Answer:
The balloon will expand.
Explanation:
Yeast is single cell micro organism. If it gets the right environment it behaves like a live micro organism. Every thing that is alive eats something, converts it into energy for self use and then creates a by product or waste. Yeast works the same way.
When warm water and sugar will be mixed with yeast, it will be activated and start eating sugar. It will convert sugar into alcohol and release carbon dioxide because of which the balloon will expand. This process is called as fermentation as well.
If the water is too cold or too hot the result will be different.
