MEASUREMENT AND UNITS

MEASUREMENT AND UNITS
✓ The SI unit means the International System of Units
(from the French Système International d’Unités)
✓ The SI unit has basic quantities and derived quantities
Basic quantities

Basic Quantity SI Unit Symbol

Length (l) metre M

Mass (M) kilogram Kg

Time (T) second s

Electric current (I) ampere A

Thermodynamic kelvin K
temperature (Θ)

Amount of substance (N) mole Mol

Luminous intensity (J) candela Cd


Basic quantities
✓ These include mass, temperature, length, time, electric
current, luminous intensity and amount of substance
(a) Temperature
✓ Is the degree of hotness or coldness of a body or a place in
a specified unit. The SI unit for measuring Temperature is

, in Kelvin (K). Other units are: Degree Celsius (0c) and
Fahrenheit (F)

To convert degree Celsius (o C) to kelvin (K) we add 273

Temperature Conversion Temperature (K)
(°C) Formula

0 °C 0 + 273 = 273 273 K

25 °C 25 + 273 = 298 298 K

100 °C 90 + 273 = 373 363 K

–10 °C –10 + 273 = 263 263 K

To convert kelvin to degree Celsius ( oC ) we subtract 273

Temperature Conversion Temperature (°C)
(K) Formula

273 K 273 – 273 = 0 0 °C

298 K 308 – 273 = 25 35 °C

373 K 373 – 273 = 100 100 °C

263 K 263 – 273 = –10 –10 °C


(b) Length