Question

During a chemical change there is a change in the mass of original substance:

• A. True
• B. False

Answer 1

The correct option is A

True

During a chemical change, there is a change in the mass of the original substance and this can be understood by a simple activity.

Take a piece of magnesium ($Mg$) in a crucible with a lid. Weigh it then heat it by opening the lid after short intervals to let the air enter the crucible. When the whole magnesium is burnt, cool the crucible and weigh it again. The final weight is more than initial weight because oxygen present in air reacts with magnesium to form magnesium oxide (white powder). This shows that when a chemical change takes place there is a gain in the mass. The reaction occurred will be:

$Mg\left(s\right)+O_2\left(g\right)\to 2MgO\left(s\right)$