3.1 Measurements and Their Uncertainty

• Measurements are fundamental to the experimental sciences.
• To evaluate accuracy, the measured value must be compared to the correct value. To evaluate precision, you must compare the values of repeated measurements.
• Calculated answers often depend on the number of significant figures in the values used in the calculation.
• In general, a calculated answer cannot be more precise than the least precise measurement from which it was calculated.

3.2 The International System of Units

• Five commonly used SI base units are the meter, kilogram, kelvin, second, and mole.
• Common metric units of length: cm, m, km. Common metric units of volume:μL, mL, L, cm³. Common metric units of mass: mg, g, kg. Common units of temperature: °C and K. Common units of energy: J and cal.

3.3 Conversion Problems

• Multiplying by a conversion factor does not change the actual size of a measurement.
• Dimensional analysis provides an alternative approach to problem solving.
• Conversion problems are easily solved using dimensional analysis.

3.4 Density

• Density is an intensive property that depends only on the composition of a substance.
• The density of a substance generally decreases as its temperature increases.