The standard SI units for measuring length, mass, and time are the metre, kilogram, and second, respectively. Smaller units are defined as fractions or multiples of these base units, such as the centimetre being 0.01 metres and the kilogram being 1000 grams. Common devices for measuring these quantities include balances and spring scales for mass, and thermometers use liquids like mercury or alcohol that change volume with temperature. Temperature is typically measured on the Celsius scale, which is defined by the freezing and boiling points of water.

1. Chapter13: Physics

2. The standard SI unit for measuring length is metre.
Unit Symbol Number of
meters
Kilometre km 1000 m
Metre m 1 m
Centimetre cm 0.01 m
Millimetre mm 0.001 m
Micrometre μm 0.000 001 m
nanometre nm 0.000 000 001 m

3. The standard SI unit for measuring mass is kilogram.
Unit Symbol Number of
kilograms
megaton Mt 1000 000 000 kg
ton t 1000 kg
Kilogram kg 1 kg
Gram g 0.001 kg
milligram mg 0.000 001 kg

4. Balance scales
Top pan balance
Spring balance

5. The 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 s
Second s 1 s
millisecond ms 0.001 s

6.  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.

7.  The lowest possible
temperature, known as
absolute zero is -273 ⁰C.
 Temperatures can go as high
as millions of degrees Celsius.

8.  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.