Asolution in a dish contains 4.0 grams of salt dissolved in 100 grams of water. if 50 grams of the water evaporate, this is evidence that the solution is a compound conserving mass an element a mixture

Answer is: a mixture.

Mixtures can be separeted y physical means, while compounds cannot.

Solution is homogeneous mixture composed of two or more substances.  

In aqueous solution, solvent is water and solute (in this example salt) is a substance dissolved in water.

Homogeneous solution of salt and water can be separated with heating (evaporating the water).

The correct answer is a mixture.

Explanation:

A compound is defined as the substance which is formed from the combination of two or more different elements in a fixed ratio.

Conserving mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another. Total mass on the reactant side is equal to the total mass on the product side in a chemical reaction.

An element is defined as the substance which is made from similar kind of atoms. It cannot be divided into simpler substances.

A mixture is defined as combination of two different substances which are not combined in the fixed ratio.

In the question, it is given that a solution is made from 4 grams of salt that is dissolved in 100 grams of water. If some water is evaporated, the salt still remains in the solution, which makes it a mixture of salt and water.

Hence, the correct answer is a mixture.

answer

i think the answer is a) as air pressure in an area increases, the density of the gas particles in that area decreases.

hope it