Science assessment task 4 section 3: chemistry

valency

the number of electrons an atom must gain, lose, or share to achieve a stable electron configuration

octet rule

an atom’s preference for having 8 electrons in its valence shell

ionic bond

electrostatic attraction between cations and anions through the transfer of electrons

ionic bonds form between

metals and non-metals

cation

positively charged atoms

anion

negatively charged atoms

covalent bond

the sharing of electrons to achieve a full valence shell

covalent bonds form between

non-metals

metallic bond

electrostatic attraction between a positive metal ion and the sea of delocalised electrons

how do you compare malleability?

hit the object to see if it will bend to shape (malleable) or crack under pressure (brittle)

how do you compare ductility?

stretch the material to see how long you can make a wire before it snaps

how do you compare conductivity?

start an electric current using the object and see whether the object lets the electricity flow through or not

how to measure reactivity?

use acids on the object and test the reaction

are ionic substances conductive as a solid? (yes or no)

no

are ionic substances conductive as a liquid? (yes or no)

yes

are ionic substances soluble? (yes or no)

yes

are ionic substances reactive as a solid? (yes or no)

no

do ionic substances have high or low melting/boiling points?

high

are ionic substances malleable? (yes or no)

no

are ionic substances ductile? (yes or no)

no

are covalent substances conductive in general? (yes or no)

no

solubility of covalent substances

depends, covalent substances can disappear in water but those that aren't dissolvable in water can dissolve in other substances

are covalent substances malleable? (yes or no)

no

are covalent substances reactive in general? (yes or no)

no

are covalent substances ductile? (yes or no)

no

do covalent substances have high or low melting/boiling points?

low

are metallic substances conductive? (yes or no)

yes

are metallic substances soluble? (yes or no)

no

are metallic substances malleable? (yes or no)

yes

are metallic substances ductile? (yes or no)

yes

are metallic substances reactive? (yes or no)

yes

do metallic substances have high or low melting/boiling points?

high

chemical formula of water

H2O

chemical formula of methane

CH4

chemical formula of ammonia

NH3

organic compound

compounds that contain carbon-hydrogen bonds

inorganic compound

compound without the presence of a carbon atom and a carbon-hydrogen bond

CO2 - inorganic or organic compound?

inorganic

combustion

exothermic reaction between a fuel and oxygen, requiring heat to vaporise the fuel and start the reaction

fuels are often…

hydrocarbons

the energy produced comes from breaking covalent bonds between…

carbon-carbon and carbon-hydrogen atoms

complete combustion occurs when

there is an excess amount of oxygen

incomplete combustion occurs when

there is a limited amount of oxygen

word equation for complete combustion

hydrocarbon + oxygen = carbon dioxide + water (+ energy)

word equation for incomplete combustion

hydrocarbon + oxygen = carbon dioxide/carbon monoxide/carbon soot + water

does complete or incomplete combustion release more energy?

complete combustion

if methane releases 55.5kJ/g, how much energy is released if 6g of methane is combusted?

333kJ

hydrocarbon

organic chemical compounds composed exclusively of carbon and hydrogen atoms

how did early civilisations rely on the use of hydrocarbons before the industrial revolution?

by relying on naturally seeping hydrocarbons for construction, warfare and everyday utility

use of hydrocarbons by mesopotamia (3000 BC)

rock oil was utilised in architectural adhesives, medicines, road building and ship caulking

use of hydrocarbons by sumerians and babylonians (4300+ years ago)

sumerians used bitumen (asphalt) to construct boats, babylonians used it to reinforce walls and towers

use of hydrocarbons by ancient china (1st century BC)

chinese discovered, extracted and refined crude oil primarily for lighting and heating

use of hydrocarbons early warfare (7th century AD)

Arabian and Persian chemists mixed lighter petroleum elements with quicklime to create “Greek Fire,” precursor to napalm

how did the modern oil industry (mid-1800s) use hydrocarbons?

they began not for transportation but to light up the night

use of hydrocarbons kerosene craze (1840s-1850s)

chemists discovered how to distill kerosene from coal, oil shale and crude oil

how did kerosene save whales?

kerosene burned much cleaner than previous options, quickly replacing whale oil as the primary fuel for lighting worldwide

why did the first commercial oil wells appear?

to meed the booming demands for lamp fuel in the mid-19th century

what countries saw the drilling of the first commercial oil wells?

Poland, Canada and the United States (Pennsylvania)

why was the use of hydrocarbons shifted in the 1900s-1950s

due to the invention of the internal combustion engine and outbreak of global wars

what did hydrocarbons shift to in the 1900s-1950s?

they shifted from illuminants to raw power and synthetic material

why was gasoline originally considered useless?

due to its high volatility and poor use in burning lamps for lighting

why was gasoline highly sought after in the 1890s and 1920s?

due to the mass production of automobiles

when and what was the first petrochemical created?

isopropyl alcohol, 1920

what are some military supplies which advanced rapidly in WW2 due to hydrocarbon chemistry?

rubber for tires, toluene for TNT explosives and polyvinylidene chloride (saran wrap) for combat boots

what else also hit the commercial market in the WW2 era?

nylon stockings and styrofoam

use of hydrocarbons from the 1960s-present

hydrocarbons became the backbone of the global economy, shaping modern conveniences but bringing severe environmental consequences

_{global energy dominance late 20th century}

oil became the world’s most used energy source for transportation, electric power generation and home heating

what was manufactured out of hydrocarbons

hydrocarbon gas liquids (HGLs), plastics, synthetic fibres, solvents, rubbers

what were HGLs heavily utilised as

as feedstocks in petrochemical plants to manufacture almost all modern plastics

when did synthetic fibres outsell natural fibres

by 1968

how did the used of hydrocarbons have a toll on the climate?

by adding massive amounts of CO2 into the atmosphere, rising historic levels of 220ppm to over 412ppm by 2018

how is the world transitioning towards greener energy?

through molecular recycling, carbon capture and bio-hydrocarbons

molecular recycling

advanced technologies to molecularly recycle complex plastics and polystyrene back into virgin materials - circular economy

carbon cabure

direct air cature facilities that pull hydrocarbon-derived CO2 directly out of the atmosphere

bio-hydrocarbons

using plants that naturally produce hydrocarbons (e.g. euphorbia lathyris) as renewable alternative feedstocks

microplastics

any fragments of plastic that measure between 1 nanometre and 5 millimetres wide

how are microplastics released inot the environment?

direct release and degredation

direct release

microplastics that enter the environment as tiny particles

how do microplastics enter the environment through direct release?

laundering of synthetic clothing (polyester/nylon), tire abrasion from driving and intentionally added microbeads in personal care products

degradation

when large plastic items slowly disintegrate over time due to UV radiation and ocean currents

what items may release microplastics through degradation?

single-use bottles, takeaway containers, fishing gear

how many tonnes of plastic enter the ocean annually?

roughly 11 million tonnes

how many marine species are affected by microplastics?

700

how many microplastics may adults consume?

between 39000 and 52000 through inhalation and ingestion