changes around us class 6 ppt
- 1. Chapter – 6 Changes around us
- 2. A change is an act or process through which something becomes different.
- 3. Learning objectives To Know about • The various changes occurring in nature. • Why changes occur • To find the causes behind different changes • Reversible and irreversible changes • Various conditions that favor changes. • Categorize different changes occurring in nature
- 4. Why do changes occur ? • Every change has a cause. • These cause can bring out the changes in shape, position, color or state of anything. • E.g. Rotation of Earth causes day and night
- 5. Classification of changes • Slow and fast changes. • Reversible and irreversible changes. • Natural and man-made changes. • Periodic and non-periodic changes. • Physical and chemical changes.
- 6. Slow and fast changes • The changes which take place in a long period of time are called slow changes whereas that changes which take place in a short period of time are called fast changes. • Examples: (a) Rusting of iron, formation of day and night, ripening of fruits, growing of trees are slow changes. (b) Burning of paper, stretching of rubber band, blowing of balloons, bursting of crackers are fast changes. Slow Change Fast Change
- 7. Natural and manmade changes • The changes which are brought about by nature are called natural changes. They are not under the control of humans. • The changes which are brought about by human beings are called man made changes. They are under the control of humans.
- 8. Periodic and Non-Periodic changes • The changes that occur at regular intervals are called periodic changes. E.g., Phases of moon, sunrise and sunset, ringing of pendulum. • The changes that occur in an irregular manner is called non-periodic changes. E.g., earthquake, accident, floods
- 9. Physical and chemical changes • A change in which a substance undergoes a change in its physical properties is called a physical change. E.g., melting of wax, breaking of sandcastle. • A chemical change is a type of change where the chemical properties of matter change. E.g., rusting of iron, dissolving of sugar in water
- 10. Reversible change. • Any change that can be reversed on removing the cause is called a Reversible change.
- 11. Irreversible change •If a change cannot be reversed, it is called an irreversible change.
- 12. Conditions favouring a change •Interaction between substances. •Mixing of substances. •Heating of substances.
- 13. Interesting facts • The Eiffel Tower can be 15 cm taller during the summer • Mount Everest, the highest peak in the world rises by an inch every year. • Hawaii moves 7.5cm closer to Alaska every year