Page 73 - Biology Form Two

Biology for Secondary Schools

2. Invert the thistle funnel and fill it 2. What are the reasons for your
with sugar solution. observation?

3. Mark the level of sugar solution in
the thistle funnel using a marker Activity 3.3: Demonstrate osmosis
FOR ONLINE READING ONLY
pen. using potato cubes

4. Slowly immerse the thistle funnel Materials
into the beaker containing water Three raw potatoes, sugar solution,
as shown in Figure 3.3. water, source of heat, and beakers or
dishes, scalpel or knife

Procedure
Thistle funnel
Stand 1. Peel three potatoes.
2. Cut each potato into half and make
a shallow hole on each half.
Sugar solution
3. Boil one of the potatoes to kill the
cells
Beaker
4. Place each half of the potato in a
beaker or dish that contains water.
Water
The water should not cover the
potato.
Cellophane membrane
Figure 3.3: Experimental set-up to Safety precautions
demonstrate osmosis
Observe safety precautions when
working with sharp, glass objects
5. Leave the set-up undisturbed for and heat.
about 3 hours.

5. Put some sugar solution in the
6. Mark the levels of the sugar shallow hole in one raw potato
solution in the thistle funnel and and the boiled potato. Leave the
the level of water in the beaker. other raw potato empty. Label
these set-ups as (a), (b), and (c),
Questions respectively.

1. What did you observe on the 6. Mark the level of water in each
levels of water and the sugar beaker or dish.
solution?

Student’s Book - Form Two 67

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BIOLOGY FORM 2 NEW.indd 67 05/10/2024 15:36:25
BIOLOGY FORM 2 NEW.indd 67