Name: The Crystallisation of Copper Sulphate
Uploaded: 2019-07-19
Duration: 2 min 8 s
Description: Crystals are made through the process of crystallisation, and here in the video, we will see how to obtain copper sulphate from a solution. Click on the play...

Question

In addition to formation of new substances, what all changes can be observed during a chemical change? Give one example of each type of change.

Accepted Answer

In addition to the formation of new substances, a chemical change may be accompanied by the following changes.
(1) Evolution of gas: When zinc granules are added to dilute Sulphuric acid $(H_{2} S O_{4})$ hydrogen gas is evolved.
$H_{2} S O_{4} + Z n \to Z n S O_{4} + H_{2} + heat$
$C a C O_{3} \overset{h e a t}{\to} C a O + {C O}_{2}$

(2) Change of colour: When solid lead nitrate is heated reddish brown nitrogen dioxide gas is evolved.
$2 P b {(N O_{3})}_{2} \to 4 N O_{2} + 2 P b O + O_{2}$

(3) Formation of precipitate: When hydrogen sulphide gas is passed through blue coloured copper sulphate, a black precipitate of copper sulphide is formed.
${CuSO}_{4} + H_{2} S \to CuS + H_{2} {SO}_{4}$

(4) Absorption or evolution of heat: When carbon and sulphur are heated, heat energy is absorbed.
$C + 2 S + heat \to {CS}_{2}$
(5) Sound may be produced: When baking soda reacts with vinegar, a gas is produced with a hissing sound.
${CH}_{3} COOH + {NaHCO}_{3} \to {CH}_{3} COONa + {CO}_{2} + H_{2} O$

In addition to formation of new substances, what all changes can be observed during a chemical change? Give one example of each type of change.

Important Questions on How Things React With One Another

Learn and Prepare for any exam you want !