Chemistry -CH01 Chemical Reactions and Equations

Difference between chemical and physical change ?

What are the conditions for a chemical change ?

• For a reactions to occur a minimum amount of energy is required this energy is called activation energy . it can be in the form of heat ,light or electricity which is used to break old bonds between reactants so that new bonds could form .

• For the occurrence of reaction or the reactants’ atoms shall collide.

• The speed of reactions determines its rate, which if is too slow it will be difficult to tell if reaction has took place or not.

Factors affecting Rate of reaction ?

• Temperature: Increasing temperature generally increases the reaction rate by providing more energy to the reacting molecules, resulting in more frequent and effective collisions. Some reactions take place at higher temp than room temp. such as coal starts burning at a specific temp called ignition temp.

• Presence of light : Some reactions take place in light not in dark such as photosynthesis or H₂ + Cl₂ ^hv→ 2HCl

• Presence of catalyst: Substances which increase or decrease (alter) the rate of reaction but does not change itself are called catalysts and this process id called catalysis. such as 2KClO3 MnO2—→ 2KCl + O2

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