Q5 of 67 Page 48

Two potato cubes each 1 cm3 in size, were placed separately in two containers (A & B), the container (A) having water and the other (B) containing concentrated sugar solution. After 24 hours when the cubes were examined, those placed in water were found to be firm and had increased slightly in size and those placed in concentrated sugar solution were found to be soft and had somewhat decreased in size. Use the above information to answer the questions that follow:

(a) Account for the firmness and increase in the size of the potato cubes placed in water.


(b) Account for the softness and decrease in size of the potato cubes which were placed in sugar solution.


(c) Name and define the physical process being investigated in this experiment.

(a) When a potato cube is placed in container A containing water, after 24 hours the cube was found to be firm and slightly increased in size. This is due to the absorption of water by endosmosis as the concentration of solute is higher in the potato cubes making it a more concentrated solution than the water present outside. This leads to the inflow of water from its higher concentration (water) to its lower concentration (potato cubes) thus, making the potato swell firm and increase in size.


(b) When a potato cube is placed in container B containing concentrated sugar solution, after 24 hours the cube was found to be soft and had somewhat decreased in size. This is due to the loss of water by exosmosis as the concentration of solute is lower in the potato cubes making it a more diluted solution than the concentrated sugar solution present outside. This leads to the outflow of water from its higher concentration (potato cubes) to its lower concentration (concentrated sugar solution) thus, making the potato soft and decrease in size.


(c) The two processes mentioned above are endosmosis and exosmosis which are the two types of osmosis. Thus, it can be concluded that the experimental setup is the demonstration of osmosis.


Thus osmosis is defined as the diffusion of water molecules across a semi-permeable membrane from a more dilute solution, that is, with a lower solute concentration to a less dilute solution, which is with a higher solute concentration.


More from this chapter

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3

The diagram given below represents an experimental set-up to demonstrate a certain process. Study the same and answer the questions that follow:


(a) Name the process.


(b) Define the above-named process.


(c) What would you observe in the experimental set-up after an hour or so?


(d) What control experiment can be set up for comparison?


(e) Keeping –hair, cell and its surroundings, name the parts that correspond to (1) concentrated sugar solution (2) parchment paper and (3) water in the beaker.


(f) Name any other substance that can be used instead of parchment paper in the above experiment.


(g) Mention two advantages of the process to the plants.

 4

The diagram below represents a layer of epidermal cells showing a fully grown root hair.

Study the diagram and answer the questions that follow:



(b) The root hair cell is in a turgid state. Name and explain the process that caused this state.


(c) Mention one distinct difference between the parts labeled A and B.


(d) Draw a diagram of the above root hair cell as it would appear when a concentrated solution of fertilizers is added near it.

 6

Given below is the diagrammatic representation of the transverse section of a part of a plant. Study it and answer the questions that follow:


(a) Name the part of the plant that is shown.


(b) Label the parts 1 to 6.


(c) Write the functions of parts 3 and 5.

 7

Study the diagram given below and answer the questions that follow:


(a) Name the process being studied in the above experiment.


(b) Explain the process mentioned in (a) above.


(c) Why is oil placed over water?


(d) What do we observe with regard to the level of water when this set up is placed in (1) bright sunlight (2) humid conditions (3) windy day?


(e) Mention any three adaptations found in plants to foster the process mentioned in (a) above.