Changes Around Us-Physical And Chemical Change, Characteristics
Characteristics of a chemical change:
1) When a chemical change occurs new substances, with entirely new properties are formed.
2) Chemical change is permanant change,i.e it cannot be easily reversed
3) There is usually a change in weight or mass during chemical reaction
4) Lot of heat is usually given off (or) absorbed during a chemical changes.
Note:
Exothermic Reaction: The chemical change or reaction that takes place by the release of energy is known as Exothermic Reaction
Example: Combustion refers to the process where a substance burns in the presence of Oxygen, giving off heat and light in the process.
These reactions give out good amounts of energy in the form of heat, but also form some byproducts such as smoke.
An example of a combustion reaction would be the combustion of Magnesium which can be represented as follows: Mg + O2 ---> MgO + Heat
Endothermic Reaction: The chemical change or reaction that takes place by the absorbtion of energy is known as Endothermic Reaction
Example: Vinegar is a form of acetic acid and baking soda is also known as sodium bicarbonate. The chemical formula for acetic acid or vinegar is CH3COOH. The chemical formula for baking soda is NaHCO3. The reaction between vinegar and baking soda is a double displacement reaction. In this reaction carbonic acid and sodium acetate are produced. The baking soda and vinegar reaction is endothermic because once combined the temperature of the mixture lowers, meaning the energy was absorbed
Every day examples of chemical changes.
1) Cooking of food
2) Food turning bad after a few days.
3) Curdling of milk
4) Germination of seeds
5) Digestion of food with in our bodies
6) Fermentation of sugar solution to alcohol.
7) Rusting of Iron.