NCERT Revision Notes for Chapter 6 Changes around Us Class 6 Science
CBSE NCERT Revision Notes1
Answer
- Introduction
- Common changes taking place in nature
- Types of changes
- Cause of change
2
Answer
→ Changes can occur everywhere at any time.
→ Change is a continuous process.
→ Some changes are reversed and some cannot be reversed.
→ Change may occur by heating a substance or by mixing it with some other substance.
3
Answer
→ Change in position, sun rise and set.
→ Change in colour, sky at day and at night time.
→ Change in shape, shape of moon.
→ Change in size, a germinate seed.
→ Change in temperature, hot summer and cold winter.
→ Change in state or form, water on cooling and heating.
→ Rusting of iron.
4
Answer
• Reversible changes
• Irreversible changes
• Chemical changes
• Physical changes
• Expansion And Contraction
5
Answer
→ It is an effect on substance in which substance get returned to its original state.
→ The change only alters the physical state of the substance that means there is no new substance is formed.
→ Examples: melting of ice, water turning into vapour, inflation of balloon etc.
6
Answer
→ In irreversible changes new material being produced, which may or may not be useful.
→ Examples: Ripening of fruits is an irreversible change because it is not possible to get back the raw fruits from ripened or mature ones.
→ Blooming of flowers is an irreversible change because flowers cannot change back into buds
7
Answer
→ In this changes, there is no new substance is formed.
→ It is reversible
→ Examples: melting of wax, Melting of ice, crushing can etc.
8
Answer
→ In this change there is a new substance is formed after the change.
→ It cannot be reversed by simple physical means.
→ Examples: rusting of iron, burning of candle etc.
9
Answer
→ Some materials expand on heating and some material contract on cooling.
→ The amount of expansion differs in solids, liquids, Physical change and gases.
→ Gases material expands the most while solids material expands the least.
→ Solids material contract the least while gases material contract the most.
10
Answer
Force
→ It can bring changes in certain thing. It can change motion, shape and size of objects by push or pull.
→ Examples
(i) When a potter applies force on a lump of soil, it gives shape to the lump.
(ii) When a goldsmith hammers a piece of gold, he makes intricate designs on it.
Temperature
→ This brings changes by causing increase or decrease in temperature.
→ Examples
(i) When ice is kept on room temperature, it melts and turns into water.
(ii) When a candle begins burning, its wax start melts because of higher temperature.