Determine whether each of the following describes a physical change or a chemical change: (a) the helium gas inside a balloon tends to leak out after a few hours. (b) a flashlight beam slowly gets dimmer and finally goes out. (c) frozen orange juice is reconstituted by adding water to it. (d) the growth of plants depends on the sun's energy in a process called photosynthesis. (e) a spoonful of salt dissolves in a bowl of soup.

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.