This document discusses different units used to measure physical quantities like length, mass, time, and temperature in the International System of Units (SI). It explains that the standard units for length, mass, and time are the metre, kilogram, and second, respectively. Smaller and larger units are defined as decimal multiples or submultiples of these standard units. Methods for measuring time, temperature, and different liquids used in thermometers are also outlined.

1. Measurements
Chapter 13.
Physics

2. Measuringlength
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. MeasuringMass
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. Measuringtime
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. MeasuringTemperature
 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. 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.