CHEMISTRY - Chemical Reactions and Energy Flashcards
what does combustion mean
burning
what are 4 ways to tell a chemical reaction is taking place
-colour change
-temperature change
-bubbles/fizzing/effervescing
-precipitate
what does the acronym MASH stand for
Metal acid salt hydrogen
give 2 examples of exothermic reaction
combustion
respiration
give 2 examples of an endothermic reaction
photosynthesis
thermal decomposition
what happens to the atoms during a chemical reaction
bonds in reactants are broken - requiring energy - endothermic
and rearranged to form new bonds - releasing energy - exothermic
*no new atoms are made, none are lost, only rearranged differently
• energy needed to break bonds in reactants
• energy released when bonds in products formed
explain an exothermic reaction
(detailed edition)
there is a release of heat, so bond making must be releasing more energy than bond breaking absorbs.
eg. 100kJ in to break the bonds
and then 250kj out to make the bonds
out energy is more than in energy, so exothermic
explain endothermic reactions
the bond breaking absorbs more heat energy than the bond making releases.
eg.350kJ in to break bonds, 250kJ out to make bonds
in energy is more than out energy so endothermic
what is the type of reaction that occurs when a fuel burns
combustion
what is the type of reaction called between an acid and an alkali
neutralisation
what gas is given off when magnesium reacts with hydrochloric acid
hydrogen
**(MASH, metal acid salt hydrogen)
what type of reaction takes place between copper sulfate and magnesium
displacement
what is an energy profile
an energy level diagram, showing whether a reaction is exothermic or endothermic,
what is a reaction profile
shows how the energy of the chemicals changes during a reaction, also includes the activation energy
what is activation energy
minimum energy needed to start reaction
shown as a “hump” in the line of a reaction profile diagram
