2. Read one more text on the problem and do the tasks.

Inflammation of Wood

1. Wood is a highly combustible substance. In favourable circumstances any wood may be burnt to ash. But inflammability of wood is not high.

2. Being heated to a temperature of about 250 С wood will decompose, producing inflammable gases and charcoal. This happens when the surface of a wooden beam, for example, is exposed to a flame. The inflammable gases being produced in great quantities and ignited, their combustion raises the temperature of wood. Therefore, the fire is kept going until all the wood is burnt.

3. The formation of charcoal on the surface of wooden beam probably acts as a screen against heat, retarding distillation of inflammable gases. In consequence, the speed of burning is much reduced. The layer of charcoal being sufficiently thick, the burning may become very slow. In this case insufficient quantity of heat is produced to continue the decomposition of wood. The fire dies out. This happens with timbers of large dimensions. We can often see that during large fires, heavy wooden posts and beams survive while a building is completely destroyed by the fire.

4. The ability of wood to resist the passage of heat is of great importance. We know the burning wood to transmit the heat not so rapidly as steel or iron. Some part of heat being produced is immediately radiated outwards, some is absorbed to raise the temperature of wood inside the burning beam and the remainder is conducted to the opposite side. It should be noted that the behaviour of flames is also important. They rise upwards and therefore transmit more heat to the part of wood above the source of the flames than that below or to the sides. Hence, wood being held vertically and ignited at the bottom will burn more rapidly than the same wood being ignited at the top. This explains why doors, panels and other vertically disposed partitions have a greater fire danger than beams and floors.

Task 1.

Define which of the statements are:

A – true B – false C – not mentioned in the text

1. Combustibility of wood is very high.

2. While decomposing wood increases its resistance to fire.

3. The charcoal retards the spread of fire.

4. During large fires posts and beams are destroyed completely.

Task 2.

Which paragraphs (A, B, C, D) express the following ideas.

1. The production of inflammable gases and charcoal in great quantities when wood is heated contributes to the fire being kept going.

2. Vertical wood will burn more rapidly ignited at the bottom than the wood ignited at the top.

Task 3.

Answer the question. Make the right choice.

How does the thick layer of charcoal on the surface of wooden beam act?

It acts as _____ .

A. a screen against heat

B. a stimulator of fire

C. a distillator of inflammable gases

D. a decomposer of inflammable gases

Task 4.

Finish the sentence in accordance with the text.

Wood being held vertically and ignited at the bottom will ______ .

A. burn not so quickly

B. burn more rapidly

C. not burn at all

D. decompose

Task 5.

Answer the question.

What will happen to wood being heated to a temperature of about 250º C?

A. Wood will decompose.

B. Wood will produce inflammable gases.

C. Wood will produce charcoal.

D. Wood will do all mentioned above.

Task 6.

What is the main idea of the text?

A. Wood doesn’t burn at all.

B. Inflammability of wood is not very high but in favourable circumstances wood can burn to ash.

C. The behavior of the flame during large fires is of great importance.

D. The charcoal retards the distillation of inflammable gases and protects the wood to some extent from burning to ash.