practicles + tests

• describe in detail rutherfords experiment and subsequent model of the atom ?

  in 1909 rutherford fired posotively charged alpha particles at a thin sheet of gold. the expected result based on Thompsons model was that the particles would go straight through of have slight diversion in their path, However the result was particles would either go straight through or change course drastically and even in some cases bounce right back.

  The conclusion by rutherford was that their must have been a concentrated mass at the center of the atom. (shell or neutrons had not been discorved yet)
• what is the required practical for measuring energy transfer (method) ?

  1.Put 25 cm^3 of 0.25 mol/dm^3 of hydrochloric acid and sodium hydroxide in sperater beakers.

  2.place the beakers in a water bath set at 25 degrees until they are both the same temperature

  3.add the hcl followed by the NaOH to a polystyrene cup with a lid

  4.take the temperature of the mixture every 30 seconds and record the highest temp

  5. repeat steps 1-4 using 0.5 mol/dm^3 and 1 mol/dm^3
• how would you measure rate of reaction using precipitation or colour change ?

  you record visual changes eg: change in colour, turning transparant to cloudy , making a mark and timing how long it takes to disappear (less time = quicker reaction
• how would you measure rate of reaction using change in mass ?

  place you beaker / test tube with the reaction inside - time how long it takes for a certain amount of mass to be lost (this is only if a gas is formed)(quicker the certain mass is lost faster the reaction)
• how would you measure rate of reaction using volume of gas given off?

  you have your test tube with the reaction inside plug the top with a bung and add a gas syringe and time how long it takes for a certain amount of gas to be produced (faster time = faster rate of reaction)
• how do you separate out the different lengths of hydrocarbon in crude oil ?


  Fractional distillation - heat up the oil (most is turned to gas) -in the collum there is a temperature gradient, cold at the top hot at the bottom, the gas evaporates up the collum until it reaches its melting point where it condeses and is collected.

  
• how can you tell how pure a substance is?

  by comparing your substances mp or bp to the pure substances mp and bp (the closer the more pure )
• what is the test for chlorine ?


  chlorine bleaches damp litmus paper (turning it white)
• what is the test for oxygen ?

  glowing splint - put in oxygen - re-lights
• what is the test for carbon dioxide ?

  bubbling carbon dioxide through an aq solution of limewater turns it cloudy
• what is the test for hydrogen ?


  put a lit split in hydrogen - squeaky pop - burning stops