Chemistry Overview: Chemistry studies the composition, properties, and interactions of matter, connecting to many STEM fields and everyday life (e.g., digestion, materials, fuels).

Scientific Method: Involves observation, hypothesis formation, experimentation, and development of laws and theories to explain natural phenomena.

Domains of Chemistry:

• Macroscopic: Observable phenomena (e.g., ice, water, vapor).

• Microscopic: Atoms, molecules, often visualized with imagination or microscopes.

• Symbolic: Chemical symbols and formulas representing matter and reactions.

Phases and Classification of Matter:

• Matter: Anything with mass and volume.

• States: Solid (definite shape/volume), liquid (definite volume, shape of container), gas (fills container).

• Plasma: Ionized gas with unique properties, found in stars and lightning.

Mass vs. Weight:

• Mass: Amount of matter, constant regardless of location.

• Weight: Force of gravity on mass, varies with location.

Law of Conservation of Matter: Matter is neither created nor destroyed in physical or chemical changes.

Elements, Atoms, and Molecules:

• Element: Pure substance, cannot be broken down by chemical means; listed in the periodic table.

• Atom: Smallest unit of an element, retains its properties.

• Molecule: Two or more atoms bonded together; can be same or different elements.

Pure Substances and Mixtures:

• Pure Substances: Constant composition (elements or compounds).

• Mixtures: Physical combinations of substances, variable composition; can be homogeneous (solutions) or heterogeneous.

Physical and Chemical Properties/Changes:

• Physical Properties: Observed/measured without changing composition (e.g., density, color, melting point).

• Chemical Properties: Describe ability to change into new substances (e.g., flammability, reactivity).

• Physical Change: Alters state or appearance, not composition.

• Chemical Change: Produces new substances.

Extensive vs. Intensive Properties:

• Extensive: Depend on amount (mass, volume).

• Intensive: Independent of amount (density, temperature).

Measurements and SI Units:

• Measurements include a number, unit, and uncertainty.

• SI Base Units: meter (length), kilogram (mass), second (time), kelvin (temperature), mole (amount), ampere (current), candela (luminous intensity).

• Prefixes indicate multiples/fractions (e.g., kilo-, centi-, milli-).

Derived Units:

• Volume: Cubic meter (m3), liter (L), milliliter (mL).

• Density: massvolume (kg/m3, g/cm3, g/L).

Measurement Uncertainty, Accuracy, and Precision:

• Exact numbers: Counting or defined values (e.g., 1 ft = 12 in).

• Measured numbers: Have uncertainty; report all certain digits plus one estimated digit (significant figures).

• Accuracy: Closeness to true value.

• Precision: Consistency of repeated measurements.

Significant Figures:

• Rules for identifying significant digits in measurements.

• Calculations: Addition/subtraction (least decimal places), multiplication/division (least significant figures).

Dimensional Analysis and Conversion Factors:

• Use conversion factors (ratios of equivalent values) to convert units.

• Example: 34 in×2.54cm=86 cm

Temperature Scales and Conversions:

• Celsius (°C), Fahrenheit (°F), Kelvin (K).

• Conversion equations:

  • TF=95×TC+32

  • TK=TC+273.15