Flame

Q.

For burning oxygen is required but how does the sun burn in vaccum without air

Q.

(a) What is a flame? What type of substances, on burning, give a flame?

(b) What is the difference between the burning of a candle and the burning of a fuel like coal ?

Q.

Give examples of substances which burn to give a flame. Why do some substances burn without a flame? [3 MARKS]

Q.

What is the meaning of incandescence???

Q. Question 2 (c)
Fill in the blank:
Fuel must be heated to its ___ before it starts burning.

Q.

Steam causes more severe burn than boiling water at the same temperature.

1. True

2. False

Q.

Why does a goldsmith blow air into the kerosene lamp flame with a blow-pipe ?

Q. Why is LPG Better than kerosene for cooking?

Q.

The substance which give heat and light after combustion are called?

Q.

The outermost region of a candle flame has highest temperature because it gets meximum supply of oxygen and the burning is complete.

1. Complete combustion of carbon particles

2. Insufficient oxygen prohibits complete combustion

Q.

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.

Q.

We have learnt that oxygen is required for something to burn but there is no oxygen in space then how do the stars burn?

Q.

Which of the following does not produce a flame on burning ?

Camphor, Charcoal, Kerosene

Q.

Name one solid, one liquid and one gas which burn by producing a flame.

Q. ___ is required for a match stick to catch fire.

1. Ignition temperature
2. Water
3. Carbon monoxide
4. Carbon dioxide

Q. Radhika was performing an experiment in the laboratory. Radhika collected three substances A, B and C. She kept all the substances in contact with air at room temperature. She observed that substance A suddenly bursts into flames. Then, she heated substance B and C and found out that substance B catches fire but C does not. However, She observed that substance C catches fire on prolonged heating. Which of the following is the correct arrangement of A, B, and C in order of their increasing ignition temperature ?

1. A<B<C
2. B<A<C
3. C<A<B
4. C<B<A

Q. Which zone of a flame does a goldsmith use for melting gold and silver and why? ​

Q. Flames of different substances __________ colours.

1. will not have different

2. will have same

3. may have different

4. do not have any

Q.

The emission of light by a solid that has been heated is called:

1. 1, 3, 5, 4 and 2

2. 1, 2, 3, 4 and 5

3. 4, 2, 5, 1 and 3

4. 4, 3, 5, 2 and 1

Q.

What happens to the golden-yellow flame of sodium when viewed through blue glass?

Q.

In a candle, the process of burning continues because

1. the wick

2. the wax

3. the air around
4. the fire

Q. Vapourised wax gets oxidised in –

1. Blue zone
2. Dark zone
3. Luminous zone
4. Middle zone

Q. The outermost region of the flame have the temperature.

1. highest
2. lowest
3. moderate

Q.

The temperature of the flame of a candle is above the ignition temperature of the wax.

1. True

2. False

Q.

Why ignition temperature is different for different materials?

Q.

By giving example define the following terms:

1. Inflammable substances
2. Supporter of Combustion
3. Ignition temperature

Q.

Wick is an absorbent and wax is the absorbate (the liquid which gets absorbed).

1. it is the wax that burns directly

2. the molten wax gets converted into vapours which then burns

Q. Why does a goldsmith blow air into a kerosene lamp with a blow pipe?

Q.

a and b are van der Waals constants. Which gas will liquefy easily?

1. Smaller values of a, but larger values of b

2. Larger values of a and b

3. Smaller values of a and b

4. Larger values of a, but smaller values of b

Q.

The flame of a candle is above ignition temperature.

1. Flame

2. Heat