SCH 4U
Unit 4 - Thermodynamics and Rates of Reactions
In a heating curve, when there is a rise in temperature that also
shows an increase in the kinetic energy of the particles. Kinetic energy is
the energy expressed as motion of the particles.
During a change of state, the temperature remains constant and there
is a change of potential energy - the way in which matter expresses motion.
Solids - have only vibrational motion
Liquids - have vibrational and rotational motion
Gases - have vibrational, rotational and translational motion
Thus, 1.0 g of water vapour at 100°C possesses more PE than 1.0 g of water
at 100°C. Water will possess more PE than 1.0 g of ice if both are 0°C.
An endothermic process involves heat going into a system from the
surroundings. The heating curve shows endothermic processes.
An exothermic process involves heat going out of a system into the
surroundings. The cooling curve shows exothermic processes.
c – specific heat capacity of water
- the heat required to change 1 g of water 1oC
∆Hfus – (molar) enthalpy of fusion, water = 334 J/g (6.07 kJ/mol)
-
the heat required to change 1 g (or mole) of ice at 0oC to water at 0oC
∆Hfus – (molar) enthalpy of vapourization, water = 2260 J/g (40.7 kJ/mol)
-
the heat required to change 1 g (or mole) of water at 100oC to water
vapour at 100oC