You can measure the amount of energy released by a chemical reaction by taking the
temperature of the reagents,mixing them in a polystyrene cup and measuring the
temperature of the solution at the end of the reaction.
problem is energy can be lost to the surroundings.
Can reduce this by putting the polystyrene cup into a beaker of cotton wool to give
more insulation and putting a lid on the cup to reduce energy lost by evaportaion.
Methods work for for reactions of solids with
water as well as neutralisation reactants.
An exothermic reaction is one which gives out energy to the surroundings,
usually in the form of heat and usually shown by a rise in temperature.
In this reaction, the energy released in bond formation is
greater than the energy used in breaking old bonds
An endothermic reaction is one which takes in energy from the surroundings,
usually in the form of heat and usually shown by a fall in temperature.
In this reaction, energy required to break old bonds is greater
than energy released when new bonds are formed
Energy must always be supplied to break bonds and energy is always released when bonds form.
During a chemical reaction, old bonds are broken and new bonds are formed
Energy must be supplied to break existing bonds so bond breaking is ENDOTHERMIC
Energy is released when new bonds are formed so bond formation is EXOTHERMIC