Question 23

Water produces gas when reacting with sodium metal.

This option illustrates a clear chemical reaction where sodium metal reacts with water, resulting in the formation of hydrogen gas and sodium hydroxide, showcasing the rearrangement of atoms and bonds.

A) Water and oil separate when combined

This statement describes a physical change rather than a chemical reaction. When water and oil are mixed, they do not chemically react; instead, they form two distinct layers due to differences in density and polarity.

B) Water boils to produce steam at 100 degrees Celsius

Boiling water to produce steam is also a physical change. In this process, water transitions from a liquid state to a gaseous state without altering its chemical composition, thus not demonstrating a chemical reaction.

C) Water dissolves sugar

While dissolving sugar in water results in a solution, it is still a physical change. The sugar molecules disperse in the water, but no new substances are formed, and the chemical structure of the sugar remains intact.

D) Water produces gas when reacting with sodium metal

This option is correct because it involves a chemical reaction. Sodium reacts vigorously with water, leading to the formation of hydrogen gas and sodium hydroxide, which are different substances from the reactants.

Conclusion

The correct answer, D, clearly indicates a chemical reaction, as it involves the transformation of reactants into new products, unlike the other options which describe physical changes. Options A, B, and C do not involve any chemical change, further solidifying D as the only choice that meets the criteria of demonstrating a chemical reaction involving water.