Introduction to Matter

Definitions and Basic Concepts

Matter is anything that has mass and occupies space (volume). All substances in the universe are forms of matter.

• Mass: The quantity of matter in an object, typically measured in grams (g) or kilograms (kg).

• Weight: The force exerted by gravity on an object’s mass.

• Volume: The amount of space an object occupies. Common units: liters (L), cubic decimeters (dm3), milliliters (mL), cubic centimeters (cm3).

Atom: The basic building block of matter, consisting of protons, neutrons, and electrons.

States of Matter

• Solid: Definite shape and volume; particles are closely packed in a fixed arrangement.

• Liquid: Definite volume but no definite shape; particles are close but can move past each other.

• Gas: No definite shape or volume; particles are far apart and move freely.

Classification of Matter

Pure Substances

• Elements: Substances that contain only one type of atom. Examples: O2 (oxygen), Cu (copper).

• Compounds: Substances composed of two or more different types of atoms chemically bonded together. Examples: H2O (water), NaCl (sodium chloride).

Allotropes: Different forms of the same element in the same physical state. Examples: oxygen (O2 and O3), carbon (diamond and graphite).

Mixtures

• Homogeneous Mixture (Solution): Uniform composition and properties throughout; particles are evenly mixed. Example: saltwater, air.

• Heterogeneous Mixture: Non-uniform composition; different parts have different properties. Example: sand in water, salad.

• Alloy: A homogeneous mixture of metals. Example: 24K gold (pure), 14K gold (mixture).

• Suspension: A heterogeneous mixture where particles settle over time. Example: muddy water.

Classification Chart

Properties of Matter

Physical and Chemical Properties

• Chemical Properties: Describe how a substance reacts with other substances (e.g., reactivity with water, flammability).

• Physical Properties: Can be observed without changing the chemical identity of the substance (e.g., color, melting point, density).

Extensive vs. Intensive Properties

• Extensive Properties: Depend on the amount of substance present (e.g., mass, volume).

• Intensive Properties: Do not depend on the amount of substance (e.g., density, boiling point).

Examples of Properties

• Electrical conductivity

• Reactivity with water

• Heat content (total energy)

• Ductile: Can be drawn into wire

• Malleable: Can be hammered into shape

• Brittle: Breaks easily

• Magnetism

Separation of Mixtures

Mixtures can be separated by physical means or physical changes:

1. Sorting

2. Filtration

3. Magnetism

4. Chromatography

5. Density separation

6. Distillation

Density

Definition and Calculation

Density is the mass per unit volume of a substance.

Formula:

• Typical units: g/cm3 for solids, g/mL for fluids

• Density of water: 1.00 g/mL (at 4°C)

The density of a liquid or solid is nearly constant, regardless of sample size.

Density Calculations (Examples)

• A sample of lead (Pb) has mass 22.7 g and volume 2.0 cm3. Find density.

• A 119.5 g solid cylinder has radius 1.8 cm and height 1.5 cm. Find density.

• A 153 g rectangular solid has edge lengths 8.2 cm, 5.1 cm, and 4.7 cm. Will it sink in water?

Changes in State and Energy

States of Matter and Changes

• Solid → Liquid: Melting

• Liquid → Gas: Vaporization

• Gas → Liquid: Condensation

• Liquid → Solid: Freezing

• Solid → Gas: Sublimation

• Gas → Solid: Deposition

Energy Changes

• Endothermic Change: System absorbs heat (e.g., water boiling, ice melting).

• Exothermic Change: System releases heat (e.g., water freezing, combustion).

Law of Conservation of Energy

Energy cannot be created or destroyed, only transformed from one form to another.

Example (combustion of acetylene):

The Mole Concept

Definition and Avogadro's Number

• Counting atoms or molecules is done using the mole (mol).

• 1 mole = particles (Avogadro's number).

• For any element, 1 mole has a mass in grams equal to its atomic mass (from the periodic table).

Island Diagram

1 mol = atoms/molecules

Sample Problems

• How many moles is atoms of zinc?

• How many atoms is 0.68 moles of zinc?

• How many grams is 5.69 moles of uranium?

• How many grams is atoms of neon?

• How many atoms is 421 g of promethium?

Elements, Compounds, and Mixtures: Comparison Table

Additional Info

• Monatomic elements: Elements that exist as single atoms (e.g., noble gases like Ne, Ar).

• Polyatomic elements: Elements that exist as molecules with more than one atom (e.g., O2, S8).

• Diatomic elements: Elements that naturally exist as molecules of two atoms (e.g., H2, N2, O2, F2, Cl2, Br2, I2).

• Allotropes: Different structural forms of the same element (e.g., diamond and graphite for carbon).