Page 115 - Biology - XII

Q3. Imbibition phenomenon is operative when there is
(a) seeds (b) liquid

(c) diff erence in the diff usion pressure between the liquids inside and outside the cells
(d) both (b) and (c)
Q4. The expansion of volume in seeds when kept in water is because of
(a) nature of seeds (b) imbibition

(c) inward movement of water (d) both (b) and (c)
Q5. Seeds do not imbibe

(a) water (b) salt solution
(c) organic solvent (d) any of these mentioned
Answer key

1. (c), 2. (b), 3. (c), 4. (d), 5. (c)

PROJECT - 10

Objective
To study the precipitation of emulsoids with electrolytes.

Materials Required
Wheat fl our, chemical balance, weight, beakers, test tube, distilled water, measuring cylinder, glass rod,
solid (NH ) SO , fi lter paper, funnel, spirit lamp, matchbox, and test tube holder
4 2 4

Procedure
1. Take 2.5 g wheat fl our in a beaker.
2. Add 25 ml of distilled water to it and stir it well. Let the contents stand for 5–10 minutes.
3. Filter the solution in a clean and dry beaker.

4. The fi ltrate has/is the emulsion of protein-in-water. Shake it again and note.
5. Take 5 ml of the fi ltrate, warm it, and add solid (NH ) SO .
4 2
4
Results
1. Froth is developed in the solution/fi ltrate.
2. A precipitate is formed.
3. Precipitate readily dissolves in water.
Repeat the experiment with emulsions of starch, protein from other sources with (NH ) SO 4
4 2
and alcohol.
Use these materials

Rice fl our for starch, starch powder, gram fl our, maize fl our, etc.

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