Board Paper of Class 10 2005 Science (SET 1) - Solutions

Why does a large increase in temperature slow down a reaction catalysed by an enzyme?

Dry ammonia gas has no action on litmus paper, but a solution of ammonia in water turns red litmus paper blue, why is it so?

What is seen to happen when a piece of sodium metal is dropped into water?

Where will the image be formed by a convex mirror if the object is placed between infinity and the pole of the mirror?

Should the heating element of an electric iron be made of iron, silver or nichrome wire?

What are the raw materials used in the manufacture of Portland Cement? What is Reinforced Cement Concrete (RCC)?

Name the catalyst used in the manufacture of ammonia by Haber’s Process. How is the ammonia formed separated from the other gases?

Describe a method for finding out the exact North-South direction at a place using the direction of sunlight.

In what S.I. units is the power of lenses stated? A convex lens has a focal length of 50 cm. Calculate its power.

Describe a nuclear chain reaction with an example.

How did Arrhenius define acids and bases? Choose a strong acid and a weak base from the following substances:

CH3COOH, NH4OH, HC1, KOH

Draw a labelled diagram of the Frasch Process for obtaining sulphur from places deep underground.

What are detergents? What change has been made in detergents to make them easily bio-degradable? Explain the cleansing action of detergents.

(a) Write a chemical equation to show how ethanol can be converted into ethanoic acid.

(b) Describe the action of ethanoic acid on sodium carbonate solution.

(c) Complete the following reaction equation:

CH3COONa (s) + NaOH (s)

OR

Define the term, ‘fermentation’. Name the enzyme which converts

(i) milk into curd (yogurt)

(ii) cane sugar into glucose and fructose, and

(iii) glucose into ethanol

A steady current is passed for 30 minutes through two voltameters connected in series:

a copper voltameter [Cu cathode in CuSO4 solution], and a silver voltameter [Ag cathode

in AgNO3 solution]. If the mass of copper deposited in the first voltameter is 21.17 g;

calculate the mass of silver deposited on the cathode in the other voltameter.

Given: Relative Atomic mass of Cu = 63.5, Ag = 108.0.

What is meant by the combustion of CH4 ? List the three essential requirements for any combustion to take place. Give reasons for the difficulty experienced in burning a piece of wood if (i) it is wet, (ii) it is large in size.

State the composition of the three main layers of the earth, centre outwards.

Describe with examples the following steps associated with the extraction of metals from their ores:

(i) Froth-floatation process

(ii) Roasting of an ore

(iii) Calcination of an ore

OR

Differentiate between an ‘alloy’ and an ‘amalgam’. How are alloys made? State with examples any two properties in which an alloy may be different from those of its constituents.

Write the constituents and special advantages of:

(i) Stainless steel

(ii) Magnalium

What are ‘simple’ and ‘compound’ microscopes? Draw a labelled ray diagram showing the image formed by a compound microscope. State the formula used to calculate the magnification produced by a compound microscope. What is the maximum magnification generally possible by using a compound microscope?

OR

(a) Explain how we see different colours of an object.

(b) Why is it that some persons cannot distinguish between different colours?

(c) The chick wakes up with the sunrise and sleeps by the sunset. How does it manage?

State Fleming’s left-hand rule. With a labelled diagram, describe the working of an electric motor. What is the function of split ring commutator in a motor?