Question

One of the indicators of a chemical change, the formation of bubbles, can also be associated with physical changes under certain contexts. Provide examples of specific substances and describe the situations in which bubbles form during i) physical change or ii) chemical changes.

Answer 1

Bubbles indicate both physical and chemical changes; boiling water causes bubbles in a physical change, while vinegar reacting with baking soda creates bubbles due to a chemical change that forms new substances.

Step-by-step explanation:

Bubbles forming in a substance can indicate both physical and chemical changes. To distinguish the two, let's consider examples:

• Physical change: When water boils, bubbles are formed due to the conversion of water from a liquid to a gaseous state (steam) at 100°C. This is a phase change, a typical physical process that does not alter the molecular structure of water (H2O remains H2O).
• Chemical change: Vinegar reacting with baking soda is a classic demonstration. Bubbles are observed due to the production of carbon dioxide gas (CO2) as a product of the chemical reaction between acetic acid in vinegar and sodium bicarbonate (baking soda). This reaction forms new substances, which characterizes a chemical change.

Therefore, while bubble formation can be an indicator of a chemical change, it's essential to consider the context and other signs, such as temperature changes, light emission, and unexpected color changes to correctly identify the type of change.