SHORT ANSWER QUESTIONS
1. what do you understand by periodic and non periodic changes? Explain giving one example of each case .
2. What do you mean by physical change?
3. How can you say boiling and melting are physical changes and not chemical changes?
4. Give an example of a change that includes more than one change.
5. Differentiate between burning of a log of wood and breaking of a log of wood.
6. Explain the term solute and solvent with an example.
7. Differentiate between slow and fast change.
Answers
Answer:
1. Day and night, changing phases of the moon, beating of heart, clock striking an hour are all examples of periodic motion whereas water becoming ice, burning of matchstick etc are non periodic changes.
2. A physical change is a change to the physical—as opposed to chemical—properties of a substance. They are usually reversible. The physical properties of a substance include such characteristics as shape (volume and size), color, texture, flexibility, density, and mass
3. Physical changes alter only the size, shape, form or matter state of a material. Water boiling, melting ice, tearing paper, freezing water and crushing a can are all examples of physical changes. On the other hand, chemical changes are a bit different. In a chemical change, a new substance is formed.
4.For example, when a candle burns, it shows both physical and chemical change. Burning of the wax of the candle is a physical change as we can again make the candle using the molten wax. On the other hand, burning if the thread of the candle is a chemical change as it is impossible to renew the thread.