C3 Energy Flashcards
Show how a catalyst works using an energy level diagram
How would you measure the energy change from burning a fuel?
The energy released when fuels burn can be measured by simple calorimetry, e.g. by heating water in a glass or metal container.
What is activation energy? (Have you shown it on the diagrams?)
The minimum amount of energy needed to start the reaction. It is shown as the distance between the energy of the reactants and the highest energy shown on the curve.
To what does m refer, in Q = mc ΔT?
m is the mass of the liquid being heated
Use the idea of bond breaking and bond making to explain an exothermic reaction.
In an exothermic reaction, the energy given out by making new bonds is greater than the energy needed to break existing bonds.
Draw the simple energy level diagram for an endothermic reaction.
Use the idea of bond breaking and bond making to explain an endothermic reaction.
In an endothermic reaction, the energy needed to break existing bonds is greater than the energy released from forming new bonds.
What is released when bonds are formed in a chemical reaction?
Energy is released when bonds are formed, i.e. bond making is exothermic.
What is needed to break bonds in a chemical reaction?
Energy must be supplied to break bonds, i.e. bond breaking is endothermic.
What equation would you use to find a value for the energy change in burning a fuel?
Q = mc ΔT
Energy change = mass x specific heat x temp change
Explain how catalysts work.
Catalysts provide a different pathway for a chemical reaction that has a lower activation energy.
Why is hydrogen preferred to petrol?
The only waste product is water, whereas petrol produces carbon dioxide and water.
Draw the simple energy level diagram for an exothermic reaction
What are the units of energy?
Joules, J, or kilojoules, kJ. Calories are used for food, one calorie is 4.2 Joules.
Hydrogen can also be used in fuel cells, how does this compare to combustion?
The fuel cell produces electricity and drives an electric motor. This is cleaner than petrol combustion and the electric motor has fewer parts than an internal combustion engine.
