2 ElectrolytesAre substances that form positive(+) and negative (-) ions in waterConduct an electric current
3 Electrolytes in the Body Carry messages sent to and from the brain as electrical signalsMaintain cellular function with the correct concentrations electrolytes
4 Conduction Illustrated LEDDrop of CaCl2 (aq)Resistor330 Ω (ohms)Electric current : flow of charged particles.One type of current is electrons flowing through a wire, from cathode (negative electrode) to anode (positive electrode).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!
5 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, HNO3, H2SO4, HClO4)Strong bases (bases end in –OH (Hydroxide)(IA and IIA hydroxides)Ex: NaOH, Ca(OH)2, KOH, Ba(OH)2Soluble Salts (Most water-soluble ionic compounds)Ex: metal – nonmetal (NaCl)metal - polyatomic ion (Na2SO4 )
16 Questions for Analysis 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 ionsNon-Electrolytes do not have ions to dissociate
17 2. Could any of these substances conduct electricity in the solid form 2. Could any of these substances conduct electricity in the solid form? ExplainNone of the substances can conduct electricity in the solid form .EX: Ionic compound. When a salt is in a molten state / dissolved in water, the ions can move and carry the electric current.in SOLID STATE= the ions cannot move, so the current cannot flow. COVALENT COMPOUNDS (non metal bonded with non metal), the outer shell electrons are used up to form the covalent bonds. thus, there are no free electrons to conduct electricity. (examples include diamond, PURE water etc) METALS: metals have free electrons which allow them to conduct electricity in both solid and molten state.EX: Copper,steel,water,plasma and most metals conduct electricity in solid form
18 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,
19 ConclusionAn 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)CuSO4(aq): Cu2+(aq) + SO42–(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 ionsA 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.
20 Conclusion thoughts + + + + + + + Dissociation Na H O H O Cl Cl Na Dissociation occurs when a (ionic) compound breaks into its ions in water. Ionization occurs when a neutral atom or molecule is converted into an ion (e.g. by water). Ionic compounds and bases dissociate. Acids ionize.DissociationNa+HOHOClClNa+++Ionization+HOHOClClH++
21 Sources of error:contaminationspilled solutionmisreading the conductivity apparatusthe conductivity apparatus shorts outNot drying off the probesH2SO3:acid,KOH:base,CH3OH:organic,HC3H5O2:acid,Na2C2H3O2:salt,Ba(OH)2:base