c5_water & solution/form2
TRANSCRIPT
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CHAPTER 5: WATER AND
SOLUTION
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Physical Characteristicsof Water
Pure water colorless ,odorless & Tasteless
Can exist in three states;i) solid ii) Liquid iii) GasConsist of many tiny particlescalled water molecules (KineticTheory)
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The changes of states of water
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Freezing point of Water
The temperature at whichwater freezes into ice.
Freezing point 0oC
The temperature isconstant at 0 oC throughoutthe freezing point
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Determining the freezing point ofwater
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Cooling graph of water
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Boiling point of water
The temperature at whichwater boils and becomes
steamBoiling point 100 0C
The temperature isconstant at 100 0C .
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Determining the boiling point ofwater Thermometer
Flat-bottomed flask
100cm 3 of distilledwater
Glass tube
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Heating graph of water
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Physical
characteristicsof water
Expand uponfreezing
Freezing point is 0 o C Boiling point is 100 o C
Poor electricalconductor
Odorless, colorless,tasteless
Has density of 1g
per cm3
at 4o C
Poor thermalconductor
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Effects of impurities in water
Impurities in water can change thephysical characteristics of water .Examples; Sea water
- Tastes salty (dissolved saltsin it)
- Lower freezing point- Higher boiling point
- High density
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Composition of Water
Water is a compound whichis made up of the elements
hydrogen & oxygenEach water molecule has 2
hydrogen atoms bound toone oxygen atom
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Model of water molecule
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Questions
1. States the physical characteristics of watera) colour ___________________
b) Smell
___________________c) Taste ___________________d) Density- ___________________
e) Freezing point- ______________f) Boiling point - _______________
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2. Water exists in three states whichare ______, __________ and
__________.
3.Water is a _______ made up of one
atom of oxygen and two atoms of __________.
4. Impurities in water cause the
boiling point of water to___________and the freezing point of waterto________
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ElectrolysisTo determine thecomposition of water
Electric current is passedthrough water so that water
break down into hydrogengas and oxygen gas
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A B
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Observation
Measuringcylinder
A B
Volume of gasafter 5
minutes (cm 3)
8.0 4.0
Test for gas The gasexplode witha pop sound
The gasrelight theglowingsplinter
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DiscussionThe gas collected in A explode with pop sound shows the presence ofhydrogenHydrogen released at the negativeelectrode (cathode )The gas collected in B relight theglowing splinter shows the presence ofoxygenOxygen gas released at the positive
electrode (Anode )
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Conclusion
The ratio of the volume ofthe oxygen gas to hydrogen
gas is 1:2A molecule of water is made
up of one atom of oxygen and two atoms of hydrogen
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Evaporation of Water
Process by which a liquid
changes into its vaporEvaporation can occur at
any temperature
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Model showing the
evaporation of water
Water
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The rate of evaporation of
water is affected bythe following factors;
The HumidityThe temperature of thesurrounding
The surface area of the waterThe movement of air (wind)
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Evaporation&
Boiling
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Differences betweenEvaporation & Boiling
Evaporation Aspect BoilingOn the
surface of theliquid
Site of
process
Throughoutthe liquid
Occurs at alltemperaturebelow 100 oc
Temperature Occurs at the100 oc
A slow process Rate A fast process
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APPLICATION OF
EVAPORATIONOF WATER IN
DAILY LIFE
DRYINGCLOTHES
DRYING HAIR
PRESERVATION OFAGRICULTURAL PRODUCT
PROCESSING OFFOOD
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SOLUTION AND
SOLUBILITY
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Solution
Exist all around usExamples Oceans, rivers &minerals waterThe dissolved substance iscalled the solute.
The substance that dissolvesthe solute is called thesolvent.
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Solute Solution
D i s s o l v e s i n a s o l v e n t
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DILUTE,CONCENTRATED
AND SATURATED
SOLUTION
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DILUTE SOLUTION Has very little solute Can dissolve a lot more solute
CONCENTRATED SOLUTION Has a lot of solute in it Can dissolved a little more solute
SATURATED SOLUTION Has the maximum solute Cannot dissolve any more solute
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Solution and Suspension
SolutionTransparent and clearMaybe colorless orcolored
HomogeneousE.g. salt solution
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Suspension
Has a lot of suspendedparticlesAppears cloudyNon-homogeneous
orheterogeneousE.g. muddy water
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SolubilityThe solubility of solutedepends on the
a) nature of the solventb) nature of the solutec) temperature
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Water as Solvent
Water is known as the universal solvent
Organic SolventOrganic compoundscontaining carbon that used
to dissolves solutesExp; alcohol, turpentine,acetone
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Acid
&
Alkali
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Acids
The word acid comes from theLatin word acidus which meanssour.
Food containing Acid
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Food Acid in FoodGrapes Tartaric acid
Apples Malic acid
Oranges, lemons Citric acidTomatoes Salicylic acid
Vinegar Acetic acid(ethanoic acid)
Yoghurt drinks Lactic acid
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PROPERTIES OFACIDS
Sour Test
PH valuesless than 7
Corrosive
React with
metal
Turns blue litmuspaper to red
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ALKALI
Often used in many
household cleanerssuch as in bath, sink
and glass cleaners
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Properties of alkaliHas bitter tasteHas a soapy feelHas a pH greater than 7Has corrosive natureTurns red litmus paper toblue
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PH Scale
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NEUTRALISATIONChemical reaction in which anacid and alkali react to form a
salt and water .
To neutralize an acid or alkali completely, we use a methodcalled Titration.
Acid + Alkali Salt + Water
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Titration
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WATER PURIFICATION
Water can be purifiedeither by
a) Boilingb) Chlorination
c) Filtrationd) Distillation
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a) BoilingHigh temperature duringboiling kills of themicroorganism.Used to make water safefor drinking at homeHowever, boiling does notremove suspended
particles
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b) Chlorination Chlorine is added towater.
The chlorine kills micro-organisms in the water.
Chlorination is used totreat the water inswimming pools.
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c) Filtration
Method involvespassing waterthrough a filter toremove suspendedparticles.
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Water Purification Equipment
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d) DistillationTo obtained pure water.Does not contain anydissolved substances.Free from anysuspended solid µ-organism.
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DISTILLATION
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WATER SUPPLY SYSTEM
Usage ofwater
Direct or in-streamuse
Domesticuse
Agricultural use Industrialuse
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WATER TREATMENT
PLANTRaw water for thewater supply isobtained from stream ,rivers and rainwater .
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Water Treatment Process
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Conservation &
Preservation of waterCleaning up polluted river
Proper disposal of wastePromoting public
awarenessLaws