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21 Thermochemistry
Q 6. Thermochemistry
| Question | Answer |
|---|---|
| thermochemistry | study of the relationship of energy to chemistry |
| Bond energy | is the average energy required to break one mole of a particular covalent bond & to separate the neutral atoms completely from each other. |
| Law of Conservation of energy | Energy cannot be created or destroyed it, it just changes from one form to another. |
| enthalpy | the heat content of a system measure at constant pressure |
| heat of reaction | heat change when the number of moles of reactants indicated in the balanced equation for the reaction react completely. |
| heat of combustion | of a substance is heat change when one mole of the substance is completely burned in excess oxygen |
| heat of formation | the amount of heat given out or taken in when 1 mole of a compound is formed from its elements in their standard states |
| Kilogram Calorific Value | heat energy given off when 1kg of the fuel is completely burned in oxygen |
| Hess's Law | the total heat involved in a reaction is equal to the sum of the individual steps. |
| Avagadro's number | the number of particles in one mole of a substance |
| Hydrocarbon | a compound that contains Carbon & Hydrogen only |
| Fossil Fuels | Fuels that are formed from the remains of plants and animals that lived millions of years ago. |
| Saturated compound | One in which there are only single bonds between the atoms in the molecule. |
| Homologous series | compounds of similar chemical properties, showing graduations in physical properties, Having a general formula, similar method of preparation & differing by a CH2 unit. |
| Structural Isomers | are compounds with the same molecular formula but different structural formula |
| Alkyl Group | An Alkane molecule that has had a Hydrogen removed e.g. Methyl - CH3, Ethyl - C2H5 |
| Dimethyl | two methyl groups |
| Alkene | a hydrocarbon that contains a double bond between the atoms in the molecule. |
| Alkane | a hydrocarbon that contains single bonds between the atoms in the molecule. |
| Alkyne | a hydrocarbon that contains a triple bond between the atoms in the molecule. |
| Meth- | one carbon atom in a compound |
| Eth- | 2 Carbon atoms in a compound |
| Prop- | 3 Carbon atoms in a compound |
| But- | 4 Carbon atoms in a compound |
| Pent- | 5 Carbon atoms in a compound |
| Hex- | 6 Carbon atoms in a compound |
| Hept- | 7 Carbon atoms in a compound |
| Oct- | 8 Carbon atoms in a compound |
| Non- | 9 Carbon atoms in a compound |
| Dec- | 10 Carbon atoms in a compound |
| Aliphatic compound | An organic compound that consists of open/closed chains of carbon atoms that resemble them in chemical properties. |
| Aromatic compounds | Compounds that contain a benzene ring structure in their molecules |
| Benzene | C6H6, A six carbon ring structure held together by bonds of equal lenght neither single or double bond lenght. |
| Auto-ignition | is premature explosion of the petrol-air mixture before normal ignition of the mixture by a spark. |
| Octane Number | is the measure of the tendency of a fuel to resist knocking, Reference Heptane Octane number = 0 & 2,2,4, trimethylpentane Octane number = 100 |
| Catalytic Cracking | Breakdown of long-chain hydrocarbon molecules by heat & catalysts into short-chain hydrocarbon molecules which are in greater demand |
| Isomerisation | Changing straight chain alkanes into their highly branched short chain isomers |
| Dehydrocyclisation | Straight chain alkanes are converted into cyclic/ring compounds and hydrogen gas is given off (Ring formation & removal of Hydrogen) |
| Heat of neutralisatioon | heat change when one mole of H+ ions from an acid reacts with one mole of OH- ions from a base |
| Organic Chemistry | the study of compounds of carbon |
| Unsaturated compound | one that contains one or more double or triple bonds between the atoms in the molecule |
| Test for unsaturation | decolourises Bromine water |
| Combustion of Ethene | burns with a yellow luminous, slightly smoky flame |
| Combustion of Ethyne | burns with a bright smoky flame & loads of soot particles formed. |
| Fractional Distillation | Heating the Crude oil and separating out the different various parts based on their boiling points, compounds with similar boiling points are called fractions. |
| Exothermic | Heat is produced, given out, temperature rises. |
| Endothermic | Heat is absorbed, taken in, temperature drops. |
| Heat given out | mass x specific heat capacityx rise in temperature |
Created by:
PRO Teacher
Ms O'Farrell
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