Transcript Unit 5 Notes - Teacher Pages

Anything that has mass and takes up
space.
Substances Versus Mixtures
 Substances- cannot be
separated by physical
means.
 Mixtures- can be
separated by physical
means
Pure Substance
 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?
Element
 Building block for everything else
 Cannot be broken down or separated by
ordinary chemical or physical means
 Represented by chemical symbol
 Ex. Iron, copper, silver, hydrogen
 Remember the diatomic elements/molecules
Compounds
 2 or more different elements chemically
combined
 Have different properties than components
 Separated into elements ONLY by chemical
means (chemical reactions)
 Definite composition (constant element
proportion)
 Represented by a chemical formula
 Ex. H2O (water), NaCl (sodium chloride)
Mixture
 A physical blend of 2 or more substances
 Can 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
Classify
Which represent
substances?
2. Which represent
mixtures?
3. Which is an element?
4. Which is a
heterogeneous
mixture?
1.
CFU
Separation Techniques
MAGNETISM
 Use when: one of the substances in the mixture is
magnetic.
FILTRATION
 Use when: one of the substances in the liquid
mixture is an insoluble solid
 Other information: the insoluble substance is
removed from the liquid mixture using a porous
barrier (filter paper).
EVAPORATION
 Use when: the mixture is an aqueous solution
containing a soluble solid
 Other information: the water will boil off and the
soluble solid will remain in the evaporating dish
DISTILLATION
http://www.youtube.com/watch?v=3VRi0KPGb3o
 Use when: the mixture is composed of two or more
liquids
 Other information: based on differences in boiling
points; liquid with lowest BP will boil (and then
condense) first
CHROMOTOGRAPHY
 Use when: separating a mixture such as ink,
chlorophyll
 Other information: based on the distance the
components of a mixture travel (mobile phase) on the
surface of, or within, another material (usually
cellulose paper, called stationary phase)
A Homogeneous Mixture that can be
separated by physical means.
Solution Vocabulary
Solution – 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 curves
 solutions are NOT pure substances
 the amount of solute varies in solutions, and so does the BP
and FP
 ↑amount of solute, ↑BP, ↓FP
 heating curves for solutions will not be consistent
Dissociate – to separate into ions
 Electrolyte-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.
 Watch this:
 Soluble
 substance dissolves
in solvent
 Ex. Sugar (solute)
is soluble in water
(solvent)
 Insoluble
 substance does not
dissolve in solvent
 Ex. Sand is
insoluble in water
Miscible- describes two
liquids that do mix
 Immiscible – describes
two liquids that do not
mix
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)
Solubility
 Maximum 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 solvent
1. Increase temperature
of solvent
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 solvent
1. Decrease
temperature of
solvent
2. Increase pressure
 Not affected by surface
area of solute
Gas solubility
High Temp
Low Temp
You want more gas particles in the liquid
Saturated Solution
 contains the maximum
amount of dissolved
solute for a given
amount of solvent at a
specific temp and
pressure.
Unsaturated Solution
 contains less dissolved
solute for a given temp
and pressure than a
saturated solution
Supersaturated Solution
 contains more dissolved
solute than a saturated
solution at the same
temp
 Must heat a saturated
solution, then slowly
cool
Determining the solubility of a
solution
 Add more solute “seed
crystal”. If…
1) It dissolves, the original
solution was unsaturated
(still more available space).
2) It does not dissolve and
falls to the bottom of the
container, the original
solution was saturated (no
more available space).
3) It crystallizes, the original
solution was
supersaturated (over full,
past capacity).
Concentration is the amount of solute dissolved in a
given amount of solvent.
Concentrated
Dilute
Molarity
 A unit of concentration
 The number of moles of solute dissolved in 1.00 L
of solution.
Molarity (M) = Moles of solute
Liter of solution
Practice Problem
 What is the molarity if 2.0 moles of glucose are added
to 5.0 L of solution?
Preparing Molar Solutions
From the
number of
moles you
need,
calculate the
mass.
Measure
solute mass.
Place solute in
volumetric flask
Add exact
volume up to
calibration
mark. Close lid,
and swirl
solution
http://wiki.chemeddl.org/mediawiki/index.php/3.5.1_Concen
tration
Changing the concentration
 Add 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 Dilution
 When you need to 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
 How many liters of 16.8M HCl is need to make 2.5L
of 3.5M HCl?
Practice problem
 Mrs. 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 Pressures
 at 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 Law
What 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?
Dalton’s Law
 Standard Deviants