
### Instruction: help me answer this question What is the difference between a compound and a mixture and a physical change and a chemical change?, think step by step
### Assistant:  , The answer is A compound is a substance composed of two or more elements in a fixed proportion by mass and is chemically combined, while a mixture is a combination of two or more substances in which each substance retains its chemical properties. A physical change is a change that does not alter the chemical identity of a substance, while a chemical change is a change that alters the chemical identity of a substance.
