1. What is Measurement?
Measurement means finding out how long, heavy, hot, cold, or large something is by comparing it with a standard unit.
For example:
- We measure the length of a pencil in centimetres (cm).
- We measure the mass of a bag in kilograms (kg).
- We measure temperature in degrees Celsius (°C).
Why do we need measurement?
Measurement helps us to:
- Compare objects.
- Buy and sell things correctly.
- Measure distances.
- Find the mass of objects.
- Check temperature.
- Carry out experiments accurately.
2. History of Weights and Measures
Long ago, people did not have standard units like metres and kilograms. They used things that were easily available around them.
🖐️ Old methods of measuring length
People used body parts such as:
- Handspan – distance from the tip of the thumb to the tip of the little finger when the hand is stretched.
- Cubit – distance from the elbow to the tip of the middle finger.
- Foot – length of a person's foot.
- Finger width – width of a finger.
The problem was that people's body parts were different sizes. Therefore, measurements were not always the same.
⚖️ Old methods of measuring mass
People also used objects such as:
- Stones
- Seeds
- Grains
- Metal weights
Different places used different weights, which made trade difficult.
📏 Need for standard units
As people travelled and traded more, they needed measurements that everyone could understand.
The metric system was developed to provide standard units.
Today, the International System of Units (SI) is widely used.
Examples:
- Length → metre (m)
- Mass → kilogram (kg)
- Temperature → degree Celsius (°C) is commonly used in everyday life.
3. Making Sense of Measurement
Every measurement has two parts:
Number + Unit
For example:
5 metres
Here:
- 5 = number
- metre = unit
Saying only "The table is 5 long" does not make sense. We must say "The table is 5 metres long."
Standard and Non-standard Units
Non-standard units are units that can vary from person to person.
Examples:
- Handspan
- Footstep
- Arm length
Standard units are fixed and accepted everywhere.
Examples:
- metre
- centimetre
- kilogram
- litre
Important idea
👉 Standard units make measurements accurate and easy to compare.
4. Measurement of Length
Length tells us how long or short something is.
Common units of length
Unit
Symbol
Used for
Millimetre
mm
Very small lengths
Centimetre
cm
Pencil, book, ruler
Metre
m
Room, height, furniture
Kilometre
km
Distance between places
Conversion of length
1 centimetre = 10 millimetres
1 metre = 100 centimetres
1 kilometre = 1000 metres
Examples
- Thickness of a coin → about a few millimetres
- Length of a pencil → about 15 cm
- Height of a door → about 2 m
- Distance between two cities → measured in kilometres
Instruments used
📏 Ruler/scale → small lengths
📏 Measuring tape → longer or curved objects
🚗 Odometer → distance travelled by a vehicle
How to measure correctly
- Place the ruler along the object.
- Start from the zero mark.
- Keep the ruler straight.
- Read the mark at the other end.
- Write the number with its unit.
5. Measurement of Mass
Mass tells us how much matter an object contains.
In everyday language, we often say something is "heavy" or "light", but scientifically we measure its mass.
Common units of mass
Unit
Symbol
Example
Milligram
mg
Very small quantities
Gram
g
Small objects
Kilogram
kg
Vegetables, school bags
Tonne
t
Very heavy objects
Conversions
1 gram = 1000 milligrams
1 kilogram = 1000 grams
1 tonne = 1000 kilograms
Examples
- A medicine tablet → measured in milligrams
- A chocolate bar → measured in grams
- A school bag → measured in kilograms
- A truck → its load may be measured in tonnes
Instruments for measuring mass
⚖️ Balance or weighing scale is used to measure mass.
Examples:
- Kitchen weighing scale
- Digital weighing scale
- Beam balance
Mass and weight
For Grade V, remember:
Mass tells us the amount of matter in an object.
Weight is related to the force of gravity acting on an object.
In everyday shopping, people commonly use the word weight when they mean mass.
6. Measurement of Temperature
Temperature tells us how hot or cold something is.
For example:
- Ice is very cold.
- Boiling water is very hot.
- Our body has a normal temperature around 37°C.
Unit of temperature
Temperature is commonly measured in degrees Celsius (°C).
The symbol for degree Celsius is °C.
Instrument used
🌡️ Thermometer is used to measure temperature.
Types of thermometers
1. Clinical thermometer
- Used to measure human body temperature.
- It usually measures temperatures around the range needed for the human body.
2. Laboratory thermometer
- Used in science experiments.
- It can measure a wider range of temperatures.
3. Digital thermometer
- Shows temperature on a digital display.
- It is easy to read.
Important temperatures
Situation
Approximate temperature
Ice melting
0°C
Normal human body
37°C
Water boiling
100°C
These values are approximate under standard conditions.
Safety while using a thermometer
- Handle a glass thermometer carefully.
- Do not use it as a toy.
- Do not put a laboratory thermometer in your mouth.
- Read the scale carefully.
7. Quick Revision
Remember these conversions:
📏 Length
- 10 mm = 1 cm
- 100 cm = 1 m
- 1000 m = 1 km
⚖️ Mass
- 1000 mg = 1 g
- 1000 g = 1 kg
- 1000 kg = 1 tonne
🌡️ Temperature
- Ice melts at about 0°C
- Normal body temperature is about 37°C
- Water boils at about 100°C
⭐ Key Words
Measurement: Finding the value of something using a unit.
Unit: A standard quantity used for measurement.
Length: The distance from one end of an object to another.
Mass: The amount of matter in an object.
Temperature: A measure of how hot or cold something is.
Thermometer: An instrument used to measure temperature.
Standard unit: A fixed unit accepted and used for measurement.
Metric system: A system of measurement based mainly on units such as metre, gram and litre.
🧠 Think and Answer
- Why did people need standard units of measurement?
- What problems could arise if everyone used their own handspan to measure length?
- Why do we write a unit along with a measurement?
- Which unit would you use to measure the distance between two cities?
- Which unit would you use to measure the mass of a school bag?
- Why is a thermometer used?
- What is the difference between a standard and a non-standard unit?
- Why should we start measuring a length from the zero mark of a ruler?
- Name two instruments used for measuring.
- Why is measurement important in our daily lives?