measurement lecture of chemistry

CHEMISTRY FOR TEXTILE1. Basic conceptsL1: Measurement

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MEASUREMENT In study of science we

frequently encounter such properties of materials which are to be assessed quantitatively. A few examples of such properties are weight, length, volume, temperature, voltage etc.

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PHYSICAL PROPERTEIS OF MATERIALSMechanical properties Tensile Strength Shear strength Fatigue Impact strength Bursting strength Tear Resistance Hardness Abrasion Resistance Peel strength

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PHYSICAL PROPERTIES OF TEXTILE MATERIALS Thermal properties

Thermal conductivity Heat capacity

Optical properties Reflection Refraction

Electrical properties Chemical resistance Weathering

Washing fastness Light fastness Rubbing fastness

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HOW WE MEASURE We measure quantities

using a suitable unit and measuring instrument.

For e.g. to measure 1 liter of milk we can use a measuring jug.

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UNITS OF MEASUREMENTBASIC UNITS IN METRIC SYSTEMMass LengthVolumeTimeTemperatueEnergy Amount of

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Kilogram Meter Liter Second

Kelvin joule Mole Second

MASS There many units for

measuring mass. There are also smaller

and larger units of each units.

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KilogramGramMilligramMicrogram

LENGTH Unit of length in SI

system is “meter”. There super and sub

units of meters to measure larger and smaller articles.

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VOLUME Volume can be measured

in liter, pound, gallon and many other units.

SI unit of volume is liter.

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MORE UNITS Force Pressure Work strength Current EMF light

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Newton Kg/m2

Newton - meter Kg/cm2

Ampere Volt Candela

UNCERTAINTY IN MEASUREMENT Measurement of any

property is made using an instrument which always has some limitations.

This weighing balance cannot measure any quantity smaller than 0.1 mg.

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UNCERTAINTY IN MEASUREMENT

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Burette is used to measure volume of liquid. In a 50 ml burette distance between two lines measure 0.1 ml. Any quantity smaller than 0.1 ml cannot be measured on this burette with accuracy.

UNCERTAINTY IN MEASUREMENT In case of

burette if the meniscus of liquid stays between two lines, accurate measurement cannot be made.

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SIGNIFICANT FIGURES

To show and understand uncertainty in measuremet the results of any measurement are expressed mathematically up to a certain number of decimal digits. These decimal digits are called significant figure.

Depending on the accuracy required, the number of decimal digits varies.

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0.1 0.01 0.001 .0001 Etc.

CONVERSION OF UNITS

There are different types of units in use throughout the world.

One type of units can be converted to another type which is equivalent to the previous one.

Kilometers to miles Meter to yard Centimeters to

inches Kg and g to pound Liter to gallons ml to liquid ounce Centigrade to

fahrenheight

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CONVERSION FACTORS

Conversion factor is a mathematical figure which converts a quantity in certain measurement system to units of another measurement system.

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1 kg = 2.2005 lb Hence to convert kg

to pound, the number of kg’s must be multiplied by 2.2005 for example:

2 kg is = (2 x 2.005= 4.014 lb)

CONVERSION FACTORS

Temperature in degree centigrade can be converted to fahrenheight

°C to °F°F = 9/5 x °C + 32

°F to °C °C = 5/9 x (°F – 32)

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CONVERSION FACTORS

Energy in Joule can be converted to calorie and vice versa

1 cal = 4.184 J

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CONVERSION FACTORS

Length in meters and kilometers can be converted to feet, yards or miles

1 meter = 39 inches

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ATOMIC AND MOLECULAR WEIGHT

Atomic weight is in fact not a weight. This is in fact a comparison of the size of atoms.

In the same way molecular weight is the total of atomic weights of all the atoms in a molecule.

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EQUIVALENT WEIGHT

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