All those holes inside a soft, chewy loaf of bread are the handiwork of microscopic (really tiny) yeast! Find out what temperature yeast likes best in this bubbly experiment.
Add ½ teaspoon yeast to each bag. Then, add ½ teaspoon sugar to each bag.
Add 2 tablespoons room-temperature water to bag labeled “Room Temperature.” Seal bag, squeezing out as much air as possible. Place bag in center of rimmed baking sheet.
Fill small bowl about halfway with water. Heat water in microwave until steaming, 30 seconds to 1 minute. Use oven mitts to remove bowl from microwave. Add 2 tablespoons hot water to bag labeled “Hot” (ask an adult for help). Seal bag, squeezing out as much air as possible. Place bag on right side of baking sheet. Discard remaining hot water.
Hold fine-mesh strainer over now-empty small bowl. Pour ice water through fine-mesh strainer. Discard ice. Add 2 tablespoons ice water to bag labeled “Cold.” Seal bag, squeezing out as much air as possible. Place bag on left side of baking sheet.