![]() In a physical change the material may change shapes or forms but no new compounds are formed and change can generally be reversed by reversing the conditions.Ī chemical change produces a new substance having new and different properties and which cannot be reversed by reversing the conditions. Iron pipes coated with zinc do not get rusted easily.įormation of manure from leaves is a physical change.Ĭutting a log of wood into pieces is a chemical change.ĭissolving sugar in water is physical change.Ĭhanges in which new substances are formed are called physical changes.īreaking down of larger food particles into smaller particles is a chemical change.įreezing water into ice is a chemical change. State whether the following statements are True or False. Iron benches kept in lawns and gardens get rusted. Grinding of wheat grain changes its size, it is a ………………. Galvanization is a process used to prevent the rusting of ………………. Make a note of the information you obtain.Ĭlass 7 Science Chapter 13 Changes – Physical and Chemical Important Questions and Answersįill in the blanks and rewrite the sentences:Ī man painted his main gate made up of iron to prevent it from ………………. Visit a place where work like powder coating. Making dough from wheat flour – Physical change.Making toys from wet soil – Physical change.Clock showing six o’clock time – It is a periodic change.Sahil was enjoying his dinner in the dim light. While eating hot purees, his attention was drawn outside the window. Mother made a dough from wheat flour and fried purees. Then he felt hungry and went into the house. Sahil was sitting in the courtyard, rolling balls of wet soil and shaping them into various toys. It was nearing six o’clock in the evening. Read the paragraph and note down the various types of changes it mentions. Whether the shape, size or state of the substance is changed.ĥ.I will take into account the following facts. What will you take into account while identifying the following: That is why wet handkerchief takes a long time to dry.Ĥ.This depends on surrounding air and heat.When wet handkerchief dries, all the water absorbed has to become water vapour by evaporation.The dry fibres of handkerchief absorbs water to its maximum capacity immediately that is why handkerchief gets wet at once. ![]() So to protect copper and brass utensils from corrosion they are coated with tin.Ī dry handkerchief gets wet at once on dipping in water, but it takes long for a wet handkerchief to dry.Due to corrosion of copper or brass a greenish layer is seen to form on it.It does not allow the wooden article to get decayed by moisture or attacked by termite.Ĭopper and brass utensils should be tinned.So a wooden article should be polished which forms a protective layer.When a wooden article comes in contact with moisture there is possibility of fungal growth and also termites will make wooden article brittle and break.So an iron article should be given a coat of paint so that it is protected against corrosion.Iron gets oxidized to iron oxide which forms a reddish brown layer on it and iron gets rusted.When an iron article is kept for long time it gets corroded due to presence of oxygen in atmosphere.If we consume such food we may get food poisoning, so we should check the expiry date.Īn iron article should be given a coat of paint.After certain period of time it may get spoilt due to some growth of micro-organism it may get intoxicated.While purchasing canned food, its expiry date should be checked. Under which different types can the following changes be classified? Burning of fossil fuels, deforestation, pollution of air, water and soil.Ģ. Examples ripening of a fruit, spoiling of milk, change in the climateĢ. Changes that are result of human activity. Changes that occur naturally on its own are called natural changes.ġ. They do not repeat themselves after a fixed interval of time.ġ. They repeat themselves after a fixed interval of time.ģ. ![]() Examples: volcanic eruption, occurrence of an earthquake, tsunami, forest fires, freezing of water to form ice, sneezing, rusting of iron.ģ. Examples: movement of clock hands in clock showing time, change of season, day and night formation, heart beat, ripening of fruit, rising and setting of the sun.Ģ. Such changes are called non-periodic changes.Ģ. In this, certain changes will recur after one occurrence, it cannot be said for sure, even if they occur interval is not fixed. Such changes are called periodic changes.ġ. Some changes occur again and again after a definite interval of time.
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