Question 1: Explain what happens to the proteins in meat when it is cooked and how this is a chemical change.

Answer: When meat is cooked, the proteins in it denature and coagulate, meaning their structure changes permanently. This is a chemical change because new substances are formed, making the meat firmer and changing its appearance and texture.

Question 2: Describe the chemical change that occurs when bread is toasted.

Answer: Toasting bread causes the Maillard reaction, which is a chemical reaction between amino acids and sugars. This produces the brown color and new flavors, indicating a chemical change.

Question 3: What is the chemical change that occurs when fruit is fermented to make alcohol?

Answer: During fermentation, yeast converts sugars in the fruit into alcohol and carbon dioxide through a chemical process called fermentation. This is a chemical change because new substances (alcohol and CO2) are produced.

Question 4: Identify one chemical change that happens when eggs are cooked and explain its significance.

Answer: When eggs are cooked, the proteins in the egg white and yolk denature and coagulate, changing from a liquid to a solid. This is significant because it makes the egg safe to eat and gives it a firm texture.

Question 5: Describe what happens during caramelization and identify which ingredients are involved.

Answer: Caramelization is the chemical change where sugars are heated and break down, forming new compounds that give a brown color and rich flavor. Sugars like sucrose are involved in this process.

Question 6: Sketch a diagram of a simple process showing how heat causes a chemical change in cooking eggs. Label the key parts of your drawing.

Answer: A correct sketch would show an egg being heated in a pan, with the proteins denaturing and coagulating, resulting in a solidified egg. Labels should include 'heat source', 'egg white', 'protein denaturation', and 'coagulation'.

Question 7: Explain why bread becomes brown when it is toasted, focusing on the chemical reactions involved.

Answer: Bread turns brown during toasting because of the Maillard reaction, a chemical process where amino acids and sugars react under heat to produce browning and new flavors.

Question 8: Identify a chemical change that occurs during the ripening of fruit and explain its effect on the fruit’s appearance or taste.

Answer: During ripening, enzymes break down starches into sugars, making the fruit sweeter. Also, chlorophyll breaks down, causing the fruit to change color from green to ripe shades.

Question 9: Describe how heating causes a chemical change in the process of making cheese from milk.

Answer: Heating milk with rennet or acid causes proteins to coagulate and form curds. This is a chemical change because new substances are formed, leading to the solid cheese structure.

Question 10: Sketch the process of caramelizing sugar in a saucepan. Include labels for the different stages of the change.

Answer: A correct sketch would show sugar in a saucepan being heated, with arrows indicating increasing temperature. Labels should include 'sugar melts', 'brown caramel', and 'smoke or bubbling' to represent different stages.