Three key measurements are length, mass, and time. Measurements are made using standardized units, with scientists worldwide using the International System of Units (SI units). The standard SI units are the meter for length, kilogram for mass, and second for time. Various instruments are used to accurately measure these quantities, including rulers, balances, and stopwatches. Temperature is also an important measurement, with the most common scale being Celsius and key reference points of 0°C and 100°C. Liquids like mercury and alcohol are commonly used in thermometers due to their freezing and boiling points.

1. Measurements

2. • Three things are measured in many investigations, they are:
-Length
-Mass
-Time
• Any measurement is made in units
• Example: unit of length is centimeter

3. • There is an international system of
units that is used by scientists
throughout the world.
• This is known as the Le Systeme
international d’Unites.
• The units in this system are known
as SI units

4. Measuringlength
The standard SI unit for measuring length is metre (m).
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

5. MeasuringMass
The standard SI unit for measuring mass is kilogram (kg).
Unit Symbol Number of
kilograms
megaton Mt 1000 000 000 kg
tonne t 1000 kg
kilogram kg 1 kg
gram g 0.001 kg
milligram mg 0.000 001 kg

6. Balance scales
Top pan balance
Spring balance

7. Measuringtime
The standard SI unit for measuring time is the second (s).
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

8. Accuracy of measurements
• You must place a ruler accurately when measuring length
• Reset a stopwatch before repeating time
• Balance is set at zero before a mass is put on it

9. Accuracy of measurements
• When taking a reading, the eye should be placed directly in
front of the pointer

10. MeasuringTemperature
 The hotness or coldness of a substance is
measured by taking its temperature.
 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.

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

12. Liquidsinthermometers
 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.

13. H.W
pages
160, 161, 162

14. C.W
pages
163 till 170