(i) Metal rim is at first heated so that it increases in size. It is then slipped on wooden wheel. Water is poured on it so that iron rim contracts on cooling and fixes firmly to hold the wooden wheel.
(ii) Bacteria and microbes can easily spoil cooked food at room temperature. But in refrigerator, the temperature is low as compared to outside which prevents (inhibits) the growth of the microbes. So, cooked food is kept in refrigeration to prevent it from spoiling.
(iii) Iron sheet can easily rust in presence of air and moisture. But tin cannot rust. So, iron sheet is coated with tin to prevent from rusting.
(iv) Trees are being cut for fuel and other numerous wood items. But cutting of trees lead to many adverse effects, such as soil erosion, less rain fall, unfertile soil etc. So, cutting of trees must be banned.
(v) A candle burns involves both chemical and physical change. In it some wax melts into liquid form while some converts into gas which bum in air to give a flame.
