Question 1: Explain what happens to the starch in a potato when it is heated and cooked thoroughly.

Answer: When a potato is heated, the starch granules absorb water and swell. Eventually, they burst, releasing starch molecules, which cause the potato to become soft and fluffy. This is a chemical change because new substances are formed.

Question 2: Describe what occurs when you cook an egg. Mention the changes to the proteins.

Answer: When an egg is cooked, the heat causes the proteins in the egg white and yolk to denature, meaning their structure changes. This results in the egg becoming firm and solid, which is a permanent chemical change.

Question 3: What is the chemical change that occurs when bread is toasted?

Answer: Toasting bread causes the Maillard reaction, a chemical process where sugars and amino acids react to form new flavors, browning the bread and creating a richer taste. It is a chemical change because new compounds are formed.

Question 4: Describe what happens to sugar when it is heated strongly in a process called caramelization.

Answer: When sugar is heated, it melts and then undergoes caramelization, where it breaks down and forms new, darker compounds with a rich flavor and brown color. This is a chemical change because the sugar molecules are altered.

Question 5: Identify two signs that indicate a chemical change has taken place during cooking.

Answer: Signs include colour change (e.g., bread turning brown), formation of new substances (e.g., cooked egg turning white and firm), or the release of gases (e.g., bubbling during baking).

Question 6: Explain why boiling vegetables can cause some nutrients to be lost.

Answer: Boiling vegetables causes water-soluble nutrients like vitamin C and B vitamins to dissolve into the cooking water. Heating can also break down some nutrients, leading to their loss during cooking.

Question 7: Sketch a simple diagram showing the process of protein denaturation in an egg when cooked. Include the raw egg and cooked egg states side by side.

Answer: A correct sketch would show two side-by-side representations: one with a liquid, transparent egg white (uncooked), and the other with a solid, opaque egg white (cooked), illustrating the change in protein structure.

Question 8: Describe what happens to the fats in butter when it is heated to make melted butter.

Answer: When butter is heated, the fats melt from a solid to a liquid state. This is a physical change because the fats are simply changing state without forming new substances.

Question 9: What is the effect of overcooking vegetables on their chemical composition?

Answer: Overcooking vegetables can destroy heat-sensitive nutrients like vitamins, and may also cause the breakdown of cell walls, leading to loss of texture and flavor. It may also result in the formation of undesirable compounds.

Question 10: Explain why cooking meat thoroughly is necessary from a safety perspective.

Answer: Cooking meat thoroughly kills harmful bacteria and parasites, preventing foodborne illnesses. This is a chemical change because the heat destroys pathogens and makes the meat safe to eat.