Overview
This lecture introduces the fundamentals of chemistry, its importance across various fields, and key concepts such as matter, scientific method, types of substances, measurements, and calculations.
What is Chemistry?
- Chemistry is the study of matter and the changes it undergoes.
- Known as the "central science" because it connects to various fields like biology, physics, medicine, energy, technology, and agriculture.
- Chemists study processes at molecular and atomic levels, including invisible changes.
Matter and Its Forms
- Matter is anything that has mass and occupies space.
- Three main states: solid (holds shape), liquid (flows, takes shape of container), gas (fills container, particles move fast).
- Substance: form of matter with definite composition and distinct properties.
- Mixture: combination of two or more substances retaining individual identities.
- Homogeneous mixture: uniform composition (e.g., milk, soft drink).
- Heterogeneous mixture: non-uniform (e.g., cement, sand with iron filings).
Elements, Compounds, and Mixtures
- Element: substance that cannot be separated by chemical means; 114+ identified.
- Compound: substance formed by the chemical combination of elements in fixed proportions; can be separated only by chemical means.
- Mixtures can be separated by physical means; compounds cannot.
Physical and Chemical Changes
- Physical change: does not alter substance's composition (e.g., melting, dissolving).
- Chemical change: results in new substances (e.g., rusting iron, burning hydrogen).
Properties of Matter
- Extensive property: depends on amount (mass, volume, length).
- Intensive property: independent of amount (density, temperature, color).
Measurement and Units
- Mass measured in kilograms (kg), volume in cubic meters (m³) or liters (L), length in meters (m).
- Density = mass/volume; common units g/cm³ or g/mL.
- Temperature: Celsius (°C), Kelvin (K); convert using K = °C + 273.
Scientific Notation and Significant Figures
- Scientific notation expresses large/small numbers as a number between 1–10 times a power of ten.
- Significant figures indicate measurement precision.
- Nonzero digits and zeros between them are significant.
- Leading zeros are not significant; trailing zeros are significant if after a decimal.
Calculations, Accuracy, and Precision
- For addition/subtraction: round to least precise decimal place.
- For multiplication/division: round to the least number of significant figures.
- Accuracy: closeness to the true value.
- Precision: closeness of repeated measurements to each other.
Dimensional Analysis
- Method to convert units by canceling units through multiplication/division.
- Ensures correct unit transformations in calculations.
Key Terms & Definitions
- Chemistry — the study of matter and its changes.
- Matter — anything that has mass and occupies space.
- Element — pure substance that cannot be broken down by chemical means.
- Compound — substance of two or more elements chemically combined.
- Mixture — physical blend of substances retaining individual properties.
- Homogeneous — same composition throughout.
- Heterogeneous — different components visible.
- Physical change — change without new substances formed.
- Chemical change — process forming new substances.
- Extensive property — depends on sample size.
- Intensive property — does not depend on sample size.
- Density — mass per unit volume.
- Accuracy — closeness to true value.
- Precision — repeatability of measurements.
- Significant figures — digits representing precision of measurement.
- Dimensional Analysis — technique for converting units.
Action Items / Next Steps
- Print SI units and conversion factors sheet from course module.
- Begin worksheets 1–5 ("fun sheets") covering measurement, properties of matter, and calculations.
- Review elements 1–82 and their symbols in the periodic table.