Transcript Chemistry - Solutions

Chemistry - Solutions
Mixtures
• Physical blend of 2 or more things
• 2 Types:
– Heterogeneous: composition is not uniform
– Homogeneous: composition is uniform
• Can be separated physically (ex. pouring, filtrating,
chromatography, distillation)
Homogeneous Mixtures
• All solutions are homogeneous
Solution: mixture of two or more substances, the
solute and the solvent.
Solvent vs. Solute…
• Solvent: the dissolving medium
– Ex: Water
• Solute: the dissolved substance
– Ex: sugar
How Stuff Dissolves
• Occurs when the attraction between the
solvent and the solute is GREATER than
between the parts of the solute.
• LIKE DISSOLVES LIKE
Which is the best solvent
for C10H12 (decane)?
• CH3OH (methyl alcohol)
• C6H14 (hexane)
Polar vs. Non-polar
• Polar molecules – Have an unequal
distribution of electrical charge
– Causes partial positive charge and partial
negative charge
• Non-polar molecules – Have equal sharing of
electrons
– Charge distribution is the same throughout
molecule
Like Dissolves Like
Water and Salt
• Both polar
Oil and Gasoline
• Both non-polar
Solubility
• Solubility: the amount of a substance that will dissolve in
a given amount of solvent to form a saturated solution at
a given temperature
• Solubility depends on RANDOM MOLECULAR MOTION,
which is affected by temperature, pressure and surface
area.
Temperature & Motion Inquiry Lab
Purpose:
Determine which is more effective, temperature or motion,
in increasing the rate of solubility of sugar in water.
Hypothesis: ?
Materials: Triple beam balance, graduated cylinders, beakers,
hot water, tap water, stir sticks and thermometers.
Procedure: ?
Data/Observations (include table): ?
Conclusion: ?
Temperature and Dissolving?
• Which dissolves faster:
sugar in hot tea
or sugar in ice tea
Higher temperatures = faster dissolving due to
greater kinetic energy of water molecules
Temperature and Solubility
• Solubility Curves
show the amount
of solute that can
dissolve at
different
temperatures
Pressure and Dissolving?
• Which has more bubbles
Just opened Soda or Soda that has been left out
Bubbles in Soda = CO2
Higher pressure = more dissolved gas.
Pressure has little/no effect on dissolving solids
Surface Area and Dissolving?
• What dissolves faster
Cube of Sugar or Spoonful of Sugar
Smaller particle size = faster dissolving
More surface that is exposed = faster dissolving
Chemistry – Balancing Chemical
Equations
Families of Elements
Chemical Formulas
Chemical Symbols
H2O
States what
elements are in
the compound
Every element has
a different letter
Subscript
How many
atoms of that
element are in
the compound
Chemical Equation
• Chemical Equation: Summarizes the details of a
chemical reaction
– Chemical reaction: Breaking and forming of chemical
bonds
Diatomic Molecule:
Reactants
Exist as two bonded atoms of the same
Chemical Reactions are
element
Products
Balanced
Ex: O2, H2, Cl2, N2, Br2, I2, F2
Balancing Reactions Activity
H = White Ball
O = Red Ball
C = Black Ball
• React one H2 with one O2 by splitting the molecules and
joining one O atom to two H atoms. Because there is
unreacted O, you must react it with another H2 to form
another water molecule.
– Summarize what happened ___H2 + ___O2  ___H2O
• React methane (CH4) with oxygen (O2) to produce Carbon
dioxide (CO2) and water (H2O). Continue reacting molecules
of CH4 and O2 until all reactant atoms have formed
products
– Summarize what happened ___CH4 + ___O2  ___CO2 + ___H2O
Keeping Track of Atoms
2H2 + O2  2H2O
Reactants
Products
Law of Conservation of Mass:
Mass of Reactants = Mass of Products
In a Chemical Reaction,
Matter is neither created
nor destroyed!
Chemical Reaction Symbols
• reactants  products
Ex:
Fe(s) + O2(g)  Fe2O3(s)
(s) :
Ex:
:
(g):
H2O2(aq)
(aq):
MnO2
H2O(l) + O2(g)
chemical :
(l):
(g):
Catalyst: substance that speeds up a reaction, but is not used
Balancing Equations
1. Determine Formulas
hydrogen gas = H2
oxygen gas = O2 water = H2O
2. Write the equation
H2 + O2  H2O
3. Determine the number of atoms of each element in the
reactants and products
Reactants
hydrogen: 2
oxygen : 2
Products
hydrogen: 2
oxygen : 1
Balancing Equations
4. Next use coefficients to balance the elements
H2
+
O2
hydrogen: 2
oxygen: 2
2H2 +
O2
hydrogen: 4
oxygen: 2

H2O
hydrogen: 2 oxygen: 1
 2H2O
hydrogen: 4 oxygen: 2
DO NOT CHANGE SUBSCRIPTS!
5. Make sure all coefficients are the lowest possible
ratio
Balancing Equations
• Methane gas (CH4) reacts with chlorine gas (Cl2)
in sewage treatment plants to create liquid
chloroform (CHCl3) and hydrogen chloride gas
(HCl). What would a balanced chemical equation
look like for this reaction?
Balance these equations
① AgNO3 + H2S  Ag2S + HNO3
② Zn(OH)2 + H3PO4  Zn3(PO4)2 + H2O
Balance these Equations
① FeCl3 + NaOH  Fe(OH)3 + NaCl
② CS2 + Cl2  CCl4 + S2Cl2
1. Label the products and reactants in the
following equation:
Iron
+
oxygen

Iron (III) oxide
2. Balance the following equation:
H2(g)
+
O2(g)

H2O(l)
Organic Chemistry
It’s all about CARBON
Organic Molecules
• Covalent Bonds – electrons are shared
• Polymers: large molecules made by repeating
subunits
– DNA
– Protein
– Carbohydrates
• Made possible by Carbon
Organic Molecules
• DNA
– Subunit: Nucleotide
Organic Molecules
• Protein
– Subunit: amino acids
Organic Molecules
• Carbohydrates
– Subunits: Saccharides or Monosaccharides
(sugars)
Organic Molecule
• Lipids
– Fatty Acids (Make up cell membrane)
– Contains repeating hydrocarbons