Question

which of the following indicate that a chemical change likely occurred? choose 2 answers: a a change in size or amount b a substance dissolves in water c bubble formation from a new gas d light and heat production e a change in the state of matter

Explanation:

• Option A: A change in size or amount is a physical change (e.g., cutting a piece of paper, adding more water to a beaker), not a chemical change.
• Option B: Dissolving a substance in water can be a physical change (e.g., dissolving sugar in water, which is a mixture and no new substance is formed in most cases of simple dissolution).
• Option C: Bubble formation from a new gas indicates a chemical reaction where a new gaseous substance is produced (e.g., reaction of acid and metal producing hydrogen gas), so this is a sign of chemical change.
• Option D: Light and heat production (e.g., combustion reactions, like burning wood which produces heat and light and new substances) is a sign of a chemical change as energy changes and new substances are formed.
• Option E: A change in the state of matter (e.g., melting ice to water, condensing steam to liquid water) is a physical change as the substance's chemical identity remains the same.

Answer:

C. bubble formation from a new gas, D. light and heat production