Here’s the matching of the examples of matter with the best description:
- Concrete - Heterogeneous mixture
- Bronze - Homogeneous mixture (it is an alloy, typically a mixture of copper and tin)
- Copper - Element
- Air - Homogeneous mixture
- Sand, silicon dioxide - Heterogeneous mixture (sand is typically a mixture and silicon dioxide refers specifically to the compound in its pure form)
- Fog - Homogeneous mixture (though it can appear heterogeneous, it is generally considered a homogeneous mixture of water droplets in air)
If you need more precise classification or have other questions, feel free to ask!