C7: Energy Changes Flashcards
Does the temperature increase or decrease during an exothermic reaction?
Increase (warmer)
Does the temperature increase or decrease during an endothermic reaction?
Decrease (colder)
Define an ‘Exothermic Reaction’?
A reaction that gives out energy to its surroundings and therefore the temperature of its surroundings increases.
Define an ‘Endothermic Reaction’?
A reaction that takes in energy from its surroundings and therefore the temperature of its surrounding decreases.
Describe how you can tell from a reaction profile that a reaction is exothermic?
In an exothermic reaction, the overall change is negative. You can tell this because the products have less energy than the reactants, and the arrow showing the overall change in energy points downwards.
Describe how you can tell from a reaction profile that a reaction is endothermic?
In an endothermic reaction, the overall change is positive. You can tell this because the products have more energy than the reactants, and the arrow showing the overall change in energy points upwards.
Define Activation Energy.
Activation energy is the minimum energy required to start the reaction process.
What is the unit for Activation Energy?
ea
Where do you measure the activation energy from?
The initial amount of energy to the peak or trough that follows.
What is on the Y and X axis of energy level diagrams and the units for both.
Y= Energy Level (joules)
X=Reaction progress/Time (seconds)
Examples of an Exothermic Reaction?
- Burning Fuels.
- Neutralisation(Acids and Alkalines).
- Metal and acid reacting.
Examples of an Endothermic Reaction?
- Sports ice pack
- Decomposition reactions
- Acid + Hydrocarbons
- Citric acid+NaHCo3
What is the measurement for energy change?
Kg/mol( Kilograms per mol)
Can you make bonds alone without breaking them?
No, you must break bonds before creating them.
How do you work out the energy change?
Energy used to break bonds-Energy given out by reaction.
