we reason for the following:
1.How would you show that the setting of a curd is a chemical change?
2.Why does an athlete breathe faster and deeper than usual after finishing the
race?
3.Why is it necessary to excrete waste products?
4.Why calamine solution is applied on the skin when an ant bites.
5.Explain why holes are made in hanging banners and hoardings.
Answers
Answer:
1.)Setting of curd is a chemical change because a new substance(lactic acid) is formed. The curd formed has a different taste than the original substance. Also, once the curd is formed, milk cannot be re-obtained from it. It is an irreversible change.
2)An athlete breathe faster and deeper than usual after finishing the race. During the run, the demand for energy is high but the supply of oxygen to produce energy is limited. ... After finishing the race, an athlete breathe faster and deeper than usual so that more oxygen is supplied to the cells.
3)It is necessary to excrete waste products because it harms our body. It contains undigested particles in human body. If waste products are not excreted it becomes a slow poision in human body
4)When an ant bites it basically injects formic acid into the skin. Calamine solution contains zinc carbonate and is basic in nature. When applied in the skin, it reacts with the acid, and neutralizes its effect, thus giving relief. ... Hence, factory waste needed to be neutralized