Final answer:
Saltwater is a homogeneous mixture, and a mixture of iron filings and sand is a heterogeneous mixture; both are combinations of substances that retain their own properties.
Step-by-step explanation:
Both saltwater (a mixture of salt and water) and a mixture of iron filings and sand are classified as mixtures because they consist of two or more different substances that are physically combined. However, they differ in terms of homogeneity. Saltwater is an example of a homogeneous mixture because the salt (sodium chloride) dissolves in water, resulting in a consistent composition throughout the mixture. Conversely, a mixture of iron filings and sand is a heterogeneous mixture because its different components are distinct and can be easily identified and separated by physical means.