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SolutionsWhy Does Pasta Expand When Cooked?
Why does Lemon Juice sting?Why Do Salt Grains Dissolve?
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How Do Solutions Form?
Polar molecules pull polar molecules apart
Water molecules break up the salt crystals
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Polar Molecules
• Salt Crystal • Water molecules attracting sodium
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Some DefinitionsA solution is a mixture of 2 or
more substances. The substance that dissolves the
others is the SOLVENT.The substance that dissolve into
the solvent are SOLUTES.
Example: Salt WaterWater = Solvent Salt = Solute
5Solute Solvent Example
Solid Solid Alloys
Bronze is copper and tin
Liquid Liquid Liquor
Ethanol dissolved in water
Gas Liquid Carbonated Water
Carbon Dioxide in Water
Gas Gas Air
Oxygen and other Gasses in Nitrogen
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DefinitionsSolutions can be classified as
saturated or unsaturated.
An unsaturated solution contains less than the maximum amount of solute.
That means you can dissolve more at that particular temperature
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DefinitionsSolutions can be classified as
saturated or unsaturated.
A saturated solution contains the maximum quantity of solute that dissolves at that temperature.
If it gets too saturated, crystals will form and drop out of solution.
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How Temperature Affects Solubility• More can dissolve in hot fluids than cool fluids.• That is why you heat water to dissolve sugar or
other substances into them.• At cooler temperatures, the crystals will just
drop to the bottom.• If it is saturated and you cool it down, crystals
will drop out of solution.
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DefinitionsSUPERSATURATED SOLUTIONS
contain more solute than is possible to be dissolved
Supersaturated solutions are unstable and temporary
Any disturbance, including shaking, stirring, or adding more solute will cause it to come out of solution.
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SupersaturatedSodium Acetate
• One application of a supersaturated solution is the sodium acetate “heat pack.”
• Click on the metal piece inside and it instantly precipitates
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How do we know ions are present in aqueous solutions?
ELECTROLYTESThey conduct
electricity
HCl, MgCl2, and NaCl are strong electrolytes.
They dissociate completely (or nearly so) into ions.
Aqueous Solutions
12Aqueous Solutions
Some compounds dissolve in water but do not conduct electricity.
They are called nonelectrolytes.
These are usually covalent compounds, not ionic
Examples include:sugarethanolethylene glycol
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Electrolytes in the Body
Carry messages to
and from the brain
as electrical signals
Maintain cellular
function.
Make your own50-70 g sugarOne liter of warm waterPinch of salt200ml of sugar free fruit
squashMix, cool and drink
14Changing Physical Properties
On adding a solute to a solvent, the properties of the solvent are modified.
• Vapor pressure decreases• Melting point decreases• Boiling point increases• Osmosis is possible (osmotic pressure)
They depend only on the NUMBER of solute particles relative to solvent particles, not on the KIND of solute particles.
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Change in Freezing Point
The freezing point of a solution is LOWER than that of the pure solvent
Pure water Ethylene glycol
16Change in Freezing Point
Common Applications of Freezing Point Depression
Propylene glycol
Ethylene glycol – deadly to small animals
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Properties of Acids
• Sour Taste
• Litmus paper turns red
• Reactivity with Metals
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Properties of Bases
• Bitter Taste
• Litmus paper turns blue
• Slippery Feel
• Corrosive
19Definitions:
An acid is a substance that increases the H+ (or H3O+) concentration in an aqueous solution. Also known as proton donors.
HCl + H2O
A base is a substance that increases the OH- concentrationin an aqueous solution. Also known as proton acceptors.
H+ + H2O + Cl-
H3O+ + Cl-
NaOH(s) Na+ + OH-
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Why is Sea Water Basic?
Alkaline substances such as limestone dissolve from rocks, head down rivers, and are deposited
in the sea
Coral, clams, snails, and others make their shells from the calcium dissolved in sea water
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Ocean AcidificationThe pH of the ocean is becoming more acidic with global warming.
That is because more CO2 is dissolving into the ocean as more if released by humans into the atmosphere
This makes it more difficult for sea creates with calcium shells to survive
Their calcium shells dissolve in the acidic water
Coral reefs are being destroyed and the ocean ecosystems affected.
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Acid/Base reactions (neutralization):Produce water and a salt (and sometimes carbon dioxide).
Hint: concentrate on the water first. Remember, water has the formula HOH.
Complete and balance the following:
HCl + KOH
HCl + Ca(OH)2
H2O + KCl
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Require equal numbers
2HOH + CaCl2