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What order were the elements put in the early periodic table?
Increasing atomic weight
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How were elements put into groups?
Similar properties
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Why was this known as the periodic table?
Periodic means repeats regularly, similar properties occur at regular intervals
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What were Newland's Octaves?
A table where every eighth element had similar properties
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Two main problems with early periodic table?
Incomplete, and elements were arranged by mass or weight so some elements didnt fit the pattern and were in the wrong groups
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How did Mendelev overcome this in 1869?
Mendelev left spaces, famously Ga and Ge, so the elements fit into groups and he predicted new elements
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What discovery led to the modern periodic table?
electrons, protons and neutrons
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What are some properies elements in each group share?
the group number refers to number of electrons in outer shell, the verticle periods refer to number of electron shells, group 0/8 have 8 full outer shells
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Describe patterns in group 1 Alkali metals
low density, first three float on water, and form hydroxides and hydrogen. the further down the group, the lower its melting and boiling point and more reactive
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Explain the pattern in reactvity in group 1
the atoms have more elctron shells further down the group, so electrons further from positive nucleus somore easily lost and they need less activation energy
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How do alkalis react with non-metals?
they form ionic compounds in which the metal ion has a +1 charge, from losing an electron e.g Li-->Li⁺ + e-
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Compare the Alkali metals with transition metals
transition metals have a higher melting point, are less reactive, dont react as vigorously with water and are denser, stronger and harder
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Give thee properties of transition metals
ions with different charges, form coloured compounds and are useful catalysts
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Describe group 7 elements/ Halogens
form halide ions e.g. iodine--> iodide, react to form ionic compounds where the halide ion has a -1 charge e.g. Cl+ e- -->Cl-
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Decribe the trends in group 7 elements
get denser and colours get more intense as you move down the group, melting point and boiling point increases and they get less reactive
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Why do the elements in group 7 get less reactive?
the higher the energy level of the outer electrons the less easily electrons are gained
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What is the displacement of Halogens?
a more reactive halogen can displace a less reactive onefrom an aqueous solution of its salt. e.g. Cl₂ + 2KBr --> 2KCl + Br
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Is the water we drink safe?
its not pure, but it is safe as its treated to remove harmful substances
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What is soft water and what causes it?
water that readily forms lather with soap, it contains hydrogencarbonate ions which decompose on heating to produce carbonate ions which react with Mg⁺ and Ca⁺ ions to form precipitate (limescale)
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What is hard water, and what causes it?
hard water reacts with soap to form scum so more soap is needed to form a lather, it contains dissolved calcium and magnesium from rocks
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What are soapless detergents?
they do not form scum
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What is the difference between permanent and temporary hard water?
permanent hard water stays hard when boiled, temporary hard water doesn't
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What are the disadvantages/advantages of hard water?
increases cost as more soap needed, temporary hard water forms scale which coats heating elements, icalcium cmpnds are god for bones and teeth and reduce heart disease
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How does sodium carbonate soften hard water?
it reacts with Ca and Mg to form a precipitate
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How do ion exchange columns soften hard water?
contain sodium ions which replace the calcium and manesium ions in the water
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Why do you need to put salt in a dsihwasher regularly?
sodium ions exchange for the calcium ions which have built up.
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How do you compare hardness of water and the effects of bath salts and ion exchange?
hardness can be tested by titration with soap solution until it forms a lather. testing effects of water softening done by passing water sample through ion exchange resin, filter, and titrate with soap
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How do you choose safe drinking water?
an appropriate source, low levels of mircobes and dissolved salts
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How is water made safe?
passed through filter beds, sterilising with chlorine, floride added for dental health, pH corrected for taste.
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What are further methods people use to treat water in the home?
filters on taps to remove dissolved substances for tatse, water filters contain charcoal, silver and ion exchange resin.
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Describe distillation in water treatment
water is boiled and the steam is condensed as pure water. requires lots of energy so only wealthy countries might use this
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State the units of energy
Joules. Calories are used for food. 1 calorie= 4.2 joules
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How do you measure energy change from a burning fuel?
using calorimetry, measure the weight of the fuel burner before and after heating water
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What eqaution could you use to measureenergy change?
Q= mcΔT, energy change= mass of liquid x specific heat capacity x temp change
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What is needed to break chemical bonds in a reaction?
energy must be supplied, so bond breaking is endothermic
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What is released when bonds are formed?
energy is released making it exothermic
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Explain exothermic reactions and bond making
exo= energy given out greater than energy needed to break existing bonds
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Explain endothermic reactions and bond breaking
in endo reactions energy needed to break bonds is greater than energy released from forming new bonds
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Show how ΔH is calculated
energy taken in - energy given out = ΔH in kj/mol e.g hydrogen + chlorine --> hydrogen chloride. break a H-H bond, and a Cl-Cl bond, make 2 mol of H-Cl, 678-862= -184 (exo)
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what is a catalyst?
provides a different pathway for a reaction lowering the activation energy. it is not used up in a reaction
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How do we use hydrogen gas in cars?
we combust it, hydrogen + oxygen --> water. 2H₂ + O₂ --> 2H₂O the only waste product is water and hydrogen fuel cells produce electricity, it is cleaner than petrol and has fewer parts
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What are the flame tests?
Lithium=crimson, sodium=yellow, potassium=lilac, calcium= red, barium=green
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The reaction of sodium hydroxide with cations?
aluminium, calcium and magnesium= white precipitate. iron(2) green precipitate, iron(3) brown, copper(2) is blue Cu²⁺ +2OH⁺ --> Cu(OH)₂
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Describe the test for anions involving the reaction of dilute acid and metal carbonate
CO₂ produced which turns limewater cloudy
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How can you test for Halide ions?
with silver nitrate and nitric acid added first to prevent silver carbonate forming, iodide gives a white precipitate, bromide a cream and chloride a white.
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How would you test for sulphate ions?
with barium chloride, it produces a white precipitate
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How would you test for Nitrate ions?
with sodium hydroxide they produce ammonia which stinks
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How would you find the volmes of a strong aci and alkali reacting together?
titration. the alkali is pipetted into a conical flask and an indictaor is added. the acid is added from a burette, checking the meniscus, until indictaor shows it has been neutralised.
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Name some indicators and other methods to measure pH
universal turn green when neutral, alkali turns it purple and acid turns it red, phenolphthalein turns pink when solution neutral. a pH meter or sensor on a data-logger
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What equation could you use to find number of moles in a solution?
moles= concentration x volume in litresdm³
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What is the Haber process?
the way in which we produce ammonia, N₂ + 3H₂⇔2NH₃
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Where does the N₂ and H₂ come from?
the nitrogen comes from air, hydrogen from cracking of oil or natural gas, any unreacted gas is recycled and ammonia is cooled below -40°C and liquefied then run off
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Describe conditions needed for ammonia production
iron catalyst, pressure of 200 atmospheres, temperature 450°C
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When is equilibrium reached in a reaction in a closed system?
when a reversible reaction occurs in a closed system equilibrium is reached when the reactions occur at the same rate in both directions
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How does increasing temp afffect an equilibrium mixture?
the yield from the endo reaction increases and exo decreases
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How does lowering the temp affect the equilibrium?
the yield from the endo reaction decreases and the exo yield increases
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How does changing pressure affect a gaseous equilibrium?
high pressure increase percentage yield and favours the reaction that prouces least number of molecules
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Explain the compromise in the Haber process
high temp decreases the percentage yield of ammonia but gives a high rate of reaction, therefore iron catalyst used to compromise, high pressure increase yield but is dangerous.
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What links Carboxylic acids, Esters and Alcohols?
Alcohols react with carboxylic acids to produce esters.
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What does 'organic' mean here?
the compound is based on carbon and may contain hydrogen.
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Explain what a functional group and a homologous series are
functional group is the reactive part of a compound, a homologous series are compounds with the same functional groupand are arranged in order of carbon chain length
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What is the functional group of alcohols?
-OH, their names end in -ol eg methanol, ethanol, propanol, butanol the formula is CnH2n+1
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What is the functional group of Esters?
-COO- their names are in two parts ending in -yl and -oate e.g methyl ethanoate. they are volatile compounds with distinctive smells used in flavourings and perfume
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What is the functional group of carboxylic acids?
-COOH their names end in -oic acid
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What are the chemical properties of alcohol?
they dissolve in water to form neutral solution, react with sodium to produce hydrogen and they burn in air. they are used as fuels and solvents particularly ethanol, a biofuel and also an alcoholic drink or oxidised to make ethanoic acid (vinegar)
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What are the acidic properties of alcohol?
dissolve in water to produce acidic solutions and react with carbonates to produce CO₂
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What is the molecular, structural, and displayed formula of ethanol?
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Card 2


How were elements put into groups?


Similar properties

Card 3


Why was this known as the periodic table?


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Card 4


What were Newland's Octaves?


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Card 5


Two main problems with early periodic table?


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