Question 1: Describe what happens at a chemical level when an egg is cooked. Why does the egg change from runny to firm?

Answer: When an egg is cooked, heat causes the proteins in the egg white and yolk to denature, meaning their structure changes. This causes the egg to turn from a liquid to a solid, making it firm.

Question 2: Explain why bread becomes toasted when heated. What chemical change is responsible for the browning?

Answer: When bread is toasted, the Maillard reaction occurs, a chemical process between amino acids and sugars that produces browning and new flavors.

Question 3: Identify two food items that undergo fermentation and describe one chemical change that occurs during fermentation.

Answer: Yogurt and bread are examples. During fermentation, bacteria or yeast convert sugars into alcohol or lactic acid, producing gas or acids that change the food's texture and flavor.

Question 4: Describe the process and chemical change that occurs when fruit is cooked to make jam.

Answer: Cooking fruit with sugar causes the fruit's pectin to dissolve and form a gel, thickening the mixture. Heat also causes chemical reactions that enhance flavor and color.

Question 5: Explain why meat changes colour when it is cooked. What chemical change causes this?

Answer: Cooking meat causes the myoglobin protein to denature, changing its colour from purple-red to a brownish shade, indicating it is cooked.

Question 6: Draw a simple diagram to show the chemical change that occurs when baking soda reacts with vinegar. Include labels for the reactants and products.

Answer: A correct sketch should show a container with baking soda and vinegar reacting to produce carbon dioxide gas (bubbles), water, and sodium acetate, with labels for each component.

Question 7: What is the effect of heating sugar beyond its melting point? Describe the chemical change involved.

Answer: Heating sugar beyond melting causes caramelization, a chemical change where sugar molecules break down and recombine, producing caramel flavours and a brown colour.

Question 8: Identify one chemical change that occurs during the process of pickling vegetables and explain its effect on the food.

Answer: During pickling, lactic acid bacteria ferment sugars into lactic acid, which preserves the vegetables and gives them a sour taste.

Question 9: Describe how cooking affects the texture and chemical composition of potatoes.

Answer: Cooking potatoes causes starch granules to absorb water and swell, softening the texture. Heat also breaks down cell walls, and enzymes are deactivated, preventing further chemical change.

Question 10: Sketch a diagram illustrating the chemical change that occurs when cheese is melted. Include labels showing the key components involved.

Answer: A correct sketch should depict the cheese with its fat and protein structure breaking down and melting, with labels indicating fats, proteins, and the melted liquid state.