write the type of change in following example. crumpling of paper,dissolving salt in water, digestion of food, melting of butter,a match is lit,rusting of iron,milk goes sour, clay moulded in new shape
Answers
there are basically two types of changes. one is physical change and the other one chemical change.
PHYSICAL CHANGE - physical change is reversible means, there's only change in the size, position or shape. no chemical reaction is involve in physical change. the object or body remains as it was.
CHEMICAL CHANGE - chemical change is irreversible change. in this type of change, chemical reaction is involve. the substance changes to something else.
now, come to your question..
⇒ crumpling of paper - crumpling means crushing. it's a physical change since no new substance is formed. there's only change in it's shape.
⇒ dissolving salt in water - it's also a physical change. we can easily get back salt and water separately by the process of evaporation. and there's no chemical reaction involved here.
⇒ digestion of food - digestion of food is chemical change. since chemical reactions takes place in our body. strong enzymes break down the food into simpler molecules so body can easily absorb it.
⇒ melting of butter - it's physical change. if we cool down the melted butter, then again it'll be as it was before. no new substance is formed only change is size and shape.
⇒ a match is lit - it's a chemical change because when we burn something, it reacts with oxygen to give of light and heat. so it's a chemical change.
⇒ rusting of iron - rusting of iron is also a chemical change because chemical reaction takes place and a new substance is formed. iron reacts with oxygen to form rust.
⇒ milk goes sour - it's a chemical change since the amount of acid increases and produce new molecules. souring of milk is basically curdling.
⇒ clay moulded in new shape - it's a chemical change because the substance remains as it is. there's only change in size and shape. no chemical reaction is involved.