Burning

Q.

Water contains Oxygen. Oxygen helps in burning. So why does not fire increases when we throw water at it?

Q.

Which of the following is not a component of the fire triangle?

1. Heat

2. Oxygen

3. Carbon Dioxide

4. Fuel

Q.

In neutralisation reaction:

1. Heat is absorbed
2. Heat is evolved
3. Neither heat is absorbed nor evolved
4. None of these

Q.

The change of a bud into a flower is a change that cannot be reversed. Give four more such examples.

Q. Liquefied petroleum gas is used in kitchens. When the gas is in a cylinder, it is in the liquid state. When it comes out of the cylinder it becomes a gas (change A), then it burns (change B). Identify the processes A and B with proper explanation.

Q.

Which of the following is an irreversible physical change?

1. Melting of butter

2. Cutting of wood

3. Freezing of water

4. Stretching of a rubber band

Q. The outermost region of a flame is the hottest because of

1. complete burning.
2. incomplete burning.
3. insulation.
4. convection.

Q. What do you observe when a little amount of curd is added to a bowl containing warm milk and kept for five hours?

Q.

Which of the following changes cannot be reversed?

1. Milk to paneer

2. Cold milk to hot milk

3. Yam to a knitted sweater

4. Wet clothes to dry clothes

Q. Study the Venn diagram and identify the points 1, 2 and 3.

Q. When we burn a candle, which of the following changes occur?

1. Physical Change
2. Chemical Change
3. Reversible
4. None of these

Q. Bursting of a balloon is a ______ change.

1. temporary
2. permanent
3. natural
4. slow

Q.

In neutralisation reaction:

1. Heat is absorbed
2. Heat is evolved
3. Neither heat is absorbed nor evolved
4. None of these

Q.

How do we get a substance back in its original form in case of a reversible change? Explain using the appropriate example(s).

Q.

A sheet of paper is used to make a paper boat. This is a ___ change. (reversible/irreversible)

Q.

What is physical change? Plz explain me.....

Q.

A small quantity of curd is added to warm milk. The milk is stirred and is set aside for few hours at a warm place. In a few hours, the curd is formed. This is an irreversible change because

1. Curd cannot be converted back to milk.

2. Curd can be converted back to milk.

3. Sometimes curd can be reverted back to milk and sometimes not.

4. No change is happening.

Q. What do you observe when a little amount of curd is added to a bowl containing warm milk and kept for five hours?

Q.

Your mom is in the kitchen. You went there to ask one question to your mom. Suddenly, you saw that your mom is putting rice into a cooker which is half filled with water. She locked the cooker and put it on the gas stove. So, the cooking of rice is a reversible change.

1. False

2. True

Q.

Which of the following is/are the component(s) required for the propagation of fire?

1. Heat

2. Oxygen

3. Fuel

4. Carbon Dioxide

Q.

We observe that some portion of wax (in a candle) melts and another portion of it is used in producing heat and light.
Statement A: The melting of wax is a physical change.
Statement B: The burning of wax for the production of heat and light is a chemical change.
State which of the statement(s) is/are true.

1. Both Statement A and Statement B are false

2. Only Statement A is true

3. Both Statement A and Statement B are true

4. Only Statement B is true

Q.

Which of the following changes are irreversible in nature?

1. Dissolution of salt in water

2. Melting of candle wax

3. Burning of a candle

4. Dissolution of sugar in water

Q. Iron undergoes a number of changes before it becomes a sword. Arrange the changes in sequence.

Q. Melting of a candy bar is an irreversible change.

1. True
2. False

Q.

Which of the following is/are a component(s) required for propagation of fire?

1. Heat

2. Oxygen

3. Fuel

4. Carbon Dioxide

Q. Which of the following is not a component of the fire triangle?

1. Heat
2. Oxygen
3. Fuel
4. Carbon Dioxide

Q. Baking soda and vinegar undergo a chemical change when mixed together. Which amongst these indicators can be observed during this change?​

1. Change of smell​
2. Change of colour​
3. Evolution of gas​
4. Evolution of heat​

Q. Bharath heated a closed vessel full of water. After some time he observed that the water started boiling. Later there was no water in the vessel.
This is a/an ___.

1. reversible change
2. irreversible change
3. chemical change
4. cannot be determined

Q.

A sheet of paper is used to make a paper boat. This is a ___ change. (reversible/irreversible)

Q. A flame is formed during burning of a substance due to -

1. Fire could be used to cook food

2. Fire could provide heat

3. Fire provided a portable form of light and could protect from predators

4. All the above options are correct.