QOTD
•Why are electric eels so effective in saltwater?
MR. DUNNUM
SOLUTIONSCONDUCTIVITY
ELECTROLYTES
oAre substances that form positive(+) andnegative (-) ions in water
oConduct an electric current
ELECTROLYTES IN THE BODY
oCarry messages sent to and from thebrain as electrical signals
oMaintain cellular function with the correctconcentrations electrolytes
•Electric current : flow of charged particles.
• One type of current is electrons flowingthrough a wire, from cathode (negativeelectrode) to anode (positive electrode).
CONDUCTIONILLUSTRATED
•Another type of current: anions andcations moving through a solutionCations move to the cathode, anionsmove to the anode.
•External source of potential (voltage) isrequired in both cases!
Drop of CaCl2 (aq)
LED
Resistor
330 Ω (ohms)
IS IT A STRONG ELECTROLYTE, AWEAK ELECTROLYTE, OR ANONELECTROLYTE?
•Strong electrolytes include:
•Strong acids (all acids begin with H)
• Ex: HCl, HBr, HI, HNO3, H2SO4, HClO4)
–Strong bases (bases end in –OH (Hydroxide)
–(IA and IIA hydroxides)
–Ex: NaOH, Ca(OH)2, KOH, Ba(OH)2
–Soluble Salts (Most water-soluble ionic compounds)
Ex: metal – nonmetal (NaCl)
metal - polyatomic ion (Na2SO4 )
NONELECTROLYTES
þDissolve as molecules only
þNo ions are produced in water
þDo not conduct an electric current
H2O
C6H12O6 (s) C6H12O6 (aq)
glucose
• Electrolytesdissociate toproduce ions.
WHICH ONEWORKS
The more the electrolyte dissociates, the more ions it produces.
•Dissolving Polar Covalent Compounds
Some dissolve only as molecules
EX: Sucrose
Timberlake, Page 239
Dissolves but does
not dissociate intoions
* Dissolving Ionic Solutes
QUESTIONS FOR ANALYSIS
1.Some substances conduct electricity because of theions present. Those substances that do not dissociateinto ions do not conduct electricity.
Electrolytes=dissociate to produce ions
Non-Electrolytes do not have ions to dissociate
2. COULD ANY OF THESE SUBSTANCES CONDUCTELECTRICITY IN THE SOLID FORM? EXPLAIN
oNone of the substances can conduct electricity in thesolid form .
oEX: Ionic compound. When a salt is in a molten state / dissolved inwater, the ions can move and carry the electric current.
oin SOLID STATE= the ions cannot move, so the current cannotflow.
oMETALS: metals have free electrons which allow them to conductelectricity in both solid and molten state.
oEX: Copper,steel,water,plasma and most metals conduct electricityin solid form
3. EXPLAIN SOME POSSIBLE REASONS FORA HIGH CONDUCTIVITY MEASUREMENT IN AFRESHWATER SAMPLE FROM A LAKE,STREAM OR POND.
High concentration of ions (unusual anions and cations)
Nutrients
(e.g., phosphorus, nitrogen, carbon, silicon,calcium, potassium, magnesium, sulfur,sodium, chloride, iron) are primarilytransported to ponds and lakes viastreamflow, surface runoff and groundwater,
CONCLUSIONCONCLUSION
An electrolyte is a compound that, in aqueous solution,conducts electricity. As liquids: salts, bases. When aq:salts, acids, bases. When ions are present it can conductelectricity.
ex> HCl(aq): H+(aq) + Cl –(aq)
NaOH(aq): Na+(aq) + OH–(aq)
CuSO4(aq):Cu2+(aq) + SO42–(aq)
Nonelectrolytes do not conduct electricity. They do not ionizeand therefore have no moveable ions.
Acid: a compound that ionizes in water to form hydrogenions.
Base: an ionic hydroxide that dissociates in water to producehydroxide ions
A strong electrolyte has a greater percentage ionization(most molecules are converted to ions).. Weak have a fewions and more molecules so they conduct electricity at alesser percentage.