A physical
change is the one during which the chemical composition
of the matter does not change.
A chemical change is the one during which entirely new
different substances are formed.
A chemical change is also called a chemical reaction.
Change or processes that can be reversed are called reversible
changes. For example melting of ice, evaporation or freezing of water.
Change or
processes that cannot be reversed are called Irreversible
changes. For example when milk turn into curd, it cannot be changed
back to milk.
Hydrocarbon is the compounds
of carbon and hydrogen only. They are mainly used as fuels.
Natural gas, petrol, diesel, gasoline oil etc. are all hydrocarbons.
The combustion products of hydrocarbons are carbon dioxide and water.
Heat is also released.
The percentage
of methane in the natural gas 85-90%.
Soap is the sodium or potassium salt of fatty acid.
Animal’s fats and vegetable oils act as raw materials in making soap.
Plastics are polymers which are usually made from
small molecules (monomers) under high pressure and
temperature.
Low density
polyethene made under a pressure of 2000 atmosphere at 2000C
is used for making bags, sheet and in insulation.
During a physical change the chemical composition of substance NTS PET24/08/2019 (1:30)
a) Change
b) Doesn’t change
c) Permanently change
d) None of these
The reason for a physical change to be named as such is that the………. a) Change occurs only in physical properties b) Is a reversible change c) Transfer of energy takes place d) all of the above
