Anything that has mass and takes up space.. Substances Versus Mixtures Substances- cannot be...
-
Upload
dorothy-horton -
Category
Documents
-
view
218 -
download
0
Transcript of Anything that has mass and takes up space.. Substances Versus Mixtures Substances- cannot be...
Substances Versus MixturesSubstances- cannot
be separated by physical means.
Mixtures- can be separated by physical means
Pure SubstanceHas a uniform composition
All samples have identical properties like boiling point, melting pt., color, and density which can be used to identify the substance
**Review: Are these intensive or extensive properties?
ElementBuilding block for everything elseCannot be broken down or separated by
ordinary chemical or physical meansRepresented by chemical symbolEx. Iron, copper, silver, hydrogenRemember the diatomic
elements/molecules
Compounds2 or more different elements chemically
combinedHave different properties than
componentsSeparated into elements ONLY by
chemical means (chemical reactions) Definite composition (constant element
proportion)Represented by a chemical formulaEx. H2O (water), NaCl (sodium chloride)
MixtureA physical blend of 2 or more substancesCan be separated by physical means like
filtration, distillation, etc.Individual components keep their identifying
properties
Homogenous mixture
Components are uniformly distributed, there are parts but you cannot see them.
Also called solutions.Ex. Salt water, air,
brass
Heterogeneous mixture
Not uniform, you can see the parts
Can settle upon standing
Ex. Oil and vinegar, salt and pepper, soil, trail mix
Classify1. Which represent
substances?2. Which represent
mixtures?3. Which is an
element?4. Which is a
heterogeneous mixture?
FILTRATIONAn insoluble solid is removed from a liquid
mixture using a porous barrier (filter paper).
DISTILLATIONhttp://www.youtube.com/watch?v=3VRi0KPGb3o
BASED ON DIFFERENCES IN BOILING POINTS, TWO LIQUIDS CAN BE SEPARATED WHEN ONE CHANGES TO A GAS AND THE OTHER REMAINS LIQUID.
CHROMOTOGRAPHYA separation technique based on the distance
the components of a mixture travel on the surface of
(or within) another material
Solution VocabularySolution – a
homogeneous mixture that consists of:
Solute – substance that dissolves, present in lesser amount
Solvent – thing that does the dissolving, present in greatest amount.
heating curvesSince solutions are NOT
pure substances, their heating curves will not be consistent…
The amount of solute varies in solutions, and so does the BP and FP.↑amount of solute, ↑BP, ↓FP
Shown is the heating curve for water. Water is a pure substance and always boils at 100°C and freezes at 0° (at standard pressure).
Dissociate – to separate into ionsElectrolyte-any
substance that dissociates and produces ions that conduct electricity. Ex. Salt (solute)
dissociates in water and the solution conducts electricity
Non-electrolyte – any substance that does not dissociate and therefore does not contain ions that conduct electricity.Ex. Sugar (solute)
does not dissociate in water so the solution does not conduct electricity
Dissolving a solvent surrounds a solute
Your body relies on water to dissolve the molecules in your body.Dissolution: the process by which one
substance (the solute) dissolves in another (the solvent)
Watch this:
Solublesubstance
dissolves in solvent
Ex. Sugar (solute) is soluble in water (solvent)
Insoluble substance does
not dissolve in solvent
Ex. Sand is insoluble in water
Solution Types
Solvent is Gas – ex. Air (nitrogen gas is the solvent)
Solvent is Liquid –ex. Sugar water (water is the solvent)WATER IS THE MOST COMMON
SOLVENT AND IS CALLED THE UNIVERSAL SOLVENT
Solvent is Solid – ex. Nitrinol (titanium dissolved in nickel, nickel is solvent, used to make braces)
SolubilityMaximum amount of solute that will
dissolve in a given amount of solvent at a given temp & pressure
Usually expressed as grams of solute per 100 g of solvent.
Affected by changes in the temperature or pressure
To Increase Solubility for a solid solute in a liquid solvent1. Increase temperature
of solvent Temp and solubility of a
solid are directly related
2. Increase surface area of solute (crush)
3. Agitate (stir or shake)
Not affected by changes in pressure
To Increase Solubility for a gas solute in a liquid solvent1. Decrease
temperature of solvent
Solubility of a gas and temperature are inversely related
2. Increase pressure Solubility of a gas and
pressure are directly related
Not affected by surface area of solute
Saturated Solutioncontains the
maximum amount of dissolved solute for a given amount of solvent at a specific temp and pressure.
Any point on the line represents a saturated solution.
Any point above the line, with solute visible, represents a saturated solution.
Unsaturated Solutioncontains less
dissolved solute for a given temp and pressure than a saturated solution
Any point below the line represents an unsaturated solution
Supersaturated Solutioncontains more
dissolved solute than a saturated solution at the same temp
Must heat a saturated solution, then slowly cool
Cannot be determined by JUST looking at a graph; you would need to know that it was saturated, heated, and cooled
Determining the solubility of a solutionAdd more solute. If…1)It dissolves, the
original solution was unsaturated (still more room).
2)It does not dissolve and falls to the bottom of the container, the original solution was saturated (no more room).
3)It crystallizes, the original solution was supersaturated (over full, past capacity).
MolarityA unit of concentrationThe number of moles of solute dissolved in
1.00 L of solution.
Molarity (M) = Moles of solute Liter of solution
Changing the concentrationAdd more solvent
(yellow) decreases concentration
The amount of solute is the same, but now the solution volume has increased
How would you increae the concentration?
http://wps.prenhall.com/wps/media/objects/1053/1078985/ist/
ch03_11.html
Solution DilutionTo make a concentrated solution more
dilute use this formula M1V1 = M2V2
M1 = concentrated solution
V1 = amount of concentrated solution need to make dilute solution
M2= dilute solution
V2 – amount of diluted solution wanted.
Practice problemMrs. Imamazing needs to make 12 liters of a
0.10 M HCl solution for her chemistry students to use in a lab. She finds a large bottle of 12.00 M HCl solution in the acid cabinet. Describe how she would make the solution?
Dalton’s Law of Partial Pressuresat constant volume & temperature, the
total pressure exerted by a mixture of gases is equal to the sum of the partial pressures
Total pressure = P gas1 + P gas2 + Pgas3….
Ptotal = P1 + P2 + P3….
Dalton’s LawWhat is the pressure of hydrogen, in atm, if it is
mixed with oxygen, which exerts a pressure of 2.1 atm, and the total pressure is 3.6 atm?