Class 8 Science


Extra Questions

Question 1: Which of these is a combustible substance?

  1. Asbestos
  2. Paper
  3. Stone
  4. Sand

Answer: (b) Paper

Question 2: Which of the following is non-combustible substance?

  1. Alcohol
  2. Coal
  3. Iron
  4. Wood

Answer: (c) Iron

Question 3: Which of the following is an inflammatory substance?

  1. Coal
  2. Alcohol
  3. Wood
  4. Stone

Answer: (b) Alcohol

Question 4: A flame has how many zones?

  1. One
  2. Two
  3. Three
  4. Four

Answer: (c) Three

Question 5: The outermost zone of flame is of which colour?

  1. Blue
  2. Orange
  3. Brown
  4. Dark

Answer: (a) Blue

Question 6: The middle zone of flame is of which colour?

  1. Blue
  2. Orange
  3. Transparent
  4. Black

Answer: (b) Orange

Question 7: Which is the best fuel for kitchen; in present times?

  1. LPG
  2. Coal
  3. Kerosne
  4. Petrol

Answer: (a) LPG

Question 8: Which part of flame is used by goldsmith?

  1. Blue
  2. Orange
  3. Black
  4. Green

Answer: (a) Blue

Question 9: Which of the following does not produce flame while burning?

  1. Wax
  2. Petrol
  3. Diesel
  4. Coal

Answer: (d) Coal

Very Short Answer Type Questions

Question 1: Define combustion?

Answer: Combustion is a chemical process in which a substance reacts with oxygen to give off heat.

Question 2: What is combustible substance?

Answer: A substance which can undergo combustion is called a combustible substance.

Question 3: What is a non-combustible substance?

Answer: A substance which cannot undergo combustion is called a non-combustible substance.

Question 4: What is ignition temperature?

Answer: Ignition temperature is the minimum temperature at which combustion starts in a substance.

Question 5: What is an inflammable substance?

Answer: A substance which has very low ignition temperature so that is can easily catch fire is called an inflammable substance, e.g. petrol, alcohol, etc.

Question 6: What is a fire extinguisher?

Answer: The substance which is used for putting off fire is called fire extinguisher.

Question 7: What is rapid combustion?

Answer: When combustion happens at a faster rate, it is called rapid combustion.

Question 8: Define calorific value of a fuel.

Answer: The amount of heat energy produced on combustion of 1 kg of a fuel is called calorific value of that fuel. It is expressed as kilo Joule per kg (kJ/kg).

Question 9: What is spontaneous combustion?

Answer: When combustion starts on its own; without an apparent cause; it is called spontaneous combustion.