In this science investigation, children explored how yeast grows under different conditions. They mixed yeast with water at different room temperatures and poured the mixtures into bottles. To observe the gas produced by the yeast, they stretched a balloon over the top of each bottle. As the yeast grew, it released carbon dioxide gas, which collected in the balloon. The more the balloon inflated, the greater the yeast activity and growth.  The children carefully observed the size of the balloons and compared the results. They discussed how temperature affected the yeast’s growth and noticed differences between the bottles. They also discovered that adding sugar helped the yeast grow more, because sugar provides food that supports yeast activity. Through this investigation, the children learned that yeast is a living organism that grows best under certain conditions, such as the right temperature and the presence of sugar.