AQA CHEMISTRY UNIT 3 KEYPOINTS ON EVERY TOPIC

THESE CARDS CONTAIN KEYPOINTS ON EVERY TOPIC FOR THE AQA C3 PEOPLE DOING GCSES IN MAY. PLEASE COULD YOU COMMENT AND RATE IT. AND PLEASE INFORM OF ANY OTHER MISTAKES THAT YOU FIND SO THAT I COULD EDIT THEM!!

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  • Created by: SONIKA
  • Created on: 13-04-11 13:14

THE EARLY PERIODIC TABLE

THE EARLY PERIODIC TABLE

  • THE PERIODIC TABLE OF ELEMENTS DEVELOPED AS AN ATTEMPT TO FIND THE ELEMENTS.
  • IT ARRANGES THE ELEMENTS IN A PATTERN ACCORDING TO THEIR PROPERTIES.
  • EARLY PERIODIC TABLES DIDN'T NOTICE THAT NOT ALL THE ELEMENTS WERE KNOWN.
  • MENDELEEV'S TABLE TOOK NOTICE OF THE UNKNOWN ELEMENTS AND SO PROVIDED THE BASIS OF THE MODERN PERIODIC TABLE.
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THE MODERN PERIODIC TABLE

THE GROUP THAT AN ELEMENT IS IN IT DETERMINED BY THE ATOMIC/PROTON NUMBER

THE NUMBER OF ELECTRONS IN THE HIGHEST ENERGY LEVEL OF AN ATOM DETERMINES ITS CHEMICAL PROPERTIES.

WE CAN EXPLAIN TRENDS IN REACTIVITY AS WE GO DOWN A GROUP IN TERMS OF THE NUMBER AS WE GO DOWN A GROUP IN TERMS OF THE NUMBER OF ENERGY LEVELS IN THE ATOMS

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GROUP 1- THE ALKALI METALS

ALKALI METALS

THEY ARE:LITHIUM, SODIUM, POTTASSIUM, RUBIDIUM, CAESIUM AND FRANCIUM

  • ARE ELEMENTS IN GROUP 1
  • ALL REACT WITH WATER TO PRODUCE HYDROGEN AND AN ALKALINE SOLUTION CONTAINING THE METAL HYDROXIDE
  • AS YOU GO DOWN:THERE ARE BIGGER ATOMS
  • THEY ARE MORE REACTIVE
  • THEY HAVE A HIGHER DENSITY
  • LOWER MELTING POINT
  • LOWER BOILING POINT
  • ALKALINE METALS:ALL HAVE 1 OUTER ELECTRON
  •  ALL FORM 1+ IONS
  • ALWAYS FORM IONIC COMPOUNDS
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GROUP 7- THE HALOGENS

  • THE HALOGEN GROUPS ARE
  • FLUORINE
  • CHLORINE
  • BROMINE
  • IODINE
  • ASTATINE
  • AS YOU GO DOWN THE GROUP:IT GETS LESS REACTIVE
  • HIGHER MELTING POINT
  • HIGHER BOILING POINT
  • THE HALOGENS ARE ALL NON-METALS WITH COLOURED VAPOURS
  • FLUORINE- VERY REACTIVE POISONOUS YELLOW GAS
  • CHLORINE- FAIRLY REACTIVE, POISONOUS GREEN GAS
  • BROMINE- DENSE, POISONOUS, RED BROWN VOLATILE LIQUID
  • IODINE- DARK GREY CRYSTALLINE SOLID OR A PURPLE VAPOUR
  • THEY ALL FORM MOLECULES WHICH ARE PAIR OF ATOMS
  • THE HALOGENS DO BOTH IONIC AND COVALENT BONDING
  • THE HALOGENS REACT WITH METALS TO FORM SALTS
  • MORE REACTIVE HALOGENS WILL DISPLACE LESS REACTIVE ONES
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TRANSITION ELEMENTS

TRANSITION METALS

  • TRANSITIONAL METALS ARE ALL GOOD CONDUCTORS OF HEAT AND ELECTRICITY
  • THEY ARE VERY STRONG, DENSE AND SHINY
  • THEY ARE ALL MUCH LESS REACTIVE THAN GROUP 1 METALS
  • THEY DON'T REACT MUCH WITH OXYGEN OR WATER
  • THEY ARE ALSO MUCH DENSER, STRONGER AND HARDER THAN THE GROUP 1 METALS
  • THEY HAVE ALL GOT HIGH MELTING POINTS EXCEPT FOR MERCURY WHICH IS LIQUID AT ROOM TEMPERATURE.
  • THEY OFTEN HAVE MORE THAN 1 ION
  • THE COMPOUNDS ARE VERY COLOURFUL
  • THEY ALL MAKE GOOD CATALYSTS
  • THEIR PROPERTIES ARE DUE TO THE WAY THEIR ELECTRON SHELLS FILL
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ACIDS AND ALKALIS

ACIDS AND ALKALIS

  • ACIDS IN AQUEOUS SOLUTIONS PRODUCE H+ IONS
  • ALKALIS IN AQUEOUS SOLUTIONS PRODUCE OH- IONS
  • A STRONG ACID OR A BASE IS 100% IONISED IN WATER
  • A WEAK ACID OR ALKALI IS ONLY PARTLY IONISED IN WATER
  • AN ACID IS A PROTON DONOR
  • A BASE IS A PROTON ACCEPTER
  • AN EXAMPLE OF A WEAK ACID IS ETHANOIC ACID
  • AN EXAMPLE OF A WEAK ALKALI IS AMMONIA SOLUTION
  • AN EXAMPLE OF STRONG ACID IS SULFURIC ACID
  • AN EXAMPLE OF A STRONG ALKALI IS SODIUM HYDROXIDE
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TITRATIONS

  • TITRATION IS USED TO MEASURE ACCURATELY HOW MUCH ALKALI IS NEEDED TO REACT COMPLETELY WITH A KNOWN AMOUNT OF ACID (OR VICE VERSA)
  • THE POINT AT WHICH AND ACID-BASE REACTION IS COMPLETE IS CALLED THE END POINT OF REACTION
  • A SUITABLE INDICATOR SHOULD BE CHOSEN TO SHOW THE END POINT OF AN END POINT OF AN ACID-BASE REACTION.
  • WEAK ACID + STRONG ALKALI - USE PHENOLPHTHALEIN
  • STRONG ACID + WEAK ALKALI - USE METHYL ORANGE
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TITRATION CALCULATIONS

TO CALCULATE THE CONCENTRATION OF A SOLUTION:

  • CALCULATE THE MASS IN g OF SOLUTE IN 1cm3 OF SOLUTION
  • CALCULATE THE MASS OF SOLUTE IN 1000cm3 OF SOLUTION
  • CONVERT THE MASS IN g TO MOLES

TO CALCULATE THE MASS OF SOLUTE IN A CERTAIN VOLUME OF SOLUTION:

  • CALCULATE THE MASS OF THE SOLUTE THERE IS IN 1dm3 OF SOLUTION
  • CALCULATE THE MASS OF SOLUTE IN 1cm3 OF SOLUTION
  • CALCULATE THE MASS OF SOLUTE THERE IS IN THE GIVEN VOLUME OF THE SOLUTION
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WATER AND SOLUBILITY

WATER AND SOLUBILITY

  • WATER EVAPORATES FROM RIVERS, LAKES AND OCEANS AND CONDENSES TO FORM CLOUDS, RETURNING TO THE SURFACE AS RAIN
  • MOST IONIC SUBSTANCES ARE SOLUBLE IN WATER, BUT MANY COVALENT COMPOUNDS ARE NOT
  • A SATURATED SOLUTION CONTAINS THE MAXIMUM AMOUNT OF SOLUTE THAT WILL DISSOLVE AT THAT TEMPERATURE

SOLUBILITY CURVES

  • THE SOLUBILITY OF MOST SOLID SOLUTES INCREASES AS THE TEMPERATURE RISES
  • THE SOLUBILITY OF GASES DECREASES AS THE TEMPERATURE RISES
  • SOLUBILITY CURVES SHOW HOW THE SOLUBILITY OF A SUBSTANCE CHANGES WITH TEMPERATURE
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HARD WATER

 HARD WATER CONTAINS DISSOLVED SUSTANCES SUCH AS CALCIUM AND MAGNESIUM SALTS

THE CALCIUM AND/OR MAGNESIUM IONS IN HARD WATER REACT WITHH SOAP PRODUCING A PRECIPITATE CALLED SCUM

THE CALCIUM SALTS AND/OR MAGNESIUM SALTS ALSO DECOMPOSE TO FORM SCALE WHEN THE WATER IS HEATED

HARD WATER MAY HAVE BENEFITS FOR HUMAN HEALTH

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REMOVING HARDNESS

  • SOFT WATER DOES NOT CONTAIN SALTS THAT PRODUCE SCUM OR SCALE
  • HARD WATER CAN BE SOFTENED BY REMOVING THE SALTS THAT PRODUCE SCUM AND SCALE
  • WATER CAN BE SOFTENED BY ADDING WASHING SODA OR BY USING AN ION-EXCHANGE RESIN TO REMOVE CALCIUM AND MAGNESIUM IONS.
  • WATER TREATMENT
  • WATER FOR DRINKING SHOULD CONTAIN LOW LEVELS OF DISSOLVED SUBSTANCES AND MICCROORGANISMS
  • WATER IS MADE FIT TO DRINK BY FILTERING IT TO REMOVE SOLIDS AND ADDING CHLORINE TO KILL BACTERIA
  • WE CAN MAKE PURE WATER BY DISTILLATION
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COMPARING THE ENERGY PRODUCED BY FUELS

WHEN FUELS AND FOOD REACT WITH OXYGEN, ENERGY IS RELEASED SO THE REACTION IS EXOTHERMIC

A SIMPLE CALORIMETER CAN BE USED TO COMPARE THE ENERGY RELEASED BY DIFFERENT FUELS OR DIFFERENT FOODS IN A SCHOOL CHEMISTRY LAB

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ENERGY CHANGES IN REACTIONS

IN CHEMICAL REACTIONS, ENERGY MUST BE SUPPLIED TO BREAK THE BONDS BETWEEN ATOMS IN THE REACTANTS

WHEN BONDS ARE FORMED BETWEEN ATOMS IN A CHEMICAL REACTION, ENERGY IS RELEASED.

IN AN EXOTHERMIC REACTION, THE ENERGY RELEASED WHEN BONDS ARE FORMED IS GREATER THAN THE ENERGY ABSORBED WHEN BONDS ARE BROKEN. THE OPPOSITE IS TRUE FOR ENDOTHERMIC REACTIONS

DELTAH IS NEGATIVE FOR EXOTHERMIC REACTIONS. IT IS POSITIVE FOR ENDOTHERMIC REACTIONS.

THE MINIMUM AMOUNT OF ENERGY TO START A REACTION IS CALLED THE ACTIVATION ENERGY

THE OVERALL ENERGY CHANGE IN A CHEMICAL REACTION CAN BE CALCULATED USING BOND ENERGIES.

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TESTS FOR POSITIVE IONS

TESTS FOR POSITIVE IONS

  • G1 AND G2 METALS CAN BE IDENTIFIED IN THEIR COMPOUNDS USING FLAME TESTS
  • SODIUM HYDROXIDE SOLUTION CAN BE USED TO IDENTIFY DIFFERENT METAL IONS DEPENDING ON THE PRECIPITATE THAT IS FORMED
  • AMMONIUM IONS PRODUCE AMMONIA WHEN SODIUM HYDROXIDE SOLUTION IS ADDED AND THE SOLUTION IS WARMED GENTLY

ELEMENT-FLAME COLOUR

  • LITHIUM-BRIGHT RED
  • SODIUM-GOLDEN YELLOW
  • POTASSIUM-LILAC
  • CALCIUM-BRICK RED
  • BARIUM-GREEN
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TESTS FOR NEGATIVE IONS

TESTS FOR NEGATIVE IONS

  • WE IDENTIFY CARBONATES BY ADDING DILUTE ACID, WHICH PRODUCES CARBON DIOXIDE GAS
  • WE IDENTIFY HALIDES BY ADDING NITRIC ACID AND SILVER NITRATE SOLUTION, WHICH PRODUCES A PRECIPITATE OF SILVER HALIDE.
  • WE IDENTIFY SULFATES BY ADDING HYDROCHLORIC ACID AND BARIUM CHLORIDE SOLUTION TO PRODUCE A WHITE PRECIPITATE OF BARIUM SULPHATE
  • WE IDENTIFY NITRATES BY ADDING SODIUM HYDROXIDE SOLUTION AND A LITTLE ALUMINIUM POWDER TO PRODUCE AMMONIA GAS

THE COLOUR OF PRECIPITATE TELLS US WHICH HALIDE IT IS

  • CHLORIDE IONS GIVE A WHITE PRECIPITATE
  • BROMIDE IONS GIVE A CREAM PRECIPITATE
  • IODIDE IONS GIVE A PALE YELLOW PRECIPITATE
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TESTING FOR ORGANIC COMPOUNDS

TESTING FOR ORGANIC COMPOUNDS

ORGANIC COMPOUNDS BURN OR CHAR WHEN WE HEAT THEM

WE CAN WORK OUT THE EMPIRICAL FORMULA OF AN ORGANIC COMPOUND FROM THE RATIO OF THE PRODUCTS PRODUCED WHEN IT BURNS

WE CAN DETECT CARBON-CARBON DOUBLE BONDS USING BROMINE WATER

UNSATURATED HYDROCARBONS+BROMINE=COLOURLESS PRODUCT

SATURATED HYDROCARBON+BROMINE=NO REACTION

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INSTRUMENTAL ANALYSIS 1

INSTRUMENTAL ANALYSIS 1

MODERN INSTRUMENTAL TECHNIQUES DEPEND ON ELECTRONICS AND COMPUTERS TO PROVIDE FAST, ACCURATE AND SENSITIVE WAYS OF ANALYSING CHEMICAL SUBSTANCES

ATOMIC ABSORBTION SPECTROSCOPY AND MASS SPECTROMETRY CAN BE USED TO ANALYSE AND IDENTIFY THE CHEMICAL ELEMENTS IN A SAMPLE

INSTRUMENTAL ANALYSIS 2

COMPOUNDS IN A MIXTURE CAN BE SEPARATED USING CHROMOTOGRAPHY

ONCE SEPARATED, COMPOUNDS CAN BE IDENTIFIED USING A VARIETY OF INSTRUMENTAL TECHNIQUES.

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