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Some Definitions A 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 Water Water = Solvent Salt = Solute
Definitions Solutions 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
Definitions Solutions can be classified as saturatedor 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.
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.
Definitions SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved Supersaturated solutions are unstableand temporary Any disturbance, including shaking, stirring, or adding more solute will cause it to come out of solution.
Supersaturated Sodium Acetate One application of a supersaturated solution is the sodium acetate “heat pack.” Click on the metal piece inside and it instantly precipitates
Aqueous Solutions How do we know ions are present in aqueous solutions? ELECTROLYTES They conduct electricity HCl, MgCl2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions.
Aqueous Solutions Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes. These are usually covalent compounds, not ionic Examples include: sugar ethanol ethylene glycol
Electrolytes in the Body
Carry messages to and from the brain as electrical signals
Maintain cellular function.
Changing 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.
Change in Freezing Point Ethylene glycol Pure water The freezing point of a solution is LOWERthan that of the pure solvent
Change in Freezing Point Common Applications of Freezing Point Depression Ethylene glycol – deadly to small animals Propylene glycol
Properties of Acids
Litmus paper turns red
Reactivity with Metals
Properties of Bases
Litmus paper turns blue
Definitions: An acid is a substance that increases the H+ (or H3O+) concentration in an aqueous solution. Also known as proton donors. HCl + H2O H++ H2O+ Cl- H3O+ + Cl- A base is a substance that increases the OH- concentration in an aqueous solution. Also known as proton acceptors. NaOH(s) Na+ + OH-
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
Ocean Acidification The 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.
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 H2O+ KCl HCl + Ca(OH)2 2 2HOH + CaCl2 Require equal numbers