Unit 1
Matter and measurement
Chemistry is a quantitative science: every conclusion starts with a reading. This unit begins with units and orders of magnitude, learns to report a measurement honestly (significant figures and uncertainty), identifies substances by density, links the grams you can weigh to the atoms you cannot see with the mole, and finally works out chemical formulas from elemental composition.
- 1 Units and orders of magnitude SI base units and prefixes, scientific notation and the factor-label method that lets units cancel themselves — then ride the scale elevator from a nucleus up to a person. 25 min
- 2 Uncertainty and significant figures Accuracy versus precision, systematic versus random error, counting and calculating with significant figures — and reading a meniscus under the magnifier. 30 min
- 3 Density: an intensive property Weigh an unknown metal and measure its volume by displacement, and see how the measurement uncertainty decides whether you can tell what it is. 25 min
- 4 The mole: counting atoms by weighing The Avogadro constant has been exact since 2019; compute molar masses from formulas and move freely between mass, moles and particles. 30 min
- 5 Formulas and composition Mass percentages, empirical and molecular formulas — and recovering the formula of vitamin C from combustion data, the way Liebig did. 30 min