When two liquids are mixed and bubbles form, what type of change has most likely occurred?

• A. A chemical change, because the temperature always increases when bubbles form.
• B. A chemical change, because a gas is produced indicating a new substance is formed.
• C. A physical change, because no new substance is formed when bubbles appear.
• D. A physical change, because mixing liquids always produces bubbles.

Answer: (B)

Verified step by step guidance

1. Understand the difference between physical and chemical changes: A physical change affects the form of a substance but not its chemical composition, while a chemical change results in the formation of one or more new substances.
2. Recognize that the formation of bubbles when two liquids are mixed usually indicates the production of a gas.
3. Recall that the production of a gas is a strong sign that a chemical reaction has occurred, because gases are often new substances formed during chemical changes.
4. Note that temperature changes can accompany chemical reactions but are not definitive proof on their own; the key indicator here is the formation of a gas (bubbles).
5. Conclude that the appearance of bubbles when mixing two liquids most likely indicates a chemical change, as it shows a new substance (gas) is being produced.