Question

I. Boiling water and producing water vapor II. Freezing liquid water into ice cubes III. Mixing salt into a beaker of water until the salt dissolves IV. Combining hydrogen gas and oxygen gas in a way to make liquid water When a chemical change occurs something new is formed. The reactants have different properties than the products. The product cannot easily be separated into its original parts. Of the four examples listed above, which describe a chemical change? A) I. B) IV C) III. D) II.

Answer 1

B) IV

why ?

because :  describes a chemical change. Something new is formed. The product, water, is very different from hydrogen gas and oxygen gas.

Answer 2

B) IV, because all the others are physical changes and cannot be reversed.