Energy Change Flashcards
Exothermic Reactions
Transfer energy from reacting chemicals to surroundings
from inside to outside
Endothermic Reactions
Takes energy from surroundings to the reacting chemicals
from outside to inside
Example of exothermic reaction
hand warmer
example of endothermic reaction
cold pack
How are surrounding temperatures affected by endothermic and exothermic
Endothermic = surroundings decrease Exothermic = surroundings increase
High to low and low to high
Exothermic = high → low Endothermic = low → high
Amount of energy in exothermic transferred into surroundings
amount of energy transferred to surroundings = energy of products - energy of reactants
What is the activation energy
Energy needed to start a reaction
Bonds breaking and making
Breaking bonds = endothermic
Making bonds = exothermic
Both use energy
How to calculate energy change
energy in - energy out = energy change
Breaking bonds and forming bonds with energy
Breaking bonds aBsorbs energy
foRming bonds
Releases energy
(B’s and R’s)
Bond Energy
Energy needed to break the bond
Batteries
2 metals join together by wire and dip in electrolyte
Electrons will flow through the wire
The greater the difference in reactivity between 2 metals used = higher voltage produced
Non-rechargeable
Fuel cells advantages and disadvantages
+do not need to be electrically recharged
+no pollutants are produced
+can be a range of sizes for different uses
- hydrogen is highly flammable
- hydrogen is sometimes produced by non-renewable sources
- hydrogen is difficult to store
Hydrogen-powered Vehicles
Hydrogen as a fuel = reaction does not produce CO2
Making hydrogen using electrolysis requires electricity form non-renewable sources
Power station will still be producing CO2 using limited energy sources
Cells are fed with H2 and O2 producing H2O
Energy released in the reaction is transferred to electrical energy
Developed many types of fuel cell and hydrogen-powered engines
Match performance, convenience and price of petrol/diesel cars
