Summer Assessment 3- more
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how can you work out the speed of a reaction on a graph
• by recording the amount of product formed or the amount of reactant used up over time • the steeper the line on a graph the fatser the reaction • line becomes less steep as reactants are used up
what do the quickest reactions show on a graph
-they have the steepest line and become flat in the least time
what does the rate of a chemical reaction depend on
• collision frequency of reacting particles- the more collisions the faster the reaction • energy transferred during a collision
what is activation energy
-the minimum amount of energy particles need to react
why to particles need activation energy
-to break the bonds in reactants to start to the reaction
explain the method you would carry out to measure how surface area affects rate
• use marble chips and HCL • set up the apparatus so you have a conical flask with marble chips in it as well as HCL- attach to the bung in the conical flask a gas syringe • measure volume of gas produced using a gas syringe • take readings at regular intervals and record the results
why does using finer particles of solid mean a higher rate of reaction
-as finer particles mean the marble has a larger surface area
what effect does changing the concentration of acid have on the rate of reaction
a higher concentration gives a faster reaction
what is the general formula for alkenes
CnH2n
what is the empirical formula (for ethene)
CH2 -simplest ratio of atoms
what is the molecular formula (for ethene)
C2H4 -actual number of atoms of each element in a molecule
what is the structural formula (for ethene)
CH2CH2 -shows arrangement of atoms carbon by carbon
what is a homologous series
-a group of compounds that can all be represented by the same general formula
what is a functional group
• a group of atoms that determine how a compound typically reacts
definition of isomer
two or more molecules with the same molecular formulae but different structural formula
what can you infer from differently shaped carbon chains
• these isomers have similar chemical properties - but different physical properties due to the change in shape of the molecules
what could you infer from functional groups being in different places
-these isomers have different physical properties
what could you infer from functional groups being different
-these isomers have different physical and chemical properties
What is a hydrocarbon?
a compound of hydrogen and carbon only
What happens when you burn a fuel?
releases energy in form of heat
What is burning a fuel also known as?
-combustion reaction
Why do hydrocarbons make great fuels?
as the combustion reaction that happens when you burn them in oxygen gives out lots of energy
hydrocarbon + oxygen =
carbon dioxide + water
What is complete combustion
-when you burn hydrocarbons in plenty of oxygen, the only products are CO2 and water