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Higher chemistry
Revision for higher chemistry exam
| Question | Answer |
|---|---|
| What are the four ways to speed up a chemical reaction? | Use a catalyst, Increase the temperature , Decrease particle size, Increase concentration |
| What is the equation for relative rate? | 1/t |
| What does collision theory state? | for reactant particles to make product they must collide with enough energy and with the correct geometry. |
| What happens to the reactant molecules when you increase the temperature? | The reactant molecules move quicker |
| When you increase temperature and/or concentration are there more or less successful collisions? | More |
| What is temperature a measure of? | A measure of the average kinetic energy of the particles in a substance. |
| What is the meaning of activation energy? | the minimum energy a reactant must have for a successful collision to happen. |
| For a pair of molecules to react the energy of collision must be what? | Greater than or equal to the activation energy |
| Does temperature affect the activation energy (Ea) | No |
| When you increase the concentration of reactants, what happens on a distribution graph? | The shaded area gets bigger which means more particles have energy greater of equal to the activation energy so more successful collisions take place. |
| When you increase the temperature of an reaction, what happens on a distribution graph? | The curve moves to the right. Now the shaded area increases which shows that more reactants have energy so more successful collisions occur. |
| What happens to the rate of reaction when you increase pressure and why? | The particles are forced closer together so they are more likely to have successful collisions. |
| What happens in a exothermic reaction? | energy is lost to the surroundings. |
| What happens in an endothermic reaction? | Energy is gained. |
| What is enthalpy? | The measure of energy stored in a chemical. |
| If the enthalpy change is negative what type of reaction must it be? | Exothermic |
| If the enthalpy change is higher than the starting starting reactants what type of reaction must it be? | Endothermic |
| What is an activated complex? | The unstable arrangement of atoms formed at maximum in a potential energy diagram |
| What is activation energy measured in? | KJmol-1 |
| What is a catalyst? | A chemical that speeds up a reaction but does not get used up. |
| What is a heterogeneous catalyst? | A catalyst in a different state than the reactants. |
| What is a homogenous catalyst? | A catalyst in the same state as reactants |
| What are the three steps of how catalsyts work? | Step 1- Reactants absorb onto the surface Step 2- Bonds break and new bonds form to make products Step 3- Products desorb off the surface |
| If the active site is blocked what do we say has happened to the catalyst? | The catalyst has been poisioned |
| What changes the activation energy? | Catalsyts |
| Does catalysts affect the enthalpy change? | No |
| What russian chemist created the periodic table in 1869 | Dmitri Mendeleev |
| How are the elements arranged on the periodic table? | They are arranged based on their atomic number |
| What is the name of group 1? | Alkali metals |
| What is the name of group 2? | Alkali Earth metals |
| What is the name of group 7? | Halogens |
| What is the name of group 8? | Noble gases |
| What is the name of the group of metals in the middle of the table? | Transition metals |
| Where does metallic bonding occur? | In metallic elements |
| How are metallic elements conductive? | They conduct due to the outer electrons of the metal atoms being loosely held so they become delocalised. These Delocalised electrons conduct electricity. |
| Are metallic bonds strong or weak? | Strong |
| How can we tell metallic bonds are strong? | They have a high melting point. |
| What happens to the boiling point when you go down a group? | It decreases |
| What happens to the atomic size when you go down a group? | It increases |
| What happens to the atomic size when you go across a period? | It decreases |
| What happens to the boiling point as you go across a period? | It increases |
| Are noble gasses monatomic or diatomic? | Monatomic |
| Meaning of monatomic | They only exist as single atoms |
| As noble gasses have low boiling points, what does this say able the forces? | They are weak |
| What are the weakest type of van der waal forces? | London Dispersion Forces. |
| How do London Dispersion forces arise? | The electrons in an atom become unevenly distributed causing a temporary dipole, this temporary dipole has a knock on effect to neighbouring atoms. The positive of one atoms and negative of the neighbouring atom causes a weak attraction making an LDF. |
| What is a covalent bond? | The electrostatic attraction between two nuclei and a shared pair of electrons |
| What is the meaning of a diatomic elements? | 2 atoms are joined together |
| What are the 7 diatomic elements? | Hydrogen Oxygen Nitrogen Iodine Chlorine Bromine Fluorine |
| When covalent molecular substances are melted or boiled what breaks? The covalent bonds or the weak inter molecular forces (LDFs) | The weak intermolecular forces break (LDFs) |
| Why does the melting point increase when the molecule gets bigger? | This is because there's more atoms present in a molecule so there are more electrons. As there are more electrons there are more LDF's which means more energy is required to separate the molecules. |
| What are the three forms of the element carbon? | Diamond, Graphite and fullerene |
| What is the formula for Fullerenes and what shape is it | The shape of a fullerene is a sphere with the formula C60 |
| What is the C60 molecule also known as | Buckminster |
| What is the formula for Phosphorus? | P4 |
| What's the formula for Sulphur? | S8 |
| What is a covalent network? | Huge structures with every atom being linked to other atoms by covalent bonds. |
| What are the properties of covalent networks? | They have a high boiling point/ Melting point They are very large |
| How many bonds does diamond form with neighbouring atoms? | 4 |
| How many bonds does Graphite form with neighbouring atoms? | 3 |
| What shape is diamond make? | Tetrahedral |
| Meaning of covalent radius? | Half the distance between the 2 nucelli in a covalent bond |
| Meaning of the first ionisation energy of an element | The energy required to remove 1 mole of electrons from 1 mole of atoms in gas state. |
| What are the units for ionisation energy? | KJmol-1 |
| What is the meaning of the second ionisation energy? | The energy required to remove 1 mole of electrons from 1 mole of position ions in the gas state. |
| What are the three types of bonding that can be found in compounds? | Ionic, Polar covalent and non-polar covalent |
| What is an ionic Bond? | The electrostatic attraction between positive and negative ions. |
| When do Ionic bonds occur? | They occur between Metals and non metals |
| When do ionic bonds conduct? | When molten or in solution |
| What is electronegativity? | The measure of the attraction an atom has for a shared pair of electrons in a covalent bond. |
| What does it mean if a bond is non-polar | The electrons are shared equally in a covalent bond. |
| What does it mean if a bond is polar? | The electrons are shared unequally in a covalent bond. |
| Are hydrocarbons more likely to polar or non-polar? | Non-polar |
| What is a permanent dipole? | A polar molecule |
| What are the three types of intermolecular forces | London dispersion forces Permanent dipole- permanent dipole interactions Hydrogen bonding |
| What are intermolecular forces also known as? | Van der Waal forces |
| How do permanent dipole- Permanent dipole forces arise? | Arise when there is a large difference in electronegativity between two atoms bonded together in a covalent bond. |
| Are permanent dipole- permanent dipole forces stronger or weaker than LDF's | Stronger |
| When does hydrogen bonding occur? | It occurs in compounds that contain a very electronegative element attached to a hydrogen atom. |
| Hydrogen bonding only occurs between hydrogen and what three element? | Nitrogen (N) Oxygen (O) Fluorine (F) |
| Put the three intermolular forces in order from strongest to weakest | Hydrogen bonding PD-PD interactions LDFs |
| Are intermolecular forces weaker or stronger than ionic/ Covalent boding | Weaker |
| What is viscosity? | a measure of a fluid's resistance to flow |
| What does viscosity depend on? | The strength of the hydrogen bonding present between molecules. |
| When an Ion is surrounded by water molecules it is said to be what? | Hydrated |
| Like dissolves... | Like |
| Meaning of Miscible | If two liquids are miscible they will mix together to form 1 layer |
| Why cant water and oil mix? | Because oil is non polar and cannot dissolve in the polar water. |
| What are esters made from? | Alcohols and a carboxylic acid |
| What group does alcohols contain? | A hygroxyl group |
| How do you determine the main chain in a branked alkanol? | Longest continuous chain of carbons that contains the hydrogen group |
| From which end is the chain numbered | End closest to hydroxyl |
| If the shorted structural formula is- CH2(OH)CH(CH3)CH2CH2CH3 What is the name? | 2-methylpentan-1-ol |
| If the shorted structural formula is- CH3CH2CH(CH3)CH2CH2CH2CH2CH(OH)CH3 What is the name? | 6-methyloctan-2-ol |
| What is the functional group found in carboxylic acids? | Carboxyl group |
| What is the general formula for a carboxylic acid | CnH2nCOOH |
| What are the three mail uses of esters? | Perfume, Flavouring, solvents |
| Why do you heat esters up in a hot water bath? (other than to speed up the reaction) | All the reagents are flammable |
| How do you tell when an ester has been formed? | Smell change |
| How do you tell when an ester has been formed after being poured into a liquid to neutralise it? | Forms an oily layer |
| What is a condensation reaction? | Two small molecules join together to make a bigger molecule and eliminate a smaller one usually water but can be methanol ammonia or HCl |
| Write out the general word equation for the formation of an ester | Alcohol + Carboxylic acid -> ester + water |
| What is the functional group in an ester? | Carboxylate |
| What type of reaction is the formation of an ester? | Condesnsation |
| What type of reaction is the breaking of an ester? | Hydrolysis |
| What is a hydrolysis reaction? | A molecule is broken down by the action of water |
| Is esters reversible (use of acid) | yes |
| Is esters reversible (use of alkali) | no |
| Give two advantages of using Alkaline hydrolysis rather than acid Hydrolysis | 1) get a higher yield as reaction is not reversible 2) The salt and alcohol are easier to separate |
| Why are fats and oils important in our diet? | They supply us with energy and vitamins |
| Are fats m.p. high or low | High |
| Are oils m.p. high or low? | low |
| Why do oils have lower melting points? | They are unsaturated |
| How do you find out if something is saturated or unsaturated? | Use bromine water |
| What can fats and oils be classified as? | Triglycerides |
| What is the other name given to glycerol | Propan-1,2,3-triol |
| Most fats and oils contain what? | Gycerol |
| Why do fats have a high m.p. | As fats are closer together they have more LDF's |
| Why do oils have a low m.p. | Due to oils having "kinks" they cannot pack as closely together meaning there is fewer LDF's |
| What type of reaction is hardening oils? | Addition/ Hydrogenation |
| Are the heads of soap polar or non polar? | Polar |
| Are the tails of soap polar or non-polar? | Non-polar |
| Meaning of Hydrophilic | term used to describe parts of molecules that attach to water |
| Meaning of hydrophobic | Parts of a molecule that don't attach to water |
| Are the heads of soap Hydrophilic or Hydrophobic? | Hydrophilic |
| Are the tails of soap Hydrophilic or Hydrophobic? | Hydrophobic |
| How does soap work? | Step 1- The non-polar tail of the soap dissolves in the non-polar grease Step 2- agitation of the mix forms droplets. The polar heads of the soap cover the outside of the droplets which then dissolve in the polar water. |
| Why do detergents not form a scum? | They react with Ca↑2+ and Mg↑2+ ions. |
| An emulsion contaions what | small droplets of 1 substance suspended in another |
| what are fibrous proteins | long and thin and are the major structural materials of animal tissue |
| What are globular proteins? | spiral chains folded into compact units, globular proteins are involved in the maintenance and regulation of life |
| Why do tertiary alcohols not undergo oxidation? | There are no hydrogens on the carbon with hydroxyl |
| Why are enzymes said to be specific? | They have a specific job to do in the body |
| When amino acids join together to form a protein, what type of reaction is this? | Condensation |
| When proteins break down, what type of reaction is this? | Hydrolysis reaction |
| What is an antioxidant? | A chemical that prevents oxidisation |
| What is stage one of primary alcohols being oxidised? | Primary alcohol -> Aldehyde |
| What is stage 2 of a primary alcohol being oxidised? | Aldehyde -> Carboxylic acid |
| What is the only stage of secondary alcohol being oxidised? | Secondary Alcohol -> Keytone |
| What can alcohols be divided up into? | Primary Alcohol Secondary alcohol Tertiary alcohol |
| What elements are in proteins? | Nitrogen Oxygen Carbon Hydrogen |
| Whats an amide link? | The link between monomers |
| What are enzymes dependant on? | Temperature and pH |
| How does a helix structure form | Hydrogen bonds |
| What 2 groups are in amino acids? | Amino group (-NH2) Carboxyl group (-COOH) |
| What happens when oxygen reacts with edible fats and oils in food? | The food gets a rancid flavour |
| What are essential amino acids? | Amino acids that can only be obtained through diet |
| Meaning of denatured | The protein (enzyme) has changed shape |
| Describe what happens to the oxygen:hydrogen ration in an oxidation reaction | In an oxidation reaction the O:H ratio increases and the H:O ratio decreases |
| What are essential oils? | Oils extracted from plants, they usually have distincitve smells |
| Are Essential oils polar or non-polar? | Non-polar |
| Are Essential oils Volatile? | Yes |
| What compounds do essential oils usually contain? | Terpenes |
| What does volatile mean? | Easy to evaporate |
| What are Essential oils used in? | Perfumes, candles, shower gels and cosmetics |
| How are essential oils extracted from plants? | Steam distillation |
| Are Essential oils Miscible? | No |
| When steam distillation finishes, the essential moves onto what step? | Solvent extraction |
| What is solvent extraction? | Where one substance is removed from a mixture of substances |
| What apparatus is used in solvent extraction? | Separation funnel |
| What are terpenes made from? | Isoprenes |
| What is the chemical name for isoprene? | 2-methylbuta-1,3-diene |
| What is the molecular formula for Isoprene? | C5H8 |
| Are terpenes saturated or unsaturated? | Unsaturated |
| What is the general formula for isoprenes | (C5H8)n |
| Why would we want to prevent the oxidation of terpenes? | The smell could change |
| What is sunlight made up from? | A rainbow of different colours from red through to violet |
| What is sunlight also made up from which we cannot see? | Ultra violet light |
| What is Ultra violet light also called? | UV light |
| Why is UV light bad for our skin? | It can develop skin cancer |
| How do we prevent UV light causing skin cancer? | use of sunscreen or Sunblock |
| What compounds does sun block contain? | Titanium doixide |
| What is a free radical? | Atoms that have unpaired electrons |
| What is the first step of free a radical reaction? | Initation |
| What is the second step of a free radical reaction? | Propagation |
| What is the third step of a free radical reaction? | Termination |
| Explain Initation | Uv light causes bonds to break Radicals on right |
| Explain propagation | Radicals react with the other element to form new bonds Radicals on both side |
| Explain Termination | Radicals react with others to from stable substance Radicals on left |
| Explain why chemicals are stored in brown glass bottles | The brown glass stops Uv light reaching the chemicals so it stops free radicals from forming and causing the chemical to go off |
| What is a free radical scavenger? | A compound that reacts with free radicals to form stable molecules that prevent chain reactions occuring |
| What are free radical scavengers added to? | Cosmetics, food, plastic |
| What is the Enthalpy of combustion? | The energy released when 1 mole of a substance burns completely into oxygen |
| Sometimes the enthalpy of combustion is lower than you may worked out, state the three reasons why. | Heat lost to surroundings, incomplete combustion, some fuel evaporation has occured before it burned |
| What 3 things does a calorimeter help with when doing a enthalpy of combustion investigation? | Stops heat from going out as all the heat goes into water Pure oxygen is used so there will be no incomplete combustion No evaporation would take place as its a sealed system |
| What is the enthalpy of solution? | The energy change when 1 mole of a substance is dissolved completely in water |
| What does Hess's Law state? | The enthalpy change for a reaction is the same no matter the route taken |
| What is the meaning of molar bond enthalpy? | The energy required to break 1 molecule of bonds |
| Meaning of mean bond enthalpy? | The average bond strength for that bond type in different compounds |
| Is bond forming exothermic or endothermic? | Exothermic |
| Meaning of oxidation | Loss of eletrons |
| Meaning of reduction | Gain of electrons |
| What is a redox reaction? | A reaction when reduction and oxidation happens at the same time |
| Does a reducing agent lose or gain electrons? | Lose |
| Does a Oxidising agents lose or gain electrons? | Gain |
| What are the conditions said to be if there is an equation that contains H+ Ions | Acidic |
| What is a feedstock? | A reactant from which other chemicals must be produced. They are obtained by raw materials |
| What is a raw material? | A useful substance for the chemical industry which is formed naturally |
| Who controls chemical manufacturing whinin the EU to prevent damage to the environment? | SEPA |
| What does SEPA stand for? | Scottish environment protection agency |
| When a reaction is reversible we actually say that the reaction is in the state of what? | Equilibrium |
| Explain why the equation is written with the two way arrow | The arrow is showing that both forward and backwards reaction are occuring at the same time |
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