Q. When we drink soft drink through a straw, why does the liquid go up into our mouth?
A. When a person sucks air from the straw, the pressure of air inside the straw is reduced as compared to the atmospheric pressure acting on the surface of the liquid. Therefore, the soft drink rushes up into the straw and to the mouth.
Q. Explain why it takes more time to cook meat and vegetables at hill stations?
A. The boiling point of water depends upon the pressure on its surface. It increases with the increase of pressure and decreases on lowering of pressure. At higher altitudes, the atmospheric pressure is low as compared to that in the plains and, therefore, water boils below 100°C. Hence, sufficient heat is not supplied for cooking the meat and vegetables at hill stations. This difficulty may be overcome by using a pressure cooker. Water can be made to boil at any desired temperature with the help of this appliance.