Heat energy changes in chemical reactions Flashcards
What do the terms exothermic and
endothermic mean?
Endothermic - a reaction that takes in
heat energy from the surroundings.
Exothermic - a reaction that gives out
energy to the surroundings.
Are neutralisation reactions endothermic or
exothermic?
Exothermic
Are displacement reactions endothermic or
exothermic?
Either exothermic or endothermic.
Is a salt dissolving in water endothermic or
exothermic?
Either exothermic or endothermic.
Are precipitation reactions endothermic or
exothermic?
Exothermic
How could you measure the temperature change of
a neutralisation reaction?
- Measure initial temperature of the solutions.
- Mix both reactants in a polystyrene cup.
- Record the highest temperature reached.
- Calculate the temperature change.
When measuring the temperature change of a
reaction, heat loss means that measurements may
be inaccurate. How could heat loss be minimised
during an experiment?
- Use polystyrene cup.
- Place reaction cup in a beaker full with cotton
wool for extra insulation. - Lid on the reaction cup.
In terms of bond energies, what happens during a
chemical reaction? Describe exothermic and
endothermic reactions in terms of bonds
breaking/forming.
Energy is needed to break bonds and is released when bonds are made.
Exothermic: Energy released from breaking bonds is greater than the energy
used to make bonds.
Endothermic: Energy released in forming new bond is greater than the energy
used to break old bonds.
What two types of reaction are exothermic?
Combustion
Neutralisation
Give an example of an endothermic reaction
Thermal decomposition
Photosynthesis
How can the energy change of a reaction be
calculated from bond energies?
Energy change (kJ mol-1) =
Total energy of bonds broken - total energy of bonds made.
If the energy change of a reaction is negative, is the
reaction exothermic or endothermic?
Exothermic, energy has been lost to the
surroundings.
What is a reaction profile?
Agraph showing the relative energies of reactants and products, as well as the activation energy of a reaction.
Draw a reaction profile for an
endothermic reaction
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Draw a reaction profile for an exothermic
reaction
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