energy changes (1) Flashcards
exothermic reaction-
endothermic reaction-
exothermic reaction- energy is lost to the surroundings
endothermic reaction- energy is taken in from the surroundings
energy transfer (endo or exo) RP
- add reactants to a polystyrene cup with a thermometer and lid and record starting temperature
- place in a beaker filled with cotton wool
- record temperature change after 3 mins
exothermic reaction profile-
endothermic reaction profile-
where is activation energy measured from
exothermic reaction profile- products at a lower energy level than reactants. The energy changed arrow goes from reactants to product line down
endothermic reaction profile- products at a higher energy level than the reactants. energy changed arrow goes from the reactants line to the products line up
activation energy measured from the reactants line to the highest energy level
Bond breaking-
Bond forming-
Bond breaking- endothermic
Bond forming- exothermic
electrochemical cell-
how is a battery formed?
how does the metal used in the electrode affect voltage
non-rechargable batteries-
electrochemical cell- two electrodes in contact with an electrolyte
the reactions between the electrodes and electrolytes set up a charge difference between the electrodes
if a wire connects them, a charge can flow and electricity is produced
a bigger difference in reactivity because of metal used= bigger voltage
non-rechargeable batteries die when the reactants are used up
What are Fuel cells-
electrical cell supplied with hydrogen fuel and oxygen
uses energy from the reaction to produce electricity
when fuel enters the cell it becomes oxidised and sets up a potential difference
How do fuel cells function-
- electrolyte is often acid, electrodes are porous carbon with a catalyst
- hydrogen goes to the anode, oxygen to the cathode ( switched)
- energy is released by electrons moving and carrying a charge
- water is created
