Matter Classification and Measurement

1. Classification of Matter

Matter is anything that has mass and takes up space.

2. Types of Matter

3. Key Definitions

• Matter: Anything that has mass and occupies space.
• Element: A pure substance made of only one kind of atom.
• Compound: A pure substance formed when two or more elements chemically combine.
• Mixture: A physical combination of two or more substances where each retains its own properties.

4. Identifying Matter Types

• Pure substances look the same everywhere and have uniform properties.
• Mixtures may have different textures, colors, or visible parts.
• Compounds have fixed chemical formulas and cannot be separated by physical means.
• Mixtures can be separated by physical methods (e.g., filtration, magnetism).

5. Observations to Distinguish Pure Substances from Mixtures

6. Examples and Corrections

• Seawater is a homogeneous mixture, not a pure substance, because it contains dissolved salts evenly distributed.
• Sand and iron filings form a heterogeneous mixture; iron can be separated with a magnet.
• Water (H₂O) is a compound because hydrogen and oxygen atoms are chemically bonded.
• Visible different parts in a sample indicate a mixture, not a compound.

To remember: Matter is classified based on particle type and arrangement into pure substances (elements or compounds) and mixtures (homogeneous or heterogeneous).

1. Measuring Matter and Density

a) Mass

• Mass is the amount of matter in an object.
• Measured using a balance.
• Common units: grams (g) and kilograms (kg).

b) Volume

• Volume is the amount of space an object occupies.
• For regular shapes, volume can be calculated using formulas.
• For irregular objects, volume is measured by the displacement method:
  • Submerge the object in water in a graduated cylinder.
  • Measure the rise in water level.
  • The increase in volume equals the object's volume.
• Units for volume: cubic centimeters (cm³) or milliliters (mL).

c) Density

• Density measures how much mass is packed into a given volume.

• Formula:

  $$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$$

• Units: grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

• Density is a property of the material, independent of sample size.

• Denser objects have more mass in the same volume.

d) Key Concepts

• Two objects with the same volume but different masses have different densities.
• The object with the greater mass in the same volume is denser.
• Density does not depend on the size of the sample but on the material itself.
• If an object’s density is greater than water (1.0 g/cm³), it will sink; if less, it will float.

e) Example Calculations

• Given mass = 60 g, volume = 20 cm³:

  $$\text{Density} = \frac{60}{20} = 3 \text{ g/cm}^3$$

• Given mass = 50 g, volume = 25 cm³:

  $$\text{Density} = \frac{50}{25} = 2 \text{ g/cm}^3$$

  Since 2 g/cm³ > 1 g/cm³ (water), the object will sink.

f) Comparing Density and Displacement

g) Particle Model of Density

• Denser substances have particles packed closer together.
• Less dense substances have particles spaced farther apart.
• Particle size does not determine density; spacing and mass do.

Density is the amount of mass in a given volume and is constant for a pure substance regardless of sample size.

1. Physical and Chemical Changes

Physical Change

• No new substances are formed.
• Usually reversible.
• Example: Melting ice (solid to liquid water).

Chemical Change

• New substances are formed.
• Usually irreversible.
• Example: Burning wood, cooking an egg.

2. Reactants and Products in Chemical Reactions

3. Conservation of Matter

• The total mass remains constant before and after a chemical reaction.
• Matter is neither created nor destroyed during physical or chemical changes.
• Example: A closed container with a chemical reaction still weighs the same before and after.

The total amount of matter does not change during a physical or chemical change.

4. Signs of Chemical Change

• Gas bubbles: Indicate a new gas is produced, not just a physical change.
• Color change: Shows formation of new substances with different properties.

5. Examples and Concepts

6. Key Definitions

• Matter: Anything that has mass and occupies space.
• Element: Matter made of only one type of atom.
• Compound: Matter made of two or more different atoms chemically combined in fixed proportions.
• Mixture: Physical combination of two or more substances without chemical bonding.

7. Critique of Particle Model for Burning Paper

• Incorrect: Showing only darkening without atom rearrangement implies a physical change.
• Correct: Burning is a chemical change where atoms rearrange to form new substances (ash, gases), conserving matter.

8. Summary Table: Physical vs Chemical Changes