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WDiffusion

region of their

demonstrate the process of diffusion in the laboratory.

Potassium permanganate tablet, beaker containing water.

is the movement of molecules of a substance from the region of their higher concentration tolower concentration when they are in contact with each other.

Take a beaker containing water.Drop a tablet of potassium permanganate in it.

1.

2.

Beaker

Water

Poiassiumpermanganate

The water turns pink in colour.

We conclude that molecules of potassium permanganatewater in the beaker turns pink.

Molecules ofpotassiumpermanganatediffusingin water

diffirse in water because after sometime

Fig. Experimental set-utrr to demonstrate the process of dififrrsion

the

Internal Assessment of Practical Work

WToshow that roots of a plant absorb water'

iit"r,oil, a young plant with roots intact'

:l

it remained the same.

We conclude that roots of a plant absorb water'

demonstrate osmosis in the laboratory'

Stand, thistle funnel, water, sugar solution, animal bladder or egg rnembrane (semi-permeable mem.

1. Two test tubqs are taken'

2. They are filled with water'

3. In one test tube a young plant is kept'

4. The level of water in the two test tubes is noted'

5. A few drops of oil are introduced in both the test tube,1 to prevent loss of water by evaporation'

6. The test tubes are left undisturbed in a stand for a while'

]M,j':^,_F'ird:-!i'#JiJ+--i4q{F'----trs*F'*itr+'ds* . r^: -r- rL^ -r^a} ."oo La re. In thg other tgst tubeThe level of water in the test tube in which the plant was kept fell after sometin

'WTo

) and beaker.

'7ord/'e q'd BiologY QCSE) -X

Osmosis is a phenomenon in which there is a movement of water molecules from a region of their higher

concentration to a region of their lower concentration through a semi-permeable membrane.

1. A thistle funnel is taken.

2. An animal bladder is tied at the mouth of the

funnel. !,;,3. The thistle funnel is fixed to a stand in an

inverbed manner.

4. A beaker filled with water is taken and kept at

the base of the stand.

5. The thistle funnel is introduced in the beaker.

6. Sugar solution is poured into the thistle funnelstem.

7. The level of the solution is marked.

8. The apparatus is left undisturbed for a few hours.Fig. Experimental set'up to demonstrate osmosis

The level of the sugar solution rises in the stem of the thistle'funnel.

The water from the beaker moves into the funnel through the animal bladder which is the semi-permeable

membrane.

Beaker

WaterThistle funnelSugar $0lution

Animal bladdet

i"

ffiTo

paper.compare the rate of transpiration from the upper and lower surface of a leaf using cobalt chloride

Filter paper, cobalt chloride (CoOlr) solution, glass slides, rubber bands, dessicator, a potted plant.

1. Dissolve 5 g cobalt chloride in 100 ml water to make \Vo cobalt chloride solution.2. Cut thin strips of filter paper and dip them in CoCl, solution.3. Dry the cobalt chloride paper strips thoroughly in a dessicator.4. The pink colour strips become blue when dried in a dessicator.5. TWo strips are taken and they are fixed on the lower and upper surface of a leaf with the help of glass

slides and rubber bands.6. Observe the time taken by each of the strips in changing its colour from blue to pink.

Fig. Experimental set-up to compare the rate of transpirationfrom upper and lower surface of a leaf. . "

It is observed that the strip fixed on the lower surface of the leaf turns pink earlier as compared to thestrip attached to the upper surface.

Totdae a,r6@ Biotogy (ICSE) -X

The strips changed colour'from blue to pinktranspiration. Since more stomata ate presentturned pink quickly.

because of the water vapour released from the leaf due toin the lower surface the strip fixed to the lower surface

1. The cobalt chloride strips should be dried completely.2. The cobalt chloride p#er strips should not be handled with wet hands. /3. The strips should be completely covered with the glass slides.4. The strips should be covered with the slides and the rubber bands should be fixed properly.

ffiTo measure the water taken in by a plant because of transpiration, with the help of Ganong,s potometer.

Ganong's potometer, twig of a plant Iike Coleus, water, beaker, colouring agent (eosin).

1. The twig of a plant is taken.2. It is cut with a sharp knife and fitted at one end of the capillary tube.3. The graduated capillary tube is frlled with water.4. One end of the tube is made to dip in a beaker containing coloured water.5. An air bubble is introduced into the horizontal graduated capillary tube by lifting the bent capillary

tube above the coloured water.6. As the process of transpiration takes place from the twig the bubble mov6s forward. Ttris is because

of the suction force which pulls the water from the beaker.7. Since the capillary tube is graduated the reading would give an idea about the volume of water lost.8. The air bubble can again be brought into the capillary tube by releasing some water from the stop-

cock.Twig of a Coleus plant

Fig. Ganong's Potometer

Internal Assessment of Practical Work

As the process of transpiration takes place from the twig the

the suction force which pulls the coloured water from the beaker.

reading would give an idea about the volume of water lost.

bubble moves forward. This is because ofSince the capillary tube is graduated the

Tlanspiration takes pface from the leaves and results in absorption of water by the roots. This water

then moves up to the leavd#through the stem.

1. The entire apparatus should be filled with water. There should be no air spaces.

2. The air bubble should be carefully introduced

Limitations of a PotofireterA potometer is a device which is used to measure the rate of water uptake by a shoot cut from a plant. It

does noi measure the transpiration rate directly. The processes oftranspiration and absorption are interre-

lated and so the rate of absorption is measr,rred and transpiration rate is assessed. It is a difficult process and

requires accurate observation hence it is often not used. In this process, some water is used by the plant for

melabolic activities. The rate at which this water is used is not shown by the potometer. The cobalt chloride

paper strip experiment is simpler and it directly helps in comparing the rate of transpiration.

ffiTo show that oxygen is evolved during photosynthesis.

Beaker, glass funnel, Hydrilla plant twig, water, splinter, matchbox, test tube, sodium bicarbonate.

l. Hydrilla plant twigs are taken in a glass funnel.2. The funnel is inverted in a beaker containing water.3. A test tube filled with water is inverted over the stem of the funnel.4. A pinch of sodium bicarbonate is added in the water contained in the beaker, so that carbon dioxide

is produced.5. The apparatus is kept in sunlight for a few hours.

Gas bubbles

Test tube filled with water

Bedker coniaining wat€r

Funnel

Hydrtila plant twigs

Fig. Experimental set-up to show that orygen is evolved during photos5rnthesis

Bubbles are seen rising from the stem of the funnel. After sometime the test tube loses all its water andbecomes empty. A glowing splinter is introduced in the test tube, it bursts irlto flames.

1..2.3.

Hydrilla plant twigs should be completely submerged in water.The empty test tube should be carefully removed by placing the thumb at the mouth of the test tube.Sodium bicarbonate should be added to the water so that the plant gets carbon dioxide which isneeded for photosynthesis.

Internal Assessment of Practical Work

WTo show that carbon dioxide is necessary for photosynthesis.

Glass bottle, split cork, potassium hydroxide, a plant with long leaves, iodine, alcohol, spirit lamp, tripodstand, beaker, water bath containing water, petri dish.

1. A healthy green plant'with long leaves is taken.2. The plant is kept in darknes s for 24hours.3. The next day, a bottle containing potassium hydroxide is tdken and its mouth is closed with a cork

which is split in the middle.4. One of the leaves of the plant is introduced through the split cork into the bottle. Only half the leaf

is introduced.5. The plant and the bottle are exposed to sunlight for a few hours.6. The leaf which was introduced in the bottle is removed.7. It is boiled in alcohol in a beaker which is kept in a water bath.8. The leaf becomes colourless.9. The colourless leaf is washed in water and dipped in iodine.

Healthy green plant

Beaker

Alcohol

Waler bathcontaining water

Tripod stand

Spirit lamp

r- Part of the leaf in the bottleI containing KOH will not giveI a bUe-black colour with iodine

l , -

M-Btu*bla* colour

Leaf being boiled in alcoholover a water bath

Fig. Experimental set-up to show that carbon dioxide is necessar5z for photos5mthesis

"ordle rr,at@ Biotogy (ICSE) -X

Boaker

Alcohol

Water bathcontaining water

Tripod stand

Spirit lamp

Blue-black

Did not turnblue-black

Blue-blackLeaf showing starch iodine test

lLtgnt ts necessary for photosynthesisl

Leaf being boiled inalcohol over a water bath

Fig' Experimental set'up to show that light is neeessar5r for photosSrnthesis

The portion of the leaf which was covered with the black strips of paper did not turn blue-black whendipped in iodine \Mhereas the rest of the leaf did.

The plant should be destarched properlyThe leaf should be boiled in alcohol over a water bath because if we boil direcgy, the alcohol cancatch fire.The black strips of paper should be fixed properly so that, that portion of the leaf is not exposed tosunlight at all.

1.2.

3.