What are some sources or inaccuracy in the specific heat capacity practical and how would you prevent them

- thermal energy passing out of the beaker to the air, prevented by using an insulator with lower thermal conductivity - not all thermal energy from immersion heater passes through to oil, to prevent this, ensure that immersion heater is fully submerged - incorrect reading of thermometer, use electric temp probe - thermal energy not being spread in oil, stir the oil