QOTD Why are electric eels so effective in saltwater?

MR. DUNNUM SOLUTIONS CONDUCTIVITY

ELECTROLYTES o Are substances that form positive(+) and negative (-) ions in water o Conduct an electric current

ELECTROLYTES IN THE BODY o Carry messages sent to and from the brain as electrical signals o Maintain cellular function with the correct concentrations electrolytes

Electric current : flow of charged particles. One type of current is electrons flowing through a wire, from cathode (negative electrode) to anode (positive electrode). CONDUCTION ILLUSTRATED Another type of current: anions and cations moving through a solution Cations move to the cathode, anions move to the anode. External source of potential (voltage) is required in both cases! Drop of CaCl 2 (aq) LED Resistor 330 Ω (ohms)

IS IT A STRONG ELECTROLYTE, A WEAK ELECTROLYTE, OR A NONELECTROLYTE? Strong electrolytes include: Strong acids (all acids begin with H) Ex: HCl, HBr, HI, HNO 3, H 2 SO 4, HClO 4 ) –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 (Na 2 SO 4 )

NONELECTROLYTES þ Dissolve as molecules only þ No ions are produced in water þ Do not conduct an electric current H 2 O C 6 H 12 O 6 (s)  C 6 H 12 O 6 (aq) glucose

Electrolytes dissociate to produce ions. WHICH ONE WORKS 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 into ions

* Dissolving Ionic Solutes

QUESTIONS FOR ANALYSIS 1.Some substances conduct electricity because of the ions present. Those substances that do not dissociate into ions do not conduct electricity. Electrolytes=dissociate to produce ions Non-Electrolytes do not have ions to dissociate

2. COULD ANY OF THESE SUBSTANCES CONDUCT ELECTRICITY IN THE SOLID FORM? EXPLAIN o None of the substances can conduct electricity in the solid form. o EX: Ionic compound. When a salt is in a molten state / dissolved in water, the ions can move and carry the electric current. o in SOLID STATE= the ions cannot move, so the current cannot flow. o METALS: metals have free electrons which allow them to conduct electricity in both solid and molten state. o EX: Copper,steel,water,plasma and most metals conduct electricity in solid form

3. EXPLAIN SOME POSSIBLE REASONS FOR A HIGH CONDUCTIVITY MEASUREMENT IN A FRESHWATER 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 primarily transported to ponds and lakes via streamflow, surface runoff and groundwater,

CONCLUSION 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 conduct electricity. ex> HCl(aq): H + (aq) + Cl – (aq) NaOH(aq): Na + (aq) + OH – (aq) CuSO 4 (aq):Cu 2+ (aq) + SO 4 2– (aq) Nonelectrolytes do not conduct electricity. They do not ionize and therefore have no moveable ions. Acid: a compound that ionizes in water to form hydrogen ions. Base: an ionic hydroxide that dissociates in water to produce hydroxide ions A strong electrolyte has a greater percentage ionization (most molecules are converted to ions).. Weak have a few ions and more molecules so they conduct electricity at a lesser percentage.