Chemistry - 90933 Flashcards
Smallest part of an element that can take part in a chemical reaction
Atom
Mass of protons, electrons, neutrons on atomic scale
Proton 1. Neutron 1. Electron 0.0005
Which atom contains no neutrons
Hydrogen
Mass number
No. protons and neutrons
Atomic number
No. protons
When are H, He, Li and Be most stable
When they lose electrons to have 2 or 0 in total.
Group (periodic table)
Vertical columns on the table, all atoms have same amount of valence electrons
Periods (periodic table)
Horizontal rows
Gradual change from metallic to non-metallic elements across each row of periodic table. T/F?
True
Physical properties
Properties that identify a substance but do not include the chemical reactions of a substance.
Which common metal is liquid at room remp
Mercury
Density of metals
Generally above 3 g mL-1. Sodium and lithium are less than 1 g mL-1 (therefore float on water).
Lustre
How well a substance shines/reflects light. Metals can have high lustre. Non-metals tend to be dull
Electrical conductivity
Measure of how easily electricity flows thorugh
Thermal conductivity
Measure of how easily heat energy passes through
Malleability
Measure of how easily a substance can be beaten or pressed
Ductility
Measure of how easily a substance can be drawn into a wire
Hardness
Measure of how easily a substance can be scratched or cut. Many metals are too soft but can be made into an alloy.
Why might a metal with high lustre appear dull
It might have reacted with oxygen or water
Atoms of metals for a close-packed ____, which results in a hard, ____ structure.
Lattice. Crystalline.
Can the weakly held valence electrons of metals move easily through the metal lattice structure?
Yes. And the metallic bond results from the attraction between the positive metal ions and the ‘sea’ of valence electrons.
Why do some metals have a high melting point
The ‘sea’ of electrons acts as a ‘glue’ binding the positive ions closely together.
Why do metals have high electrical and thermal conductivity
Because of the mobility of valence electrons
Why are metals malleable and ductile
The layers of atoms in the lattice can move over each other and deform without breaking.
How are alloys formed
By mixing 2 or more molten metals and allowing them to cool
Melting point of alloys
Indistinct, given they are 2 or more different metals
Why are alloys used
Because the properties of 2 or metals combined is more useful than one of the metals alone
Why are alloys hard
A small amount of metal atoms replace a number of atoms in the lattice of the parent metal, reducing the ability for atoms to move over each other.
Properties of brass
Copper and zinc. Less corrosive than copper and retails electrical conductivity of copper
Properties of bronze
Copper and tin. Attractive coating that lasts a long time.
Properties of solder
Tin and lead. Melts at lower temp and can bond with many metals.
Properties of pewter
Tin and lead, and small amounts of copper and antimony. Harder than lead and does not release lead.
Properties of duralumin
Aluminium and magnesium. Higher strength but low density.
Properties of cupronickel
Copper and nickel. Harder and longer lasting than nickel.
Steel
An alloy that contains 0.5-2% carbon as well as iron and other metals (depending on need). High tensile strength and resist corrosion.
Uses of aluminium
Window frames, ranchsliders, ladders, aeroplane bodies, small boats, caravans, drink cans, tennis racquets etc
Uses of copper
Wiring, hot-water piping, roofing.
Bronze (alloy) - statues.
Brass (alloy) - electrical terminals, marine/household fittings.
Cupronickel (alloy) - gold/silver coins.
Uses of iron ally (steel - actual iron is difficult to obtain and is soft)
Cars/vehicles/trains/ships etc.
Reinforced concrete, bridges, scaffolding.
Large and small containers.
Tools/instruments - hammers, cutlery, forceps, drills.
Uses of zinc
Protection of steel (galvinised).
Battery casings.
Brass alloy (with copper)
Used of lead
Roofing, solder alloy (with tin)
Uses of magnesium
Duralumin alloy for airframes and car wheels.
In flares - bright, white light.
Uses of silver and gold
Decoration/jewellery (high lustre/colour)/
Gold as alloys to produce harder (less yellow) gold.
Chemical reactivity
Properties that allow metal atoms to undergo chemical reaction
Reactivity is determined by
The ease with which the valence electrons are removed from the atom (positive ion formed)
Order of reactivity of some metals
Lithium > sodium > calcium > magnesium > aluminium > zinc > iron > lead > (hydrogen) > copper > silver > gold
Oxidise
Metals oxidise at different rates depending on their reactivity.
Word equation for oxidation reaction
Metal + oxygen -> metal oxide
Can gold and silver react with oxygen under any conditions?
No
Can metals react with water/steam?
Yes, depending on the metal (reactivity) (metal + water -> metal hydroxide + hydrogen gas)
e.g lithium + water -> lithium hydroxide + hydrogen (and the heat produced can be enough to ignite the hydrogen)
Are non-metals good conductors of electricity and heat, and do they have lustre, malleability and ductility?
No, there are exceptions though.
Allotrope
Allotropes are different forms of the same element. Different bonding arrangements between atoms result in different structures with different chemical and physical properties. Allotropes occur only with certain elements, in Groups 13 through 16 in the Periodic Table.
Percentage O2 in atmosphere
21%
Percentage O2 in earth’s crust
50%
Do most elements react with O2
Yes, most react, causing heat and light.
Ozone
Allotrope of oxygen (O3). Colourless gas with strong smell.
Is ozone beneficial or harmful?
Harmful to animals’ respiratory tracts. Beneficial in keeping UV rays from reaching Earth’s surface.
Uses for ozone
Purify and disinfect air and water. More effect than chlorine and other oxidising agents, and leaves no harmful or odourous by-products.
How is carbon usually found?
In a combined form. E.g calcium carbonate, carbon dioxide, organic molecules, coal.
Well known allotropes of carbon
Graphite, diamond, fullerenes
Graphite vs diamond bonding
Graphite: 3 electrons per C atom covalently bond, the 4th bonds weakly to other C atoms in layers above and below it.
Diamond: strong 3-D network of covalent bonds with all 4 electrons
Why does graphite feel slippery and why is it a good conductor of electricity?
Slippery because the layers of hexagonal rings can slide over each other.
Good conductor because the loose electron can move around.
Fullerene
Graphite-like structure of C but with pentagonal and heptagonal structures as well as the normal hexagonal ones.
Two examples of structures in the fullerene family
Buckminsterfullerene (buckyball) (C60) and carbon nanotube (buckytube)
Sulfur + oxygen
Sulfur dioxide
Uses of sulfur
Production of sulfuric acid, which has many uses.
Process used to produce pure H2SO4
Contact Process (uses a catalyst)
Properties of sulfuric acid
Acidic when in aqueous solution. Ionises completely in water. Releases H gas when reactive metals are added to it. Neutralises bases to form salts. Dehydrates other chemical substances. Oxidises metals and non-metals. Sulfonates organic molecules (to make detergents). Catalyst in many reactions.
Uses of sulfuric acid
Production of fertilisers. Manufacture of chemicals (e.g HCl, nitric acid, sulfate salts, synthetic detergents, dyes, pigments, explosives, drugs). Petroleum refining. Cleaning metals. Manufacture of synthetic fibres. Battery acid.
Is chlorine reactive
Yes, very
How is chlorine commonly found
As sodium chloride
How is hydrogen chloride produced?
Hydrogen and chlorine are heated form HCl, which is highly soluble.
How does chlorine kill bacteria?
Chlorine reacts with water to produce HCl and HOCl. The HOCl (hypochlorous acid) kills bacteria.
Uses of chlorine in pulp/paper industry and in plastics
Bleaches pulp/paper.
Used to make the monomer of the plastic PVC (polyvinylchloride).
Percentage N in Earth’s atmosphere
79%
Reactivity of N gas
Chemically unreactive, though lightening can cause a small amount of nitric oxide.
What causes smog?
Nitric oxide combines with other atmospheric pollutants to produce photochemical smog.
Ammonia
NH3. Strong-smelling gas at room temp. Soluble in water. Forms ammonia solution (basic). Neutralises to form ammonium salts.
How is ammonia made in NZ?
Modified Haber Process. Natural gas is the source of hydrogen. Air is the source of nitrogen. A catalyst is used in some stages.
- Preparation of gas mixture of hydrogen and nitrogen.
- Remove of CO2 and CO.
- Formation using Haber Process.
Uses of ammonia
Making nitric acid (for explosives). Agricultural chemical for soil. Synthetic fibre manufacture. Liquid for use as a refrigerant.
