List of top Questions asked in CBSE Class X

You are given a hammer, a battery, a bulb, wires and a switch.
  1. How could you use them to distinguish between samples of metals and non-metals?
  2. Assess the usefulness of these tests in distinguishing between metals and non-metals.
Food cans are coated with tin and not with zinc because
What is the difference between displacement and double displacement reactions? Write equations for these reactions.
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be
Why are decomposition reactions called the opposite of combination reactions? Write equations for these reactions.
Which of the following methods is suitable for preventing an iron frying pan from rusting?
Why is respiration considered an exothermic reaction? Explain.
What does one mean by exothermic and endothermic reactions? Give examples.
Write the balanced chemical equation for the following and identify the type of reaction in each case. 
(a) Potassium bromide(aq) + Barium iodide(aq) \(→\) Potassium iodide(aq) + Barium bromide(s) 
(b) Zinc carbonate(s) \(→\) Zinc oxide(s) + Carbon dioxide(g) 
(c) Hydrogen(g) + Chlorine(g) \(→\) Hydrogen chloride(g) 
(d) Magnesium(s) + Hydrochloric acid(aq) \(→\) Magnesium chloride(aq) + Hydrogen(g)
A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
Find the focal length of a lens of power −2.0 D. What type of lens is this?
Write the balanced chemical equations for the following reactions. 
(a) Calcium hydroxide + Carbon dioxide \(→\) Calcium carbonate + Water 
(b) Zinc + Silver nitrate \(→\) Zinc nitrate + Silver 
(c) Aluminium + Copper chloride \(→\) Aluminium chloride + Copper 
(d) Barium chloride + Potassium sulphate \(→\) Barium sulphate + Potassium chloride
An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.
An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
Balance the following chemical equations.
(a) HNO3 +Ca(OH)2 \(→\) Ca(NO3)2 + H2O 
(b) NaOH + H2SO4 \(→\) Na2SO4 + H2O 
(c) NaCl + AgNO3 \(→\) AgCl + NaNO3 
(d) BaCl + H2 SO4 \(→\) BaSO4 + HCl
Translate the following statements into chemical equations and then balance them. 
(a) Hydrogen gas combines with nitrogen to form ammonia. 
(b) Hydrogen sulphide gas burns in air to give water and Sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate. 
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
What is a balanced chemical equation? Why should chemical equations be balanced?
What happens when dilute hydrochloric acid is added to iron fillings? Tick the correct answer.
Fe2O3 + 2Al → Al2O3 + 2Fe 
The above reaction is an example of a:
The magnification produced by a plane mirror is +1. What does this mean?
An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.
Name the type of mirror used in the following situations. 
  1. Headlights of a car
  2. Side/rear-view mirror of a vehicle
  3. Solar furnace

Support your answer with reason.