R 1.1
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What is energy?
the ability to do work or cause a change measured in joules
What are the 3 main processes of energy transfer?
conduction - by direct contact convection - movement of fluids radiation - electromagnetic waves
What is a chemical reaction?
a process where a rearrangement of atoms occurs, forming new substance/s with different properties
What is temperature vs heat?
temperature: a measure of the average kinetic energy of particle heat: energy transferred from a region of high temp. to an area of low. temp (joules)
What are exothermic reactions?
reactions that release energy to the surroundings increasing the temperature of the system
What are endothermic reactions?
reactions that absorb energy from the surroundings and decrease the temperature of the system
What is chemical potential energy?
energy stored in the chemical bonds between particles
What does an exothermic graph look like?
reactants high, and products are low
What does an endothermic graph look like?
reactants low, products high
endothermic processes ____ energy so that the products _____
release energy products end with a lower potential energy, more stable
What does a lower potential energy mean?
greater stability
What is biodiesel produced from?
waste vegetable oil or animal fats
What is enthalpy?
the amount of heat that a system has (deltaH)
How are the changes in enthalpy in exothermic and endothermic reactions?
exo - negative change in enthalpy as heat is released endo - positive change in enthalpy as heat is absorbed
What is the standard enthalpy change of reaction?
heat transferred at constant pressure and under standard conditions/states
What is a thermochemical equation?
A chemical equation that shows the enthalpy change (∆H) of a reaction
thermal energy =
mcAT
molar change in enthalpy =
• Q/n
Ways to reduce heat loss?
insulation of calorimeters insulating materials, increasing thickness of materials, minimising air contact
What do chemical reactions involve?
a transfer of energy between the system and the surroundings, while total energy is conserved
How can we calculate thermal energy transfer and enthalpy change?
Monitoring temperature changes during chemical reactions