1. Elements, Compounds & Mixtures
Chapter 3
Elements, Compounds & Mixtures

2. Mixtures Properties of Mixtures All mixtures share certain properties!
mixture = combination of 2 or more substances that are not chemically combined
Substances that are not chemically combined retain their identity if they don’t react to form a cmpd
ex: cheese & pizza sauce don’t mix

3. Mixtures Everything in a mixture keeps its properties
NO chemical reactions occurs .·. ea substance in mixture has same chemical makeup as before
Maintains its identity
ex: pizza, granite have apparent individual components, salt water does not
Mixtures can be physically separated
Distillation = separates based on boiling points
Magnet = separation based on magnetism
Centrifuge = separates according to densities
several techniques … mix with solvent, filter, evaporation

4. Mixtures Components of a mixtures do not have definite ratios
Components don’t need to be combined in definite ratio
ex: granite
Regardless of ratio, combination is always a mixture
ex: still granite!
ex: air = mixture composed mostly of N, O, sml amts of CO2, H2O vapor
P. 64 Chart!

5. Mixtures
Solutions
Solution = a mixture that appears to be a single substance but is composed of 2 or more substances that are evenly distributed amongst eachother
They are often described as homogeneous mixtures b/c they have same appearance and properties throughout the mixture
“homo” = same
In sol’n, solute = substance being dissolved

6. Solvent = substance in which solute is dissolved
In sol’n,
Solvent = substance in which solute is dissolved
soluble = solute able to be dissolved in solvent
insoluble = unable to dissolve
.·. forms a mixture that isn’t homogeneous  not a Solute is dissolved in solvent!
sol’n
In salt water, which is solute? which is solvent?

7. Sol’ns aren’t limited to liquids!
Mixtures
Sol’ns aren’t limited to liquids!
When 2 liquids or 2 gases form a sol’n, substance w/ most volume is solvent.
Check out p. 65 table!
Alloy = solid sol’ns of metals/nonmetals dissolved in metals
ex: brass Zn dissolved in Cu
steel C & other elements dissolved in Fe

8. Particles in sol’ns are extremely small They are so small, they…
Don’t scatter light
Can’t be separated by filtration
Can’t see different particles
Don’t settle out

9. Mixtures
Concentration : How much solute is dissolved
Concentration = measure of amt of solute dissolved in solvent
units: solute = g solvent mL
Knowing concentration [ %] is v. impt for medicine/chemistry b/c incorrect [% ] can be _harmful or dangerous.

10. sol’ns can be described as concentrated or dilute
_________________ = more solute dissolved in equal solvent
____________ = less solute dissolved in equal solvent
Neither specify amt of solute dissolved!
MathBREAK

11. Mixtures Solubility: How much solute can dissolve?
ex: add too much sugar to lemonade  not all will dissolve
solubility (of solute) = amt of solute needed to make saturated sol’n using given amt of certain temp
units: usually expressed in grams of solute per 100 mL of solvent
The solubility of (________) at (____) deg C is (____) grams per 100 mL of H2O.

12. Solubility of solid in liquid – positive relationship.
Mixtures
Change of temperature
Solubility of most solids increase as solvent gets heated .·. more solute can higher temp… but this is not the case for all solids
Solubility of solid in liquid – positive relationship.
[general rule]

13. Solubility of a gas in liquids decreases as temperature gets higher
Solubility of gas in liquid – indirect (negative) relationship
ex: bubbles of gas appear in hot H2O before H2O begins to boil  gases dissolved in H2O can’t remain dissolved as temp increases b/c solubility of gases is higher temp
GRAPH p. 67

14. Solubility of Common Compounds in Water
Common compounds that contain the following ions are SOLUBLE.
Sodium (Na+), potassium (K+), Ammonium (NH4+)
Nitrates (NO3-)
Acetates (C2H3O2-), except silver acetate, which is only moderately soluble
Chlorides (Cl-), except silver, mercury (I), and lead chlorides; PbCl2 is soluble only in hot water
Sulfates (SO42-), except barium and lead sulfates; calcium, mercury (I), and silver sulfates are slightly soluble
Common compounds that contain the following ions are INSOLUBLE.
Silver (Ag+), except silver nitrate and silver perchlorate
Sulfides (S2-), except those of sodium, potassium, ammonium, magnesium, barium, and calcium
Carbonates (CO32-), except those of sodium, potassium, and ammonium
Phosphates (PO43-), except those of sodium, potassium, and ammonium
Hydroxides (OH-), excpet those of sodium, potassium, ammonium, and barium

15. Mixtures Solute… @ given T Where? What happens? Saturated Un-saturated
Saturation
given T
Where?
What happens?
Saturated
All solute the solvent can hold
ON graph line
Solute will sink to bottom if more is added
Un-saturated
Solvent could hold more solute
UNDER graph line
Solute will dissolve if more is added
Super-
saturated
Solvent holds more solute than should hold
ABOVE graph line
Solute will crystallize if more is added

16. Mixtures What affects how quickly solids dissolve in liquid?
Increase rate by…
… stirring/shaking  solute particles separate and spread out more quickly among solvent
… heating  solute particles move more quickly due to E increase
… crushing  increases amt of contact between solute and solvent

17. Mixtures
Suspensions
suspensions = mixture in which particles of material are dispersed throughout a liquid or gas but are large enough that they settle out
Often described as heterogeneous b/c particles are easily seen
Particles are …
Insoluble
Fairly large .·. scatter or block light
Too heavy to remain mixed w/o being shaken or stirred
Separation by passing thru filter
ex: snow globe, Italian dressing

18. Mixtures
Colloids
Colloid = mixture in which particles are dispersed throughout but aren’t heavy enough to settle out
Properties of both solutions & suspensions
Particles are…
Relatively small, but still large enough to scatter light
Fairly well mixed
Do not settle out .·.
Solids, liquids, gases can be used to make colloids
ex: milk, mayonnaise, stick deoderant, Jell-O, whipped cream, fog
Cannot be separated by filtration