Introduction to General Chemistry

This section introduces the foundational concepts of General Chemistry, focusing on the study of matter, its properties, and the changes it undergoes. Understanding these basics is essential for success in subsequent chemistry topics.

Course Logistics and Success Strategies

• Course Structure: Includes online homework (Mastering), quizzes, exams, and opportunities for extra credit.

• Resources: Science tutoring centers, supplemental instruction, lecture videos, and worked textbook problems are available to support learning.

• Study Tips:

  • Do not fall behind; study regularly (about an hour daily).

  • Review lecture slides before class and notes after class.

  • Practice with homework and textbook examples.

  • Rephrase concepts in your own words to ensure understanding.

Chapter 1: Matter and Its Classification

What is Chemistry?

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Chemists seek to classify matter and identify its properties to better understand the material universe.

Classifying Matter

Matter can be classified by its physical state (solid, liquid, gas) and chemical composition (substance or mixture).

Physical States of Matter

• Solids:

  • Definite shape and volume; particles are closely packed in an ordered arrangement (often crystalline).

  • Particles vibrate but do not move past each other.

  • Non-compressible and do not flow.

  • Example: Table salt (NaCl) crystals.

• Liquids:

  • Definite volume but no definite shape; take the shape of their container.

  • Particles are close together but can move past one another (flow).

  • Non-compressible and can be poured.

  • Example: Water.

• Gases:

  • No definite shape or volume; expand to fill their container.

  • Particles are far apart and move randomly at high speeds.

  • Compressible and do not have a fixed volume.

  • Example: Air.

Properties Used to Describe Physical State

• Shape

• Volume

• Particle motion

• Compressibility

• Ability to flow (pouring)

Chemical Composition: Substances and Mixtures

Matter can also be classified by its chemical composition as either a substance (pure) or a mixture.

Substances

• Composed of only one type of particle (atom or molecule).

• Have a definite, fixed composition and distinct properties.

• Can be elements or compounds.

• Examples: Pure water (H2O), table salt (NaCl), neon gas (Ne).

Elements vs. Compounds

• Element: A substance that cannot be broken down into simpler substances by chemical means. Each element is represented by a unique symbol (e.g., H for hydrogen, Li for lithium).

• Compound: A substance formed from two or more elements chemically combined in a fixed ratio. Compounds have properties different from their constituent elements (e.g., water is made from hydrogen and oxygen, both gases, but is a liquid).

Mixtures

• Physical combinations of two or more substances.

• Components retain their individual properties.

• Composition can vary from sample to sample.

• Can be separated by physical means (e.g., filtration, distillation).

• Types of Mixtures:

  • Homogeneous: Uniform composition throughout (e.g., black coffee, saltwater).

  • Heterogeneous: Non-uniform composition (e.g., orange juice with pulp, salad).

Separation of Mixtures vs. Substances

• Mixtures can be separated by physical means (e.g., filtration, distillation).

• Compounds can only be separated into their elements by chemical means (e.g., electrolysis of water).

Properties and Changes of Matter

Physical vs. Chemical Properties

• Physical Properties: Can be measured or observed without changing the chemical composition of the substance.

  • Examples: Color, mass, volume, temperature, density, boiling point, melting point.

  • Classified as intensive (independent of amount, e.g., temperature) or extensive (dependent on amount, e.g., volume).

• Chemical Properties: Describe a substance's ability to undergo chemical changes, forming new substances.

  • Examples: Flammability, reactivity, toxicity, corrosiveness.

Physical vs. Chemical Changes

• Physical Change: Alters the form or appearance of matter but does not change its composition.

  • Examples: Melting, freezing, boiling, breaking, cutting.

• Chemical Change: Results in the formation of one or more new substances (chemical reaction).

  • Indicators: Color change, temperature change, gas formation (bubbles), formation of a solid (precipitate).

  • Examples: Burning wood, rusting iron, frying an egg.

Units of Measurement and Scientific Notation

SI Base Units

The International System of Units (SI) is the standard for scientific measurements. The seven SI base units are:

Scientific Notation

• Used to express very large or very small numbers as a product of a number between 1 and 9 and a power of ten.

• Format: where and is an integer.

• Example:

Metric Prefixes

Metric prefixes indicate multiples or fractions of base units. Common prefixes include:

Significant Figures

Significant figures are the digits in a measurement that are known with certainty plus one digit that is estimated. They reflect the precision of a measuring device and are important for reporting scientific data accurately.

Rules for Identifying Significant Figures

• All nonzero digits are significant.

• Zeros between nonzero digits are significant.

• Leading zeros (to the left of the first nonzero digit) are not significant.

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

• Exact numbers (e.g., counting numbers, defined conversion factors) have infinite significant figures.

Significant Figures in Calculations

• Addition/Subtraction: The result should have the same number of decimal places as the measurement with the fewest decimal places.

• Multiplication/Division: The result should have the same number of significant figures as the measurement with the fewest significant figures.

Dimensional Analysis and Conversion Factors

Dimensional analysis is a problem-solving method that uses conversion factors to move from one unit to another. Conversion factors are ratios that express the same quantity in different units (e.g., ).

Steps for Dimensional Analysis

1. Identify the starting and desired units.

2. Select the appropriate conversion factor(s).

3. Set up the calculation so that units cancel appropriately.

4. Check that the result is reasonable and has the correct units.

Derived Units: Volume and Density

Volume

• Volume is the amount of space an object occupies.

• SI unit: cubic meter (); commonly used: liter (L), milliliter (mL).

Density

• Density is an intensive property defined as mass per unit volume.

• Formula:

• Common units: (solids), (liquids), (gases).

• Example: A cube with side length 1.50 cm and mass 9.20 g has a density of (matches aluminum).

Temperature Conversions

• To convert between Fahrenheit (°F), Celsius (°C), and Kelvin (K):

Summary

• Matter is classified by physical state and chemical composition.

• Physical and chemical properties and changes are fundamental to understanding chemistry.

• Accurate measurement and reporting require understanding of SI units, scientific notation, metric prefixes, and significant figures.

• Dimensional analysis and conversion factors are essential tools for problem-solving in chemistry.

• Volume and density are important derived units for characterizing substances.