- Natural and man-made changes
- Periodic and non-periodic changes
- Desirable and undesirable changes
- Reversible and irreversible changes
- Physical and chemical changes
- Expansion and contraction of materials
- Expansion and contraction of solids
- Expansion and contraction of liquids
- Expansion and contraction of gases
- Applications of expansion and contraction
SLOW AND FAST CHANGES
• Some changes are very slow.
• They may take hours, days, weeks or months to occur.
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Or
• Like: Milk sets into curd in three hours.
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• One revolution of earth around the sun takes one year.
Read More...PERIODIC AND NON-PERIODIC CHANGES
• Those changes which repeat themselves after regular intervals of time are called periodic changes.
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• Formations of day and night, motion of a swing, movement of a pendulum are all examples of periodic motion.
• Changes which do not repeat themselves regularly are called non-periodic changes.
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DESIRABLE AND UNDESIRABLE CHANGES
• Some changes are useful to us and we want them to take place. Such changes are called desirable changes.
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• We want the plants to grow, the fruits to ripen, wet clothes to dry and food to be cooked.
• Some changes are harmful to us and we don’t want them to happen. These are called undesirable changes.
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