General Chemistry Study Guide: Matter, Measurement, and Atomic Theory

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The physical state of matter determines its properties and behavior. Understanding these characteristics is fundamental in chemistry.

Solids: Definite shape and volume; particles are closely packed and vibrate in place.
Liquids: Definite volume but no definite shape; particles are less tightly packed and can move past each other.
Gases: No definite shape or volume; particles are far apart and move freely.
Example: Ice (solid), water (liquid), steam (gas).

Matter can be classified based on its composition.

Element: Pure substance consisting of only one type of atom (e.g., Oxygen).
Compound: Pure substance composed of two or more elements chemically combined (e.g., Water).
Mixture: Combination of two or more substances not chemically bonded (e.g., air, saltwater).

Scientific notation is used to express very large or small numbers conveniently.

Conversion to Scientific Notation: Move the decimal point so only one nonzero digit remains to the left; count the number of places moved for the exponent.
Conversion from Scientific Notation: Move the decimal point according to the exponent value.
Example:

The International System of Units (S.I.) uses prefixes to denote multiples or fractions of base units.

Common Prefixes: kilo (k, ), centi (c, ), milli (m, ), micro (, ), nano (n, ).
Unit Conversions: Use conversion factors to switch between units.

Dimensional analysis is a method for converting between units using conversion factors.

Squared and Cubic Units: When converting area or volume, apply conversion factors to each dimension.
Example: To convert to , use , so .

Density is a physical property defined as mass per unit volume.

Formula:
Units: Solids (g/cm3), Liquids (g/mL), Gases (g/L)
Using Density as a Conversion Factor: Density can convert between mass and volume in dimensional analysis.
Example: If a liquid has a density of and a volume of , mass is .

Dalton's atomic theory laid the foundation for modern chemistry, describing the nature of atoms and their role in chemical reactions.

Dalton's Atomic Theory:
1. All matter is composed of atoms.
2. Atoms of a given element are identical; atoms of different elements are different.
3. Atoms cannot be created or destroyed in chemical reactions.
4. Atoms combine in simple whole-number ratios to form compounds.
Law of Conservation of Mass: Mass is neither created nor destroyed in a chemical reaction.

Atoms consist of protons, neutrons, and electrons. Their numbers determine the identity and properties of the atom.

Protons: Positively charged, found in the nucleus; number equals atomic number.
Neutrons: Neutral, found in the nucleus; number equals mass number minus atomic number.
Electrons: Negatively charged, found outside the nucleus; number equals protons in a neutral atom.
Example: Carbon-12 has 6 protons, 6 neutrons, 6 electrons.

The atomic number and mass number are key identifiers for elements.

Isotopes are atoms of the same element with different numbers of neutrons.

The average atomic mass of an element is calculated based on the masses and abundances of its isotopes.

Formula:
Example: If chlorine has two isotopes: (75.8%, mass 34.97 u) and (24.2%, mass 36.97 u):

The periodic table organizes elements by increasing atomic number and groups elements with similar properties.

Metals: Left and center; shiny, conductive, malleable.
Nonmetals: Right; dull, poor conductors, brittle.
Metalloids: Border metals and nonmetals; intermediate properties.
Group Names: Alkali metals (Group 1), Alkaline earth metals (Group 2), Halogens (Group 17), Noble gases (Group 18).

Each element is represented by a unique one- or two-letter symbol.

Additional info: Students should memorize the required element symbols as specified by their instructor.