several hours. Then, test one of the leaves for starch

Question 11

Why do you need to de-starch a plant before carrying out photosynthesis experiments?

Answer 11

So the starch can start from nothing

Question 12

How can you de-starch a plant?

Answer 12

You place it in total darkness for 24 hours

Question 13

How can you prove light is needed for photosynthesis?

Answer 13

Get a de-starched plant and cover one if it’s leaves with black card. Light can’t reach the area of this leaf, place the plant in sunlight. Then, test the starch in the same leaf

Question 14

How can you prove that carbon dioxide is needed for photosynthesis?

Answer 14

Take a de-starched plant, and place it inside a polythene bag. Before you seal the bag, add a pot of soda lime. Then, place the plant in sunlight for several hours, before testing one if its leaves for the presence of starch

Question 15

What is soda lime?

Answer 15

A chemical that absorbs carbon dioxide and water

Question 16

How can you prove oxygen is given off surging photosynthesis?

Answer 16

Place and upturned test tube above an aquatic plant. Put the apparatus in the sunlight for maximum photosynthesis.
Once you have collected a full tube of gas, place a glowing splint inside the tube, it will relight because of the oxygen present