Introduction to Matter

Definitions and Basic Concepts

Matter is anything that has mass and occupies space. Understanding the fundamental properties and classification of matter is essential in general chemistry.

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

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

• State of Matter: Matter exists primarily as solids, liquids, or gases, each with distinct properties.

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

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

Classification of Matter

Elements and Compounds

Matter can be classified as either a pure substance or a mixture. Pure substances include elements and compounds.

• Element: A substance that contains only one type of atom.

• Monatomic Elements: Consist of unbonded, "like" atoms (e.g., noble gases such as He, Ne).

• 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, N2).

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

Compound: A substance that contains two or more different types of atoms chemically bonded together. Compounds have properties different from their constituent elements (e.g., NaCl is very different from sodium and chlorine).

• Atoms can only be altered by chemical means.

• Molecules can be altered by physical or chemical means.

Examples of Chemical 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 Mixture (Solution): Has uniform composition and properties throughout (e.g., saltwater, air).

• Heterogeneous Mixture: Has different composition and properties in different parts of the sample (e.g., salad, sand in water).

• Alloy: A homogeneous mixture of metals (e.g., brass, bronze).

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

Chart for Classifying Matter

The following chart summarizes the classification of matter:

Separation of Mixtures

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

1. Sorting: Separating substances based on physical characteristics.

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

3. Magnet: Using a magnet to separate magnetic materials from non-magnetic ones.

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

5. Density: Separating substances based on differences in density.

6. Distillation: Separating substances 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, flammability).

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

States of Matter and Changes of State

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.

Changes of State

• Melting: Solid to liquid

• Freezing: Liquid to solid

• Vaporization (Boiling/Evaporation): Liquid to gas

• Condensation: Gas to liquid

• Sublimation: Solid to gas

• Deposition: Gas to solid

Density and Density Calculations

Definition and Units

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)

Sample Density Calculations

1. A sample of lead (Pb) has mass 22.7 g and volume 2.0 cm3. Find the sample's density.

2. Another sample of lead occupies 16.2 cm3 of space. Find the sample's mass (if density is known).

3. A 119.5 g solid cylinder has radius 1.8 cm and height 1.5 cm. Find the sample's density.

   • Volume of cylinder:

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

   • Volume:

Energy in Chemistry

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:

Energy Changes: Endothermic and Exothermic

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

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

The Mole Concept

Definition and Avogadro's Number

• Atoms are counted in moles due to their extremely small size.

• 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

The island diagram helps convert between grams, moles, and number of particles (atoms or molecules):

• Grams ↔ Moles ↔ Particles (atoms/molecules)

• 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

• Many of the sample problems require knowledge of molar mass, percent composition, and stoichiometry, which are foundational for later topics in general chemistry.

• Tables and diagrams in the original material have been recreated and expanded for clarity.