Question

t/f (change false statements to be true)

1. in a physical change, a substances composition changes.
2. density is an extensive physical property because its calculated using both mass and volume.
3. cutting a piece of paper is a chemical change.
4. another term for “to react” is “to create” and is represented by an arrow in a reaction equation.
5. in a chemical change, bonds are broken and a new composition is formed.
6. when green mold grows on bread, the color change is indicating a physical change is occurring.
7. a chemical change does not have to obey the law of conservation of mass if the temperature is cold enough.
8. when milk “goes bad” in the fridge, a chemical reaction has taken place.
9. color changes can indicate both a physical or a chemical change.
10. during a chemical change, the total mass of the reactants is equal to the total mass of the products.

Explanation:

1. In a physical change, a substance's composition remains the same.
2. Density is an intensive physical property as it is a characteristic of the substance and does not depend on the amount.
3. Cutting paper is a physical change as no new substances are formed.
4. "To react" means substances interact to form new substances, not "to create". The arrow in a reaction equation represents the direction of the reaction.
5. In a chemical change, bonds are broken and new bonds are formed, creating a new composition.
6. Green mold growing on bread is a chemical change as new substances (mold and its by - products) are formed.
7. All chemical changes must obey the Law of Conservation of Mass regardless of temperature.
8. Milk going bad is a chemical reaction as new substances are formed due to spoilage.
9. Color changes can be signs of both physical (e.g., changing color of a metal due to heating) and chemical (e.g., rusting) changes.
10. The Law of Conservation of Mass states that during a chemical change, the total mass of reactants equals the total mass of products.

Answer:

1. False. In a physical change, a substance's composition does not change.
2. False. Density is an intensive physical property.
3. False. Cutting a piece of paper is a physical change.
4. False. Another term for "to react" is not "to create". The arrow in a reaction equation represents the direction of the reaction.
5. True.
6. False. When green mold grows on bread, a chemical change is occurring.
7. False. A chemical change always obeys the Law of Conservation of Mass.
8. True.
9. True.
10. True.