Combustion and Flame

Q1. Fill in the blanks.

                          i.        Burning of wood and coal causes pollution of air.

                         ii.        A liquid fuel, used in homes is Liquified Petroleum Gas (LPG).

                        iii.        Fuel must be heated to its ignition temperature before it starts burning.

                        iv.        Fire produced by oil cannot be controlled by water.

                         v.        The fuel may be solid, liquid or gas.

                        vi.        Spontaneous forest fires are sometimes due to the heat of the sun or due to lightning strike.

Q2. True/False

                          i.        Petrol is a liquid fuel. True

                         ii.        Spontaneous combustion of coal dust has resulted in many disastrous fires in coal mines. True

                        iii.        Cutting of trees leads to afforestation. False

                        iv.        Fuels differ in their efficiency and cost. True

                         v.        There are four different zones of a flame. False

Q3. Name some of the substances which burn without producing a flame.

Ans. Coal and Charcoal

Q4. Name two substances having low ignition temperature.

Ans. paper and white phosphorus

Q5. Name two substances having high ignition temperature.

Ans. coal and log of wood

Q6. Name some common fuels.

Ans. wood, charcoal, petrol and kerosene

Q7. Name some solid fuels.

Ans. wood, charcoal, coal, coke and cow-dung cakes

Q8. Name some liquid fuels.

Ans. kerosene, petrol and diesel

Q9. Name some gaseous fuels.

Ans. natural gas, petroleum gas, biogas and coal gas

Q10. Which is the most common fire extinguisher?

Ans. The most common fire extinguisher is water.

Q11. Name one substance which burn in air at room temperature?

Ans. Phosphorus burns in air at room temperature.

Q12. How are heat and light produced in the sun?

Ans. In the sun, heat and light are produced by nuclear reactions.

Q13. Name the term which is used to express the efficiency of a fuel.

Ans. The term Calorific value is used to express the efficiency of a fuel.

Q14. Describe one method of putting out a fire caused by burning wood or paper.
Or
How will you put out a fire caused by burning wood or paper?

Ans. Water can be used when things like wood and paper are on fire.

Q15. Name the unit in which the calorific value of a fuel is expressed.

Ans. The calorific value of a fuel is expressed in a unit called kilojoule per kg (kJ/kg).

Q16. What is global warming?

Ans. Global warming is the rise in temperature of the atmosphere of the earth.

Q17. What is fuel?

Ans. The substance that undergoes combustion is said to be combustible. It is also called a fuel.

Q18. Which gas is produced due to incomplete combustion of fuel?

Ans. Incomplete combustion of fuels produces a very poisonous gas called carbon monoxide.

Q19. Name the fuel which is gradually replacing petrol and diesel in automobiles.

Ans. The use of diesel and petrol as fuels in automobiles is being replaced by CNG (Compressed Natural Gas).

Q20. What is ignition temperature?
Or
What is the ignition temperature of a substance?

Ans. The lowest temperature at which a substance catches fire is called its ignition temperature.

Q21. What is meant by the calorific value of a fuel?

Ans. The amount of heat energy produced on complete combustion of 1 kg of a fuel is called its calorific value.