Chemistry: Measurement Systems

• Chemistry, a physical science, relies on measurements.
• Common parameters measured include length, mass, volume, pressure, temperature, density, and specific gravity.
• The International System of Units (SI), which includes the metric system, is favored in science.
• SI units includes meter (m) for length, kilogram (kg) for mass, and cubic meter (m³) for volume.
• Liter (L) is a commonly used non-SI unit.
• Measurements of observations are essential in scientific studies.
• Measurement consists of a number followed by a unit.

Measurement Systems

• Metric System: SI is a specific metric system and a decimal system of measurement.
  • MKS system uses meter, kilogram, and second as base units.
  • CGS system uses centimeter, gram, and second as base units.
  • Many units in SI and metric systems are built upon combinations of base units, known as derived units.
• English System: A pre-SI system with units like yard (length), ounce (volume), and pound (force).
• International System of Units (SI): A modified metric system adopted worldwide.
  • Based on multiples of 10, it comprises seven base units.

SI Base Units:

• Mass: kilogram (kg)
• Time: second (s)
• Temperature: Kelvin (K)
• Length: meter (m)
• Electric current: Ampere (A)
• Luminous intensity: candela (cd)
• Amount of substance: mole (mol)

Prefixes Used in SI Measurements:

• Exa (E): 10^18
• Peta (P): 10^15
• Tera (T): 10^12
• Giga (G): 10^9
• Mega (M): 10^6
• Kilo (k): 10^3
• Hecto (h): 10^2
• Deka (da): 10^1
• Deci (d): 10^-1
• Centi (c): 10^-2
• Milli (m): 10^-3
• Micro (µ): 10^-6
• Nano (n): 10^-9
• Pico (p): 10^-12
• Femto (f): 10^-15
• Atto (a): 10^-18

Volume Measurement

• Volume is the space occupied by a substance.
  • Metric unit: liter (L)
  • SI unit: cubic meter (m³)
• Non-SI units like liter (L) and milliliter (mL) are commonly used in chemistry.
• Graduated cylinders, beakers, volumetric pipets, burets, and volumetric flasks can measure volume.

Mass Measurement

• The mass of an object is the quantity of material it contains.
• Platform balance, triple balance, and weighing scales can measure mass.
  • Metric unit: gram (g)
  • SI unit: kilogram (kg)
• Mass remains constant, regardless of an object's state or location.

Key conversions

• Length:
  • 1 kilometer (km) = 1000 meters = 0.6214 mile
  • 1 meter (m) = 100 centimeters = 1.094 yards
  • 1 centimeter (cm) = 0.01 meter = 0.3937 inch
• Volume:
  • 1 cubic meter (m³) = 1,000,000 cubic centimeters = 35.31 cubic feet
  • 1 cubic decimeter (dm³) = 1000 cubic centimeters = 0.2642 gallon
  • 1 cubic centimeter (cm³) = 0.001 dm³ = 0.03381 fluid ounce
• Mass:
  • 1 kilogram (kg) = 1000 grams = 2.205 pounds

Density

• Density (d) is the mass of an object divided by its volume (d = mass/volume).
• Density indicates if a substance floats in another; less dense substances float above denser ones.
• To calculate density, you need mass (kilograms or grams) and volume (cubic centimeter or cubic meter).
• The SI unit for density is kilograms per cubic meter (kg/m3), in chemistry, it's often expressed as g/L (g/dm3) or g/mL (g/cm3).
• Gases have much lower densities than liquids or solids.

Temperature

• Temperature measures the direction of heat transfer and indicates how hot or cold an object is.
• Temperature is measured using a thermometer.
• Three temperature scales exist: Fahrenheit, Celsius (Centigrade), and Kelvin.
• Celsius scale sets water's freezing point at 0°C and boiling point at 100°C.
• Fahrenheit scale sets water's freezing point at 32°F and boiling point at 212°F.
• Kelvin scale is the SI scale for temperature, where absolute zero (0 K) is -273.15°C. All temperatures on the Kelvin scale are positive.

Temperature Conversions:

• Celsius from Kelvin: °C = K - 273
• Kelvin from Celsius: K = °C + 273
• Fahrenheit from Celsius: °F = (9/5)°C + 32
• Celsius from Fahrenheit: °C = (5/9)(°F - 32)

Accuracy and Precision

• Accuracy indicates how close a measurement is to the true value.
• Precision indicates how close a series of measurements are to each other as well as how exact a measurement is.

Lab Equipment

Glassware: (Not Used for Measurement)

• Erlenmeyer Flask:
  • Designed for easy stirring by hand.
  • Not used for precise measurements (only accurate to 5%).
  • Commonly used for titrations.
• Beaker:
  • Used to hold varying volumes of liquid.
  • Not used for measuring volumes accurately (only accurate to 5%).
• Test Tube:
  • Used to hold/mix small samples.

Glassware (Used for Measurement)

• Volumetric Flask:
  • Used for accurate liquid volume measurements in laboratory experiments.
• Graduated Cylinder:
  • Used to measure many different volumes of liquid.
• Pipet:
  • Used to measure/transfer small quantities of liquid in milliliters (mL).
• Buret:
  • Used in quantitative chemical analysis to measure liquid/gas volume.

Other Equipment:

• Ring Stand:
  • Used with clamps to hold equipment.
• Buret Clamp:
  • Holds two burets when attached to a ring stand.
• Utility Clamp:
  • Holds glassware onto a ring stand.
• Funnel:
  • Aids in liquid transfer.
• Watch Glass:
  • Evaporates liquids, heats small substances, or covers beakers.
• Crucible Tongs:
  • Transfers hot crucibles/other hot items.
• Glass Stir Bar:
  • Stirs substances, often in beakers.
• Disposable Pipet:
  • Transfers small liquid amounts.
  • Drops can be counted, but it's not precise.
• Safety Goggles:
  • Worn in the lab to protect eyes from fumes/spills.
• Bunsen Burner:
  • Used to heat things.