* Homogeneous mixtures have a uniform composition throughout. This means that the components are evenly distributed and you can't visually distinguish between them.

* Heterogeneous mixtures have a non-uniform composition. You can see distinct parts or phases.

Club soda is made of water, carbon dioxide, and sometimes minerals. These components are dissolved into the water, making the mixture uniform throughout. You can't see the individual components, making it a homogeneous mixture.