December 15, 2014

10th Biology Important Questions from New Syllabus

Q: How do you test the changes during combustion of sugar? Write the experiment you have conducted in your school. (4 Marks)
i) Is heat production always the same in our body?
ii) How are carbon dioxide and water formed in this experiment?

Aim: To observe changes during combustion of sugar.
Apparatus: Wooden stand, test tubes, rubber stopper, delivery tube, glucose or sucrose powder, lime water.

Procedure: Take a small test tube and add a little amount of glucose to it.
Arrange the apparatus as shown in the figure.
Heat the test tube with a Bunsen burner.
Heat until the glucose catches fire.

Observation: When glucose in the test tube starts burning, you will observe that carbon dioxide and water are produced and energy is released as heat.
Glucose is burnt at high temperature so that it liberates energy.
Once the glucose burns, we cannot stop the process easily.
When water is added to the burning sugar, the combustion stops.
The carbon dioxide released in this process changes lime water to milky white.

Inference: From this experiment, we can conclude that during combustion of glucose in the laboratory, carbon dioxide, water and heat are produced.
The carbon dioxide produced changes lime water to milky white in nature.
i) Heat production is not the same always in our body. It is normal when we are at rest. It increases when we do some strenuous work.
ii) When sugar is burned, the bonds holding the atoms together in the oxygen molecules and sugar molecules break and the atoms rearrange themselves to form carbon dioxide and water molecules.
(There are other experiments too in this lesson. See activities 2, 5 and 6 in the textbook and prepare the same type of answers).

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