CBSE X SCIENCE PAPER 2009

CBSE X SCIENCE PAPER 2009
1. In electrolysis of water, why is the volume of gas collected over one electrode double the volume of gas collected over the other electrode?

2. What effect does an increase in the concentration of H+ (aq.) in a solution have on the pH of the solution?

3. What happens when a small piece of sodium is dropped into ethanol?

4. Draw a schematic diagram of an electric circuit consisting of a battery of two cells 1.5 V each, 5 Ω, 10 Ω and 15 Ω resistors and a plug key, all connected in series.

5. When is the force experienced by a current-carrying conductor placed in a magnetic field the largest?

6. State the rule that gives the direction of the magnetic field associated with a current-carrying conductor.

7.(i) Name the products formed when sodium hydrogen carbonate is heated.

(ii) Write the chemical equation for the above chemical reaction.

8. (i) What is formed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?

(ii) What type of a reaction is this?

(iii) Write a balanced chemical equation to represent the above reaction.

9. What is an electric circuit? Distinguish between an open and a closed circuit.

10. Calculate the resistance of an electric bulb which allows a 10 A current to flow when connected to a 220 V power source.

11.(a) What is meant by periodicity in properties of elements with reference to the periodic table?

(b) Why do all the elements of the same group have similar properties?

(c) How will the tendency to gain electrons change as we go from left to right across a period?Why?

12 (a) Distinguish between esterification and saponification reactions of organic compounds.

(b) With a labeled diagram describe an activity to show the formation of an ester.

13. For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram.

14. (a) Define the term ‘volt’.

(b) State the relation between work, charge and potential difference for an electric circuit.

Calculate the potential difference between the two terminals of a battery if 100 joules of work is required to transfer 20 coulombs of charge from one terminal of the battery to the other.

15. (a) Distinguish between ionic and covalent compounds under the following properties:

(i)Strength of forces between constituent elements

(ii) Solubility of compounds in water

(iii) Electrical conduction in substances

(b) Explain how the following metals are obtained from their compounds by the reduction process:

(i) Metal M which is in the middle of the reactivity series.

(ii) Metal N which is high up in the reactivity series.

Give one example of each.

16. (a) What is myopia? State the two causes of myopia. With the help of labelled ray diagrams show

(i) the eye defect myopia.

(ii) correction of myopia using a lens.

(b) Why is the normal eye unable to focus on an object placed within 10 cm from the eye?