Energy Changes
- Created by: elle2121
- Created on: 10-09-19 16:41
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- Energy Changes
- Exothermic
- A reaction which transfers energy to the surroundings
- Temperature increases
- If products store less energy then reactants
- Combustion
- Neutralisation
- Handwarmers & self heating cans
- A reaction which transfers energy to the surroundings
- Endothermic
- A reaction which takes in energy from the surroundings
- Temperature decrease
- If products store more energy then reactants
- Thermal decomposition
- Citric acid and sodium hydrogencarbonate
- Sports injury packs
- A reaction which takes in energy from the surroundings
- Bond Energies
- Bond breaking is endothermic (takes in energy)
- Endothermic
- A reaction which takes in energy from the surroundings
- Temperature decrease
- If products store more energy then reactants
- Thermal decomposition
- Citric acid and sodium hydrogencarbonate
- Sports injury packs
- A reaction which takes in energy from the surroundings
- Endothermic
- Bond making is exothermic (releases energy)
- Exothermic
- A reaction which transfers energy to the surroundings
- Temperature increases
- If products store less energy then reactants
- Combustion
- Neutralisation
- Handwarmers & self heating cans
- A reaction which transfers energy to the surroundings
- Energy released by forming bonds is greater then energy needed to break bonds
- Exothermic
- Activation energy
- Minimum amount of energy needed to break bonds & start reaction
- Overall energy change = energy required to break bonds - energy released to form bonds
- Bond breaking is endothermic (takes in energy)
- Cells
- Electrochemicalcell
- 2x diff. electrodes in electrolyte (contains ions which react with electrodes)
- Reactions between electrodes & electrolyte set up charge diff. between electrodes
- When electrodes connect by a wire, charge flows & electricity produced
- Batteries
- Rechargeable
- Reaction can be reversed when connected to an external electric current
- Non-rechargeable
- Reaction at electrodes are irrreverisible
- When reactants run out reaction cant take place, no electricity
- Reaction at electrodes are irrreverisible
- 2+ cells, connected in series
- Battery voltage = voltage of all cells combines
- Rechargeable
- Voltage
- Increasing the difference of electrodes reactivity increases the cells voltage
- Diff. metals react diff. with same electrolyte
- The electrolyte used affects voltage size
- Diff. ions react diff. with electrodes used
- Increasing the difference of electrodes reactivity increases the cells voltage
- Electrochemicalcell
- Fuel Cells
- Hydrogen Oxygen Fuel Cells
- Redox
- Hydrogen looses electrons at the anode producing H+ ions
- Oxidation
- H+ ions move to cathode
- Oxygen gains electrons from the cathode
- At the cathode oxygen and H+ ions react, producing water
- Reduction
- Oxygen gains electrons from the cathode
- Electrons flow from the anode to the cathode from an external circuit
- This creates electric current
- Less polluting
- Only produce water & heat
- Better than electrical vehicles batteries
- Batteries store less energy - charges more often
- Hydrogen Oxygen Fuel Cells
- Exothermic
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