Studied by 14 people
Physical Change
A change where the reactants undergoes changes only in its physical properties such as shape, size, colour and state.
Chemical Reaction
A reaction where the reactants react chemically to form new substances with different chemical properties.
Reactants
Original substances participating in a chemical reaction.
Products
The new substances formed during or after the chemical reaction.
Rust
A substance formed when iron is left exposed to moist air.
Rust II
It is known as iron oxide(Fe2O3)
Rust formation
4Fe+3O2+H2O———————2Fe2O3•H2O
The effect of rust
It corrodes the iron
Prevention of rusting
It can be prevented by not allowing the iron to come in contact with moisture and air.
Methods of prevention of rusting
1) Painting the surface
2) Greasing the surface
3) Galvanization
Galvanization
The process of transferring a layer of zinc on the surface of iron
Types of characteristics of chemical reactions
1) Evolution of a gas
2) Change of colour
3) Formation of precipitate
4) Changes in energy
5) Change of state
Evolution of a gas
A gas may evolve during a chemical reaction
Effervescence
Bubbling of a gas during a chemical reaction
An arrow pointing upwards
The sign of the evolution of a gas
Reactants: Calcium carbonate and Hydrochloric acid
Products: Carbon Dioxide, Calcium Chloride and Water
Limewater turns milky
Reason: Presence of Carbon Dioxide
Reactants: Limewater(Calcium hydroxide) and Carbon Dioxide
Products: Calcium carbonate and water
Calcium carbonate
A substance which is white in colour and not soluble in water
Reactants: Zinc and Sulphuric acid
Products: Zinc sulphate and Hydrogen
To test hydrogen
Put a burning matchstick near the hydrogen and hydrogen will burn making a pop sound
Note 
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