(chemical reactions are the processes in which new substances with new properties are formed)
--the substances which take part in a chemical reaction are called reactants
--the new substances produced as a result of chemical reaction are called products
when a magnesium ribbon is heated it burns in air with a dazzling white flame to form a white powder called magnesium oxide, on heating Magnesium oxide combines with oxygen present in air to form magnesium oxide,example
(heat)
Magnesium + oxygen ---> Magnesium oxide
(As ribbon) (from air) (white powder)
this is an example of chemical reaction...
{characteristics of Chemical reactions}
- Evolution of gas.
- Formation of a precipitate.
- Change in color.
- Change in temperature.
- Change in state.
- Formation of new substances
1.}Evolution of gas
some chemical reactions are characterised by the evolution of gas
for example when zinc granules reacts with dilute sulphuric acid,the bubbles of hydrogen gas are produced so this chemical reaction in characterised by the evolution of hydrogen gas
[A precipitate is a solid substance that forms in a solution during a chemical reaction.]
2.}
Precipitation reactions are usually double displacement reactions involving the production of a solid form residue called the precipitate. These reactions also occur when two or more solutions with different salts are combined, resulting in the formation of insoluble salts that precipitate out of the solution
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