Chemistry 3.5 Flashcards
Describe the structure of a metal.
Lattice of positive metal ions
Sea of delocalised electrons
What is metallic bonding?
Electrostatic attraction between positive metal ions and negative delocalised electrons.
Why do metals tend to have a high melting point?
Giant lattice of positive metal ions and delocalised outer electrons held together by strong electrostatic forces of attraction. Takes a lot of energy to overcome these forces.
Why are metals good conductors of electricity?
Charged delocalised electrons are free to move through the lattice.
Why are metals malleable?
Metal ions form layers which can slide over each other.
What is thermal decomposition?
When heat energy is used to break down a substance.
What do metal carbonates thermally decompose to form?
Metal oxide + carbon dioxide.
What colour change occurs during the thermal composition of copper (II) carbonate?
Green to black
What do metals react with cold water to form?
Metal hydroxides + hydrogen
What are two observations of all metals with cold water?
Effervescence (hydrogen gas produced)
Sold disappears (it is used up in the reaction)
What are the metals in Group 1 called?
The alkali metals.
What are the observations of Group 1 metals (Li,Na,K) with water?
Solid floats (less dense than water)
Effervescence (hydrogen gas is produced)
Solid moves (effervescence propels it)
Solid disappears (it is used up in the reaction)
What colour does universal indicator turn when added to the water with dissolved metal hydroxide and why?
Dark blue, they are alkalis because they donate OH- ions.
Observations of sodium in water
It melts (specific to sodium and potassium)
Effervescence
Floats on surface
Solid disappears
Moves around (faster than lithium)
Observations of potassium in water
Lilac flame (specific to potassium)
It melts (specific to sodium and potassium)
Effervescence
Floats on surface
Solid disappears
Moves around fastest)
Observations of lithium in water
Moves around (not as fast as sodium and potassium)
Effervescence
Floats on surface
Solid disappears
Why do Group 1 metals become more reactive as you go down the group?
When a Group 1 metal reacts, it loses its outer shell electron to get a full shell. This happens more easily down the group because the atoms get bigger and have bigger shells (larger atomic radius). The outer electron is further from the nucleus and nuclear attraction between the (positive) nucleus and the (negative) outer shell electron is weaker and more easily lost. Less energy is needed to break the attraction. Shielding increases.
Why do metals react with cold water and hot steam to produce different products?
Steam has more energy so both bonds in the water molecules can break.
What do metals form when they react with steam?
Metal + steam –> metal oxide + hydrogen
What is the chemical name for rust?
Hydrated iron (III) oxide
Why are alloys harder than pure metals?
Different-sized atoms/ions prevent the layers of
metal ions from sliding over each other. This means the alloy is less malleable.
Word equation for reaction with metal and acid
metal + acid –> salt + hydrogen
What happens in a metal and acid reaction?
metal displaces the hydrogen in the acid.
Two observations between metal + acid
Metal disappears - used up in the reaction
Fizzing - gas (hydrogen) produced
Why do some metals not react with acids?
They are below Hydrogen in reactivity series, they are less reactive than hydrogen so cannot displace the hydrogen in the acid.
Which metals are less reactive than Hydrogen?
Gold, silver, copper
Chemical test for hydrogen
Lit splint –> squeaky pop
Colour change for magnesium + copper sulfate
magnesium (grey) + copper sulphate (blue) –> copper (pink-orange solid) + magnesium sulphate (colourless solution)
Displacement reactions
Metals can displace less reactive metals from their compound,
Name for rocks containing metal compounds
Ores
How are metals found in the Earth’s crust?
As compounds with oxygen and sulphur.
How are gold and sliver found in the Earth’s crust?
‘Native metals’. They are so unreactive they haven’t reacted with oxygen and sulphur so they already exist on their own. They are chemically uncombined.
How are metals more reactive than carbon extracted from their ores?
Using electricity (electrolysis)
How are metals less reactive than carbon extracted from their ores?
They can be heated with carbon and be displaced by carbon as they are less reactive than carbon.
What is an example of a redox reaction?
Using carbon to displace a metal from its oxide.
Definition of a redox reaction in terms of oxygen.
Reduction = loss of oxygen
Reducing agent = takes oxygen away from something else
Oxidation = gain of oxygen
Oxidising agent = gives oxygen to something else
Redox = reduction and oxidation in the same reaction
What is rusting?
A chemical process in which iron is oxidised to form rust, hydrated Iron (III) oxide.
What is required for rusting?
Oxygen and water.
Describe how and why iron is oxidised to form Iron (III) oxide.
Iron has gained oxygen and lost electrons to from Fe3+ ions.
Describe the barrier method to prevent rusting.
Iron is coated in paint, oil, grease or plastic to prevent the iron from coming into contact with oxygen or water. Therefore, the rusting reaction cannot occur. Only works as long as coating is intact, as soon as it breaks, rusting occurs.
Describe sacrificial protection.
Attach a block of a more reactive metal to the iron. The block displaces the iron from the rust as soon as the rust forms.
What is the downside of sacrificial protection.
The block of metal has to be replaced frequently.
Describe galvanising.
Coating iron in zinc. Coating prevents 02 and H20 from coming into contact with the iron. If a crack appears, the zinc is more reactive then the iron so acts as sacrificial protection (zinc displaces iron from its compound as rust). Zinc will be oxidised more readily than iron.
What is the alloy of steel made out of?
Iron and carbon.
What is the alloy of brass made out of?
Copper and zinc.
What is the alloy of bronze made out of?
Copper and tin.
Why are metal alloys harder than pure metals?
Different sized ions prevent the layers of metal ions from sliding over each other. This means the metal is less malleable.
Use of low-carbon steel.
Ships, cars bridges. Strong but low carbon so is still malleable so can be hammered into various shapes. 0.1% carbon, Fe.
Use of high-carbon steel.
Tools (knives, screwdrivers). High carbon so less malleable and stiffer than low-carbon steel. 1% carbon, Fe.
Use of stainless steel.
Cutlery, cooking utensils, kitchen sinks. Cr forms oxide layer that resists corrosion, so it stays shiny and clean. 1% carbon, 10% Cr, Fe.
Use of copper.
Wires - Excellent conductor of electricity, ductile.
Cooking pans - Excellent conductor of heat. Water pipes - Unreactive and malleable.
Use of aluminium.
Aircraft bodies - Low density and high strength.
Power cables - Low density and conducts.
Use of Iron.
Making steel - Steel is more useful than iron.
Reactivity series mnemonic
Please Stop Like Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold
What is the reducing agent in terms of electrons?
Something that gives something else electrons. Helps the substance being reduced to gain electrons.
What is the oxidising agent in terms of electrons?
Substance that takes electrons from another substance. Helps the other substance to be oxidised by helping it to lose electrons.
What type of reaction occurs when iron rusts?
Oxidation
