Science:2010:CBSE:[Delhi]:Set-I
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Q1
What changes in colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?
Marks:1View AnswerAnswer:
The blue-coloured copper sulphate solution becomes a green-coloured solution due to the formation of iron sulphate while a reddish brown-coloured layer gets deposited on grey-coloured iron nails.
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Q2
State two characteristic features of carbon which when put together give rise to a large number of carbon compounds.
Marks:1View AnswerAnswer:
1. Catenation i.e., self linking property of carbon
2. Tetravalency i.e., tendency to form 4 bonds with same or different atoms.
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Q3
Explain why a ray of light passing through the centre of curvature of a concave mirror gets reflected along the same path.
Marks:1View AnswerAnswer:
A ray of light passing through the centre of curvature of a concave mirror gets reflected along the same path as the incident ray fall on the mirror along the normal to the reflecting surface.
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Q4
A charged particle enters at right angles into a uniform magnetic field as shown. What should be the nature of charge on the particle if it begins to move in a direction pointing vertically out of the page due to its interaction with the magnetic field?
Marks:1View AnswerAnswer:
The charge on the particle is positive.
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Q5
Name the part of our eyes that helps us to focus near and distant objects in quick succession.
Marks:1View AnswerAnswer:
Eyelens.
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Q6
Name the green dot like structures in some cells observed by a student when a leaf peel was viewed under a microscope. What is this green colour due to?
Marks:1View AnswerAnswer:
Green dot like structures: Chloroplasts,
Green colour is due to the green pigment chlorophyll. -
Q7
How is the spinal cord protected in the body?
Marks:1View AnswerAnswer:
The spinal cord is enclosed by the vertebral column, which offers it protection.
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Q8
How is the increasing demand for energy adversely affecting our environment?
Marks:1View AnswerAnswer:
Increasing demand for energy due to increasing population is straining the natural resources, disturbing ecological balance and causing climatic changes and pollution.
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Q9
What is the main constituent of biogas? How is biogas obtained from the biomass? Write any two advantages of using this gas.
Marks:2View AnswerAnswer:
The main constituent of biogas is methane. Biogas contains upto 75% methane.
Biogas is obtained from the biomass like cow dung, dried leaves and other vegetables and animal remains.
Advantages of using biogas:
1. The calorific value of biogas is high.
2. It burns without smoke and leaves no residue like ash etc.
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Q10
What happens when an aqueous solution of sodium sulphate reacts with an aqueous solution of barium chloride? State the physical conditions of reactants in which the reaction between them will not take place. Write the balanced chemical equation for the reaction and name the type of reaction.
Marks:2View AnswerAnswer:
White precipitate of barium sulphate is formed.
Na2SO4(aq) + BaCl2(aq)
2NaCl(aq) + BaSO4(s)This is an example of double displacement reaction which takes place only when reactants are in aqueous solution and if reactants are in solid form the reaction will not take place.
