Length, Mass and Time
Measuring Length

Is the distance from one point to another.

The SI or the standard unit of length is the metre (m)

Measured using ruler, trundle wheel, measuring tape.
Unit
Symbol
Number of Metres
kilometre
km
1000 m
metre
m
1m
centimetre
cm
0.01 m
millimetre
mm
0.001 m
micrometre
μm
0.000 001 m
nanometre
nm
0.000 000 001 m
Measuring Mass

The quantity of matter that an organism/object contains.

The SI or standard unit of mass is the kilogram (kg)

Measured using top pan balance, weighing machine, weighing balance.
Unit
Symbol
Number of kilograms
megatonne
Mt
1 000 000 000 kg
tonne
t
1000 kg
kilogram
kg
1 kg
gram
g
0.001 kg
milligram
mg
0.000 001 kg
Measuring Time

A measure used to define smaller divisions of a day.

The SI or standard unit of time is the second (s)

Measured using stopwatch.

To make events like the Olympics very accurate, and to avoid human reaction time,
special timers called light gates are used.
Unit
Symbol
Number of seconds
day
d
86 400 s (1440 min or 24 h)
hour
h
3600 s (60 min)
minute
min
60 s
second
s
1s
millisecond
ms
0.001 s
Heat and Temperature
Measuring Temperature

The hotness or coldness of a substance is measured by taking its temperature.

This temperature is measured on a scale that has 2 fixed points.

The Celsius scale is the most used scale.

Its two fixed points are 0’ C (melting point of pure ice + freezing point of pure water)
and 100’ C (boiling point of pure water).

In between these two values, the scale is divided into 100 units or degrees.

The thermometer compares the temperature of the substance, with the freezing and
boiling point of water.

The lowest possible temperature is -273’ C (known as absolute zero)
Liquids in Thermometers

Alcohol or Mercury are the common liquids used inside thermometers.

If the bulb of the thermometer is placed in a hot substance, the liquid
inside expands and spreads up inside the tube. The level it reaches depends on the
hotness of the substance, and the temperature can be read in the scale.

If the bulb is placed in a cold substance, the liquid inside contracts and backs down the
tube. The level it settles can be read from the scale.