AQA GCSE 9-1 higher combined science - chemistry paper 2 Questions & Answers

what is a rate of reaction? - ANSWERSthe speed of a reaction what is the equation for rate of reaction? - ANSWERSquantity of reactant used up/time taken or quantity of product formed/time taken what unit do we normally use for time? - ANSWERSseconds what unit do we normally use for mass? - ANSWERSgrams what unit do we normally use for a rate of a reaction? - ANSWERSgrams/second you can also measure a rate of a reaction using ... - ANSWERSa graph how do you calculate the gradient? - ANSWERSchange in y/change in x what key factors affect the rate of reaction? - ANSWERStemperature pressure concentration surface area catalysts what happens to the rate as you increase the temperature? - ANSWERSthe rate increases what is concentration a measurement of? - ANSWERSthe number of particles dissolved in a given volume of solvent what is pressure a measurement of? - ANSWERSthe number of particles in a given volume of gas what happens to the rate of a reaction when you increase its pressure or concentration? - ANSWERSit increases what happens to a rate of reaction when you increase its surface area? - ANSWERSit increases what is a catalyst? - ANSWERSa substance that speeds up a chemical reaction without being used up how do a catalyst work? - ANSWERSit decreases the activation energy that a reaction needs what is the collision theory? - ANSWERSchemical reactions can only take place if reaction particles collide into each other with sufficient energy what happens when the concentration, pressure or surface area is increased? - ANSWERSthe frequency of collisions increases so the rate of reaction also increases what happens when the temperature is increased? - ANSWERSthe frequency of collisions increases and are made more energetic so the rate of reaction increases what is a reversible reaction? - ANSWERSwhere the products of a reaction can react again and produce the original reactants what is equilibrium? - ANSWERSwhen the forward and reverse reactions happen at exactly the same rate what is the le chateliers principle? - ANSWERSif a system is at equilibrium and a change is made to the conditions the system responds to counteract the change what happens if you increase the concentration of an equilibrium reactant? - ANSWERSit causes the forward reaction to happen at a faster rate than the backward reaction shifting the position of equilibrium - more products are formed and more reactants are used up what happens if you increase the pressure of an equilibrium system? - ANSWERSit will go to the side with lower pressure (fewer moles of gas) what happens when a temperature change happens to an equilibrium system? - ANSWERSit will favour the side opposite (temp increase - endothermic reaction) what is crude oil? - ANSWERSa non renewable resource that is a mixture of compounds mainly hydrocarbons what is an alkane? - ANSWERSa kind of hydrocarbon with only single carbon-carbon bonds (they are called saturated hydrocarbons as no more hydrogen atoms can be added)