General Chemistry Unit 1: Matter, Measurement, and Chemical Nomenclature

Dimensional Analysis and Measurement

Significant Figures

Significant figures are the digits in a number that convey the precision of a measurement or calculation. Understanding which digits are significant is essential for reporting scientific data accurately.

• Rules for Significant Figures:

  • All nonzero digits are significant.

  • Captive zeros (zeros between significant digits) are significant.

  • Leading zeros (zeros before the first nonzero digit) are not significant.

  • Trailing zeros (zeros at the end of a number) are significant only if there is a decimal point.

• Rounding Rules:

  • If the number ends in something greater than 5, round up.

  • If the number ends in something less than 5, round down.

  • If the number ends in a perfect 5, round to the even number.

• Addition & Subtraction: Round the result to the smallest number of decimal places to the right of the decimal.

• Multiplication & Division: Round the result to the number that has the least number of significant digits from the measured or given values.

Percent Yield and Percent Error

• Percent Yield: Compares the amount of product produced to the amount that should have been produced.

  • $\text{Percent Yield} = \frac{\text{Lab Yield}}{\text{Theoretical Yield}} \times 100$

• Percent Error: Calculation used to determine percent of accuracy.

  • $\text{Percent Error} = \frac{|\text{Experimental Value} - \text{True Value}|}{\text{True Value}} \times 100$

Dimensional Analysis

Dimensional analysis is a method to convert between units using conversion factors.

• Base Units: SI system uses base units for fundamental quantities.

  • Distance/Length: meter (m)

  • Time: second (s)

  • Mass: gram (g)

  • Volume: liters (L) or milliliters (mL)

  • Density: grams per milliliter (g/mL)

• Important Derived Unit: $1\,\text{cm}^3 = 1\,\text{mL}$

Fundamental Laws of Chemistry

Law of Conservation of Mass

The law of conservation of mass states that mass can neither be created nor destroyed in a chemical reaction.

Law of Definite Proportions

In a specific compound, the ratio of elements is always consistent.

Law of Multiple Proportions

Elements can combine in different ratios to form different compounds.

Matter and Its Classification

Definition of Matter

Matter is anything that occupies space and has mass.

States of Matter

Matter exists in three primary states: solid, liquid, and gas. Each state has distinct physical properties.

• Solid: Atoms or molecules are tightly packed, leading to a fixed volume and rigid shape. Solids are not easily compressed and can be crystalline (ordered structure, e.g., table salt, diamonds) or amorphous (disordered structure, e.g., glass, plastic).

• Liquid: Atoms or molecules can move freely relative to each other. Liquids have a fixed volume but no fixed shape and are not easily compressed.

• Gas: Atoms or molecules are far apart and move freely. Gases have neither fixed shape nor volume and are easily compressed.

Pure Substances and Mixtures

• Pure Substance: Has only one component. Can be an element or a compound.

• Element: A substance that cannot be broken down into simpler substances by chemical means. Elements are made of only one type of atom and can be metals, nonmetals, or metalloids.

• Compound: A substance made up of two or more elements in a fixed proportion. Compounds can be classified as binary ionic compounds (BICs) or binary covalent compounds (BCCs).

• Mixture: A substance with two or more components. Mixtures can be:

  • Heterogeneous: Distinct regions, often different states of matter.

  • Homogeneous: No distinct regions; composition is uniform throughout.

Classification of Elements

• Metals: Good conductors of heat and electricity, malleable, ductile, typically form cations, and are found on the left side of the periodic table.

• Nonmetals: Poor conductors of electricity, found on the right side of the periodic table, and include the 7 diatomic elements (H2, N2, O2, F2, Cl2, Br2, I2).

• Metalloids: Have properties of both metals and nonmetals, found along the "staircase" on the periodic table.

Diatomic Elements

Certain elements naturally exist as molecules composed of two atoms. The seven diatomic elements are:

• H2, N2, O2, F2, Cl2, Br2 (liquid), I2 (solid)

Chemical and Physical Changes

Physical Properties and Changes

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

• Physical Change: Alters appearance or state but not composition (e.g., melting, boiling, dissolving).

Chemical Properties and Changes

• Chemical Property: Only observed when a substance undergoes a chemical change (e.g., flammability, reactivity).

• Chemical Change: Atoms are rearranged, transforming the original matter into new substances (e.g., rusting, combustion).

Types of Chemical Reactions

• Precipitation: Two liquids form a solid (precipitate).

• Synthesis: Creation of compounds from simpler substances.

• Decomposition: Breaking down compounds into simpler substances.

• Combustion: Burning, often involving oxygen.

• Electrolysis: Breaking compounds using electricity.

• Oxidation: Loss of electrons.

• Reduction: Gain of electrons.

• Redox Reactions: Involve both oxidation and reduction.

Exothermic and Endothermic Reactions

• Exothermic: Release energy (usually as heat) to surroundings.

• Endothermic: Absorb energy from surroundings.

Measuring Instruments in Chemistry

• Buret: Used in titrations to measure liquid delivered. Graduations go downward; always estimate one digit past the smallest graduation.

• Graduated Cylinder: Used to measure liquid volumes (less precise than burets or pipets). Read at eye level at the bottom of the meniscus.

• Pipet (Volumetric or Graduated): Delivers a single fixed volume (very precise). Fill to the calibration line.

• Volumetric Flask: Designed to contain a single exact volume. Fill until the bottom of the meniscus just touches the etched line.

Naming Compounds

Binary Ionic Compounds (BICs)

• Composed of a metal and a nonmetal.

• The first element is the metal (may include a Roman numeral for charge).

• The second element is named with the root of the anion and the suffix "-ide".

Binary Covalent Compounds (BCCs)

• Composed of two nonmetals or a metalloid and a nonmetal.

• The first element is named first; if more than one, use a prefix.

• The second element is named with a prefix and the suffix "-ide".

Prefixes for Number of Atoms

• 1 = mono- (only used on second element)

• 2 = di-

• 3 = tri-

• 4 = tetra-

• 5 = penta-

• 6 = hexa-

• 7 = hepta-

• 8 = octa-

• 9 = nona-

• 10 = deca-

Summary Table: Classification of Matter

Type	Description	Examples
Element	Cannot be broken down by chemical means	O2, Fe, H2
Compound	Composed of two or more elements in fixed ratio	H2O, NaCl
Homogeneous Mixture	Uniform composition throughout	Salt water, air
Heterogeneous Mixture	Non-uniform composition, distinct regions	Salad, oil and water

Additional info:

• Some context and definitions were expanded for clarity and completeness.

• Examples and applications were added to illustrate key concepts.