Why is phosphorus preserved in the water?

Important Questions on Chemical Changes and Reactions

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

State any two conditions required for combustion.

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Why do you have to use paper or kerosene oil to start fire in wood or coal?

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

A chemical process in which a substance reacts with oxygen to give off heat is called?

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Define ignition temperature of a substance.

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

For combustion _______ is necessary?

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Explain why, when a burning candle is covered with an inverted gas jar, the candle gets extinguished after some time.

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

The temperature of the substance should be lowered below the _____ temperature. (room / kindling)

HARD

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Maximum greenhouse gases are released by.

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Can the process of rusting be called combustion? Give reason for your answer.

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Gases mainly responsible for the greenhouse effect are

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Choose the option representing a set of greenhouse gases.

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Which of the following is not true about combustion?

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Why does a goldsmith blow air into the kerosene lamp flame with a blow-pipe?

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Coal burns in air and produces?

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Can you burn a piece of wood by burning a lighted matchstick near it? Explain.

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

The lowest temperature at which a substance catches fire is called?

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

What are the conditions necessary for combustion to take place?

MEDIUM

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Fire caused due to electrical faults should be put out using water.

EASY

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

Which one is a supporter of combustion?

HARD

Science>Chemistry>Chemical Changes and Reactions>Combustion and Respiration

How will you show that air is necessary for combustion?