Photosynthesis

Question 1

Variables in an experiment

Answer 1

independent, dependent, control

Question 2

Word equation of photosynthesis

Answer 2

Carbon dioxide + water → glucose + oxygen

Question 3

Storage of glucose

Answer 3

Starch

Question 4

Test for starch

Answer 4

Iodine test: color change from brown to dark blue

Question 5

Procedure for testing if starch is present in a leaf

Answer 5

1. Heat a plant leaf in boiling water for 30 seconds (this kills the leaf, stopping any chemical reactions)
2. Add the leaf to boiling ethanol in a water bath for a few minutes
3. Wash the leaf with water to rehydrate and soften the leaf and spread it onto a white tile.
4. Add iodine solution from a dropping pipette.
5. Colour of the iodine solution change from brown to dark blue.

Question 6

Why do we boil the leaf before performing an iodine test?

Answer 6

To kill the leaf and stop any chemical reactions

Question 7

Why do we add ethanol to the leaf before performing an iodine test?

Answer 7

The boiling ethanol dissolves the chlorophyll and removes the green color from the leaf so it is easy to see the change in color.

Question 8

Test for essential components for photosynthesis - light

Question 9

Test for essential components for photosynthesis - chlorophyll

Answer 9

variegated leaf

Question 10

Steps to take before performing tests for photosynthesis

Question 11

Word equation of respiration

Answer 11

glucose + oxygen → carbon dioxide + water

Question 12

Purpose of soda lime in respiration test

Answer 12

Absorb carbon dioxide

Question 13

Members in the food chain and energy transfer

Answer 13

Energy is transferred from the producer to the primary consumer and then the secondary consumer

Question 14

Where does gas exchange in plants take place?

Answer 14

At the stomata

Question 15

Describe gas exchange in plants during the day and at night.

Answer 15

During the day, plants undergo both photosynthesis and respiration as there is light. The rate of photosynthesis is higher than that of respiration. At night, plants only undergo respiration.

Question 16

In a burning food test, the results obtained from this experiment are lower than the actual energy content of the food. Why?

Answer 16

During the experiment, some energy is lost to the air and some is used to heat the glass of the boiling tube instead of heating up the water.