topic 5 Flashcards
how do you calculate percentage uncertainty
absolute uncertainty/ measured value x 100
absolute uncertainty eg ± 0.1 cm
if you use the equipment twice for e.g initial and final readings then you multiply the absolute uncertainty by 2
what are random errors
when reading an instrument and estimate the final digit it may be read slightly too high or slightly too low
what can random errors be affected by
- how easily the instrument or scale is to read
- person reading the scale poorly
- fluctuations in the temperature of the lab
how can you reduce the effect of random errors
repeat the experiment
calculate mean averages
what are systematic errors
errors that occur due to experimental procedure
what are examples of systematic errors
not zeroing a balance
not reading the burette at eye level
heat loss due to lack of insulation
how do you convert from cm3 to m3
divide by a million
when repeating an experiment to measure the amount of substance in something such as coral, why may the results be inconsistent
different samples may have different amounts of the substance
what does an enthalpy level diagram look like for an exothermic reaction
enthalpy of products is lower than the reactants
what does an enthalpy level diagram look like for an endothermic reaction
enthalpy of products is higher than reactants
what happens to the value of the enthalpy of combustion when the water in the colorimeter is heated for longer/ heated at a higher temperature
the value will be less exothermic
as there would be a greater heat loss due to higher temperature
also because water can only be heated up to 100C
how do you decrease percentage uncertainty when measuring masses
use a larger mass of the solid
use a balance that weighs to 3 d.p
name and explain the 4 types of errors
