Questions

Radon gas is a source of natural groundwater pollution.

Potentially hazardous foods are foods that might contain food poisoning bacteria and are capable of supporting growth of these bacteria or formation of toxins to levels that are unsafe for consumers, if the foods are not stored at correct temperatures. Toxins are poisonous chemicals produced by some types of bacteria.

The food can be left at room temperature until it reaches 60 deg C because food-poisoning bacteria will not multiply at 60 deg C or above. However, do not leave food cooling at room temperature unless you are sure that the temperature of the food is still at least above 60 C.

Heat from the sun travels in the form of rays and are called as heat rays. This heat is called as radiation.