# 1: Chapter 1 - Descriptions in the Physical Sciences

• 1.1: Chemistry as a Science
Science is a process of knowing about the natural universe through observation and experiment. Scientists go through a rigorous process to determine new knowledge about the universe; this process is generally referred to as the scientific method. Science is broken down into various fields, of which chemistry is one. Science, including chemistry, is both qualitative and quantitative.
• 1.2: Expressing Units
Numbers tell "how much," and units tell "of what." Chemistry uses a set of fundamental units and derived units from SI units. Chemistry uses a set of prefixes that represent multiples or fractions of units. Units can be multiplied and divided to generate new units for quantities.
• 1.3: Converting Units
Units can be converted to other units using the proper conversion factors. Conversion factors are constructed from equalities that relate two different units. Conversions can be a single step or multistep. Unit conversion is a powerful mathematical technique in chemistry that must be mastered. Exact numbers do not affect the determination of significant figures.
• 1.4: Other Units - Temperature and Density
Chemistry uses the Celsius and Kelvin scales to express temperatures. A temperature on the Kelvin scale is the Celsius temperature plus 273.15. The minimum possible temperature is absolute zero and is assigned 0 K on the Kelvin scale. Density relates a substance's mass and volume. Density can be used to calculate volume from a given mass or mass from a given volume.
• 1.5: 0.1 Introduction and Review