Question

a student takes four samples of a white crystalline solid and places each in a well - plate. on top of each sample, she carefully places 20 drops of clear mystery liquids a, b, c and d. her results by each well are: liquid a: the solid dissolves quickly. liquid b: the solid appears unchanged. liquid c: a brownish - colored liquid is produced. liquid d: fizzing occurs and the well becomes warmer. in which well does a physical change occur?

Explanation:

A physical change is a change in which the form or appearance of matter changes, but not its chemical composition. Dissolving a solid quickly (Liquid A) is a physical change as it just changes the state of the solid from solid - phase to dissolved in the liquid phase without forming new substances. Fizzing (Liquid D) indicates a gas - forming reaction (usually a chemical change), production of a brownish - colored liquid (Liquid C) suggests a chemical reaction that forms a new colored substance, and no change (Liquid B) is not a physical change in the sense of a transformation occurring.

Answer:

A. The solid dissolves quickly