What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.
Sewage: The waste water and faeces (human excretion) from homes and other buildings which is carried into the sewers is called sewage. Sewage includes household wastewater from kitchen sink, washing machine, washbasin, bathroom shower, bath tub and faeces from the toilet. Sewage is also produced and released by shops, offices, schools, hospitals, factories, industries and all other places where humans work or live. Sewage also includes rainwater that has run down the streets and roads during rains carrying harmful substances with it which also spreads various diseases along it, and flows into sewer pipes. Sometimes, sewage contains harmful and poisonous chemicals that are being discharged by factories and industries. Most of the dirty water contains dissolved and suspended impurities in it which are known as contaminants or pollutants.
Popular Questions of Class 7 Science
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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
- Q:-
Sketch the cross section of soil and label the various layers.
- Q:-
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?
- Q:-
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
7. A chemical to disinfect water - Q:-
Sketch the reproductive parts of a flower.
- Q:-
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.
- Q:-
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.
Recently Viewed Questions of Class 7 Science
- Q:-
Why is blood needed by all the parts of a body?
- Q:-
Fill in the blanks:
(a) An image that cannot be obtained on a screen is called ____________.
(b) Image formed by a convex __________ is always virtual and smaller in size.
(c) An image formed by a __________ mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a _________ image.
(e) An image formed by a concave ___________ cannot be obtained on a screen. - Q:-
Choose the correct option from the following:
Plants take carbon dioxide from the atmosphere mainly through their:
(i) roots (ii) stem (iii) flowers (iv) leaves - Q:-
Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.
- Q:-
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:-
List the similarities and differences between aerobic and anaerobic respiration.
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Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
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Ammonia is found in many household products, such as window cleaners. It turns red litmus blue. What is its nature?
- Q:-
Explain why there is no waste in a forest.
- Q:-
Suggest two methods to find out wind direction at a given place.
- NCERT Chapter