Which sample of matter is classified as a substance?
(1) air (3) milk(2) ammonia (4) seawater

A chemical substance has the characteristics that it cannot be separated by physical  methods. Seawater and milk can be separated by sedimentation, and air has different components depending on other aspects (such as elevation). Only ammonia is a substance. (thus it can have a formula: NH3)

Option (a) is the correct answer.

Explanation:

According to collision theory, more is the number of collisions between the particles of reactants or a substance then more will be the rate of reaction.

Therefore, when we heat the solution then it will take time to heat up and thus, molecules will gain kinetic energy after a few minutes. As a result, collisions will start to occur and eventually rate of reaction will increase.

Whereas when we stir the solution while heating then immediately a disturbance is caused due to which atoms start to move and thus they gain kinetic energy. Therefore, rate of reaction will increase much faster due to stirring while heating.

On the other hand, when solute is dissolved into the solution and if no disturbance is caused then the reaction will be slow in nature as molecules are not colliding rapidly.

Hence, we can conclude that ranks who would fully dissolve the solute, from first to last are as follows.

                        Larry → Jessica → Hunter