Unit 2 Science Test

Unit 2 Science Test

Concept 1:

Classification of Matter

Objectives:

Classify whether the following examples are matter or Non-matter.

Your desk- Matter

Air in the room- Matter

Your shadow- Non-matter

Water in a bottle- Matter

The sound of your voice- Non-matter

Heat from a light bulb- Non-matter

A pencil- Matter

Your thoughts- Non-matter

Steam from hot water- Matter

Light from the sun- Non-matter

Vocabulary:

Matter- Anything that takes up space and has mass.

Substance- All particles in matter are identical (fixed composition).

Mixture- Two or more substances physically combined (variable composition).

Element- Just 1 substance; the simplest form.

Compound- 2 or more elements chemically combined

Practice:

Differentiate between a homogeneous mixture and a heterogeneous mixture.

Homogeneous mixture: when one substance is dissolved into another.

Ex. Bleach, Lemonade, coffee

Heterogeneous mixture: when different components are easy to see or separate over time

Ex. Salad dressing, paint, cereal

Explain the main difference between a compound and a mixture.

Compound: Can be broken down only by chemical reactions; different than the elements that make them up; made up of Molecules

Mixture: Multiple substances physically combined

Draw a flow chart to represent how matter can be classified.

Classify each example below as the type of matter it is (element, compound, homogeneous mixture, or heterogeneous mixture).

Element: A pure substance made of only one type of atom (found on the periodic table).

Compound: A pure substance made of two or more elements chemically bonded together (like water or salt).

Homogeneous mixture: A mix of substances that looks completely uniform throughout (like salt water or air).

Heterogeneous mixture: A mix where you can see the different parts or phases (like salad, sand, or oil and water).

Compare the properties of suspensions, colloids, and solutions.

Suspensions: Heterogeneous mixtures with the largest particles that settle out over time and can be filtered.

Colloids: Heterogeneous mixtures with medium particles that do not settle out but do scatter light.

Solutions: Homogeneous mixtures with the smallest particles that never settle out or scatter light.

Concept 2: Properties of Matter

Vocabulary

Melting point: The temperature at which a solid becomes a liquid.

Boiling point: The temperature at which a liquid turns into a gas/vapor throughout the entire liquid.

Viscosity: The resistance of a fluid (liquid or gas) to flow.

Solubility: The maximum amount of a solute that can dissolve in a given amount of solvent at a specific temperature.

Solute: The substance that is dissolved in a solution (e.g., salt in salt water).

Solvent: The substance that does the dissolving in a solution (e.g., water in salt water).

Solution: A homogeneous mixture formed when a solute dissolves completely in a solvent.

Density: Measure of compactness or consistency of a material; defined as mass per unit volume ($D = \frac{m}{V}$).

Combustibility: How easily a substance will ignite or catch fire in the presence of oxygen.

Reactivity: How readily a substance undergoes a chemical change when combined with another substance.

Oxidation: A chemical change in which a substance combines with oxygen (e.g., rusting of iron or tarnishing of silver).

Chemical reaction: A process in which one or more substances are transformed into entirely new substances with different physical and chemical properties.

Law of Conservation of Matter: Matter cannot be created or destroyed in a chemical reaction; the total mass of the reactants must equal the total mass of the products.

Kinetic Theory: An explanation of how particles in matter behave, stating that all matter is made of small particles in constant, random motion that constantly collide with each other and the walls of their container.

Sublimation: The phase change in which a substance transitions directly from a solid state to a gas state without passing through the liquid state (e.g., dry ice).

Thermal expansion: The increase in the volume of a substance in response to an increase in its temperature.

Buoyancy: Ability of a fluid to exert an upward force on an object immersed in it.

Pascal’s Principle: Pressure applied to a fluid is transmitted equally and undiminished throughout the fluid in all directions.

Archimedes’ Principle: The buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by that object.

Bernoulli’s Principle: As the velocity of a fluid increases, the pressure exerted by that fluid decreases (fluid velocity increases when the flow is restricted).

Boyle’s Law: For a fixed amount of gas at constant temperature, volume decreases as pressure increases

Charles’ Law: For a fixed amount of gas at constant pressure, volume increases as temperature increases

Practice Problems & Concept Questions

1. Difference between physical and chemical properties (with 3 examples each)

Physical Property: An observable or measurable characteristic of a substance that does not alter its chemical composition.

Examples: Density, melting point, color.

Chemical Property: A characteristic that describes a substance's ability to undergo a specific chemical change and form a new substance.

Examples: Flammability/combustibility, reactivity with acid, tendency to rust/oxidize.

2. Difference between physical and chemical changes

Physical Change: Alters the form, shape, or state of a substance without changing its chemical identity. No new substance is formed.

Chemical Change: Alters the chemical structure of a substance, forming one or more new substances with different chemical properties.

3. Mass calculation (Regularly Shaped Object)

Volume calculation:

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

Mass calculation:

$\text{Mass} = \text{Density} \times \text{Volume} = 2\text{ g/cm}^3 \times 80\text{ cm}^3 = 160\text{ g}$

4. Density calculation (Irregularly Shaped Object via Water Displacement)

Volume displacement:

$\text{Volume of plastic} = 55\text{ mL} - 30\text{ mL} = 25\text{ mL}\text{ (or } 25\text{ cm}^3\text{)}$

Density calculation:

$\text{Density} = \frac{\text{Mass}}{\text{Volume}} = \frac{15\text{ g}}{25\text{ mL}} = 0.6\text{ g/mL}\text{ (or } 0.6\text{ g/cm}^3\text{)}$

5. Classify the following changes:

a. Boiling: Physical (phase change)

b. Crumpling: Physical

c. Burning: Chemical

d. Freezing: Physical (phase change)

e. Evaporating: Physical (phase change)

f. Rotting: Chemical

g. Rusting: Chemical

h. Sawing: Physical

i. Crushing: Physical

6. Evidence of a chemical change / reaction