Explanation:
Physical changes are defined as the changes in which there does not occur any change in chemical composition of a substance.
For example, mass, density, volume are all physical changes.
On the other hand, a change that leads to formation of a new compound by changing the chemical composition of reactants or combining atoms is known as a chemical change.
For example, combustion, toxicity, reactivity etc are all chemical changes.
Therefore, given situations are identified as follows.
(a) The helium gas inside a balloon tends to leak out after a few hours : It is a physical change as there is no formation of any new compound.
(b) A flashlight beam slowly gets dimmer and finally goes out : It is a chemical change as a chemical process leads to formation of flashlight that emerges out.
(c) Frozen orange juice is reconstituted by adding water to it : It is a physical change as physical state of juice is changing.
(d) The growth of plants depends on the sun's energy in a process called photosynthesis : It is a chemical process.
(e) A spoonful of salt dissolves in a bowl of soup : It is a physical process as no new compound forms when a salt is dissolved in a bowl of soup.
