Chemistry: Chemical Reactions in the Kitchen
Explore evidence of chemical change using everyday foods
Chemistry: Chemical Reactions in the Kitchen
Explore evidence of chemical change using everyday foods
Chemistry - Grade 6-8
- 1
When you mix baking soda and vinegar, the mixture bubbles and produces a gas. Identify the reactants and one product of this reaction.
Reactants are the substances you start with, and products are the substances made by the reaction.
The reactants are baking soda and vinegar. One product is carbon dioxide gas, which causes the bubbling. - 2
A slice of bread turns brown and crispy in a toaster. Is this mainly a physical change or a chemical change? Explain your answer.
This is mainly a chemical change because new substances form as the bread browns and its smell, color, and texture change. - 3
List three signs that a chemical reaction may be happening in a kitchen experiment or cooking process.
Think about what you can see, smell, or feel during cooking.
Three signs of a chemical reaction are gas production, color change, and temperature change. Other signs can include a new smell, light production, or formation of a solid. - 4
When an egg is cooked, the clear liquid egg white turns solid and white. Explain why this is a chemical change.
Cooking an egg is a chemical change because heat changes the structure of the proteins in the egg white. The new solid texture cannot easily be changed back into raw egg white. - 5
In baking, yeast uses sugar and releases carbon dioxide gas. How does this chemical reaction help bread dough rise?
Think about gas getting trapped inside soft dough.
The carbon dioxide gas forms bubbles inside the dough. These bubbles expand and make the dough rise. - 6
A student melts butter in a pan. No new substance is made. Is melting butter a chemical reaction? Explain your answer.
Melting butter is not a chemical reaction. It is a physical change because the butter changes from solid to liquid, but it is still butter. - 7
Lemon juice can prevent apple slices from browning quickly. The browning is caused by a chemical reaction with oxygen in the air. What role does the lemon juice play?
A substance can slow down a reaction without being the main food being changed.
The lemon juice slows the chemical reaction that causes browning. It helps prevent oxygen from reacting with substances in the apple as quickly. - 8
When sugar is heated in a pan, it melts and then turns brown as caramel forms. Which part is a physical change, and which part is a chemical change?
The sugar melting is a physical change because it changes state. The sugar turning brown and forming caramel is a chemical change because new substances with new color and flavor form. - 9
A cake recipe uses baking powder. During baking, baking powder reacts and releases carbon dioxide gas. What evidence could you observe that shows a reaction is occurring?
Look for signs caused by gas being produced inside the batter.
Evidence of the reaction includes the cake rising as gas bubbles form. You may also observe a change in texture as the batter becomes a fluffy solid cake. - 10
A metal spoon left in hot soup becomes warm. Is this an example of a chemical reaction? Explain your answer.
This is not a chemical reaction. Heat is transferred from the soup to the spoon, but no new substance is formed. - 11
Vinegar is acidic, and baking soda is basic. When they are mixed, they react to form new substances. Why is this different from simply stirring sugar into water?
Compare whether new substances are made in each case.
Mixing vinegar and baking soda is different because a chemical reaction forms new substances, including carbon dioxide gas. Stirring sugar into water is usually a physical change because the sugar dissolves but does not become a new substance. - 12
A recipe says to avoid overmixing muffin batter because too much mixing can develop gluten, which changes the texture. Is gluten development a chemical change, a physical change, or both? Explain your answer at a middle school level.
Gluten development can be described as both physical and chemical at a middle school level. Mixing stretches and links proteins in the flour, which changes the batter's structure and affects the final texture of the muffins.