Question

1. describe the results of a physical change and list three examples of physical change.
2. describe the results of a chemical change. list three examples of chemical change.
3. thinking critically a friend tells you, “because composition does not change during a physical change, the appearance of a substance does not change.” is your friend correct? explain why
4. classifying classify each of the following examples as a physical change (p) or a chemical change.(a. crushing an aluminum can

b. recycling used aluminum cans to make new aluminum cans
c. aluminum combining with oxygen to form aluminum oxide
d. silver jewelry tarnishing (turns black)
e. a fallen log rotting
f. sugar dissolved in coffee
g. burning a candle
t/f (change false statements to be true)

1. in a physical change, a substance’s composition changes.
2. density is an extensive physical property because it’s 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 high 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:

Step1: Define physical and chemical changes

Physical change: Substance's composition remains the same, only physical properties like shape, state change. Chemical change: Substance's composition changes, new substances are formed.

Step2: Answer question 9

Results of physical change: Change in physical properties (shape, state, size etc.), composition unchanged. Examples: melting ice, tearing paper, bending metal.

Step3: Answer question 10

Results of chemical change: New substances formed with different chemical properties. Examples: rusting iron, burning wood, baking a cake.

Step4: Answer question 11

Friend is incorrect. In a physical change, composition doesn't change but appearance can change (e.g., melting ice from solid to liquid).

Step5: Answer question 12

a. P - Just changes shape.
b. P - Recycling is a physical process of reforming.
c. C - Chemical reaction forms new substance (aluminum oxide).
d. C - Chemical reaction with sulfur in air.
e. C - Decomposition by microorganisms forms new substances.
f. P - Dissolving is a physical process.
g. C - Combustion forms new substances (carbon - dioxide, water etc.).

Step6: Answer T/F questions

1. F - In a physical change, a substance's composition does not change.
2. F - Density is an intensive physical property as it is independent of the amount of substance.
3. F - Cutting a piece of paper is a physical change.
4. F - Another term for "to react" is "to undergo a chemical change", arrow in reaction equation represents "yields".
5. T
6. F - Green mold growing on bread is a chemical change.
7. F - All chemical changes obey the Law of Conservation of Mass.
8. T
9. T
10. T

Answer:

1. Results: Change in physical properties, composition unchanged. Examples: melting ice, tearing paper, bending metal.
2. Results: New substances formed. Examples: rusting iron, burning wood, baking a cake.
3. Incorrect. Appearance can change in physical change.
4. a. P; b. P; c. C; d. C; e. C; f. P; g. C

T/F: 1. F; 2. F; 3. F; 4. F; 5. T; 6. F; 7. F; 8. T; 9. T; 10. T