Chapter 2

- Introduction to instruments and units used

1. Observation is a science process skill used in investigations2. Observations •Qualitative

•Quantitative

3. Qualitative observations

-5 senses-descriptions e.g. It is smooth.

The gas is pungent and colourless. It is moving quickly.

4. Quantitative observation-accurate measurements using instruments

e.g metre rule, measuring tape, vernier calipers, measuring cylinder, pipette, burette, electronic balance, spring balance

1. A physical quantity is a quantity 1. A physical quantity is a quantity which can be measuredwhich can be measured..e.g. length, area, volume, time, e.g. length, area, volume, time, temperature, masstemperature, mass

2. A non-physical quantity is one 2. A non-physical quantity is one which cannot be measured.which cannot be measured.e.g beauty, kindness, humour, sadness, e.g beauty, kindness, humour, sadness, untidinessuntidiness

Physical Quantities

Exploring Science 1-CDIS

Physical QuantityPhysical Quantity SI Unit SI UnitSymbolSymbol

lengthlength metremetre m

timetime secondsecond s s

massmass kilogramkilogram kg kg

weight newton N

Measuring Measuring LengthLength

1 m =1 m = 100

1 cm = _____ mm1 cm = _____ mm10

1 cm = 1 cm = m== 0.01 m

SI unit:SI unit: metre (m)Smaller units:

millimetre (mm) andcentimetre (cm)

1 100

cmcm 1 m =1 m = 1000 mmmm

1 mm = 1 1000 m

--metre rule and measuring tapemetre rule and measuring tape-accuracy of 0.1 cm (1 mm)-accuracy of 0.1 cm (1 mm)

Instruments for LengthInstruments for LengthInstruments for LengthInstruments for Length

External Caliper - accuracy of 0.1 External Caliper - accuracy of 0.1 cmcm

Instruments for LengthInstruments for LengthInstruments for LengthInstruments for Length

Internal Caliper - accuracy of 0.1 Internal Caliper - accuracy of 0.1 cmcm

External CalipersExternal CalipersExternal CalipersExternal CalipersMeasuring the external diameter of a beakerMeasuring the external diameter of a beaker

External CalipersExternal CalipersExternal CalipersExternal CalipersMeasuring the external diameter of a beakerMeasuring the external diameter of a beaker

Internal CalipersInternal CalipersInternal CalipersInternal CalipersMeasuring the internal diameter of a beakerMeasuring the internal diameter of a beaker

Internal CalipersInternal CalipersInternal CalipersInternal CalipersMeasuring the internal diameter of a beakerMeasuring the internal diameter of a beaker

-for measuring short lengths-for measuring short lengths-accuracy of 0.01 cm -accuracy of 0.01 cm or 0.1mmor 0.1mm

Vernier CalipersVernier CalipersVernier CalipersVernier Calipers

Physics - A Course for ‘O’ Level

Federal

Physics - A Course for ‘O’ Level

Federal

is an error in a measurement due to the eye not is an error in a measurement due to the eye not being in the correct position when taking a being in the correct position when taking a reading.reading.

For accurate measurements using the metre For accurate measurements using the metre rule or measuring tape, rule or measuring tape, the eye must be placed vertically above the the eye must be placed vertically above the mark being read to prevent parallax error.mark being read to prevent parallax error.

Parallax ErrorParallax ErrorParallax ErrorParallax Error

- accuracy of 0.001 cm- accuracy of 0.001 cm

Micrometer Screw Gauge

anvil

ratchet

frame

spindle

sleeve

thimble

Micrometer Screw Gauge

- placing the eye vertically above the marking - placing the eye vertically above the marking on the scale to be read.on the scale to be read.

- placing a thick ruler on its edge beside the - placing a thick ruler on its edge beside the object to be measured so that the scale is object to be measured so that the scale is touching ittouching it

- using a thin ruler so that the scale is touching - using a thin ruler so that the scale is touching the object to be measuredthe object to be measured

When using a ruler, parallax errors

can be avoided by