Describe the ‘Green House Effect’ in your own words.
Green house effect is caused by green house gases. When the average temperature of the earth increases due to the increment in the level of the carbon dioxide in the atmosphere. When solar radiations reaches the earth, some of these radiations are absorbed by Earth and released back into the atmosphere. But the green house gases trap the solar radiation and do not allow the heat to leave. The excessive increase in the temperature of Earth leads to global warming.
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.
What are the different ways in which water gets contaminated ?
Explain the differences between pure air and polluted air.
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.
In order to meet the ever-increasing demand in factories and for shelter, trees are being continually cut. Is it justified to cut trees for such projects? Discuss and prepare a brief report.
Can the process of rusting be called combustion? Discuss.
Write a paragraph in your own words on each of the following.
(a) Preparation of soil (b) Sowing
(c) Weeding (d) Threshing
Mark (✓) the correct answer:
Rayon is different from synthetic fibres because
(a) it has a silk like appearance
(b) it is obtained from wood pulp
(c) its fibres can also be woven like those of natural fibres
Fill in the blanks:
(a) Microorganisms can be seen with the help of a ____________.
(b) Blue green algae fix __________ directly from air to enhance fertility of soil.
(c) Alcohol is produced with the help of __________.
(d) Cholera is caused by __________.
Fill in the blanks :
(a) Fossil fuels are , and .
(b) Process of separation of different constituents from petroleum is called .
(c) Least polluting fuel for vehicle is .
The table below shows the data on likely heights of boys and girls as they grow in age. Draw graphs showing height and age for both boys and girls on the same graph paper. What conclusions can be drawn from these graphs?
Which of the following statements is correct?
(a) All metals are ductile.
(b) All non-metals are ductile.
(c) Generally, metals are ductile.
(d) Some non-metals are ductile.
Explain why objects moving in fluids must have special shapes.
Give reasons for the following:
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.