Balloons can be used to demonstrate that gas is released when yeast is combined with sugars. Fill a water bottle 3/4 full of warm water. Pour in 3 tablespoons of granulated sugar, and one packet of active dry yeast. Stir the mixture well with a chopstick. Stretch the opening of a balloon over the top of the water bottle, and allow the bottle to sit undisturbed for around thirty minutes. The yeast will combine with the sugars to release gas, which will slightly inflate the balloon.
Students can inspect the way yeast acts alive by creating a yeast creature in a plastic bag. Start by pouring 2 cups of warm water into a sealable plastic bag. Pour in 2 tablespoons of granulated sugar and two packets of active dry yeast. Seal the bag tightly, and use your hands to mix the substances together well. After a few minutes, allow your students to examine the yeast close-up, using a magnifying glass or a microscope. The yeast will appear to grow and move.
One way to teach students about the usefulness of yeast is to allow them to make yeast bread. Yeast bread uses the gases released by sugar and active dry yeast to create air pockets in bread, making it light and fluffy. In a small bowl, combine 1 cup of warm water and 1 tablespoon of granulated sugar. Add in one packet of active dry yeast. Allow the mixture to sit for ten minutes until it is frothy. In the meantime, combine 4 cups of flour and 1 teaspoon of salt in a large bowl. After the yeast is ready, pour it into the flour mixture. Use your hands to knead the dough for 10 minutes. Let the dough rest for one hour, which will make it double in size. Place the dough into a greased bread pan, and bake it in a preheated, 350-degree oven for 15 to 20 minutes.