What is the role of a catalyst in a chemical reaction?
Important Points to Remember in Chapter -1 - Changes Around Us from Tamil Nadu Board Standard Eight Science Solutions
1. Chemical Change
(i) Chemical changes may also be called as chemical reactions as new substances are formed after reacting.
(ii) A chemical reaction may take place via physical contact in solid state, solution of reactants, electricity, heat, light and catalyst.
2. Chemical Reactions based on Physical Contact
Rusting is a chemical reaction in which iron objects form hydrated ferric oxide in presence of oxygen and water.
3. Chemical Reactions based on Electricity
Electrolysis is a process in which electricity is used to carry out chemical reactions.
4. Chemical Reactions based on Light
Photolysis is a process in which light is used to carry out chemical reactions.
5. Chemical Reactions based on heat
Thermolysis is a process in which heat is used to bring about chemical reactions.
6. Chemical Reactions based on Catalyst
Chemical substance used to alters the speed of the reaction is called catalyst and the process is called catalysis.
7. Effects of Chemical Reactions
(i) Chemical reactions cause spoilage of food,vegetables and fruits, acid rain, green house effect and damage to materials.
(ii) Global warming is a dangerous condition in which earth’s average temperature rises alarmingly due to various human activities.
(iii) Rancidity is a condition in which the food items develop bad odour due to chemical reactions by microbes.
