Chemistry Chapter II: Measurements and Calculations

Chemistry Chapter II: Measurements and Calculations

Units of Measurement
Measurements are quantitative information and are more than numbers.
❖ Unit-help describe the specific amount
● Examples: teaspoons, cups, grams, or liters
❖ Quantity-something that has magnitude, size, or amount
● Examples: length, mass, time, temperature, amount of substance



➢ I. SI Measurements
❖ SI (Le Système International d'Unités or the International System of Units)-the
measurement system that is accepted worldwide

SI Base Units
Quantity Quantity Symbol Unit Name Unit Abbreviation

Length l meter m

Mass m kilogram kg

Time t second s

Temperature T kelvin K

Amount of Substance n mole mol




➢ II. Converting Units
Converting has things changing its units to another unit. For example, changing feet into inches
or kilograms to grams.
❖ Conversion Factor-a ratio that is derived from the equality of two different units and that
can be used to convert one unit to the other; where the top units are equivalent to the
bottom units, ratio = fraction
12 𝑖𝑛 1 𝑘𝑔
● Example: 1 𝑓𝑡
= 1000 𝑔
Other Examples:
1. How many seconds are in the month of January?
30 𝑑𝑎𝑦𝑠 12 𝑚𝑜𝑛𝑡ℎ𝑠 60 𝑚𝑖𝑛 60 𝑠
1 * 1 𝑑𝑎𝑦 * 1 ℎ𝑟
= 1 𝑚𝑖𝑛
= 2592000 s
2. An average American eats 0.48 pounds of sugar a month, how many pounds of sugar per
year is that?
0.48 𝑙𝑏 12 𝑚𝑜𝑛𝑡ℎ𝑠
1 𝑚𝑜𝑛𝑡ℎ * 1 𝑦𝑟
= 5.76 lb/yr