Question 1: Describe what happens to the starch in potatoes when they are cooked. Include the chemical change involved.

Answer: When potatoes are cooked, the heat causes the starch granules to absorb water and swell, a process called gelatinisation. This is a physical change, but the heat also causes some chemical changes, such as the breakdown of complex carbohydrates into simpler sugars, making the potato taste sweeter.

Question 2: Explain how the process of caramelisation changes the appearance and flavour of sugar when heated.

Answer: Caramelisation occurs when sugar is heated to a high temperature, causing the sugar molecules to break down and form new compounds. This results in a brown colour and a rich, sweet, and slightly bitter flavour.

Question 3: Identify two chemical changes that occur when eggs are cooked and describe their effects on the egg's texture.

Answer: When eggs are cooked, the proteins denature and coagulate, turning from a liquid to a firm solid. This chemical change makes the egg white and yolk firm and opaque.

Question 4: Describe the chemical process that causes bread to rise when baking.

Answer: Yeast ferments the sugars in the dough, producing carbon dioxide gas and alcohol. The carbon dioxide gets trapped in the dough's gluten network, causing it to expand and the bread to rise.

Question 5: What is the chemical change involved in the browning of meat during cooking? Explain briefly.

Answer: The browning of meat involves the Maillard reaction, a chemical process where amino acids and reducing sugars react under heat, forming brown pigments and new flavors.

Question 6: Draw a simple diagram of a chemical change occurring in cooking, such as the transformation of sugar during caramelisation. Label the key parts of your diagram.

Answer: A correct sketch would show sugar molecules breaking down and forming new compounds, with labels indicating 'sugar molecules', 'heat', and 'caramelised products'.

Question 7: List two signs that indicate a chemical change has taken place in food during cooking.

Answer: Colour change and the formation of new flavours or aromas are signs of chemical change.

Question 8: Explain why cooking can sometimes destroy some nutrients in food, mentioning a specific nutrient as an example.

Answer: Cooking can cause nutrients like vitamin C to break down due to heat, light, or water, reducing their nutritional value in the food.

Question 9: Sketch a diagram showing the process of protein coagulation in an egg during cooking. Label the parts involved.

Answer: A correct sketch would depict an egg white changing from a clear liquid to a white, solid mass, with labels such as 'protein molecules', 'heat', and 'coagulation process'.