Question

Which of the following is a mixture?
A. Water
B. Oxygen
C. Carbon dioxide
D. Air

Answer 1

Hint: Mixture can be defined as that resulting substance when two or more substances mix with each other without participating in a chemical change. This resulting substance does not lose their individuality and they don’t combine chemically.

Complete answer:
The main properties of the mixture are that the components of a mixture maintain their original properties, separations of the components is also easy to be done and proportion of the components is variable.
Mixture is of two types: Heterogeneous mixture and Homogeneous mixture. Where homogeneous mixtures are those who have the same properties and combinations throughout the mass whereas heterogeneous mixture possess different properties and compositions in various parts. Out of the example given in the question air is the mixture of many gases. The composition of air is also not fixed and changes from place to place like in polluted areas the percentage of carbon dioxide is very large as compared to less polluted one. The main components of air are: Nitrogen, oxygen, carbon dioxide, argon and also some other gases. Therefore it is considered as a mixture.

Hence we can say that option D is the correct answer.

Note:
When two or more substances are mixed then no chemical force is acting between them but they still exist together. The substance can be homogeneous or heterogeneous in nature and the constituents of the mixture can be easily separated with the help of physical techniques.