Chemical Reaction – Science
- Matter: The Various substances around us, which have weight and volume are called matters. Glass, Plastic, Air, Iron, Paper etc. are an example of Matter. Matter exists in three states I.e. solid, liquid and gas.
- Physical Change: A temporary and usually reversible change in which no new substance is formed. – A physical change is a change in properties like state, colour, speed, motion, shape, size etc. but the chemical composition of the substance remains the same. For Example: Melting of Ice, Magnetizing a needle, solution of salt and water etc.
Chemical Reaction Chemical Change: A chemical change is a permanent change and gives rise to a new substance having composition and properties altogether different from original substances. It is usually irreversible. For Example Formation of curd from the milk, Rusting of iron, burning of magnesium ribbon, burning wood etc.
Di- atomic element: The elements whose molecules are made up of two atoms are called di-atomic elements. The molecules of gases like Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, Iodine are di-atomic.