the prefix hetero- means 'different' so a heterogeneous mixture would be a mixture in which you can clearly see all of the components.
(like a salad)
sugar and baking soda would dissolve in the water (t<em>hat would be an example of a </em><em>homogeneous</em><em> mixture, the prefix homo- means 'same' homogeneous mixtures have a uniform appearance throughout)</em>
However the sand will definitely not dissolve in the water, it will simply sink to the bottom, and stay there. you would clearly be able to see both the water and the sand.
The reaction that would take place if hot tungsten was
surrounded by air is that it would react to the oxygen in air to form non
conducting tungsten oxide and burns out instantly.