chemistry of water starter: the answer is ‘water’ what was the question? in the back of your...
TRANSCRIPT
Chemistry of Water Starter:
The answer is ‘Water’
What was the question?
• In the BACK of your book, write at least 3 questions (or as many as you can think of), to which the answer would be ‘Water’
SirWhat do I do if I’m
stuck?
Chemistry of WaterChemistry of WaterPGCE Science Booster Session
Graham Clarke
Chemistry of WaterChemistry of Water
Traffic light Activity
Not too SureDo not Know OK
Physical Properties of WaterHow the hardness of Water Occurs
Difference Between Temporary and Permanent Hard Water
Acids and Alkalis
Physical Properties of WaterHow the hardness of Water Occurs
Difference Between Temporary and Permanent Hard Water
Acids and Alkalis
Traffic Light Activity:
• RED – Don’t know
• AMBER - Unsure
• GREEN - OK
A Strange Molecule A Strange Molecule
Ubiquitous
No Taste No
Smell
NoForm
Transparent
WATERWATER
Water is EverywhereWater is Everywhere
80% Potato
75% Bacterium
74%Cow
65%Human
1.3 billionKm3
Water is so common we tend to overlook what an extraordinary
molecule it is
Water is so common we tend to overlook what an extraordinary
molecule it is
Phases of WaterPhases of Water
ICEICE WATERWATER STEAMSTEAM
If you compare water with similar molecules:
It should be a gas at room temperature
It should contract and become more dense when it freezes
If you compare water with similar molecules:
It should be a gas at room temperature
It should contract and become more dense when it freezes
Why?Hydrogen bonding
Why?Hydrogen bonding
Bonds between water molecules are very strong
Hydrogen bonds:Surface tension
Water is a liquid at room temperature
Hydrogen bonds:Surface tension
Water is a liquid at room temperature
HARD and SOFT WATER:HARD and SOFT WATER:
Many compounds dissolve in water without chemical
change but may have a variety of consequences! Some of these dissolved substances make the water
hard. This means the water does not readily give a
good lather Most hardness is due to water containing dissolved
calcium or magnesium compounds.
Hard water can be made softHard water can be made soft
• By: • removing the dissolved calcium and
magnesium ions. – If due to hydrogencarbonates it is removed by
boiling
• The addition of sodium carbonate (as 'washing soda' crystals), which dissolves and precipitates out the calcium or magnesium ions as their insoluble carbonates
Practical 1Practical 1
• Testing for Hardness of Water
Acids and AlkalisACIDSACIDS
Acids and AlkalisACIDSACIDS
2. acids have a pH less than 7, and turn universal indicator:
red (if strong) or yellow (if weak)
2. acids have a pH less than 7, and turn universal indicator:
red (if strong) or yellow (if weak)
1. acids are substances that form hydrogen ions, H+ (aq), when added to water
1. acids are substances that form hydrogen ions, H+ (aq), when added to water
Acids and AlkalisALKALISALKALIS
Acids and AlkalisALKALISALKALIS
2. alkalis have a pH more than 7, and turn universal indicator dark blue (if strong) or blue (if weak)
2. alkalis have a pH more than 7, and turn universal indicator dark blue (if strong) or blue (if weak)
1. alkalis are substances that form hydroxide ions, OH– (aq), when added to water
1. alkalis are substances that form hydroxide ions, OH– (aq), when added to water
The Arrhenius definition of an acid and a base:Acids - substances that when dissolved in water
release H+ ions Bases - substances that when dissolved in water
release OH- ions
The Arrhenius definition of an acid and a base:Acids - substances that when dissolved in water
release H+ ions Bases - substances that when dissolved in water
release OH- ions
ACIDS and BASES
ACIDS and BASESACIDS and BASES
• HCl is an Arrhenius acid:
• • When HCl dissolves in water it actually transfers a proton to a water molecule:
• HCl(g) + H2O(l) H3O+(aq) + Cl-(aq)
The Brønstead-Lowry definition of an acid and a base:Acids - a substance that can transfer a proton to another
substance Base - a substance that can accept a proton from another
substance These definitions emphasize proton transfer, and can
include solvents other than water
The Brønstead-Lowry definition of an acid and a base:Acids - a substance that can transfer a proton to another
substance Base - a substance that can accept a proton from another
substance These definitions emphasize proton transfer, and can
include solvents other than water
ACIDS and BASES
ACIDS and BASESACIDS and BASES
• HCl(g) + H2O(l) H3O+(aq) + Cl-(aq)
• In the reaction of HCl with H2O, HCl is a Brønstead-Lowry acid (donates a proton to H2O),
• and the H2O (in this particular reaction) is a Brønstead-Lowry base
• (accepts a proton from the HCl)
The pH Scale
Practical 2Practical 2
• Chemical Remedy Investigation
1
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4 5 6
2 3
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The three key words The three key words this lesson were…this lesson were…
They link together They link together because… because…
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Next, I think we Next, I think we will be learning will be learning
how to…how to…
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Pass!Pass!
Ask the teacher a Ask the teacher a question!question!
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I think it’s I think it’s important to important to understand… so understand… so we can…we can…
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The key idea The key idea today was…today was…
The reasons for The reasons for this are…this are…
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I wonder if… is I wonder if… is also the reason also the reason
we…we…
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The main ideaThe main idea today was that… today was that… and this happens and this happens because…because…
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The most difficult The most difficult thing to understand thing to understand this lesson was... this lesson was... Because...Because...
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One thing we One thing we need to need to understand more understand more about is… about is… because…because…
