Most baked goods have a leavening agent, such as yeast or baking soda, that causes breads, cakes and cookies to rise. Yeast feeds on the sugar and causes bread to rise, while baking soda or baking powder release carbon dioxide, which enlarges bubbles that are already in the batter. Baked goods also require the right ratio of flour to sugar to fat to liquid. If one part of this ratio changes significantly, the texture of the baked goods will be off. Fat makes baked goods tender, while sugar and milk keep them moist and aid with browning.
Washing our hands with soap also involves a chemical reaction. When soap is added to water, it creates an emulsion of oil and water, two substances that normally cannot mix together. This allows oil from a stain to come off your hands or fabric and into the soap and water mixture. Rinsing then removes the stain and soap so your hands or the fabric are clean.
There are chemical components in onions that contain sulfur. When you cut an onion, the cells that hold the sulfur are cut and they release it into the air. The sulfur compounds then react with the moisture in your eyes to create sulfuric acid, which causes sensitive eyes to water. If you place onions in the freezer for a few minutes before cutting them, the cold slows down the chemical reaction and you will experience less burning in your eyes.
Using a cotton ball dipped in lemon juice, write a secret message on a piece of white paper. Let it dry completely so your message is invisible. When you want someone to read the message, place the paper in the sun or close to a light bulb until the lemon juice appears brown. This works because the lemon juice breaks down the paper slightly, so that area of the paper will burn more quickly when exposed to heat. Be careful not to get the paper too hot or it will catch fire.