slide1 n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Measuring Length & Volume PowerPoint Presentation
Download Presentation
Measuring Length & Volume

Loading in 2 Seconds...

play fullscreen
1 / 40

Measuring Length & Volume - PowerPoint PPT Presentation


  • 134 Views
  • Uploaded on

Measuring Length & Volume. Science is based on empiricism - a search for knowledge based on experimentation and observation. Observations can be either qualitative or quantitative. Qualitative observations describe while quantitative observations measure.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Measuring Length & Volume' - selia


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

Measuring

Length & Volume

slide2

Science is based on empiricism- a search for knowledge based on experimentation and observation.

Observations can be either qualitative or quantitative.

Qualitative observations describe while quantitative observations measure.

slide3

In science, quantitative observations are preferred because they can be clearly communicated.

They are normally measured according to standard procedures.

Measuring allows us to make accurate observations that are required in scientific work as well as in everyday uses.

slide4

Instruments have been invented to make more accurate measurements.

Some instruments which you will use to measure with are the- metre rule- vernier calipers- burette- pipette- measuring cylinder

- Micrometer screw gauge.

slide5

Physical Quantities, SI Units and Prefixes

A physical quantity is a quantity which can be measured.Examples of some of them are length, volume, mass, time, temperature, etc.

A non-physical quantity is one which cannot be measured.Examples of some of them are beauty, kindness, humour, sadness, untidiness, etc.

slide6

Since 1960, scientists from different parts of the world have agreed to adopt a single system of units called the SI Units (SI stands for Système International d’Unités in French). This system is an adaptation of the metric system.

There are altogether seven basic quantities: length, mass, time, electric current, thermodynamic temperature, luminous intensity and amount of substance.

slide7

All the other physical quantities are derived from the seven basic quantities.For example, area, volume, speed.

slide8

The International System of Units (SI units)

Out of these seven basic quantities, only five will be covered at your level.They are length, mass, time, electric current and temperature.

slide9

Prefixes are used to change them by factors of ten into smaller or bigger units.

Prefix Symbol Factor

micro  10-6 one millionth

milli m 10-3 one thousandth

centi c 10-2 one hundredth

deci d 10-1 one tenth

kilo k 103 one thousand times

mega M 106 one million times

slide11

Class Work:

Convert the following to SI unit:

(a) 24 km = _________ m(b) 55 cm = _________ m(c) 56 MJ = _________ J(d) 9.8 g = _________ kg(e) 35 mg = _________ kg(f) 77 s = _________ s

24000

0.55

56000000

0.0098

0.000035

0.000077

slide12

Measurement of Length

Length is the distance between two points.

SI unit: metre, m

1 m = 100 cm1 cm = 10 mm

Short distance - cm or mmLong distance - km

slide13

Metre rule

This instrument is commonly used in the laboratory to measure the lengths of objects such as wires or distance between two points.

Metre rules are graduated in millimetres therefore readings taken from a metre rule should be given to the nearest millimetre.

slide14

If a metre rule is thick, it should be placed so that the scale is as near to the object as possible so that readings can be taken without parallax error.

slide15

When taking readings from the metre rule, make sure that the line of vision is perpendicular to the scale so as to avoid parallax error.

slide16

Parallax error

For accurate measurements using the metre rule, the eye must be placed vertically above the markings of the metre rule to avoid parallax error.

Parallax errors are errors due to the incorrect positioning of the eye and the object not touching the markings of the scale.

slide18

Parallax errors can be avoided by

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

- placing the metre ruler on its edge beside the object to be measured so that the scale is touching it.

- using a thin rule so that the scale is touching the object to be measured.

slide21

Calipers

External Caliper- accuracy of 0.1 cm

Internal Caliper- accuracy of 0.1 cm

slide22

External Calipers

Measuring the externaldiameter.

slide23

Internal Calipers

Measuring the internaldiameter.

slide24

Vernier Calipers

The vernier calipers is most commonly used for accurate measurement of up to ±0.1 mm or ±0.01 cm.

By means of a vernier scale, the second decimal place in cm can be obtained without having to estimate fractions of a division using the eye.

slide25

Vernier calipers have a set of inside jaws, outside jaws and a tail.

The inside jaws are used for measuring internal diameters, the outside jaws is for measuring externaldiameter while the tail isfor measuring depth.

slide27

Micrometer Screw Gauge

The micrometer screw gauge is used to give very accurate measurements of length up to 25 mm. It has an accuracy of ±0.01 mm (or ±0.001 cm).

slide28

Measurement of Volume

Volume is a measure of the space occupied by a substance.

SI unit: cubic metre, m3

1 km3 = 1000 000 000 m31 cm3 = 0.000 001 m31 mm3 = 0.000 000 001 m3

slide29

r

r

l

h

h

l

l

l

b

Some objects have regular shapes, for example, books, basketballs, pyramids and soft-drink cans. The volume of regular-shaped objects can be calculated using formulae.

Volume of a cube = l3Volume of a rectangular block = l  b  hVolume of a sphere = 4/3 r3Volume of a cylinder =  r2 h

slide30

pipette

burette

Instruments commonly used in the laboratory for measuring volume of liquids include the measuring cylinder, burette, pipette and volumetric flask.

Liquids are drawn into a pipetteby means of a pipette filler up to|a mark showing the exact volumeof a liquid in the pipette. Suckingby mouth is not recommendeddue to safety and hygiene reasons.

slide31

When using a measuring cylinder,readings are taken to the nearesthalf-division.

When reading, the measuring cylindermust not be held in hand. It must beplaced on a horizontal bench.

slide32

Meniscus reading

When you pour water into a measuring cylinder and place it on the bench or any flat surface, you will observe that the water surface is curved.

The meniscus of most liquids curves downwards. The correct way to read the meniscus is to position the eye at the same level as the meniscus.

slide33

The mark corresponding to the bottom of the meniscus is taken as the reading.

The meniscus of mercury curves upwards. The correct reading is the mark that corresponds to the top of the meniscus.

slide34

When taking readings from the measuring cylinder, the bottom of the water meniscus is read horizontally at the eye level to avoid parallax error.

slide35

Measuring the volume of a small irregular-shaped object

1. Partly fill a measuring cylinder with water. Observe and record the initial water level, V0, in the measuring cylinder.

2. Tie the irregular-shaped object with a piece of string. Lower it gently into the measuring cylinder so that it is completely covered with water. Observe and record the final water level, V1.

slide36

V1

V0

3. The volume of the irregular-shaped object, V, is the difference between the two water level readings and is given V = V1 - V0.

slide37

Measuring the volume of a small irregular-shaped object that floats on water

- use a sinker (an object that sinks)

slide38

Measuring the volume of a large irregular-shaped object

1. Fill the displacement can with water until excess water flows out of its spout into a beaker. Remove the beaker when water stops flowing into it.

slide39

2. Place an empty measuring cylinder below the spout of the displacement can. Tie the irregular-shaped object with a piece of string. Lower it gently into the can until it is completely immersed in the water.

slide40

3. When the water stops flowing into the measuring cylinder, observe and record the volume of water displaced by the object and collected in the measuring cylinder. The volume of the water in the measuring cylinder is equal to the volume of the irregular-shaped object.