Question

four preparations involving table sugar (sucrose) are described below. analyze the sugar - preparation processes and the end products.

sugar water	sugar floss	sugar caramel	rock sugar
sugar is added to water, and the water is stirred until the sugar is no longer visible.	sugar is melted and blown with a fan to make thin threads of solid sugar.	pure sugar is melted and cooked until it changes color and becomes a thick, sticky liquid.	a highly concentrated solution of sugar - water is prepared, large sugar crystals are allowed to form slowly, and then dye is added.

which of the following is evidence that a chemical reaction has taken place in one of the processes?
o a. the slow growth of giant sugar crystals from a highly concentrated sugar - water solution and added dye
o b. the dissolution of solid sugar in water to form a thin, colorless, odorless liquid
o c. the melting and re - solidification of sugar into threads, which are different from sugars natural cube - shaped crystals
o d. the color change that takes place after heat melts and begins to decompose the sugar

Explanation:

A chemical reaction is characterized by the formation of new substances with different chemical properties. In option D, heating sugar causes it to decompose and change color, indicating the formation of new substances. Options A, B, and C are physical changes as no new substances are formed. In A, sugar crystallization is a physical separation process. In B, dissolving sugar is a physical change of state. In C, melting and re - solidifying sugar is a physical transformation of its physical form.

Answer:

D. the color change that takes place after heat melts and begins to decompose the sugar