u3aos1 - exothermic/endothermic reactions (ch2.1)

Question 1

fuels

Answer 1

a substance that can release energy relatively easily. this energy is stored within the bonds of the molecule.

Question 2

enthalpy (H)

Answer 2

the chemical energy a substance consists of. Also known as the heat content.

Question 3

enthalpy change (△H)

Answer 3

the difference of chemical energy between products and reactants

Question 4

enthalpy change (△H) formula

Answer 4

△H = Hp - Hr
△H = Products (chem energy) - Reactants (chem energy)

Question 5

activation energy (Ea)

Answer 5

the energy required to break bonds between reactant molecules.

Question 6

combustion reactions

Answer 6

an exothermic reaction that releases energy, heat, water (l) or (g) and carbon dioxide (g)

Question 7

exothermic reaction

Answer 7

chemical reactions that release more energy than it absorbs.

Question 8

exothermic reaction characteristics (3 marks)

Answer 8

• enthalpy change is always negative
• products have less energy than the reactants.
• releases heat to environment as it is releasing energy.

Question 9

endothermic reaction

Answer 9

chemical reaction that absorbs more energy than it releases

Question 10

endothermic reaction characteristics (3 marks)

Answer 10

• enthalpy change is always positive
• reactants have less energy than the products
• surrounding environment is cool as it is absorbing energy and therefore heat.

Question 11

energy profile diagrams
1 mark

Answer 11

a diagram that demonstrates the energy changes that occur during a chemical reaction