Questions
Which of the following is/are true?
- The increase in percentage of carbon monoxide in air causes global warming.
- The increase in percentage of carbon dioxide in air causes global warming.
- The increase in percentage of methane in air causes global warming.
- Both (2) and (3).
What is the difference between spontaneous combustion and rapid combustion?
- In spontaneous combustion, the substance suddenly bursts into flames while in rapid combustion, the substance burns slowly for a very short time and then extinguishes itself.
- In spontaneous combustion, the substance burns rapidly into flames while in rapid combustion, the substance burns suddenly into flames without any external source of heat.
- In spontaneous combustion, the substance burns into flames without the application of external heat and in rapid combustion, the substance burns rapidly producing heat and light
- None of these
_________ is used as a fuel in automobiles.
- Liquefied Natural Gas (LNG)
- Compressed Natural Gas (CNG)
- Liquefied Petroleum Gas (LPG)
- All of the above
What are the ill effects of burning of fuels?
- It causes asthma.
- It causes diarrhoea.
- It causes plague.
- It causes flu.
What happens when a burning candle is placed at some distance under a paper so as not to burn it?
- The paper will catch fire as soon as the candle is placed.
- Nothing will be observed.
- Blackish circular ring will form on the paper without catching fire.
- Red circular ring will form on the paper without catching fire.
Which of the following is not true?
- The substances which vapourise on burning gives flame.
- Camphor on burning gives no flame.
- Magnesium ribbon on burning gives a bright white flame.
- The luminous zone has unburnt carbon particles.
What is the difference between the flames of a Bunsen burner and a candle?
- A Bunsen burner's flame is red in colour and a candle’s flame is yellow in colour.
- A Bunsen burner’s flame is reddish yellow in colour and a candle’s flame is red in colour.
- A Bunsen burner’s flame is yellow in colour and candle’s flame is red in colour.
- A Bunsen burner’s flame is blue in colour and a candle’s flame is yellow in colour.
What type of flame does a coloured candle give?
- Flame's colour will be the same as that of the candle.
- Flame will be of yellow colour.
- Flame will be of white colour.
- Flame will be of red colour.
Why is a blanket wrapped around a person who has caught fire?
- To cut off the supply of oxygen from air
- To form a barrier between the fire and the person
- To cut off the supply of nitrogen from air
- Both (2) and (3)
The process of combustion is a _______ change.
- chemical and reversible
- chemical and irreversible
- reversible and physical
- irreversible and physical
Why do dry leaves catch fire more easily than green leaves?
- The dry leaves have high ignition temperature.
- The dry leaves have a lower ignition temperature.
- The dry leaves contain moisture which helps in burning.
- None of these
Radha and Ramesh heated the same quantity of water under similar conditions using a candle. Radha kept the beaker near the wick of the candle flame and Ramesh kept the beaker above the outermost part of the flame.
Choose the correct sentence out of the sentences given below.
- Water in both the beakers will be heated at the same time.
- Radha’s water beaker will be heated faster.
- Ramesh’s water beaker will be heated faster.
- Water will not be heated by the candle.
What are the requirements for combustion of fuel to take place?
- Water and heat
- Oxygen and heat
- Carbondioxide and heat
- Carbon and heat
What happens to a candle when a substance is heated on it?
- Wax at the outer region of the heated wick melts quickly.
- Wax at the inner region of the heated wick melts quickly.
- Wax at both the regions melts quickly.
- Wax at the outer regions becomes cold.
Flammable materials must be stored _________.
- in an indoor enclosure
- in an enclosure away from other things
- on the roof of a building
- outdoors in the open