The identities of substances are the same before and after which type of change?A.A change of stateB.A physical changeC.A chemical changeD.No change

1. Break Down the Problem

We need to identify which type of change preserves the identities of substances.

2. Relevant Concepts

1. Physical Change: A change that affects one or more physical properties of a substance without altering its chemical composition.
2. Chemical Change: A change that results in the formation of new chemical substances.
3. Change of State: A specific type of physical change where a substance transforms from one state (solid, liquid, gas) to another without changing its chemical identity.

3. Analysis and Detail

• Option A: A change of state — This is a specific example of a physical change; the identity of the substance remains the same.
• Option B: A physical change — Similar to a change of state, the identity of the substance does not change, as the chemical composition remains constant.
• Option C: A chemical change — This involves the transformation of substances into different chemical compositions, thereby changing their identities.
• Option D: No change — Implies that the identity is unchanged, but it is not a type of change.

4. Verify and Summarize

From the analysis, both a change of state (A) and a physical change (B) do not alter the identity of substances. However, since the question specifically asks for the answer that encompasses all forms of physical changes, the best option is:

Final Answer

B. A physical change