Chemical Change And Physical Change solution

Chemical  Change And Physical Change solution:

Physical changes are changes affecting the form of a chemical substance, but not its chemical composition. Physical changes occur when objects or substances undergo a change that does not change their chemicalcomposition. This contrasts with the concept of chemical change in which the composition of a substance changes orone or more substances combine or break up to form new substances. In general a physical change is reversibleusing physical means. For example salt dissolved in water can be recovered by allowing the water to evaporate.   Reactants must be moving fast enough and hit each other hard enough for a chemical reaction to take place.Increasing the temperature increases the average speed of the reactant molecules.As more molecules move faster,the number of molecules moving fast enough to react increases, which results in faster formation of products.