Question

Which of these suggest that a chemical reaction may be occurring?

• A. Change of colour
• B. Change of state
• C. Reduction of temperature
• D. Release of a gas

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A Change of colour
B Change of state
C Reduction of temperature
D Release of a gas

There are several observations which can identify that some chemical reactions have taken place within a system.

Change in temperature
-Usually, when a reaction takes place, heat will be absorbed or released which results in a temperature change.
-eg:If put a piece of sodium in water. we will feel or observe that the temperature is increased.


Change in colour
-Sometimes we see a colour change in the media when a reaction takes place.


Emission of gas
-Sometimes, when a reaction takes place, a gas is emitted from the system.
-eg: If we put a piece of sodium in water, we will observe that a gas is emitted as shown by the formation of bubbles.


Smell or odour
-When some reactions take place, the formation of some substances can give us a smell or odour.