Question

4a what event is occuring? 4b circle chemical change or physical change liquid a 25℃ liquid b 25℃ 7a what event is occuring? 7b circle chemical change or physical change

Explanation:

Step1: Analyze the reaction

Two liquids at 25°C are combined and the resulting mixture has a temperature of 60°C and gas (H₂) is produced. A chemical reaction is occurring as new substances are formed and there is a temperature - change indicating an energy change associated with chemical bond - breaking and forming.

Step2: Determine the type of change

Since a new substance (hydrogen gas) is formed and there is an energy change (temperature increase), this is a chemical change. Physical changes do not result in the formation of new substances.

Answer:

7a. A chemical reaction is occurring.
7b. Chemical Change