NCERT Class 9 Science Lab Manual – Osmosis in Raisins

NCERT Class 9 Science Lab Manual – Osmosis in Raisins

EXPERIMENT

Aim
To determine the mass percentage of water imbibed by raisins.

Theory

1. Imbibition: It is a special type of diffusion in which movement of water takes place due to difference in water molecule concentration between the adsorbant and the imbibant. For e.g., the dry plant part or dry seeds when placed in water increases in size or swells.
   Mass percentage of water imbibed by raisins can be calculated as:Mass % of water imbibed=\(\frac { Mass\quad of\quad water\quad absorbed\quad by\quad the\quad raisins }{ Intial\quad mass\quad if\quad raisins } X100\)
2. Osmosis: When the solution of higher water concentration moves into the solution of lower water concentration through a semipermeable membrane, till the concentration on both the sides of the membrane is equal. This process is called osmosis.
3. Hypotonic solution: When a cell (dry raisin) is dropped in water, the cell has a less water concentration than the medium in which it is kept. The water molecules will flow into the cell, and it will swell up or even can burst as in case of animal cells. Such a solution is called hypotonic solution. This is Endosmosis.
4. Isotonic solution: If the medium has exactly the same water concentration as that of the cell, the water does not move either in or out of the cell, the size of cell remains the same. Such solution is called isotonic solution.
5. Hypertonic solution:If the medium has lower concentration of water than the cell, the cell will lose water by osmosis and become smaller in size. Such a solution is called hypertonic solution. This is Exosmosis.
6. Plasmolysis: When a cell loses water through osmosis and contracts, the contraction of the contents of the cells is away from the cell wall. This phenomenon is known as plasmolysis.

Materials Required
Five raisins, a beaker, filter paper, weighing balance, watch glass, weight box.

Procedure

1. Take 5 dry raisins and weigh it.
2. Place these raisins in a beaker containing water. Allow all the raisins
3. Next day remove all the raisins and place them on filter paper.
4. Gently dry the outer surface of raisins by using filter paper.
5. Weigh the raisins which are swollen.
   

Observations

1. Weight of raisins taken = 10 g.
2. Weight of swollen raisins = 13 g.

Calculations

1. Weight of water absorbed by the raisins = (13- 10) = 3 g.
2. The percentage of water absorbed by the raisins = \(\frac { 3 }{ 10 } X100\)=30%

Conclusion
The percentage of water imbibed (absorbed) by raisins is 30 %.

Precautions

1. Raisins should be with intact stalks, dry and clean.
2. While soaking raisins in water, they should be properly immersed in water.
3. Soaking should be for sufficient time.
4. Before weighing, gently dry the raisins with the help of filter paper.

VIVA VOCE

Question 1:
How do roots absorb water?
Answer:
By osmosis.

Question 2:
What is endosmosis?
Answer:
When the water enters the cell from the medium, it is called endosmosis.

Question 3:
What is exosmosis?
Answer:
When the water leaves the cell and enters into the medium, the cell shrinks and it is called exosmosis.

PRACTICAL BASED QUESTIONS

Question 1:
What is osmosis?
Answer:
Flow of solution from higher water concentration to lower concentration is called osmosis. The exchange of molecules takes place through the semi-permeable membrane.

Question 2:
What will happen if a raisin is dipped in a hypotonic solution?
Answer:
The raisin will absorb water by osmosis and swell.

Question 3:
What will happen to the grapes if they are kept in isotonic solution?
Answer:
The size of cell (grapes) will remain the same.

Question 4:
What will happen to a cell if it is kept in a hypertonic solution?
Answer:
The cell will shrink and become smaller in size, it loses water due to exosmosis.

Question 5:
Give two functions of osmosis.
Answer:

1. Plant root cells absorb water by osmosis.
2. The unicellular organisms like amoeba takes in the required material by osmosis.

Question 6:
Give two examples of semi-permeable membrane.
Answer:
Plasma membrane.

Question 7:
What is a hypertonic solution?
Answer:
When the concentration of a solute in solution is more than the concentration of cell-sap, it’s called hypertonic.

NCERT LAB MANUAL QUESTIONS

Question 1:
Will a piece of iron also swell when kept in water? Justify your answer.
Answer:
Iron is a metal which may undergo rusting when kept in water. But it will not swell.

Question 2:
Have you experienced difficulty in closing wooden doors during rainy season? Give a suitable explanation.
Answer:
Yes, it is difficult to close or open the wooden doors or windows during rainy season because the wood absorbs water from the atmosphere and swells. ‘

Question 3:
Suggest an experiment by which the swollen raisins can be shrunk again.
Answer:
By placing the swollen raisins in salt solution they will shrink again.

Question 4:
What will happen to the shape of a grape when it is placed in a viscous sugar solution?
Answer:
Grapes will shrink.

Question 5:
What is the effect of temperature on the rate of imbibition?
Answer:
Imbibition increases with increase in temperature.

Question 6:
What is the difference between endosmosis and exosmosis?
Answer:
Endosmosis: When the cell has less water concentration than the medium in which it is kept, the water molecules will flow into the cell. The cell swells.
Exosmosis :When the cell has more water concentration than the medium in which it is kept, the water molecules will flow out of the cell. The cell shrinks.

Question 7:
What will happen if a de-shelled egg is placed in a solution with the same osmotic concentration, as in the egg?
Answer:
As animal cells always gets bathed when kept in a solution having the same osmotic strength as their cytoplasm and the size of the egg will remain the same.

Question 8:
Why did the egg swell when placed in water?
Answer:
The water concentration outside the cell is more than inside. Hence the water diffuses inside the egg and the egg swells.

Question 9:
Movement of water during osmosis takes place across-
(a) cell wall
(b) cell membrane
(c) cytoplasm
(d) protoplasm.
Answer:
(b) cell membrane

Question 10:
The plasma membrane which selectively allows solvent molecules and solute molecules to pass through it is
(a) a permeable membrane,
(b) a selectively permeable membrane,
(c) an impermeable membrane,
(d) a semi-permeable membrane
Answer:
(b) a selectively permeable membrane.

Question 11:
Why pigments and other cell contents do not move out of the cells?
Answer:
The pigments cannot cross the membrane.

Question 12:
Why are living cells always turgid?
Answer:
To maintain the pressure inside the cell so that it does not die and the organelle functions well Q13. What will happen if the cells are kept for a very long time in the salt (or sugar) solution? Explain.
Ans. The salt solution is hypertonic because it has less water potential so the water will be lost by the cell inside the solution and the cell will shrink.

Question 13:
Between the cell sap and solution (salt or sugar) in the experiment, which is the hypertonic solution?
Answer:
The salt or sugar solution will be hypertonic.

Question 14:
Will plasmolysis occur when cells are placed in isotonic solution?
Answer:
The plasmolysis will not occur in isotonic solution.

MULTIPLE CHOICE QUESTIONS (MCQs)
Questions based on Procedural and Manipulative Skills

Question 1:
If x represents weight of soaked raisins and y represents weight of dry raisins then \(\frac { x-y }{ y } X100\) is a  way to calculate percentage of
(a) water absorbed by raisins in hypertonic solution
(b) water absorbed by raisins in hypotonic solution
(c) water lost by raisins in hypotonic solution
(d) water lost by raisins in hypertonic solution.

Question 2:
Raisins are made from:
(a) Grapes
(b) Guava
(c) Peanuts
(d) Almonds

Question 3:
Which of the following materials is required to set up
an experiment to determine the percentage of water imbibed by raisins? .
(a) Raisins, beaker, water, blotting paper, weight box, balance
(b) Raisins, beaker, water, balance, weight box
(c) Raisins, beaker, balance, weight box
(d) Raisins, water, blotting paper, balance

Question 4:
For determining the percentage of water imbibed by raisins in a given time, apart from water, raisins and a watch glass, we shall also require:
(а) a beaker, a graduated cylinder, a thermometer, a weighing balance
(b) a watch glass, a graduated cylinder, a thermometer, filter paper
(c) a beaker, a thermometer, a filter paper, a weighing balance
(d) a graduated cylinder, a thermometer, a weighing balance.

Question 5:
The raisins are wiped just before weighing. This is to ensure that
(a) hands do not get wet
(b) raisins lose water before weighing
(c) the weighing scale does not get wet
(d) only water imbibed by raisins is weighed.

Questions based on Observational Skills

Question 6:
Endosmosis occurs in a cell when they are placed in a:
(a) hypotonic solution
(b) Isotonic, solution
(c) hypertonic solution
(d) saturated solution.

Question 7:.
Exosmosis occurs in a cell when it is placed in a:
(a) hypotonic solution
(b) Isotonic solution
(c) hypertonic solution
(d) none of these.

Question 8:
A student soaked 5 grams of raisins in 25 mL of distilled water in each of two beakers A and B. Beaker A was maintained at 25°C and beaker B at 50°C. After one hour, the student observed that the water absorbed by the raisins was
(a) same in case of A and B
(b) less in case of A than in B
(c) exactly double in A, of that in B
(d) exactly four times in A, of that in B.

Question 9:
A student put five raisins each in two beakers A and B. Beaker A contained 50 mL of distilled water and beaker B has 50 mL of saturated sugar solution. After some time the student would observe that
(a) raisins in beaker A were more swollen than those in beaker B
(b) raisins in beaker B were more swollen than those in beaker A
(c) raisins in both beakers A and B were equally swollen
(d) raisins in beaker A did not swell up at all.

Question 10:
A teacher soaked 10 raisins in 35 mL of distilled water in a beaker labelled A and similar activity she performed and labelled the other beaker B. She maintained the temperature of beaker A at 20°C and B at 40°C. After an hour what will be the percentage of water absorbed by raisins in beaker A and by those in beaker B?
(a) the same
(b) more in A and less in B
(c) more in B and less in A
(d) exactly twice as much in B as in A.

Question 11:
A student soaked 10 g of raisins in 25 mL of water in beaker A and 20 g of raisins in 50 mL of water in beaker B and measured the quantity of water left in beaker after an hour. What will he find?
(a) There will be no change in the quantity of water in beakers A and B
(b) Beaker B will have as much water as in beaker A
(c) Beaker B will have more water than in beaker A
(d) Beaker A will have more water than in beaker B.

Question 12:
Twenty dry raisins were soaked in 50 mL of water and kept for one hour at 50°C . Which one of the following was the correct observation?
(a) 8 raisins imbibed water, 12 did not
(b) 10 raisins imbibed water, 10 did not
(c) 15 raisins imbibed water, 5 did not
(d) All the 20 raisins imbibed water

Question 13:
A student dissolved lg of sugar in 10 mL of distilled water in a beaker A. He dissolved 1 Og of sugar in 100 mL of distilled water in beaker B. Then he dropped a few raisins in each. After two hours, he found the raisins
(a) swollen in A and shrunken in B
(b) shrunken in B only
(c) swollen in both
(d) shrunken in A only

Questions based on Reporting and Interpretation Skills

Question 14:
The process by which dry raisins swell on putting them in water is:
(a) endosmosis
(b) exosmosis
(c) plasmolysis
(d) diffusion.

Question 15:
A potato cup (peeled potato) is kept in a solution with half dipped and half floating, the potato cup also has a solution in it. After few hours the amount of solution in a cup remained the same because:
(a) both the solutions are isotonic
(b) the potato may be boiled one
(c) both (a) and (b)
(d) none of these.

Question 16:
Osmosis can occur through a:
(a) cell wall
(b) plasma membrane
(c) both (a) and (b)
(d) none of these.

Question 17:
If the weight of dry raisins is 10 g and the weight of same swollen raisins is 15 g. Percentage of water absorbed by raisins will be:
(a) 50%
(b) 25%
(c) 75%
(d) 100%.

Question 18:
While performing an experiment to determine the percentage of water absorbed by raisins, the following data was obtained:
Mass of water taken in a beaker = 50 g
Mass of dry raisins = 5 g
Mass of soaked raisins in water = 8 g
The percentage of water absorbed by raisins would
be:
(a) \(\frac { (8-5)g }{ 8g } X100\)
(b) \(\frac { (8-3)g }{ 8g } X100\)
(c) \(\frac { (8-5)g }{ 3g } X100\)
(d) \(\frac { (8-5)g }{ 5g } X100\)

Question 19:
A student soaked 5 g raisins in 50 mL of distilled water in two beakers A and B. She maintained beaker A at 30°C and beaker B at 60°C. After an hour, the percentage of water absorbed will be:
(a) same in both A and B
(b) more in A than in B
(c) more in B than in A
(d) twice in B than in A.

Question 20:
A cell is placed in a solution X and the volume of cell increases. Hence the cell with respect to medium is
(a) hypertonic
(b) hypotonic
(c) isotonic
(d) none of these.

Question 21:
An experiment was set up to determine the percentage of water imbibed by raisins. If the mass of dry raisins was 40 g and mass of wet raisins was 45 g. The percentage of water imbibed would be
(a) \(\frac { 45g }{ 40g } X100\)
(b) \(\frac { 40g }{ 45g } X100\)
(c) \(\frac { (45-40) }{ 40g } X100\)
(d) \(\frac { (45-40) }{ 45g } X100\)

Question 22:
Some raisins weighed 10 g before they were placed in water for four hours. The raisins were then removed, wiped and weighed again. Their weight was found to be 12.5 g. The percentage of water imbibed by them is
(a) 2.5%
(b) 5%
(c) 12.5%
(d) 25%

Question 23:
On rainy days the wooden door of our house swells due to the process of
(a) imbibition
(b) osmosis
(c) diffusion
(d) transpiration

Question 24:
While performing an experiment with raisins, a student recorded the following data.
Mass of water taken in the beaker = 50 g
Mass of raisins before soaking = 20 g
Mass of raisins after soaking = 30 g
Mass of water in beaker left after experiment = 40 g
The % of water aboserbed by the raisins is
(a) 10%
(b) 20%
(c) 45%
(d) 50%

SCORING KEY WITH EXPLANATION

1. (b) The formula is constant.
2. (a) Dry grapes are called raisins.
3. (a) It is the method of the experiment.
4. (c) It is the method of the experiment.
5. (d) The water on the surface of the raisins is removed to calculate the accurate reading.
6. (a) The solution with more water is called hypotonic
7. (c) The solution with less water is called hypertonic and water always flows from higher concentration to lower concentration.
8. (b) Osmosis is affected by the temperature of water, as the temperature of water is more, the rate of diffusion (osmosis) is more.
9. (a) In beaker A the raisins have hypotonic solution and hence they swell but in beaker B the solution is hypertonic.
10. (c) Osmosis is affected by the temperature of water, as the temperature of water is more, the rate of diffusion (osmosis) is more.
11. (c) As in beaker B the amount of water is more as compared to beaker A.
12. (d) When dry raisins are kept in hypotonic solution all of them will absorb water.
13. (c) For raisins both the solutions are hypotonic and hence they absorb water in both the solutions given.
14. (a) The movement of water into the cell is called endosmosis.
15. (c) If the solution is isotonic then there is an equilibrium/ if potato is boiled then the cells are dead and osmosis does not occur.
16. (c) Both cell wall and plasma membrane allows the diffusion of water through it.
17. (a) Percentage of water absorbed = 15 – 10/10 x 100 = 50 %.
18. (d) % of water absorbed by raisins = final mass – initial mass/initial mass x 100.
19. (c) Osmosis is affected by the temperature of water, as the temperature of water is more, the rate of diffusion (osmosis) is more.
20. (a) The cell is hypertonic, with less concentration of water hence when placed in a solution containing more water the cell absorbs water.
21. (c) The correct formula to calculate the percentage of water absorbed by raisins.
22. (d) 2.5/10 x 100 = 25%.
23. (a) The dry wood absorbs water.
24. (d) Correct calculation.

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