Matter and Its Classification

Introductory Definitions

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

• Mass: The amount of matter in an object. Measured in grams (g), kilograms (kg), etc.

• Volume: The amount of space an object occupies. Common units: , , , .

State of matter: The physical form in which matter exists: solid, liquid, or gas.

Composition: The types and amounts of simpler substances that make up a sample of matter (e.g., copper, water).

Properties: Characteristics used to identify and distinguish substances.

Atom: The basic building block of matter, consisting of a nucleus surrounded by electrons.

Elements

Elements are pure substances that contain only one type of atom.

• Monatomic elements: Consist of unbonded, single atoms (e.g., noble gases like Ne, Ar).

• Polyatomic elements: Consist of several like atoms bonded together (e.g., O2, P4).

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

• Allotropes: Different forms of the same element in the same state of matter (e.g., oxygen as O2 and O3; carbon as diamond and graphite).

Compounds

Compounds are pure substances that contain two or more different types of atoms chemically bonded together. Their properties are different from those of their constituent elements.

• Examples: NaCl (sodium chloride), H2O (water).

• Atoms can only be altered by chemical means; molecules can be altered by physical means.

Example reactions:

• Dehydration of sugar:

• Electrolysis of water:

Mixtures

Mixtures are combinations of two or more substances that are not chemically bonded. They can be separated by physical means.

• Homogeneous mixtures (solutions): Uniform composition and properties throughout (e.g., saltwater, air).

• Heterogeneous mixtures: Non-uniform composition; different parts have different properties (e.g., salad, sand in water).

• Alloy: A homogeneous mixture of metals (e.g., 24K gold is pure, 14K gold is an alloy).

• Suspension: A heterogeneous mixture that settles over time (e.g., muddy water).

Chart for Classifying Matter:

A flowchart showing the classification of matter: Matter → Pure Substance (Element, Compound) and Mixture (Homogeneous, Heterogeneous).

Separating Mixtures

Mixtures can be separated by physical means or physical changes, including:

1. Sorting: Separating based on physical characteristics.

2. Filtration: Separating solids from liquids using a filter.

3. Magnet: Using a magnet to separate magnetic materials.

4. Chromatography: Separating substances based on their movement through a medium.

5. Density: Separating based on differences in density.

6. Distillation: Separating based on differences in boiling points.

Properties of Matter

Chemical and Physical Properties

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

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

Extensive and 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: Electrical conductivity, ductility (can be drawn into wire), malleability (can be hammered into shape), brittleness, magnetism.

States of Matter and Changes of State

There are three primary states of matter:

• Solid: Particles are closely packed in a fixed arrangement.

• Liquid: Particles are close but can move past each other.

• Gas: Particles are far apart and move freely.

Changes of state: Include melting, freezing, condensation, evaporation, sublimation, and deposition.

Diagram: Shows transitions between solid, liquid, and gas states.

Density and Density Calculations

Definition and Units

Density is the mass per unit volume of a substance.

• Typical units: for solids, for liquids.

• The density of water is approximately at room temperature.

Density Calculations

• To find density: Measure mass and volume, then use the formula above.

• To find mass:

• To find volume:

Example: A sample of lead (Pb) has mass 22.7 g and volume 2.0 cm3. Its density is .

**Additional info:** For irregular objects, volume can be found by water displacement.

Energy and Changes in Matter

Kinetic Energy and Conservation of Energy

• Kinetic energy: The energy of motion.

• Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed from one form to another.

Example: Combustion of acetylene:

Endothermic and Exothermic Changes

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

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

Energy diagrams show reactants (R) and products (P) with energy changes for endothermic and exothermic processes.

The Mole and Counting Atoms

The Mole Concept

Atoms and molecules are counted using the mole, a fundamental unit in chemistry.

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

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

Island Diagram

A diagram showing the relationships between mass, moles, and number of particles (atoms or molecules):

• Mass ↔ Moles ↔ Particles

• 1 mole = atoms or molecules

Sample Problems

1. How many moles is atoms of zinc?

2. How many atoms is 0.68 moles of zinc?

3. How many grams is 5.69 moles of uranium?

4. How many grams is atoms of neon?

5. How many atoms is 421 g of promethium?

Additional info: To solve these, use the relationships: and .