Take three test-tubes. Fill æth of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2?
Three test-tubes are taken and labelled A, B and C. Each test- tube is half filled with water.
(a) In test-tube A, a snail is kept,
(b) In test-tube B, a water plant is kept, and
(c) In test-tube C contains both a snail and a water plant.
(a) Test-tube A contains a snail in water. The snail will use up oxygen for respiration and produce carbon dioxide.
(b) Test-tube B contains a ‘water plant’ in water. The water plant will do photosynthesis by using carbon dioxide and water and produce oxygen. The water plant will use some of this oxygen for respiration and produce carbon dioxide will then be used by the plant in photosynthesis.
(c) Test-tube C contains both, a snail and a water plant. The carbon dioxide produced by the snail through the respiration is used by the plant for the synthesis of food and oxygen is released by the plant which is used by the snail for the respiration.
From the above, we conclude that the test-tube A containing only snail will have the highest concentration of carbon dioxide because there is no plant to use up the carbon dioxide produced during the respiration in snail.
Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food
Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.
Down Across
(D) 1 : Thorough washing (A) 1 : Keeps warm
2 : Animal fibre 2 : Its leaves are eaten by silkworms
3 : Long thread like structure 3 : Hatches from egg of moth
Sketch the cross section of soil and label the various layers.
Here is a crossword puzzle: Good luck!
Across
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from human body
Down
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water
Sketch the reproductive parts of a flower.
Solve the following crossword puzzle with the clues given:
Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.
Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.
Describe how crystals of copper sulphate are prepared.
Match the items in Column I with those in Column II:
Column I Column II
(i) A home for living organisms (a) Large particles
(ii) Upper layer of the soil (b) All kinds of soil
(iii) Sandy soil (c) Dark in colour
(iv) Middle layer of the soil (d) Small particles and packed tight (v) Clayey soil (e) Lesser amount of humus
Write one similarity and one difference between the nutrition in amoeba and human beings.
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
Fig. 13.15 shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?
Fig. 13.15 Distance-time graph for the motion of two cars
Show with the help of a sketch that the plants are the ultimate source of food.
Fill in the blanks.
(i) The blood from the heart is transported to all parts of the body by the.
(ii) Haemoglobin is present in cells.
(iii) Arteries and veins are joined by a network of .
(iv) The rhythmic expansion and contraction of the heart is called.
(v) The main excretory product in human beings is.
(vi) Sweat contains water and.
(vii) Kidneys eliminate the waste materials in the liquid form called.
(viii) Water reaches great heights in the trees because of suction pull caused by .
Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) Carbon dioxide is released during photosynthesis. (T/F)
(ii) Plants which synthesise their food themselves are called saprotrophs. (T/F)
(iii) The product of photosynthesis is not a protein. (T/F)
(iv) Solar energy is converted into chemical energy during photosynthesis. (T/F)
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
Explain how soil is formed.
Why do we often sneeze when we inhale a lot of dust-laden air?
Which of the two changes frequently, weather or climate?
Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T/F)
(b) Water shortage is a problem faced only by people living in rural areas. (T/F)
(c) Water from rivers is the only source for irrigation in the fields. (T/F)
(d) Rain is the ultimate source of water. (T/F)
What are decomposers? Name any two of them. What do they do in the forest?