Explain the differences between pure air and polluted air.
Pure air contains 78% nitrogen, 21% oxygen, 0.03% carbon dioxide and other gases that present in the minute quantity. When some harmful substances or other poisonous gases mixed up in the air then the air become polluted. When these pollutants react with water and lead to acid rain.
Describe the threat to the beauty of the Taj Mahal.
Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Which of the following is not a greenhouse gas?
(a) Carbon dioxide
(b) Sulphur dioxide (c) Methane
(d Nitrogen
Prepare a brief speech on global warming that you have to make in your class.
Explain circumstances leading to acid rain. How does acid rain affect us?
Clear, transparent water is always fit for drinking. Comment.
Describe the ‘Green House Effect’ in your own words.
What are the different ways in which water gets contaminated ?
At an individual level, how can you help reduce air pollution?
You are a member of the municipal body of your town.
Make a list of measures that would help your town to ensure the supply of clean water to all its residents.
Which of the following can be beaten into thin sheets?
(a) Zinc (b) Phosphorus (c) Sulphur (d) Oxygen
Fill in the blanks
(a) Most liquids that conduct electricity are solutions of , ______________ and ______________.
(b) The passage of an electric current through a solution causes ______________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the terminal of the battery.
(d) The process of depositing a layer ofany desired metal on another material by means of electricity is called .
Give two examples each of situations in which you push or pull to change the state of motion of objects.
Fill in the blanks:
(a) Friction opposes the _____________ between the surfaces in contact with each other.
(b) Friction depends on the _____________ of surfaces. (c) Friction produces __________.
(d) Sprinkling of powder on the carrom board ________ friction.
(e) Sliding friction is ___________ than the static friction.
List conditions under which combustion can take place.
Indicate whether the following statements are True (T) or False (F).
(a) Unicellular organisms have one-celled body. (T/F)
(b) Muscle cells are branched. (T/F)
(c) The basic living unit of an organism is an organ. (T/F)
(d) Amoeba has irregular shape. (T/F)
Which of the following cannot be charged easily by friction?
(a) A plastic scale
(b) A copper rod
(c) An inflated balloon
(d) A woollen cloth.
Fill in the blanks:
(a) A place where animals are protected in their natural habitat is called .
(b) Species found only in a particular area is known as .
(c) Migratory birds fly to far away places because of changes.
Suppose you are in a dark room. Can you see objects in the room? Can you see objects outside the room. Explain.
Explain the importance of reproduction in organisms.
Abida and Ramesh were doing an experiment in which water was to be heated in a beaker. Abida kept the beaker near the wick in the yellow part of the candle flame. Ramesh kept the beaker in the outermost part of the flame. Whose water will get heated in a shorter time?
Boojho stands at A just on the side of a plane mirror as shown in Fig. 16.20. Can he see himself in the mirror? Also can he see the image of objects situated at P, Q and R?
List conditions under which combustion can take place.
Give two examples each of situations in which you push or pull to change the state of motion of objects.
Explain the importance of reproduction in organisms.
Answer in brief:
(a) Why should we conserve biodiversity?
(b) Protected forests are also not completely safe for wild animals. Why?
(c) Some tribals depend on the jungle. How?
(d) What are the causes and consequences of deforestation?
(e) What is Red Data Book?
(f) What do you understand by the term migration?
Make a labelled diagram of a candle flame.
The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.
Fill in the blanks :
(a) Phosphorus is very _________ non-metal.
(b) Metals are ________ conductors of heat and ________ .
(c) Iron is __________ reactive than copper.
(d) Metals react with acids to produce _________ gas.
Name the petroleum product used for surfacing of roads.