Unit 3 Flashcards
(47 cards)
Metals properties
- they are good conductors of heat and electricity
- the tend to be shiny
- the can be shaped( malleable)
- they can be drawn into wires(ductile)
Metallic bonding
the atoms in a metal are arranged as positively charged metal ions surrounded by a sea of delocalised negatively charged electrons.
METALLIC BONDING is the electrostatic attraction between positive metal ions and the delocalised electrons.
The ability of metals to conduct thermal and electrical energy stems from their delocalised electrons. As these are free to move, an electrical current can flow through metallic materials.
REDOX
Oxidation is the loss of electrons
Reduction is the gain of electrons
Metals reacting with Oxygen
Metal + Oxygen—— Metal Oxide
Results of metals with Oxygen
MAGNESIUM- dramatic-heat/ light given off
ZINC- flash/heat
TIN- smell/flash - Grey—– white powder
COPPER- glow- Pink—- black
Metals reacting with Water
Metal + Water——- Metal Hydroxide + Hydrogen
Results of metals with Water
MAGNESIUM- pH indicator--- purple(lots of bubbles) ALUMINIUM- "" ------ blue(some bubbles) ZINC- ""---- Greeny blue(few bubbles) TIN-""---- Greeny blue (few bubbles) COPPER-"" Green( very few bubbles)
Metals reacting with an Acid
Metal + acid ——- Salt + Hydrogen
Results of metals with an Acid
MAGNESIUM-pH- acid— neutral/ lots of bubbles/ able to test for hydrogen
ALUMINIUM- pH- acid— neutral/ few bubbles
ZINC- Quite a few bubbles/ able to test for hydrogen
IRON- Couple of bubbles
COPPER - ————
Reactivity series
Metals are more reactive the further to the left and to the bottom of the periodic table they are e.g Potassium is more reactive than Sodium POTASSIUM SODIUM LITHIUM CALCIUM MAGNESIUM ALUMINIUM ZINC IRON TIN LEAD COPPER MERCURY SILVER GOLD
Extraction of metals (Heating)
Most metals exist in the earths crust as compounds(chemically combined to other elements)
Rocks from which metals can be obtained are known as ORES
Gold is found uncombined, as it is very un-reactive
Metal ores can be reduced by heating alone to extract the metals when quite un-reactive
Extraction of metals (Smelting)
Smelting is a process for extracting a metal from it’s ore by mixing with a source of carbon and heating.
IRON is extracted by a blast furnace
Extraction of metals( using electricity)
Very reactive metals are strongly bonded their ores, and cannot be extracted using carbon/carbon monoxide. More energy is needed, and this is provided in the process of electrolysis.
Electrolysis
Electrolysis is the breaking down of an ionic compound by passing an electric current though the compound in the aqueous state.
- REACTIVE metals such as aluminium and zinc can be extracted using electrolysis
During electrolysis, the positively charged metal ions will be attracted to the negative electrode, and negative ions contains the non-metal will be attracted to the positive electrode.
ELECTROLYSIS IS A REDOX PROCESS
Aluminium
-very useful due to it’s physical properties
- low density (used in aircrafts)
- maleable
- strong(used to build bikes)
- conducts heat/ electricity (saucepans)
Percentage mass
= mass of element x 100
total mass of formula
Making a Lead- Acid battery
Two identical lead plates were placed in sulphuric acid, and connected to a 2V direct current supply. Then plates changed colour, and bubbles of gas were seen at the positive. The lamp will then be able to light up.
THIS CELL CAN BE RECHARGED TIME AND TIME AGIAN.
Displacement reactions
A displacement reaction occurs when a metal HIGH up in the electrochemical series displaces a metal in solution which is LOWER than itself
- if a displacement reaction is happening, there will be a colour change, bubbles and a smell
HYDROGEN CAN TAKE PART IN DISPLACEMENT REACTIONS ( DUE TO BEING IN THE METAL SECTION)
Electrochemical cell
Electricity can be produced when half-cells are joined together. Half cells consist of a metal electrode placed in a solution of its ions.
The metal electrodes are connected by wires. A piece of filter paper soaked in an electrolyte (such as sodium chloride) acts as an ION BRIDGE to complete the circuit.
An ion bridge completes the circuit by connecting the solutions together, allowing the ions to move from one solution to the other.
-ELECTRONS FLOW FROM THE MOST REACTIVE TO THE LEAST REACTIVE
-THE MOST REACTIVE BECOMES THINNER
THE LEAST REACTIVE BECOMES THICKER (ELECTRONS STICK FROM ZINC)
Hydrogen fuel cell
The hydrogen fuel makes contact with one electrode, and oxygen comes into contact with the other. At the negative electrode, electrons are released from the hydrogen molecules, producing hydrogen ions. The oxygen molecules attract the electrons and combine to form water.
The water can be recycled (broken down into into hydrogen and oxygen again)
-THEY ARE RENEWABLE
-THEY DON’T DAMAGE THE ENVIRONMENT
Plastics
Most plastics are hard wearing, heat and electrical insulators, cheap, rust and rot proof as well as being waterproof and easy to shape.
SYNTHETIC= man made plastics
Disposing of plastics(Biodegradable)
Most plastics are not biodegradable(they are not naturally decomposed by living organisms.) This mans that plastic litter takes a long time to disappear. BIOPLASTIC is an exception.
Disposing of plastics(Recycle)
Plastics can be recycled, but there are problems. A plastic bottle may contain 3 different polymers. One for the bottle, one for the cap, and one for the label.
Disposing of plastics(Combustion)
Incomplete combustion results in CARBON MONOXIDE which is very poisonous.
one or two elements don’t form oxides easily.
NITROGEN
-Nylon and other polymers that contain nitrogen can produce NITROGEN DIOXIDE (toxic) if the temp of the fire is hot enough
CHLORINE
-P.V.C is a polymer that contains chlorine. Chlorine does not form oxides easily, instead it combines with hydrogen to form HYDROGEN CHLORIDE(toxic) gas.
HYDROGEN CYANIDE
- Polyurethane foam is used in houses as fillings for chairs. When it burns, it produces deadly HYDROGEN CYANIDE gas. All modern furniture has been made with flame resistant foam.
