kindly give answers to these
Answers
1.
Endothermic reaction
Any process which requires or absorbs energy from its surroundings, usually in the form of heat.
Combustion
The process of burning something
Rusting
The coating that forms on the surface of iron when exposed to air or moisture.
Pollutants
Substances that pollute the environment
Boiling
Rapid vaporization of a liquid, which occurs when a liquid is heated to its boiling point.
Chemical change
Chemical changes occur when a substance combines with another to form a new substance. They may or may not be reversible.
2.
a) Formation of dew is a physical change.
b) Solar energy is converted into chemical energy during photosynthesis.
c) A precipitate is usually known as insoluble substance.
d) Nitric acid is formed by dissolution of nitrogen dioxide in water.
e) Acetylene gas is used for burning fuel in welding torches.
3.
a) Combustion
Rocket propellant
Oxidising agent
b) pollution
Causes respiratory problems
Leads to formation of smog in winters ( smoke + fog )
Leads to asthma
Blackening of buildings
Skin infections
c) evolution of gas
HCl + Zn --------> ZnCl2 + H2
Change of state
HCl (aq) + Zn (s) --------> ZnCl2 (aq) + H2 (g)
Formation of precipitate
Ca(OH)2 + CO2 --------> CaCO3 (white precipitate) + H2O
4. Physical change
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