Chapter 1: Introduction to Matter, Energy, and Measurement

Chemistry: The Central Science

Chemistry is the study of matter, its properties, and the changes it undergoes. It is foundational to many scientific disciplines, including energy, biochemistry, technology, and medicine.

Matter and Its Classification

Definition of Matter

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

States of Matter

Matter exists in three primary states: solid, liquid, and gas. Each state is characterized by the arrangement and movement of its particles.

• Solid: Definite shape and volume; particles are closely packed.

• Liquid: Definite volume but no definite shape; particles are less tightly packed than in solids.

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

Classification of Matter by Composition

Matter can be classified based on its uniformity and composition:

• Pure Substances: Have a fixed composition and distinct properties. Subdivided into elements and compounds.

• Mixtures: Combinations of two or more substances where each retains its own identity. Can be homogeneous (uniform, also called solutions) or heterogeneous (not uniform).

Elements and Compounds

Elements are substances that cannot be decomposed into simpler substances. Each element is made of one kind of atom. Compounds are substances composed of two or more elements in fixed proportions and can be decomposed into those elements.

Elements in the Earth and Human Body

There are 118 named elements. A small number of elements make up most of the Earth's crust and the human body, with oxygen being the most abundant in both.

Representing Elements

Chemists use symbols (one or two letters, first capitalized) to represent elements. Some symbols are derived from Latin or Greek names.

Law of Constant Composition

Compounds always have the same relative number of atoms of each element. This is known as the Law of Constant Composition (or Law of Definite Proportions).

Mixtures

Mixtures can be separated by physical means and retain the properties of their components. They are classified as:

• Homogeneous mixtures (solutions): Uniform composition throughout.

• Heterogeneous mixtures: Non-uniform composition.

Properties of Matter

Physical and Chemical Properties

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

• Chemical properties: Can only be observed when a substance is changed into another (e.g., flammability).

Intensive vs. Extensive Properties

• Intensive properties: Independent of the amount of substance (e.g., density, boiling point).

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

Physical and Chemical Changes

• Physical changes: Do not alter the composition of a substance (e.g., melting, boiling).

• Chemical changes: Result in the formation of new substances (e.g., combustion, oxidation).

Separation of Mixtures

Filtration

Filtration separates solids from liquids using a porous barrier.

Distillation

Distillation separates components of a mixture based on differences in boiling points.

Chromatography

Chromatography separates substances based on their ability to adhere to a solid surface.

Energy and Its Forms

Definition of Energy

Energy is the capacity to do work or transfer heat. Work is energy transferred when a force moves an object. Heat is energy transferred due to temperature difference.

Kinetic and Potential Energy

• Kinetic energy (KE): Energy of motion, calculated as

• Potential energy: Energy due to position or composition.

Measurement in Chemistry

SI Units and Metric System

The International System of Units (SI) is used for scientific measurements. Each physical quantity has a base unit.

Metric System Prefixes

Prefixes are used to indicate multiples or fractions of base units (e.g., kilo-, milli-, centi-).

Volume

Volume is a derived unit (from length). Common units are liter (L) and milliliter (mL). , .

Glassware for Measuring Volume

Different types of glassware are used for measuring and delivering specific volumes in the laboratory.

Temperature Scales

Temperature is measured in Celsius (°C), Kelvin (K), and Fahrenheit (°F). The Kelvin scale is the SI unit and has no negative values.

• Conversion:

Energy Units

The SI unit of energy is the joule (J): . The calorie (cal) is also used: .

Density

Density is a physical property defined as mass per unit volume: . Common units are g/mL or g/cm3.

Numbers in Chemistry

Exact and Inexact Numbers

Exact numbers are known with complete certainty (e.g., 12 eggs in a dozen). Inexact numbers are measured and have some uncertainty.

Uncertainty, Accuracy, and Precision

• Accuracy: How close a measurement is to the true value.

• Precision: How close repeated measurements are to each other.

Significant Figures

Significant figures reflect the precision of a measured quantity. Rules for counting significant figures:

• All nonzero digits are significant.

• Zeros between nonzero digits are significant.

• Leading zeros are not significant.

• Trailing zeros are significant if there is a decimal point.

Significant Figures in Calculations

• Addition/Subtraction: Round to the least significant decimal place.

• Multiplication/Division: Round to the same number of significant figures as the measurement with the fewest significant figures.

Dimensional Analysis

Dimensional analysis is a method for converting units using conversion factors. Set up ratios so that units cancel appropriately.