Revolution of the earth around the sun:
This is a periodic change because it occurs at regular intervals and is predictable. It’s also a natural change.
Stretching of a spring:
This is a physical change because the material of the spring retains its composition, and no new substance is formed.
Giving Reasons:
While purchasing canned food, its expiry date should be checked:
Canned food has a limited shelf life due to the potential for chemical changes and microbial growth over time. Checking the expiry date ensures that the food is safe to consume.
An iron article should be given a coat of paint:
A coat of paint acts as a barrier, preventing exposure to oxygen and moisture, which can cause iron to rust (a chemical change).
A wooden article should be polished:
Polishing helps protect the wood by providing a protective layer, enhancing its appearance, and preventing it from getting damaged or deteriorating.
Copper and brass utensils should be tinned:
Tinning forms a protective layer on the copper or brass, preventing them from corrosion when they come in contact with acidic or alkaline foods.
A dry handkerchief gets wet at once on dipping in water, but it takes long for a wet handkerchief to dry:
This is due to the difference in water absorption rates. A dry handkerchief quickly absorbs water upon contact, but evaporation, the process of drying, takes longer as it requires heat and air circulation to remove the moisture from the fabric.
