Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) Nitric acid turn red litmus blue. (T/F)
(ii) Sodium hydroxide turns blue litmus red. (T/F)
(iii) Sodium hydroxide and hydrochloric acid neutralise each other and form salt and water. (T/F)
(iv) Indicator is a substance which shows different colours in acidic and basic solutions. (T/F)
(v) Tooth decay is caused by the presence of a base. (T/F)
(i) Answer: False
Nitric acid is not right to turn the red litmus paper into blue. The explanation is that the colour of the paper does not change when an acid comes into contact with a red litmus paper. Only if an acid comes into contact with blue litmus paper will the colour of the litmus paper change into red. Nitric acid is an acid so it does not turns the litmus paper into blue.
(ii) Answer: False
This statement is false because sodium hydroxide is not an acid, it is base which turns red litmus to blue.
(iii) Answer: True
When acid and base reacts with each other, they form an neutral substance, this process is called neutralisation. When the solution of sodium hydroxide (a base) and hydrochloric acid (an acid) is mixed in test tube in proper ratio, both neutralize each other.
(iv) Answer: True
This statement is true because different solution show different colours in acidic or basic medium. Indicators are chemical compounds that change Colour according to pH of the solution they are put in. They are used to determine pH of the body (acidity/basicity).
(v) Answer: False
This statement is false because tooth decay is caused by acids which is formed in our mouth when the food particles left over all night. They constantly damage tooth enamel and thus cause tooth decay.
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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 - Q:-
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
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Sketch the cross section of soil and label the various layers.
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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 bodyDown
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
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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?
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Sketch the reproductive parts of a flower.
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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. - Q:-
Describe how crystals of copper sulphate are prepared.
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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 - Q:-
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
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When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
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Fill in the blanks:
(a) Cleaning of water is a process of removing ____________.
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(c) Dried ____________ is used as manure.
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(i) Speed = Distance × Time (ii) Speed = Distance
Time(iii) Speed = Time (iv) Speed = 1
Distance Distance × Time
- NCERT Chapter