3.2 PHYSICAL CHEMISTRY

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Total cards: 24•Content version: v4•Public deck•Updated: 8/1/2026

Card preview (24)

Front (Question)

Define chemical energy

Back (Answer)

• The energy held within the bonds between atoms

Front (Question)

Define enthalpy

Back (Answer)

• A measure of the heat/thermal energy content of a substance

Front (Question)

Define enthalpy change ∆H

Back (Answer)

• The heat exchange with the surroundings during a chemical reaction

Front (Question)

Define system and surroundings

Back (Answer)

System = the atoms and bonds in the chemical reaction Surroundings = everything around

Front (Question)

Describe the relationship between energy and system/surroundings

Back (Answer)

• Heat/energy loss in a chemical system = heat/energy gain to the surroundings • Heat/energy gain in a chemical system = heat/energy loss to the surroundings

Front (Question)

Draw a labled exothermic diagram for enthalpy change

Back (Answer)

Front (Question)

Draw a labled endothermic diagram for enthalpy change

Back (Answer)

Front (Question)

Describe the term exothermic reaction in three ways

Back (Answer)

1) Heat energy is given out to surroundings from chemical reaction 2) More energy is released when product bonds are formed than the energy absorbed when breaking the reactant bonds 3) The enthalpy of reactants higher than enthalpy of products (thus, negative value)

Front (Question)

Is bond breaking an exothermic or endothermic process?

Back (Answer)

• Endothermic

#10

Front (Question)

Is bond forming an exothermic or endothermic process?

Back (Answer)

• Exothermic

#11

Front (Question)

State and lable the two equations needed to work out ∆H from heat energy

Back (Answer)

#12

Front (Question)

Define activation energy Eₐ

Back (Answer)

• The minimum amount of energy required for a reaction to take place

#13

Front (Question)

Define calorimetry

Back (Answer)

• Working out the enthalpy change of a reaction

#14

Front (Question)

State what is measured during calorimetry to determine enthalpy change

Back (Answer)

• The temperature change of a chemical system (the reaction)

#15

Front (Question)

Conclude the type of reaction if a temperature rise is detected during calorimetry

Back (Answer)

• The reaction is exothermic • Heat energy has been released to the surroundings

#16

Front (Question)

Conclude the type of reaction if a temperature drop is detected during calorimetry

Back (Answer)

• The reaction is endothermic • Heat energy has been taken in from the surroundings

#17

Front (Question)

State the equation used after calorimetry

Back (Answer)

#18

Front (Question)

State why a polystyrine cup is used in a beaker during calorimetry

Back (Answer)

• Polystyrine acts as an insulator to reduce heat loss by evapourisation

#19

Front (Question)

Draw and lable a graph for calorimetry

Back (Answer)

#20

Front (Question)

Describe the term copper calorimetry for combustion enthalpy

Back (Answer)

• When the heat energy from the combustion of a fuel is used to increase the temperature of a known mass of water

#21

Front (Question)

State the three reasons why experimental values differ from data values for combustion enthalpy

Back (Answer)

1) Non-standard conditions (298K 100kPa) 2) Incomplete combustion 3) Potential heat loss to surroundings

#22

Front (Question)

Define average bond enthalpy

Back (Answer)

• The energy needed to break 1 mole of gaseous bonds in GASEOUS MOLECULES to form gaseous atoms

#23

Front (Question)

State why bond enthalpy values are always positive

Back (Answer)

• Because bond breaking is an endothermic process

#24

Front (Question)

Describe what a smaller bond enthalpy indicates about that bond

Back (Answer)

Smaller bond enthalpy = weaker bond = less energy to break = more reactive