Write True/False against the following statements and also correct
the false statement.
(a) A physical process in which a substance reacts with oxygen
to give off heat is called combustion.
(b) Water is the best extinguisher for fires involving electrical
equipment.
(c) Alcohol, CNG and LPG are inflammable substances.
(d) Increased concentration of nitrogen in air is believed to cause
global warming.
(e) Greater the calorific value, better is the fuel.
(f) Middle zone is the hottest zone of a flame.
(g) The substances which vapourise during burning, give flame.
People usually keep Angethi/burning coal in their closed rooms during winter season. Why is it advised to keep the door open?
Fill in the blanks using the words given in the box
ignition, petrol, combustion, calorific value, combustible, inflammable
(a) A chemical process in which a substance reacts with oxygen to give off heat is called __________.
(b) Wood, paper, CNG are __________ substances.
(c) The lowest temperature at which a substance catches fire is called its __________ temperature.
(d) Ignition temperature of __________ is lower than that of wood.
(e) The substances which have very low __________ temperature and can easily catch fire with a flame are called __________ substances.
(f) The amount of heat energy produced on complete combustion of 1kg of a fuel is called its __________.
Match the items of Column A with the items of Column B.
Column A Column B
(a) Oxides of sulphur and nitrogen (i) fire extinguisher
(b) CNG (ii) incomplete combustion of coal
(c) Oxygen (iii) very low ignition temperature
(d) inflammable substance (iv) acid rain
(e) carbon dioxide (v) necessary for combustion
(f) carbon monoxide (vi) fuel for automobiles.
Indicate whether the following statements are True or False. Also
write the false statements in their correct form.
(a) Air is necessary for combustion.
(b) Magnesium is a non-combustible metal.
(c) Carbon dioxide is an excellent fire extinguisher.
(d) Calorific value of wood is higher than that of coal
Boojho wants to separate the following materials as combustible and non-combustible. Can you help him?
Charcoal, chalk, stone, iron rod, copper coin, straw, cardboard, glass, paper, candle, wood.
Why is the use of diesel and petrol as fuels in automobiles being
replaced by Compressed Natural Gas (CNG) in big cities?
Anu wants to boil water quickly in a test tube. On observing the
different zones of the flame, she is not able to decide which zone
of the flame will be best for boiling water quickly. Help her in
this activity
Two glass jars A and B are filled with carbon dioxide and oxygen
gases, respectively. In each jar a lighted candle is placed
simultaneously. In which jar will the candle remain lighted for a
longer time and why?
Some words (underlined) in the following sentences are jumbled
up. Write them in their correct form.
(a) Seldie is a combustible substance.
(b) Slags is a non-combustible material.
(c) Chittsmack does not burn by itself.
(d) Some substances on combustion produce thea and mafel.
(e) The amount of heat energy produced on complete combustion
of 1 kg of a fuel is called its ficalroic value.
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