5.1 Flashcards
Energy
a measure of the ability to do work
Examples of energy
heat, light, sound, electricity and chemical energy
What increases the average kinetic energy?
heat
What is a system?
an area of interest
What is an open system?
can exchange energy and matter with surroundings
What is an closed system?
can exchange energy but not matter with the surroundings
What is a surrounding?
in theory, everything in the universe outside the system
Enthalpy (H)
a measure of the amount of heat energy contained
Where is enthalpy stored?
in the chemical bonds and intermolecular forces as potential energy
What happens if heat is added to a system?
the enthalpy increases and therefore the ∆H is positive
What happens if heat is released from the system?
the enthalpy of the system decreases and ∆H is negative
Exothermic reaction
result in a transfer of enthalpy from the system to the surroundings
- The reactants have more enthalpy than the products
- ∆H is negative
- Most combustion and neutralization reactions are exothermic
Endothermic reaction
result in a transfer of enthalpy from the surroundings to the system
- The products have more enthalpy than the reactants
- ∆H is positive
Standard conditions for enthalpy changes
- A pressure of 100 kPa
- Concentrations of 1 mol dm-3 for all solutions
- All the substances in their standard states
What does kinetic energy and movement depends on?
the temperature, if the temperature is decreased – the kinetic energy is decreased.
