Today’s lesson Demonstrate understanding of the term thermal capacity Describe an experiment to measure the specific heat capacity of a substance Recall and use the equation: Energy = mass x specific heat capacity x change in temperature

Imagine… Heating a 1 kg block of copper and a 1 kg block of brass for the same time. Would their temperature rise be the same? copper brass

Why are the temperature rises different? When a substance is heated, its internal energy increases (potential and kinetic). The stronger the force between the particles in the substance, the more heat energy goes into potential energy (and less into kinetic), so the temperature rise is less than in substances with little force between particles. (Remember temperature is a measure of the kinetic energy)

Specific heat capacity Specific heat capacity is the amount of energy needed to raise the temperature of one kilogram of a substance by 1°C Specific heat capacity of water = 4186 J/kg/°C Specific heat capacity of kerosene = 2010 J/kg/°C Specific heat capacity of mercury = 140 J/kg/°C Can you COPY this please?

Calculations using S.H.C. Energy absorbed = Mass x Specific Heat capacity x Temp rise   E = mcΔT J kg J/kg/°C °C Can you COPY this too please?

For example 0.5 kg of olive oil is heated until its temperature rises by 120 °C. If the specific heat capacity of olive oil is 1970 J/kg/°C, how much heat energy was used? Energy absorbed = Mass x Specific Heat capacity x Temp rise Energy absorbed = 0.5 x 1970 x 120 Energy absorbed = 118200 J

An analogy: Water and wetness “This analogy is one of my ideas!” Richard Feynmann – Nobel prize winning Physicist, lock-picker and bongo player

Two towels – same size/mass You can add the same amount of water (heat), but the cheap towel will be “wetter” You can add the same amount of water (heat), but the cheaper towel will be “wetter” (temperature). They have different capacities for absorbing water

Questions

Investigation time! Let’s do an experiment to measure specific heat capacities solid block immersion heater thermometer

Measuring SHCs Energy put IN to metal = voltage x current x time Energy = mass x specific heat capacity x temp rise voltage x current x time = mass x specific heat capacity x temp rise Specific heat capacity = (voltage x current x time)/(mass x temp rise)

The answers! Aluminium 897 J/kg/°C Copper 385J/kg/°C Steel 380 J/kg/°C Brass 377 J/kg/°C

Let’s try some questions! “What would Richard Feynmann do?” If you read biographies it is very true! Let’s try some questions!