Q5 of 18 Page 62

Suggested Activities

Remove the shell of an egg by dissolving it in dilute hydrochloric acid. A thin outer skin now encloses the egg. Put the egg in water. Observe after a few minutes. What is your inference?

The shell of an egg is basically calcium carbonate. So when it is placed in dilute HCl, the shell dissolves. Now the inner thin covering is exposed which acts as a semi-permeable membrane.

When this de-shelled egg is placed in water, it swells up. Water molecules move inside as a result of osmosis to maintain equilibrium. The surrounding medium has a higher concentration of water than that present in the egg. The surrounding solution is hypotonic. The water molecules move along the concentration gradient from a region of higher concentration to a region of lower concentration.



DE-SHELLED EGG


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4

Answer the following questions:

0.9% sodium chloride solution is good and balanced to RBC. A lab technician accidentally places a sample of RBC’s in 1.8% sodium chloride solution. What happens? Why?

 4

Answer the following questions:

Diagrams of two different cells are given below. Which one of the two is a plant cell? Support your answer.



(i) Name the parts 1, 2, 3 and 4.


(ii) Write the functions of 1 and 3.


(iii) Draw a diagram to show the structure of 4 and label the parts.


(iv) Draw a diagram of a plant cell and label the parts.

 5

Suggested Activities

Put dried raisins (dry grapes) in a dish with water. What is the change in the raisins after some time? Why?

 5

Suggested Activities

Place a similar de-shelled egg in a concentrated salt solution for a few minutes. Observe the changes. Record your observations giving reasons.