The World of Metals and Non-metals — Science STD 7 — Question

Why Calamine solution is applied on the skin when an ant bites?

Why does silk have different varieties?

Write short notes on:

1. In filtration.
2. Aquifer.

Baking soda is mixed with lemon juice, bubbles are formed with the evolution of gas, explain the changes occurred here.

State the factors on which the time period of a simple pendulum depend.

Why does an athlete breathe faster and deeper than usual after finishing the race?

Adolescents sometimes experience mood swings. On some days, they feel very energetic and happy, while on other days, they may feel low. What other behavioural changes are associated with this age?

Alimentary canal is different from digestive system. Comment.

Mary and Manoj were classmates and good friends. On turning 11, Mary developed a little bulge on the front of her neck. She visited the doctor who gave her medication and asked to take iodine-rich diet. Similarly, a bump developed on the front of Manoj’s neck when he turned 12. However, the doctor told him that it was a part of growing up. According to you, what could be the possible reason for advising Mary and Manoj differently?

Write the difference between natural silk and artificial silk.