electricity and chemical change
electrical current
stream of electrons
how does a battery function in a circut
electrons leave through the negative terminal anf enter the battery at the positive terminal
are solids conductors
the only solid conductors are metals and carbon due to their free electrons
are molecular compounds conductors
no because they have no free electrons or charged particles
are ionic compounds conductors
ionic compounds are not conductors when solid but do conduct when dissolved in water or melted
how does electricity effect ionic compounds
electricity can be used to bring the decomposition of ionic compounds
electrolysis
the decomposition of an ionic compound when molten or in an aqaeous solution
what is an electrolyte?
lquid which undergoes electrolysis
how does electrolysis break down a compound at a battery
the compound is broken down into elements metals are left at the cathode and non-metals are at the anode
rules of electrolysis at the cathode
-the more reactive an element the more it 'likes' to be an ion -if the metal is less reactive than hydrogen it stays a metal -if it is a concentrated halide compound then chlorine iodine or bromine form
what is a halide
compound containing cl- Br- or I- ions
what happens to ions in molten lead(II) bromide when the switch is closed in electrolysis
the ions move and carry the current -at the cathode lead ions recive 2 electrons and become atoms
-at the anode the bromine gives up one electron anf become atoms forming a molecule
half equations for electrode reactions
-name ions present -write half equation -add state symbols
describe electrolysis of copper sulfate using carbon electrode (inert)
at the cathode -copper ions are discharged and coat the electrode at the anode -oxygen bubbles off -copper and oxygen are produced
describe electrolysis of copper sulfate using copper electrodes (not inert)
At the cathode -copper is formed and coats the electrode At the anode -anode dissolves giving copper ions -copper moves from the anode to the cathode
electroplating
using electricity to coat one metal with the other
the set up to electroplate something
cathode -object to be electroplating -anode-metal x -electrolyte0-solution of soluble compound of x
uses of electroplating
-steel taps are coated in chromium to prevent rusting -steel cans are covered in tin to be food cans -cheap metal is coated in silver to look better