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Reactions and Energy
Chemistry
| Question | Answer |
|---|---|
| During a chemical reactions bonds are.... | Broken and new ones are made |
| Breaking bonds... | Releases energy |
| Making bonds.... | Absorbs energy |
| Overall energy change... | Energy released when breaking bonds - Energy absorbed when making bonds If it's a negative value then it is exothermic |
| Exothermic | Takes in energy and is energetically unfavourable so less common |
| Endothermic | Releases energy and is common E.g. Neutralisation, combustion and oxidation |
| Calculating moles | Moles= Mass / Mr |
| Specific heat capacity | q=-m x c x delta t Delta h=-m x c x delta t/n ( for calculating per moles) |
| A calorie is... | The energy required to heat 1 cm^3 of an object by 1 degree |
| A calorimeter is... | A device used to measure change in thermal energy |
| Styrofoam cup | Used for in solution reactions Two styrofoam cups are placed in each other with lids for insulation Digital thermometer gives an accurate reading Stirrer evenly distributes the heat |
| Bomb calorimeter | Designed for a combustion reaction A steel container filled with water with a combustion chamber inside Combustion chamber has oxygen supply and ignition wires and is conductible Thermometer and stirrer are in the water |
| Spirit burner | Hold spirit burner under water and measure the temperature change and mass of fuel burnt. Water and burner must be a constant distance away each time. |