Question

The volume of water in a beaker was 315 mL. After 7 days, the volume of the water was 300 mL. Kayla says that a chemical change occurred, but Maria says it was a physical change. Who is correct?

A. Maria is right. The water in the beaker changed from a liquid to a gas when it evaporated. Changing states of matter is a physical change.


B. Neither Kayla nor Maria are correct since the water just evaporated. No change took place.


C. Kayla is right. The water changed from a water to a gas. A gas is a new and different substance. This is a chemical change.


D. Both Kayla and Maria are correct. The water changed states which is a physical change, but it also changed into a new substance which is a chemical change.
(I think that it could be A or B, but idk.)

Answer 1

Answer: A. Maria is right. The water in the beaker changed from a liquid to a gas when it evaporated. Changing states of matter is a physical change.

Explanation: A physical reaction is defined as the reaction in which a change in shape, size takes place. No new substance gets formed in these reactions as no rearrangement of atoms take place.

A chemical reaction is defined as the reaction in which a change in chemical composition takes place. A new substance is formed in these reactions as rearrangement of atoms take place.

Evaporation of water is a physical change as only state of the water changes from liquid to gas and no new substance gets formed.Thus Maria is right.

Answer 2

Answer is "A".

Explanation;

Physical changes mean an arrangement of particles of a given substance without producing new substance but changes in physical form of the substance.

Example : vaporization of water ( water goes its gaseous phase from liquid form).

Chemical changes mean an arrangement of particles while forming new substance.

Example : heating of CaCO₃. (In this process CaO and CO₂ are formed).

In this problem, the volume of water has decreased. Hence, it can be said that this is an example of physical changes due to not forming of new substance.