Question 1: Describe what happens to the proteins in meat when it is cooked. Mention the chemical change involved.

Answer: When meat is cooked, heat causes the proteins to denature, meaning their structure changes permanently. This results in the meat becoming firm and cooked through.

Question 2: Explain why bread becomes brown when toasted. Include the name of the chemical process involved.

Answer: Bread turns brown when toasted due to the Maillard reaction, a chemical process where amino acids and sugars react under heat, producing browning and flavor changes.

Question 3: Identify what type of chemical change occurs when fruit is preserved by adding sugar or vinegar.

Answer: Adding sugar or vinegar to fruit causes a chemical change by creating an environment that inhibits microbial growth, preserving the fruit, and sometimes causing fermentation or acidification.

Question 4: Describe what happens to starch in potatoes when they are cooked.

Answer: When potatoes are cooked, the heat causes the starch granules to absorb water and swell, a process called gelatinisation, making the potato soft and edible.

Question 5: Explain the chemical change that causes an egg to turn from transparent to white when cooked.

Answer: The heat causes the proteins in the egg white to denature and coagulate, turning the egg white from transparent to white.

Question 6: Draw a simple diagram showing the process of caramelisation. Label the key stages involved.

Answer: A sketch should show sugar molecules breaking down and forming complex compounds, with stages labeled as 'sugar melting,' 'caramelising,' and 'browning.'

Question 7: Sketch a diagram to illustrate the process of coagulation in eggs during cooking. Include labels for the egg white and yolk.

Answer: A sketch should display an egg with the whites and yolk, showing the whites turning solid and opaque due to protein coagulation.

Question 8: Describe what happens to the pectin in fruit when it is heated with sugar to make jam.

Answer: Heating fruit with sugar causes the pectin to gel, forming a thick, jam-like consistency due to chemical interactions that create a gel network.

Question 9: Explain why adding lemon juice to a dish with tomatoes can affect the chemical composition.

Answer: Lemon juice contains acid, which can lower the pH of the dish. This causes certain chemical reactions, such as changing the color of tomatoes and helping to preserve the food.

Question 10: Describe the chemical changes that occur when baking soda is used in baking.

Answer: Baking soda reacts with acids in the mixture to produce carbon dioxide gas, which causes the dough or batter to rise, and results in a light, fluffy texture.