click below
click below
Normal Size Small Size show me how
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. |