Which of the following samples of matter can be separated into different substances by physical means?

• A. Copper metal (Cu)
• B. Carbon dioxide (CO2)
• C. Pure water (H2O)
• D. A mixture of sand and salt

Answer: (D)

Verified step by step guidance

1. Understand the difference between pure substances and mixtures: Pure substances have a fixed composition and cannot be separated into other substances by physical means, while mixtures consist of two or more substances physically combined and can be separated by physical methods.
2. Analyze each given sample: Copper metal (Cu) is an element, so it is a pure substance and cannot be separated by physical means into different substances.
3. Carbon dioxide (CO2) is a compound, a pure substance made of two elements chemically bonded, so it cannot be separated into different substances by physical means.
4. Pure water (H2O) is also a compound and cannot be separated into different substances by physical means.
5. A mixture of sand and salt is a physical combination of two different substances, so it can be separated by physical methods such as filtration (to separate sand) and evaporation or dissolution (to separate salt).