Chemistry Fundamentals and Scientific Method

Chemistry Fundamentals

• Chemistry is the study of the composition, structure, and changes of matter.
• Matter is anything that occupies space and has mass.
• A substance has a definite composition and distinct properties.

Scientific Method

• The scientific method is a systematic approach to research, involving observation, representation (hypothesis), and interpretation.
• A hypothesis is a tentative explanation for observations.
• A law is a concise statement of a relationship between phenomena that is always the same under the same conditions.
• A theory is a unifying principle that explains a body of facts and/or laws based on them.
• Experiments are crucial for testing hypotheses and refining theories. Results from experiments can impact how a theory is modified.

States of Matter

• Solids have fixed shape and volume.
• Liquids have fixed volume but no fixed shape.
• Gases have neither fixed volume nor shape.

Types of Changes

• Physical changes affect the form of matter but not its chemical identity (e.g., melting, dissolving).
• Chemical changes transform one or more kinds of matter into new kinds of matter (e.g., rusting, burning).

Properties of Matter

• Physical properties can be observed without changing the chemical identity of a material (e.g., physical state, boiling point, color).
• Chemical properties describe how a material behaves when undergoing a chemical change (e.g. ability to react with oxygen).

Classification of Matter

• Substances: Cannot be separated into other kinds of matter by physical processes (e.g., distillation, sublimation).
  • Elements: Cannot be decomposed into simpler substances by any chemical reaction (e.g., hydrogen, carbon, oxygen).
  • Compounds: Composed of two or more elements chemically combined (e.g., water (H₂O), carbon dioxide (CO₂)).
• Mixtures: A combination of two or more substances (e.g., Italian salad dressing, saltwater).
  • Homogeneous mixtures: Uniform in properties throughout (solution - e.g., saltwater, air). - A solution is a homogeneous mixture.
  • Heterogeneous mixtures: Mixture composed of physically distinct parts with different properties. Heterogeneous mixtures are not uniform

Measurements

• Measurement compares a physical quantity with a fixed standard (unit).
• Precision refers to the closeness of a set of repeated measurements.
• Accuracy refers to the closeness of a single measurement to its true value.
• Significant figures indicate the precision of a measurement or calculation.

Significant Figures in Calculations

• Addition and subtraction: the result has the same number of decimal places as the measurement with the fewest decimal places.
• Multiplication and division: the result has the same number of significant figures as the measurement with the fewest significant figures
• Rounding Procedures are used to determine the correct number of significant figures (use the first nonsignificant digit to determine the rounding procedure used)

SI Units

• SI Units (System International d’Unités) is an international system of metric units.
• Base units are fundamental units from which all other units can be derived. (meter, kilogram, second etc)

Scientific Notation

• Scientific notation represents numbers in the form A × 10ⁿ, where 1 ≤ A < 10 and n is an integer.
• Digits in A are significant.

Temperature Conversions

• Temperature is a measure of "hotness," with heat flowing from higher to lower temperature.
• Common units include Celsius (°C), Fahrenheit (°F), and Kelvin (K).
• Conversion formulas exist to change between these units.

Density

• Density is mass per unit volume.
• Density is expressed in units like g/cm³, g/mL, or g/L

Units and Dimensional Analysis

• Dimensional analysis (factor-label method) is a method of calculation using units through conversions to get to the desired unit.
• Conversion factors are used to convert between different units.