Introduction to Measurement

Junior Science

Lesson Objectives

• Understand the importance of measurement.

• Know the principles behind the SI System (metric system).

• Identify the units for measuring –Length, Mass, Area and volume.

• Be able to convert between the various metric units.

• List the types of measurement errors which can be made when carrying out investigations.

Why do we Measure?

Measurement gives a base to understand the world around us.

We are "measuring" things to understand them one way or the other.

Measurement is the process of attaching a numeric value to an aspect of a natural phenomenon. For example: Weather (temperature, Pressure, Wind speed, Rain fall).

This enables us to form an opinion or make a comparison against something else we know

Temperature

Mass

Length

Volume

Time

Area

Things we Measure

Measurement Systems

• Two Systems of measurement in use today include

– International System of Units (SI), the modern form of the metric system.

– The Imperial or English system.

Imperial System

• The English system of measurement has been in use for a very long time.

• It involves units such as pounds and ounces for weight, miles, yards, feet and inches for distance, and pints and gallons for volume.

• It’s not a simple or intuitive system.

Systeme International (SI) System

• During the French Revolution (1789–1799), the French Academy of Sciences was asked to “deduce an invariable standard for all the measures and all the weights”.

• The Academy decided on two founding principles. The system would be:

– based on scientific observation

– a decimal or base 10 system.

• The metric system is simpler with a series of basic units, one for each of distance, mass, and volume, and a series of prefixes to tell you what multiple of the basic unit is being used.

The Systeme International (S.I) units

• Length (km, m, cm, mm)

• Mass (kg, g, mg)

• Volume (L, ml, cm3)

• Area (m2, cm2)

• Time (s)

• Temperature (oC Celsius, oK Kelvin)

Length

• Standard unit of measure is the meter (m)

• 1m = 100cm (centimeter)

• 1cm = 10mm (milimeter)

• 1000m = 1 km (kilometre)

Measuring Length

Length is the straight line distance between two points.

The SI unit for length is the meter (m)

• Measuring instruments include:

–Ruler

–Opisometer

–Vernier Calipers

–Trundle Wheel

The Opisometer

An opisometer, also called, is an instrument for measuring the lengths of arbitrary small curved lines.

Trundle Wheel

• Trundle wheel is used for measuring longer lengths accurately

– Measuring out a pitch length

and width or running track.

• The pointer on the wheel helps to measure distances and Incorporates a clicker that can be adjusted from every 10cm and to a metre.

The Vernier Calipers

• The Vernier Caliper is a precision instrument that can be used to measure internal and external distances extremely accurately.

1. The first reading is taken where the zero in the sliding scale meets the fixed scale.2. The second reading is taken where the sliding scale matches the fixed scale exactly.

1. Can you find the exact reading above?

ANSWER : 3.7mm

MassThe mass of an object is the amount of matter in

it.• Standard unit of measure is the

kilogram (kg)

• Mass can be measured using an electronic balance.

• Mass is measured in kilograms (kg) or grams (g).

• 1kg = 1000g

Area

The area is the amount of surface that covered an object.

• To measure the area of an regular object we multiply the length x width.

• Area is normally measured in units called squared metres (m2) or squared centimetres (cm2).

Area

• The area of an irregular object can be estimated using graph paper.

• When measuring count the whole squared and any square more that 50%

1cm2

Solid VolumeThe Volume of an object is the

amount of space it takes up.

For regular shaped objects we can use formula’s to calculate the volume.

Liquid VolumeThe Volume of an object is the

amount of space it takes up.

• To measure the volume of a liquid we use a measuring cylinder(graduated cylinder).

• Volume can be measured in units called cubic metres (m3)cubic centimetres (cm3), Litres (L) or millilitres (ml).

Using a Graduated Cylinder

• When reading the volume, the cylinder should be at rest on a bench and your eye should be level with the bottom of the meniscus.

Meniscus50

40

30

20

10

Measuring Liquid VolumeBurette, Pipette and Droppers

• To transfer a definite volume of liquid to a container we use a Burette or Pipette ordroppers.

Burette Pipette Dropper

Accuracy and Error

• All experiments are subject to some errors.

• The most common to occur are:

–Parallax errors

–Zero errors

–Reading errors

Parallax Errors

Occur when the eye is not placed directly

opposite a scale when the reading is take.

31 32

31.431.45 31.5

Zero Error

This error occurs when the measuring instrument does

not begin with zero.

Reading Error

This occurs when you are required to guess the

reading from a scale when the

reading lies between the

scales of division.

Summary• Mass is the quantity of matter in a substance measured in grams or kilograms.

An electronic balance is used to measure the mass of an object.

• Length is measured in metres (m), centimetres (cm) or kilometres (km).

Length can be measured using a metre stick, a vernier callipers (to measure the diameter of an object), or a trundle wheel or opisometer (for curved lengths, e.g. curved roads on a map).

• The area of an object is the amount of surface it has measured in m2, cm2 or km2.

• For a regularly shaped object (like a square or a rectangle), area is equal to the length multiplied by the width.

• Volume is the amount of space an object takes up measured in L, m3, cm3 or km3

• The volume of an object is equal to its length multiplied by its width multiplied by its height .

• A graduated cylinder, burette or pipette will accurately measure volume of liquids.