MeasurementsChapter 13.

Physics

Measuring lengthThe standard SI unit for measuring length is metre.

Unit Symbol Number of metersKilometre km 1000 mMetre m 1 mCentimetre cm 0.01 mMillimetre mm 0.001 mMicrometre μm 0.000 001 mnanometre nm 0.000 000 001 m

Measuring MassThe standard SI unit for measuring mass is kilogram.

Unit Symbol Number of kilograms

megaton Mt 1000 000 000 kgton t 1000 kgKilogram kg 1 kgGram g 0.001 kgmilligram mg 0.000 001 kg

Balance scales

Top pan balance

Spring balance

Measuring timeThe standard SI unit for measuring time is the second.

Unit Symbol Number of kilograms

Day d 86 400 s (1440 min. or 24 h)

Hour h 3600 s (60 min.)Minute min 60 sSecond s 1 smillisecond ms 0.001 s

Measuring Temperature The hotness or coldness of a substance is

measured by taking its temperature. The temperature of a substance is measured on

a scale. The most commonly used temperature scale is

the Celsius scale. Its two fixed points are 0 ⁰C and 100 ⁰C. Laboratory thermometers usually have a scale

from -10 ⁰C to 110 ⁰C.

The lowest possible temperature, known as absolute zero is -273 ⁰C.

Temperatures can go as high as millions of degrees Celsius.

Liquids in thermometers Two liquids that are commonly used in

thermometers are mercury and alcohol. Mercury has a freezing point of -39 ⁰C and a

boiling point of 360 ⁰C. Alcohol has a freezing point of -112 ⁰C and a

boiling point of 78 ⁰C.