Chemistry and Measurements Study Notes

Chemistry and Measurements

Overview of Measurements in Chemistry

• Importance of measurements in everyday life.

• Learning goals include writing names and abbreviations for metric and SI units in various measurements.

2.1 Units of Measurement

• Scientists utilize the metric system of measurement with a specific focus on the International System of Units (SI), which serves as the global standard.

• International System of Units (SI): An official measurement system adopted worldwide for units of length, volume, mass, temperature, and time.

Units of Measurement: Metric and SI Systems

• Table 2.1 visually represents various units of measurement and their abbreviations:

  • Volume:

  • Metric: liter (L)

  • SI: cubic meter (m³)

  • U.S. customary: quart (qt)

  • Length:

  • Metric: meter (m)

  • SI: meter (m)

  • U.S. customary: mile (mi), inch (in.)

  • Mass:

  • Metric: gram (g)

  • SI: kilogram (kg)

  • U.S. customary: pound (lb), ounce (oz)

  • Temperature:

  • Metric: degree Celsius (°C)

  • SI: kelvin (K)

  • U.S. customary: degree Fahrenheit (°F)

  • Time:

  • Metric: second (s)

  • SI: second (s)

  • U.S. customary: second (s)

Volume

• Definition: Volume refers to the space occupied by a substance.

• Measurement Units:

  • Commonly measured in liters (L) and milliliters (mL) in the SI system.

  • Graduated cylinders are standard tools used for measuring small volumes.

• Useful Relationships Between Units of Volume:

  • $1 ext{ L} = 1000 ext{ mL}$

  • $1 ext{ L} = 1.06 ext{ qt}$

  • $946 ext{ mL} = 1 ext{ qt}$

Length

• Definition: Length is measured as the distance between two points.

• Measurement Units:

  • Measured in meters (m) in both metric and SI systems.

  • Centimeters (cm) are also used frequently by chemists.

• Useful Relationships Between Units of Length:

  • $1 ext{ m} = 100 ext{ cm}$

  • $1 ext{ m} = 39.4 ext{ in.}$

  • $1 ext{ m} = 1.09 ext{ yd}$

  • $2.54 ext{ cm} = 1 ext{ in.}$

Mass

• Definition: Mass is a measure of the quantity of material contained in an object.

• Measurement Units:

  • Measured on an electronic balance.

  • The SI unit for mass is a kilogram (kg), while grams (g) are commonly used in chemistry.

• Useful Relationships Between Units of Mass:

  • $1 ext{ kg} = 1000 ext{ g}$

  • $1 ext{ kg} = 2.20 ext{ lb}$

  • $454 ext{ g} = 1 ext{ lb}$

Temperature

• Definition: Temperature is a metric of how hot or cold an object feels.

• Measurement Scales:

  • Measured in degrees Celsius (°C) and kelvin (K) in the SI system.

  • Water freezes at 0 °C and boils at 100 °C.

  • The Kelvin scale, which starts at absolute zero, where 0 K is the lowest possible temperature.

Time

• Definition: Time is based on the frequency of radiation emitted by cesium atoms of an atomic clock.

• Measurement Units:

  • Measured in seconds (s) for both metric and SI systems.

  • A stopwatch is often used to measure time intervals, such as during races.

Learning Check 1

• Determine whether the unit described indicates:

  • A. A bag of onions with mass of 2.6 kg: (2) Mass

  • B. A person with a height of 1.7 m: (1) Length

  • C. A medication containing 0.50 g of aspirin: (2) Mass

  • D. A bottle containing 1.5 L of water: (3) Volume

Learning Check 2

• Identify the SI unit for each measurement:

  • A. Volume: cubic meter (m³)

  • B. Mass: kilogram (kg)

  • C. Length: meter (m)

  • D. Temperature: kelvin (K)

Learning Check 3

• Identify the measurement given in an SI unit:

  • A. John’s height: 1.9 m (Correct)

  • B. The mass of a lemon: 0.145 kg (Correct)

  • C. The temperature: 255 K (Correct)

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