Introduction to Chemistry

• Chemistry studies matter's properties and behavior.
• Chemistry is essential for understanding science-related fields.

Matter

• Anything that has mass and takes up space.
• Atoms are matter's building blocks.
• An element consists of one kind of atom (e.g., H, O, Na, Fe).
• A compound has two or more different elements (e.g., H₂O, NaCl).
• Molecules are groups of atoms connected together.

States of Matter

• The three states of matter are solid, liquid, and gas.
• Ice, liquid water, and water vapor are respective examples.

Classification of Matter Based on Composition

• Matter classification can be determined by various attributes.
• Homogeneous mixtures have uniform composition throughout.
• Heterogeneous mixtures have varying composition.
• Elements cannot be broken down into simpler substances.
• Compounds can be broken down into simpler substances.

Substances

• A substance has distinct properties and a stable composition
• Elements and compounds are two types of substances.

Compounds and Composition

• Compounds possess a definite composition, meaning that the relative number of atoms of each element in the compound is the same in any sample.
• Compounds follow the Law of Constant Composition (or Law of Definite Proportions).

Mixtures

• Mixtures exhibit properties of the substances they're made of.
• Mixtures have varied composition (heterogeneous) or uniform composition (homogeneous).
• Homogeneous mixtures are also called solutions.

Types of Properties

• Physical properties are observable without changing the substance (e.g., boiling point, density, mass, volume).
• Chemical properties are observable when a substance changes into another (e.g., flammability, corrosiveness, reactivity with acid).

Intensive vs. Extensive Properties

• Intensive properties are independent of the amount of substance (e.g., density, boiling point, color).
• Extensive properties depend on the amount of substance (e.g., mass, volume, energy).

Types of Changes

• Physical changes do not alter the composition of a substance (e.g., state changes, temperature, volume).
• Chemical changes result in new substances (e.g., combustion, oxidation, decomposition).

Changes in State of Matter

• Converting between solid, liquid, and gas is a physical change.
• When ice melts or water evaporates, each molecule still contains two hydrogen atoms and one oxygen atom.

Chemical Reactions

• Reacting substances turn into new substances.
• Hydrogen and oxygen turn into water.

Separating Mixtures:

• Mixtures get separated through physical means based on their components’ properties
• Filtration separates solids from liquids.

Simple Distillation

• Uses boiling point differences to separate a homogeneous mixture.

Chromatography

• Separates substances based on their ability to adhere to a surface.

Magnetic Separation

• Extracts magnetic materials using a magnetic force.

Evaporation

• Evaporation occurs when a liquid turns into a gas.

Liquid-liquid extraction

• Separates liquid components in a mixture

Numbers and Chemistry

• Numbers are very important in chemistry
• Topics such as units of measurement, quantities, uncertainty of measurement, significant figures, and dimensional analysis make use of numbers

Units of Measurements—SI Units

• Système International d'Unités is the international System of Units
• Each quantity has a different base unit

Units of Measurement–Metric System

• Base units in the metric system:
• Mass (g)
• Length (m)
• Time (s or sec)
• Temperature (°C or K)
• Amount of a substance (mol)
• Volume (cc or cm³ or l)

Units of Measurement–Metric System Prefixes

• Prefixes convert base units for common usage.

Mass and Length

• Mass is the amount of material in an object, measured in kilograms (SI) or grams (metric).
• Length is the measure of distance with meter as the base unit.

Volume

• Volume is derived from length (m × m × m = m³).
• Volume is measured in liters(L) and the milliliter (mL).
• One liter is a cube with sides of 1 decimeter (dm) and one milliliter and is 1 cubic centimeter (cm) long on each side

Temperature

• Temperature measures "hotness and coldness", determining heat flow direction.
• Heat spontaneously flows from higher to lower temperature objects.
• Celsius and Kelvin scales are common in scientific measurements.
• The Celsius scale is water-based: 0°C (freezing), 100°C (boiling).
• The Kelvin scale is the SI unit based on the properties of gases.
• There are no negative Kelvin temperatures.
• Absolute zero is 0 K.
• K = °C + 273.15
• Fahrenheit scale is not used in science but is found in weather reports.
• °F = 9/5(°C) + 32
• °C = 5/9(°F – 32)

Density

• Density is a physical property derived from mas and volume (g/mL or g/cm³).
• D = m/V

Specific Gravity

• Specific gravity (relative gravity) is a dimensionless ratio of a substance's density to water's density.

Numbers Encountered in Science

• Exact numbers are counted or defined and inexact (measures) numbers depend on how they were determined
• There are limitations with scientific instruments

Uncertainty in Measurements

• Measuring devices have distinct accuracy levels
• all measures has some degree of uncertainty

Accuracy versus Precision

• Accuracy is a measurement's proximity to its true value.
• Precision is the proximity of several measurements to each other.

Significant Figures

• Significant figures represent the digits that were measured.
• Rounding calculated numbers preserve the accuracy with significant figures.
• All nonzero digits are significant.
• Zeroes between significant figures are significant.
• Zeroes at the beginning of a number are never significant.
• Zeroes at the end of a number if a decimal point is also written in the number.

Significant Figures: Mathematical Operations

• Answers from adding or subtracting are rounded to the least significant decimal place.
• Answers are rounded to the least number of digits for multiplication or division.

Dimensional Analysis

• Dimensional analysis converts one quantity to another via conversion factors
• Comparisons are set up as a ratio to change units based on their presence in the denominator.