Question

practice:

1. explain the difference between physical properties and chemical properties, and list three examples of each.
2. explain the difference between physical changes and chemical changes.
3. a piece of metal is 4 cm by 10 cm by 2 cm. find its mass if it has a density of 2 g/cm³.
4. a piece of plastic with a mass of 15 g is placed in a graduated cylinder. the water level in the graduated cylinder rises from 30 ml to 55 ml when the plastic is added. find the density of the plastic.
5. classify the following changes as physical or chemical.

a. boiling
b. crumpling
c. burning
d. freezing
e. evaporating
f. rotting
g. rusting
h. sawing
i. crushing

1. list evidence that a chemical change has occurred.

Explanation:

Question 5

Physical properties describe observable/measurable traits of a substance without altering its chemical identity. Chemical properties describe how a substance reacts to form new substances.

Physical changes alter a substance's form but not its chemical makeup. Chemical changes create new substances with different properties.

Step1: Calculate metal volume

$$V = l \times w \times h = 4\ \text{cm} \times 10\ \text{cm} \times 2\ \text{cm} = 80\ \text{cm}^3$$

Step2: Solve for mass using density

Density formula: $
ho = \frac{m}{V}$, rearranged to $m =
ho \times V$
$$m = 2\ \text{g/cm}^3 \times 80\ \text{cm}^3$$

Answer:

• Physical Properties: Characteristics observable without changing the substance's chemical composition.

Examples: Density ($\frac{\text{mass}}{\text{volume}}$), color, melting point.

• Chemical Properties: Characteristics describing a substance's ability to form new substances.

Examples: Flammability, reactivity with acid, oxidation resistance.

---

Question 6