Question

1. which observations serve as evidence of a chemical reaction? mark all that apply.

change in the color of a solution
formation of a gas
formation of a new product
change from a solid to a liquid

1. match the term with its correct definition

chemical change
a change in a substance that does not involve a change in its composition
the result of a chemical reaction producing change in composition
the process by which one or more substances (reactants) change into new substances with different properties (products)
physical change
chemical reaction

Explanation:

• Question 2:
• A change in the color of a solution can indicate a chemical reaction as new substances with different properties (like color - related compounds) may be formed.
• Formation of a gas is a common sign of a chemical reaction. For example, when an acid reacts with a carbonate, carbon dioxide gas is produced.
• Formation of a new product is the essence of a chemical reaction. In a chemical reaction, reactants are transformed into products.
• A change from a solid to a liquid is a physical change (like melting of ice). It does not involve a change in the chemical composition of the substance.
• Question 3:
• A chemical change is the result of a chemical reaction producing a change in composition.
• A physical change is a change in a substance that does not involve a change in its composition.
• A chemical reaction is the process by which one or more substances (reactants) change into new substances with different properties (products).

Answer:

• Question 2:
• change in the color of a solution
• formation of a gas
• formation of a new product
• Question 3:
• chemical change: the result of a chemical reaction producing change in composition
• physical change: a change in a substance that does not involve a change in its composition
• chemical reaction: the process by which one or more substances (reactants) change into new substances with different properties (products)