Which of the following is the best example of a heterogeneous mixture?

• A. Pure water
• B. Sand and iron filings
• C. Table salt (NaCl)
• D. Air

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the definition of a heterogeneous mixture. A heterogeneous mixture is one in which the components are not uniformly distributed and can be visually distinguished or separated physically.
2. Step 2: Analyze each option: Pure water is a pure substance, not a mixture; table salt (NaCl) is a pure compound; air is a homogeneous mixture because its components are uniformly mixed at the molecular level.
3. Step 3: Consider sand and iron filings. These are physically mixed but remain distinct and can be separated by physical means (like using a magnet for iron filings), making it a heterogeneous mixture.
4. Step 4: Conclude that the best example of a heterogeneous mixture among the options is sand and iron filings because the components are visibly distinct and not uniformly distributed.
5. Step 5: Remember that identifying mixtures involves checking if the composition is uniform (homogeneous) or non-uniform (heterogeneous) and whether components can be physically separated.