stg2 study guide

Study Guide - Smart Notes

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Intro to General Chemistry

Classification of Matter

Chemistry is the study of matter and the changes it undergoes. Matter is anything that occupies space and has mass. Understanding the classification of matter is fundamental to general chemistry.

Element: The simplest type of matter, composed of only one kind of atom.
Compound: Matter composed of two or more different elements that are chemically bonded together.
Mixture: Matter composed of elements and/or compounds that are physically mixed together, not chemically bonded.

Examples:

Gold bar: Element
Ammonia (NH3): Compound
Orange juice: Mixture

Key Point: Compounds can only be separated into their elements by chemical means, while mixtures can be separated by physical means.

Physical and Chemical Changes

Changes in matter can be classified as physical or chemical:

Physical Change: Alters the physical state or appearance without changing the composition (e.g., melting, dissolving, tearing paper).
Chemical Change: Alters the chemical composition, resulting in new substances (e.g., burning, rusting, cooking an egg).

Reversible changes (such as phase changes and dissolving) can be undone, while irreversible changes (such as most chemical reactions) cannot.

Chemical and Physical Properties

Chemical Properties

Chemical properties describe a substance's ability to undergo chemical changes, resulting in new substances.

Examples: Reactivity with acids, flammability, toxicity, radioactivity.

Examples of chemical properties: flammability, toxicity, reactivity, radioactivity

Physical Properties

Physical properties can be observed or measured without changing the substance's chemical identity.

Examples: Color, mass, density, melting point, boiling point, luster, hardness.

Color palette representing color as a physical property Weight representing mass as a physical property Cube representing shape as a physical property Diamond representing luster as a physical property

Intensive vs. Extensive Properties

Intensive Properties

Intensive properties do not depend on the amount of substance present. They are useful for identifying substances.

Examples: Density, color, melting point, boiling point, luster.

Color palette representing color as an intensive property Diamond representing luster as an intensive property

Extensive Properties

Extensive properties depend on the amount of substance present. They are additive for independent, non-interacting subsystems.

Examples: Mass, volume, length, total charge.

Weight representing mass as an extensive property Cube representing volume as an extensive property

Temperature and Heat

Temperature vs. Heat

Thermal energy is the sum of the kinetic and potential energies of all atoms in an object. Temperature is the average kinetic energy of the particles, while heat is the transfer of thermal energy from a hotter object to a cooler one.

Thermometer showing temperature

Temperature Conversions

Celsius (ºC), Fahrenheit (ºF), and Kelvin (K) are common temperature units.
Conversion formulas:

Thermometer with Celsius and Fahrenheit scales

Scientific Notation and SI Units

Scientific Notation

Scientific notation expresses very large or small numbers in the form , where and is an integer.

Example:

SI Base Units

The International System of Units (SI) is based on seven base units:

Physical Quantity	Name	Symbol
Mass	kilogram	kg
Length	meter	m
Time	second	s
Temperature	kelvin	K
Amount of substance	mole	mol
Electric current	ampere	A
Luminous intensity	candela	cd

Weight representing kilogram (kg) Ruler representing meter (m)

Metric Prefixes

Metric prefixes are used to express multiples or fractions of base units. For example, kilo- (k) means , milli- (m) means .

Common prefixes: kilo- (k), centi- (c), milli- (m), micro- (µ), nano- (n)

Significant Figures

Rules for Significant Figures

All nonzero digits are significant.
Zeros between nonzero digits are significant.
Leading zeros are not significant.
Trailing zeros are significant only if there is a decimal point.

Example: 0.003840 has 4 significant figures.

Significant Figures in Calculations

For multiplication/division: The result should have as many significant figures as the value with the fewest significant figures.
For addition/subtraction: The result should have as many decimal places as the value with the fewest decimal places.

Conversion Factors and Dimensional Analysis

Conversion factors are ratios that relate two units. Dimensional analysis is a systematic approach to problem-solving that uses conversion factors to move from one unit to another.

Example: To convert 10 inches to centimeters, use the conversion factor .

Density

Definition and Formula

Density is the amount of mass per unit volume. It is a physical property that can be used to identify substances.

Formula:

Cube representing volume for density calculations

Density of Geometric and Non-Geometric Objects

For regular shapes, use geometric formulas to find volume. For irregular objects, use water displacement to determine volume.

Glass of water with objects, illustrating water displacement method

Summary Table: Intensive vs. Extensive Properties

Property Type	Examples	Depends on Amount?
Intensive	Density, color, boiling point	No
Extensive	Mass, volume, length	Yes