3 Types of Mixtures
•
Solutions
•
Suspensions
1 - Solutions
• Solution – a homogeneous mixture of two or more substances. Are clear and CANNOT be separated by a filter.
• Homogeneous – small particles that are spread out evenly
• Can be solid (14K gold - alloys), liquid (beer, liquor), solids in liquid (Kool-Aid), gas in liquid
Solution Parts:
•
Solvent – what does the dissolving
•
Solute – what
’
s being dissolved
2 - Suspension
• Heterogeneous: larger (visible) particles that are spread out unevenly
• Heterogeneous mixture of particles in a fluid
(liquid or gas). The particles settle out, over time.
Suspensions - continued
3 - Colloids
•
A homogeneous mixture that
’
s between
suspensions and solutions.
•
Large (you can see them) particles are
suspended in a solution, but DO NOT
settle out.
Examples: whipped cream (gas
suspended in liquid); smoke
Colloids (Continued)
•
EMULSION – special case – a
liquid/liquid colloid that requires an
emulsifier (which coats and stabilizes
the particles of one in the other) –
All mixtures can be separated by
physical properties
• Physical property: a characteristic of the substance that can be observed directly or measured without
changing the composition of the substance
Solubility curve
• A method of
graphically expressing a substance’s
solubility
• On the curve – saturated
• Under the curve – unsaturated
Mendelev
Periodic Table…
• Groups/Families
• Periods
• Atomic Number = # of protons
• # of protons = # of electrons (if neutral)
• Mass number – atomic number = number of neutrons
What does the information in the box tell
me?
1
H
1.008
Atomic Number = # of protons
Atomic Mass Number = # of
Atom!
• Nucleus = protons + neutrons
• Electrons – outside the nucleus
• Electrons have no mass
Ions & Isotopes
• Change the number of electrons = ions
• Add electrons = negative ion (anion)
• Subtract electrons = positive ion (cation)
• Change neutrons = isotope
• The electrons around a nucleus can be found in one of seven shells. Each shell can hold a set number of
electrons.
• Each shell can hold 2n2 electrons, where n is the shell
number.
• Electrons fill shells before moving on to the next
• Atoms want their valence shells to be full, WITH 8 ELECTRONS. Full shells = lower energy state.
• The closer they are to full, the more reactive the atom is.
• Lewis Dot Model: The dots show the valence electrons only.
• Those that have more, want more – the halogens & neighbors.
• Those that have the least, give the most – the alkalis and neighbors.
• Halogens – just need one – take one.
• Valence electrons – where it’s at.
• Periods – correspond to the shells
• For Groups 1-18 (skipping Transition Metals), the # of valence electrons kinda = Group # in Periodic Table
• Members of groups have the same number of valence electrons. Elements in Groups share reactivity,
Radiation
• Alpha – two protons, two neutrons, weak
• Beta – one electron
Nuclear Reactions
• Fission – one large atom being split into smaller pieces. In: bombs, nuclear power plants
Nuclear Power
• Pros: very efficient – lots of energy produced per fuel, lowish cost.
Half-Life
What do I need to know?
• Density
• Mixtures
• Solution, suspension, colloid (emulsion)
• Solute, solvent
• Heterogeneous, homogeneous
• Solubility
• Gas vs. solid in a liquid
What do I need to know?
• Periodic Table
• Groups, periods, characteristics
• Types of substances, states of matter
• Trends: Reactivity, atomic radius (size)
• Atomic number, atomic mass
• Valence electrons (how many)
• Atomic Structure
• Protons, neutrons, electrons (where and how many)
• Bohr model, Lewis Dot model
What do I need to know?
• Nuclear radiation
• Types of radiation (alpha, beta, gamma)
• Nuclear Decay: What happens when you lose an alpha or a beta?
• Types of reactions (fusion, fission – where, what, who)
Ionic Bonds
• Happen between a metal and nonmetal
• Electrons from metal (that have 1,2, or 3 valence -e’s) go to nonmetal (that need 1,2 or 3 valence –e’s)
I say
“
ionic,
”
you say:
Signs of an ionic compounds:
• At room temperature, most are crystals.
• Dissolve well in water, but NOT in a non-polar liquid
• High melting/boiling points
• The crystals DO NOT conduct electricity
•
Polyatomic ions
Cluster of atoms that form a charged particle. Stay together, even in compounds.
• Positively charged polyatomic ions act like metals and combine with non-metals or negative polyatomic ions.
• Negatively charged polyatomic ions act like
nonmetals and combine with metals or positive polyatomic ions.
Covalent Bonds
• Non-metal and non-metal atoms together
• Electrons are shared to fill valence shells. NO IONS ARE FORMED
• Number of electrons shared is equal to the number of electrons
Covalent bonds/compounds:
• Sometimes crystals, sometimes gases, sometimes liquids. Wider range of forms.
• Have lower melting and boiling points than ionic compounds
• Many don’t dissolve well in water – but there are exceptions; dissolve well in nonpolar liquids
I say
“
covalent,
”
you say:
Naming compounds: covalent
• Element furthest on the left named first
• 2nd element’s last letters replaced with –ide (example:
chlorine -> chloride)
• Use Greek prefixes for the number of atoms (mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca) Don’t use
Polar Molecules:
• Only happens in covalently bonded molecules.
• “Polar” means that the molecule has “poles” or a (+) area and a (-) area.
I say
“
polar,
”
you say:
Metallic Bonds
Happens between metal atoms.
Physical Change:
•
Only the
form
of the substance changes – a
state or a change in phase is a physical
change.
•
Matter stays the same
, but changes in size,
shape or appearance – physical changes
•
At the smallest level, molecules are
Chemical Changes – a.k.a.: Reactions
• CHEMICAL BONDS ARE MADE OR BROKEN.
• NO MATTER IS DESTROYED OR CREATED.
• Examples: iron rusting (iron oxide forms),
gasoline burning (water vapor and carbon dioxide form), eggs cooking (fluid protein molecules uncoil and crosslink to form a network), bread rising (yeast converts
carbohydrates into carbon dioxide gas), milk souring
Reviewing …
Balancing Equations Challenge… Part A
Subscripts – modify what came right in front
of it.
Reviewing…
Balancing Equations Challenge… Part B Example: 2Mg + O2 -> 2MgO
Mg and O are the reactants
MgO is the product
The arrow means “yields” NOT “equals.”
Stepwise…
Count the number of atoms in the reactants and products.
Balance the elements one at a time, using coefficients.
•
If there
’
s no coefficient, it
’
s assumed to
be 1
•
NEVER CHANGE SUBSCRIPTS
•
Make sure the coefficients are in the
Type of Reaction
Definition Equation
Synthesis Decomposition Single Replacement Double Replacement
A = Red B = Blue C = Green D = Yellow
A + B → AB
AB → A + B
AB + C → AC + B
AB + CD → AC + BD
Two or more elements or compounds combine to
make a more complex substance
Compounds break down into simpler substances
Occurs when one element replaces another one in a
compound
The four types of reactions:
Neutralization: A special case of double replacement reaction:
Same formula: AB + CD -> AD + CB.
But your players are an acid and a base. Your products are ALWAYS water and a salt.
Acids
• Release hydrogen ions (H+)
in solution (H3O+)
• Have more H+ than OH
-• Recognize by “H” at start of formula
• Examples: HCl, H2SO4, HNO3
• Taste sour
• Feel like water
• React with metals such as zinc and magnesium
Bases
• Release hydroxide ions (OH-) in solution
• Have more OH- than H+
• Many formulas end with
“OH”
• Examples: NaOH, Ca(OH)2
• Group 1 elements plus OH- =
strongest bases
• Taste bitter
Measuring Acidity/Alkalinity
• Uses the pH scale – pH measures the concentration of H+ ions in a solution.
• Scale ranges in value from 0 to 14 – neutral is 7. Less than 7: ACIDIC. Greater than 7: BASIC.
• Based on the concentration of H+ ions in a
solution. More H+, lower the pH, less H+, higher the pH.
Measuring pH
• Indicators: change color in solution. Example: phenolphthalein – colorless in acid, red in base.
• Litmus paper – turns different colors when exposed to acids or bases. Blue litmus turns red when dipped in acid, red litmus turns blue when dipped in base.
