energy transfer during exothermic and endothermic reactions

what happens to energy in chemical reactions?

energy is moved around, but the total amount stays the same because energy is conserved

what determines if a reaction takes in or gives out energy?

if products store more energy than reactants, the reaction takes in energy. if they store less, energy is released to the surroundings

what is an exothermic reaction?

a reaction that transfers energy to the surroundings, usually by heating, causing a temperature rise

what are examples of exothermic reactions?

combustion (burning fuels), neutralisation (acid + alkali), and many oxidation reactions like sodium + water

how are exothermic reactions used in everyday life?

hand warmers (oxidation of iron), self-heating cans (chemical reactions in the base)

what is an endothermic reaction?

a reaction that takes in energy from the surroundings, causing a temperature drop

what are examples of endothermic reactions?

reaction between citric acid and sodium hydrogencarbonate, thermal decomposition (e.g. heating calcium carbonate)