Look at the questions labelled A, B, C, D. A How many substances are there in drinking water? B How much fluoride is in drinking water? C Is fluoride soluble in drinking water? D Should fluoride be added to drinking water? Which one of the questions cannot be answered by science alone? Tick one box.

Magnesium, calcium and sodium.

Explanation:

Magnesium, calcium, sodium, and other beneficial minerals are the substances present in drinking water. Different regions have different fluoride concentration in their water such as in sea water, fluoride level is 1.1 mg/L while in surface water, the concentration is 0.01–0.3 ppm. Yes, fluoride is soluble in water. No, fluoride should not be added to drinking water because it harm for health. All the questions can be answered by science because it is related to chemistry.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.