Question

Physical changes like boiling do not make new materials and are easily reversed e.g. boiling which causes …………………
A. Condensation
B. Reactants
C. Reaction
D. Color

Answer 1

Hint: Physical changes mainly involve states of matter and energy. During a physical change a matter will take a different form but no new substance is formed. It occurs when substances are mixed but they do not react chemically with each other.

Complete Solution :
- To check whether a compound undergoes physical change or not we have to look at whether that change may be reversible especially phase change. For example if we freeze water into an ice cube then we can melt it into water again. But it is also not possible or easy to reverse all physical changes. Color change, bubble formation, or formation of a precipitate all are signs of a chemical change not a physical change.
- Reversible changes are those changes which can be undone or reversed. Melting, freezing, boiling, evaporating, condensing, dissolving and also changing the shape of a substance are examples of reversible changes. Boiling causes condensation and term condensation refers to the process of water vapor changing into liquid water. Therefore we can say that condensation is a change in the state of water from a gas in a liquid form.
So, the correct answer is “Option A”.

Note: Condensation takes place when the vapor in the warm air meets a cool surface. However it does not necessarily require a solid surface. In simple manners we can say that condensation is just the opposite of evaporation. In evaporation liquid gets converted into vapors and in condensation opposite happens.