Lab : density, accuracy and precision Aim: to determine the relative precision and accuracy of different glassware items by calculating the density of a known substance. Introduction: the density of a substance is its mass per unit volume. (where P-density, m- mass and v- volume). Different materials usually have different densities and densities vary according to the pressure, temperature and purity of a substance. When measuring, there is always a small uncertainty or error and therefore no measurement is exact. Variables: Independent: the type of liquid used Dependent: the volume and density of the liquidControlled: the same type of beaker as the mass of the beaker is never changed Hypothesis : the larger the divisions on the glassware items the bigger the percentage of error.
Materials: Car oil Coke Zero Liquid soap Salty water lax mall beaker 1 x mall beaker 1 x ml cylinder 1 x weighing scale 1 x thermometer Procedure: 1. Weigh a dry 100 ml beaker, a 10 ml graduated cylinder and a 10 ml pipette (in this case weigh a 150 ml beaker that you will transfer into a pipette, pipettes cannot be weighted effectively) and record the mass for each case.Do not forget that trailing zeros are significant figures and should be recorded.
. Obtain a fair amount of water and measure its temperature. (Remember here some students are measuring different substances, so the procedure must be the same but with the substance assigned by the teacher) 3.
Put 10 ml of water in each glassware item. Record the volume for each one. 4. Weigh and record the mass for each item. 5. Do this 3 times for each piece of glassware, making sure you dry (as best as you can) the glassware in between trials. 6.