What is an example of a homogeneous mixture?

Under low temperatures and pressure, the mixture of water, sugar, and carbon dioxide is homogeneous; however, as the pressure is released, carbon dioxide bubbles appear, causing the mixture to become heterogeneous.

First and foremost an homogeneous mixture is a mixture where all the components are in the SAME PHASE, but where the composition of the mixture is more or less uniform.

And so, the air we are breathing right now is an excellent example of an homogeneous mixture: its composition is more or less uniform, i.e. approx. 78% dinitrogen, and 21% dioxygen, an increasing quantity of carbon dioxide, and some small percentage of Noble Gases. That it is in the gaseous phase does not differentiate.

Most solutions, especially aqueous solutions, may certainly fall under the umbrella of homogeneous mixtures. Certainly the composition of the solution may vary. Sometimes the behaviour (e.g. the vapour pressure) of homogeneous solutions behave ideally, and solution vapour pressures are linear functions of their percentage compositions. Alkali metals can dissolve in mercury metal to form amalgams.

And, also some solids may be classed as homogeneous mixtures. All alloys, which can have varying compositions, i.e. brass, steel, pewter, solders, bronze, fall under this umbrella.

The common factor in all these mixtures, is that they are in the same phase. And the mixture (especially as the alloy) may have different properties from the individual component. And such properties may be desirable to a materials scientist.

@David, sorry for trumping your earlier answer.....

Saltwater.