unit 3 aos 1 chem

hydrolysis reaction def

chem breakdown compound bc of reaction with water

condensation products of monomer C6H12O6 and carbs general formula

• disaccharides and polysaccharides

• Cx(H2O)y — ratio of H:O in carbs always 2:1

when condensation of glycerol and 3 fatty acids occur

glycerol loses H+ (from OH side) and each fatty acid loses OH- then bond between the gap to form triglyceride (bond between C from COOH fatty acid and O from glycerol)

fatty acid def

long carbon chain of carboxylic acid (more than 4c)

draw fatty acid general structure

in book

process of carbs

condensation reaction (form di/polysacch in plants) → hydrolysis (break di/polysacch in human digestion into glucose) → respiration (glucose oxidised to release energy)

cellulose is…

an indigestible carb

at room temp fats and oils…

• fats = solid

• oils = liquid

why do molecules starch, protein, fat need to be digested

so they are converted into smaller molecs that can be absorbed into bloodstream

metabolism def

chem processes by living orgs to maintain life

cellular respiration (aerobic)

• exothermic

• series of biochem steps to oxidise glucose in O2 presence and form CO2, H2O, energy

• C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l)

  deltaH in databook

fats and oils aka triglyceride formation reaction

• 3 fatty acids + glycerol → triglyceride + 3 H2O

• condensation reaction

anaerobic respiration

• no oxygen presence

• less energy produced (per glucose)

• used when high demand fast energy and oxygen shortage

• for animals = C6H12O6 (aq) → 2 CH3CH(OH)COOH (aq)

• for plants (fermentation) = C6H12O6 (aq) → 2 C2H5OH (aq) + 2 CO2 (g)

starch def

• condensation polymer of glucose

• plant digestible polysaccharide

proteins

• broken down into amino acids via hydrolysis

• body doesn’t store excess amino a’s — excreted or conv into glucose

fats

• used when food scarce

• used by muscle, liver, fat cells (not brain)

• fats (trigly?) broken down by exothermic oxidation process (hydrolysis) into 3 fatty acids + 1 glycerol

lipids def

fats, oils, waxes insoluble in water

how fats broken down reaction

fats → (above arrow = hydrolysis, below arrow = enzymes) 3 fatty acids + 1 glycerol

sustainable energy def

energy that meets present needs w/o compromising future gen. ability to meet their needs

for all chem reactions…

energy changes

in chem. reactions the bonds…

for reactants are broken and for products are formed

proteins def

molecs made of amino acid chain/chains

coal seam gas (CSG)

• fossil fuel (type of natural gas?)

• extracted via drilling into underg coal deposits & using fracking

combustion is…

fuels being oxidised in exothermic reaction

activation energy def

min energy required to initiate reaction by breaking reactant bonds

each fuel diff energy content bc…

• type of fuel

• % of combustible material within

fuel def

subs that burns in oxygen to release energy from stored chem energy within

secondary fuels def

fuels prod from another source

(e.g. gasoline?)

energy needs recently in aus has…

• declined in energy needs met by coal and oil

• grown in energy needs met by renewable sources

fossil fuel def

carbon-based fuels formed from dead org material over millions of years to provide energy

how complex carbs broken down

complex carbs → (hydrolysis above arrow, enzymes below arrow) monosaccharides

why d. booklet food energy values not accurate as actual energy given by food?

bc not all food energy absorbed by body (some conv into heat)

photosynthesis

• convert light energy from sun into chem energy in the form of glucose

• endothermic

• 6CO2 (g) + 6H2O (l) → C6H12O6 (aq) + 6O2 (g)

• but actual amount solar energy stored in plant lower as not all sunlight wavelengths absorbed

fat def

triglyceride made of 3 fatty acids and glycerol

carbs def

grp of org compounds in food that gives energy to body — broken down into glucose for respiration

incomplete combustion

• limited supply oxygen

• less energy produced per kg fuel use

• produces pollutants like NOx, CO, soot

energy profile diagram notes

• peak = energy needed to break reactant bonds

• reactant enthalpy to peak = activation energy (Ea)

• Ea needed b4 reaction occurs, given from kinetic energy of particle collisions

limiting reactant def

reactant limits product quantity as its completely consumed in reaction, hence causes reaction stop

are alcohols liquid or aqueous

liquid

thermochem eq rules

• +ve or -ve with enthalpy change value (to show if endot. or exot.)

• enthalpy change in eq specific to eq given ratios

thermochem eqs def

balanced chem eqs with amount energy released/absorbed (enthalpy change)

measuring enthalpy change

• at SLC

• in KJ/mol, KJ/g, or KJ

exothermic def

• chem reaction where energy released

• -ve enthalpy change value

• energy absorbed when reactant bonds break less than energy released when product bonds form

endothermic def

• chem reaction where energy absorbed

• +ve enthalpy change value

• energy absorbed when reactant bonds break more than energy released when products bond form

when product bonds form…

• energy released

• exothermic

when reactant bonds break…

• energy absorbed

• endothermic

enthalpy change types (HEAT OF…)

• solution (1 mol subs dissolve in water)

• neutralisation (acid react base form 1 mol water)

• vaporisation (1 mol liquid into gas)

• combustion (substance burns in air)

enthalpy change formula

product enthalpy - reactant enthalpy

reactant enthalpy - product enthalpy

fossil fuel type — coal

• most plentiful

• got from open-cut mining (remove soil layer → use explosives → coal pieces blast) — cheap and easy

• made of C, O, H2O (in chem eqs just use C?)

• ADV = cheap, aus large reserves

• DISADV = prod heavy pollutants, highest CO2 emissions per MJ

black coal vs brown coal

• black coal = older, less H2O hence more energy content (bc under high pressure + temp longer)

• brown coal = newer, more H2O hence less energy content (use Coldry)

coal-fired power station

coal combusted → chem to thermal energy in water → water boils → thermal energy in water to thermal energy in steam → steam turns turbine (thermal to mech energy) → generator → mech to electrical energy

fossil fuel types — natural gas

• alkanes of low molec mass (mainly methane)

• formed with oil in muds (low in O, high in org matter)

• dangerous as methane readily undergo complete combustion — explosion (odour added)

• adv = high energy content + efficiency, less pollutants than coal

• disadv = moderate CO2 emissions, leaks can cause explosions (constant watch need)

fracking process

• extract CSG

• coal seams injected with water → pressure increase → crack rocks → methane desorb from coal → goes to surface via well

fossil fuel type — crude oil (petroleum)

• liq formed by geo processes on marine orgs over millions yrs

• refined via fractional distillation into petrochem fuels

• adv = high energy content

• disadv = mid to high CO2 emissions

bioethanol def

ethanol prod via sugar fermentation as petrol alternative

bioethanol production

1. fermentation: yeast ferments glucose in anaerobic envo to make ethanol (know equation)

2. distillation: separate ethanol from water (ethanol vaporises then collected once cooled)

bioethanol advantages + disadvantages

• ADV = less pollutant emissions, CO2 released initally captured, oxygen in ethanol allows complete combustion, can be used as E10 for car engines without further mods

• DISADV = food vs fuel debate, high cost, lower energy yield/gram, can degrade some vehicle parts

how many methanol needed for transesterification

3

drawing of triglyceride condensation reaction

1. get rid of H+ from glycerol from the OH side

2. red rid of OH in each fatty acid

3. then link O-C respectively

4. left with 3 water molecules as products

fatty acid basic structure diagram

insert image

enthalpy def

ttl stored energy/heat content in substance

symbol — H

enthalpy change def

energy amount absorbed/released in chem reaction

temp rise/fall

symbol — delta H

chem. energy in substance has potential to convert into...

heat or electricity

non-renewable sources def

sources consumed faster rate than being replenished

renewable sources def

sources replenished faster or same rate than being used

energy efficiency % formula

energy transformations not 100% efficient bc...

• when energy converts some lost to surroundings as heat

• if combustion then some maybe lost to H2O

glycerol loses what in condensation reaction

H+ from OH side (x3)

fatty acid loses what in condensation reaction

loses OH from COOH part

transesterification reaction

• triglyceride + 3 methanol → 3 biodiesel molecules + glycerol (and catalyst above arrow)

• triglyceride — glycerol part to glycerol → rest to biodiesel molecule

• methanol — CH3OH → H+ to complete glycerol → CH3O- to biodiesel molecule

what if combine 1 fatty acid and 1 methanol

• condensation reaction

• produce 1 biodiesel molecule + 1 water molecule

biodiesel

• fuel prod from plant oils/animal fats combo with alcohol via transesterification reaction

• adv = lower pollutant emissions

• disadv = production needs land, can be problematic in lower temps

how is biomethane produced

• upgrading = remove other gases in biogas

• break down solid biomass at high temps in anaerobic envo

biogas

• prod when organic matter rots in anaerobic envo

• mainly methane

• organic matter (e.g. livestock manure) into airtight digester → ferments → biogas

• adv = reduce greenhouse effect, uses organic waste

• disadv = lower energy content

biofuel def

renewable C-based energy source formed in short time period from waste plant + animal matter

fractional distillation def

process of separating components based on diff boiling points

petrochemical fuel types

KLAPD

• kerosene

• LPG (liquified petroleum gas)

• aviation fuel

• petrol (gasoline?)

• diesel

carb types

• monosaccharide = glucose in simplest form, soluble hence not storable

• disaccharide = 2 glucose molecs bonded via glycosidic bond from condensation reaction, soluble hence not storable

• polysaccharide = more than 10 glucose molecs bonded tgt, insoluble hence storable

what is molar gas volume

vol occupied by 1 mole of any gas at SLC

• 24.8

standard lab conditions

• 25 degrees Celsius

• 100 kPa

when temp and pressure change for a gas…

volume the gas occupies changes too

if gases at same pressure and temp…

their molar ratios = volume ratios

density def

the ratio of mass per volume

density formula

density = mass / volume

how does temp affect fuel density

as temp increase → kinetic energy increases → density decreases

what does energy output depend on

• energy density

• energy transformations efficiency

why does incomplete combustion release less energy

carbon in fuel doesn’t fully oxidise (carbon to CO or soot not CO2) → hence less heat energy released

the more transformations to turn chem energy into useful energy...

the less energy efficient (more energy lost)

how to calc total energy of a food

multiply mass of nutrients in food by stated energy value in kJ/g in data booklet then add together as needed

(note: account for differences in food serving if necessary)

calorimetry def

method to find energy changes by measuring heat exchanges with envo

1 MJ how many kJ

1000 kJ

specific heat capacity def

energy needed to raise temp 1g substance by 1 degree Celsius

spirit burner def

eq used to measure heat content of a fuel mass for prac calorimetry

specific heat capacity equation

q = mc(delta T)

q = energy (J)

m = mass (g) — of water for prac calorimetry

c = specific heat capacity — in data book for water

delta T = temp change (degrees Celsius)

practical calorimetry steps

• measure initial fuel amount

• measure initial water temp

• ignite burner to combust fuel

• water temp increases

• measure final water temp and calculate delta T

• measure fuel amount left

• use q = mc(delta T) where m is mass of water

• calculate heat of combustion using formula (heat of combustion = E (which is q) / amount fuel burnt

• note that q is in J so may need to convert to kJ and that fuel amount could be asked in g or mol

ways practical calorimetry not accurate

• energy loss to envo when transferring from spirit burner flame to water

• energy loss to envo once in water container

• energy loss to actual container

hence not all energy released heats water → temp doesn’t rise as much → underestimate sample energy content

solution calorimetry def

using calorimeter to measure heat changes solution

limitations of solution calorimetry

• chem changes need to happen spontaneously

• needs to happen below water boiling temp

simple solution calorimeter e.g.

coffee-cup calorimeter

calorimeter def

insulated apparatus measures heat changes during chem reaction