Evolution or Absorption of Heat

Q. Sam blows air into limewater using a straw. He notices that the limewater turns milky. Identify the gas responsible for the change and the type of change involved.

1. Gas - oxygen
   Change - chemical
2. Gas - carbon dioxide
   Change - chemical
3. Gas - carbon dioxide
   Change - physical
4. Gas - oxygen
   Change - physical

Q. The burning of magnesium ribbon is an example of a chemical change because:

1. a new substance is getting formed.
2. heat is released during this process.
3. change in composition occurs
4. a loud sound is produced.

Q. Magnesium ribbon when burnt in air forms ash. The chemical composition of the ash formed and the change involved is:

1. Magnesium oxide, physical
2. Magnesium oxide, chemical
3. Magnesium hydroxide, physical
4. Magnesium hydroxide, chemical

Q.

A chemical reaction involves the breaking up of chemical bonds between atoms resulting in the _______ and simultaneously the formation of bonds with the ________.

Q. In addition to formation of new products what changes do chemical changes acccompany.

Q. Heat energy is either absorbed or evolved during a chemical change.

1. False
2. True

Q. Burning of wood is a chemical reaction in which heat is released.

1. False
2. True

Q. In addition to formation of new products what changes do chemical changes acccompany.

Q. Which of the following processes does not involve the absorption or evolution of heat?

1. Rolling of dough
2. Combustion of fuel
3. Respiration
4. Lighting a candle

Q. Burning of paper is a chemical change.

1. True
2. False

Q.

When potassium permanganate is heated it produces potassium manganate, manganese dioxide and oxygen gas. This is an example of ______ reaction.

1. exothermic

2. electrolytic

3. endothermic

4. electrochemical

Q. Heat energy is either absorbed or evolved during a chemical change.

1. False
2. True

Q. Magnesium ribbon when burnt in air forms ash. The chemical composition of the ash formed and the change involved is:

1. Magnesium oxide, physical
2. Magnesium oxide, chemical
3. Magnesium hydroxide, physical
4. Magnesium hydroxide, chemical

Q.

What do you mean by exothermic reaction?

Q.

Conversion of frost to water vapour is an example of

1. endothermic reaction

2. exothermic reaction

3. photochemical reaction

4. none of the above