Chapter 1: Introduction to Matter, Energy, and Measurement

What is Chemistry?

Chemistry is the scientific study of matter, its properties, and the changes it undergoes. It is central to our fundamental understanding of many science-related fields, including energy, biochemistry, medicine, and technology.

• Matter: Anything that has mass and takes up space.

• Properties: Characteristics used to describe matter, such as color, odor, density, melting point, boiling point, and hardness.

• Changes: Transformations matter can undergo, including physical and chemical changes.

Classification of Matter

Matter can be classified by its state and composition. Understanding these classifications is essential for studying chemistry.

States of Matter

There are three primary states of matter:

• Solid: Has a definite shape and volume. Particles are closely packed in a fixed arrangement.

• Liquid: Has a definite volume but takes the shape of its container. Particles are close but can move past one another.

• Gas: Has neither definite shape nor volume. Particles are far apart and move freely.

Example: Water exists as ice (solid), liquid water, and water vapor (gas).

Classification by Composition

Matter can also be classified based on its composition:

• Pure Substance: Has distinct properties and a composition that does not vary from sample to sample.

• Mixture: Contains two or more substances that retain their individual properties. Composition can vary.

Types of Mixtures and Substances

• Homogeneous Mixture (Solution): Uniform composition throughout (e.g., salt water).

• Heterogeneous Mixture: Composition is not uniform (e.g., sand in water).

• Element: A substance that cannot be decomposed into simpler substances. Made of one kind of atom.

• Compound: A substance composed of two or more elements, which can be decomposed into simpler substances.

Flowchart: Classification of Matter

Additional info: The flowchart helps determine if a sample is a mixture or pure substance, and further, if it is an element or compound.

Atoms, Elements, and Compounds

• Atom: The smallest unit of an element that retains its chemical properties.

• Element: Made of only one kind of atom.

• Compound: Made of atoms of two or more different elements, chemically bonded together.

Example: Oxygen gas (O2) is an element; water (H2O) is a compound.

Summary Table: Types of Matter

Key Laws

• Law of Constant Composition (Law of Definite Proportions): The relative number of atoms of each element in a compound is the same in any sample.

Physical and Chemical Properties

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

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

Physical and Chemical Changes

• Physical Change: Changes in matter that do not change the composition (e.g., change of state, temperature, volume).

• Chemical Change: Results in new substances (e.g., combustion, oxidation, decomposition).

Separation of Mixtures

• Filtration: Separates solids from liquids.

• Distillation: Uses differences in boiling points to separate components.

• Chromatography: Separates substances based on differences in their ability to adhere to surfaces.

Energy

• Energy: The capacity to do work or transfer heat.

• Kinetic Energy: Energy of motion.

• Potential Energy: Energy due to position relative to other objects.

Units of Measurement

• SI Units: International System of Units. Each physical quantity has a base unit (e.g., meter for length, kilogram for mass).

• Metric System: Uses base units and prefixes to indicate multiples or fractions (e.g., kilo-, milli-).

Common SI Base Units

Volume

• Volume is a derived unit: (cubic meter).

• Common units: liter (L), milliliter (mL), cubic centimeter (cm3).

Temperature Scales

• Celsius: Based on water properties. 0°C = freezing point, 100°C = boiling point.

• Kelvin: SI unit. Absolute zero is 0 K.

• Fahrenheit: Used in weather reports. and

Energy Units

• Joule (J): SI unit of energy.

• Calorie (cal):

• Nutritional Calorie (Cal):

Density

• Density: Physical property defined as mass per unit volume.

• Common units: g/mL or g/cm3

Numbers in Chemistry

• Exact Numbers: Counted or defined values (e.g., 12 eggs in a dozen).

• Measured Numbers: Obtained from measurements; have uncertainty.

Uncertainty, Accuracy, and Precision

• Uncertainty: All measurements have some degree of uncertainty.

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

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

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

• For addition/subtraction: Round to the least significant decimal place.

• For multiplication/division: Round to the same number of significant figures as the measurement with the fewest significant figures.

Dimensional Analysis

• Used to convert units using conversion factors (equalities).

• Set up ratios so that units cancel appropriately.

• Multiple conversions can be used in sequence.

Additional info: This guide covers the foundational concepts of general chemistry, including matter, energy, measurement, and the classification and properties of substances.