INTRODUCTION:INTRODUCTION:MATTER AND MEASUREMENTMATTER AND MEASUREMENT

Chapter 1Chapter 1

Classifications of MatterClassifications of Matter

SolidSolid rigid, definite volume and shape. rigid, definite volume and shape.

LiquidLiquid relatively incompressible fluid, relatively incompressible fluid, definite volume, takes shape of definite volume, takes shape of container.container.

GasGas easily compressible fluid, no fixed easily compressible fluid, no fixed volume or shape.volume or shape.

The three forms of matter

- solid, liquid and gas -

are referred to as the states of matter.

Pure Substances and MixturesPure Substances and Mixtures

A purepure substancesubstance is a kind of matter that cannot be separated into other kinds of matter by any physical process.

A A mixturemixture is a material that can be is a material that can be separated by physical means into two or separated by physical means into two or more substances.more substances.

Get two types of mixtures:– A homogeneous mixture is a mixture that

is uniform in its properties throughout given samples.

– A heterogeneous mixture is a mixture that consists of physicallly distinct parts, each with different properties.

Note : A phase is one of several homogeneous materials present in the portion of matter under study.

Separation of MixturesSeparation of Mixtures

Examples to separate heterogeneous mixtures:

- Magnetic

- Filtration

Examples to separate homogeneous mixtures:

- Distillation

- Chromatography

Basic Distillation SetupBasic Distillation Setup

Separation of Mixtures by Paper Separation of Mixtures by Paper ChromatographyChromatography

Separation of Mixtures by Column Separation of Mixtures by Column ChromatographyChromatography

Elements and CompoundsElements and Compounds

Laviosier defined an element as a substance that cannot be decomposed by any chemical reaction into simpler substances.

A compoundcompound is a substance composed of two or more elements chemically combined..

A A physical changephysical change is a change in the form of is a change in the form of matter but not in its chemical identity.matter but not in its chemical identity.

Example:Example:- Dissolution of salt.- Dissolution of salt.

- Distillation- Distillation

A chemical changechemical change or chemical reaction is a change in which one or more kinds of matter are transformed into a new kind of matter or several new kinds of matter.

Example:- The rusting of iron.

Physical and Chemical ChangesPhysical and Chemical Changes

Intensive vs Extensive PropertiesIntensive vs Extensive Properties

Extensive property:Extensive property: is dependent on the is dependent on the amount of substance in a system. amount of substance in a system.

eg. mass, volume etc.eg. mass, volume etc.

Intensive property:Intensive property: is NOT dependent on is NOT dependent on the amount of substance in a system. the amount of substance in a system.

eg. density, temperature, pressure etc.eg. density, temperature, pressure etc.

In flow-diagram form:In flow-diagram form:

Physical MeasurementsPhysical Measurements

Chemists characterise and identify substances by their particular properties. To determine many of these properties requires physical measurements.

In a modern chemical laboratory, measurements often are complex, but many experiments begin with simple measurements of mass, volume, time, and so forth.

Units of Measurement Units of Measurement

Any measurement consists of three interlinked concepts:

a measured a measured numbernumbera a unitunita measure of the a measure of the uncertaintyuncertainty

If you repeat a particular measurement, you usually do not obtain precisely the same result, because each measurement is subject to experimental error.

The Length of a Steel RodThe Length of a Steel Rod

SI Base units and SI PrefixesSI Base units and SI Prefixes

The International System or SI was The International System or SI was adopted in 1960 and is a particular choice adopted in 1960 and is a particular choice of metric units.of metric units.

There are seven base units from which all There are seven base units from which all other units can be derived.other units can be derived.

In SI a larger or a smaller unit for a In SI a larger or a smaller unit for a physical quantity is indicated by a SI physical quantity is indicated by a SI prefix.prefix.

SI Base UnitsSI Base Units

SI PrefixesSI Prefixes

Length, Mass and TimeLength, Mass and Time

Self study

TemperatureTemperature

Converting from one temperature Converting from one temperature scale to anotherscale to another

K273.15TT CK

F3259TT o

CF

C32T95T o

FC

Example:Example:

In winter the average low temperature of interior Alaska is –30°F. What is the temperature in degree Celsius? And in Kelvin?

Derived SI unitsDerived SI units

AreaArea

Once base units have been defined for a Once base units have been defined for a system of measurement, then other units system of measurement, then other units can be derive.can be derive.

SI unit of area = (SI unit of length) x (SI unit of length)

VolumeVolume

Volume is defined as length cubed and has the SI unit of cubic meter (m3).

1 L = 1 dm3    and    1 mL = 1 cm3

DensityDensity

The density of an object is its mass per unit volume.

d =m

v

Suppose an object has a mass of 15.0 g and a volume of 10.0 cm3

Which is more dense?

Calculating the Density of a SubstanceCalculating the Density of a Substance

Alternate Example

Oil of wintergreen is a colourless liquid used as a flavouring. A 28.1 g sample of oil of wintergreen has a volume of 23.7 ml. What is the density of wintergreen?

Using Density to relate Mass and VolumeUsing Density to relate Mass and Volume

A sample of gasoline has a density of 0.718 g/mL. What is the volume of 454 g of gasoline?

d =mv

Alternate Example

The The advantages advantages of this are:of this are:– The The correct unitscorrect units for the answer follow for the answer follow

automatically.automatically.– ErrorsErrors are more easily identified. are more easily identified.

eg. when the final units are nonsenseeg. when the final units are nonsense

Dimensional analysis the method of calculation in which one carries along the units for quantities

Dimensional AnalysisDimensional Analysis

Example

Calculate the volume, V, of a cube, given s, the length of one of its sides.

V = s3 , if s = 5.00 cm

NO guesswork in the final units

Converting Between Units.Converting Between Units.

What is 5 liters in terms of cm3?

We know: 1 mL = 1 cm3

Converting Units: Metric Unit to Metric Converting Units: Metric Unit to Metric UnitUnit

Alternate Example

A sample of sodium metal is burned in chlorine gas, producing 573 mg of sodium chloride. How many grams is this? How many kilograms?

573 mg

An experiment calls for 54.3 mL of ethanol. What is the volume in cubic meters?

Converting Units: Metric Volume to Converting Units: Metric Volume to Metric VolumeMetric Volume

Number of Significant FiguresNumber of Significant Figures

Number of significant figures number of digits reported for the value of a measured or calculated quantity, indicating the precision of the value.

Scientific notation is the representation of a number in the form:

A x 10A x 10nn

eg. 3x10eg. 3x10-8 m-8 m

Sig. Fig. Rules!Sig. Fig. Rules! All digits are significant except zeros at All digits are significant except zeros at

thethe beginningbeginning of the number and possibly of the number and possibly terminal zeros.terminal zeros.eg. 0.00231eg. 0.00231 5900059000

Terminal zeros ending at the right of the Terminal zeros ending at the right of the decimal point are significant.decimal point are significant.eg. 0.2540eg. 0.2540

Terminal zeros in a number without an Terminal zeros in a number without an explicit decimal point or may not be explicit decimal point or may not be significant.significant.

Determine the number of sig. fig.’s in the following:Determine the number of sig. fig.’s in the following:

27.53 cm

39.240 cm

102.0 g

0.00021 kg

0.06080 L

0.0002 L

Sig. Fig.’s in CalculationsSig. Fig.’s in Calculations

Multiplication and division:Multiplication and division:– result must have as many sig. fig.’s as result must have as many sig. fig.’s as

there are in the measurement with the there are in the measurement with the least number of sig. fig.’s.least number of sig. fig.’s.

Addition and Subtraction:Addition and Subtraction:– result must have same number of result must have same number of

decimal places as there are in the decimal places as there are in the measurement with the measurement with the least number of least number of decimal placesdecimal places..

Suppose you have a substance believed to be cis-platin and, in an effort to establish its identity, you measure its solubility.

You find that 0.0634 g of the substance dissolves in 25.31 g of water.

The amount dissolving in 100.0 g is :

100.0 g of water x 0.0634 g cis-platin25.31 g of water

Example:

In performing the calculation 100.0 X 0.0634 ÷ 25.31,

the calculator display shows 0.2504938.

We would report the answer as

because the factor has the least number of significant figures

Exact Numbers & RoundingExact Numbers & Rounding An An exact numberexact number is a number that arises is a number that arises

when you count items or sometimes when when you count items or sometimes when you define a unit.you define a unit.

The conventions of significant figures do The conventions of significant figures do NOT apply to exact number.NOT apply to exact number.eg. suppose you want the total mass of 9 coins when each coin has a mass of 3.0 grams.The calculation is:

RoundingRounding is the procedure of dropping is the procedure of dropping nonsignificant digits in a calculation and nonsignificant digits in a calculation and adjusting the last digit reported.adjusting the last digit reported.

ExampleExample

Perform the following calculations, roundingthe answers to the correct number of sig. fig.’s.

5.8914

1.289 x 7.28

One more ExampleOne more Example

92.34 x (0.456 - 0.421) =