English Medium कक्षा १० - CBSE Important Questions for Science

What is atmospheric refraction? Use this phenomenon to explain the following natural events:

Twinkling of stars

Draw diagrams to illustrate your answers.

Write Joule's law of heating.

Decomposition reactions require energy either in the form of heat or light or electricity for breaking down the reactants. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light and electricity

2 mL of sodium hydroxide solution is added to a few pieces of granulated zinc metal taken in a test tube. When the contents are warmed, a gas evolves which is bubbled through a soap solution before testing. Write the equation of the chemical reaction involved and the test to detect the gas. Name the gas which will be evolved when the same metal reacts with dilute solution of a strong acid.

What is observed when a solution of sodium sulphate is added to a solution of barium chloride taken in a test tube? Write equation for the chemical reaction involved and name the type of reaction in this case.

The pH of a salt used to make tasty and crispy pakoras is 14. Identify the salt and write a chemical equation for its formation. List its two uses.

A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.

Show how would you join three resistors, each of resistance 9 Ω so that the equivalent resistance of the combination is 

1) 13.5 

2) 6 Ω

Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason?

Define the term dispersion of white light.

What are alloys?

Draw a ray diagram to show the dispersion of white light.

State the cause of dispersion of white light

Three incandescent bulbs of 100 W each are connected in series in an electric circuit. In another circuit another set of three bulbs of the same wattage are connected in parallel to the same source.

1. Will the bulb in the two circuits glow with the same brightness? Justify your answer.
2. Now let one bulb in both the circuits get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

With the help of an appropriate example, justify that some of the chemical reactions are determined by the evolution of a gas.

Give a chemical equation for the reaction involved in the above case.

With the help of an appropriate example, justify that some of the chemical reactions are determined by a change in colour.

Give a chemical equation for the reaction involved in the above case. 

With the help of an appropriate example, justify that some of the chemical reactions are determined by a change in temperature.

Give a chemical equation for the reaction involved in the above case.

State the change in colour observed in the following case, mentioning the reason:

Silver chloride is exposed to sunlight.

Bronze is an alloy of ______.