part c - short response\n11. a student dissolves sugar in water. is this a physical or chemical change…

Brief Explanations:

11. Dissolving sugar in water is a physical change. Sugar molecules disperse in water but no new substances are formed.
12. According to the law of conservation of mass, in a sealed - container, the total mass of reactants equals the total mass of products in a chemical reaction, so the mass remains the same.
13. You can use pH indicators like litmus paper (red litmus turns blue in basic solutions and blue litmus turns red in acidic solutions), or measure the pH value with a pH meter (pH < 7 for acidic, pH > 7 for basic).
14. Noble gases are placed in Group 18 because they have a full outer - electron shell, making them very stable and unreactive under normal conditions.
15. The density of the metal remains the same. Density is a characteristic property of a substance and is defined as mass per unit volume. When the metal is cut in half, both the mass and volume are halved, so the ratio (density) remains constant.

Answer:

11. Physical change.
12. Due to the law of conservation of mass.
13. Use pH indicators or a pH meter.
14. Because they have a full outer - electron shell and are stable.
15. The density remains the same.