Reactivity 1.1—Measuring enthalpy changes Flashcards
Law of conservation of energy
Energy cannot be created or destroyed in a closed system, it can only be transferred or transformed from one form to another.
A chemical reaction
A process that results in the formation of new substances in which reactants are converted into products.
How do you identify a “system” and “surroundings” in a chemical reaction?
The “system” includes the components directly involved in the reaction. The “surroundings” encompass everything outside the system. Energy transfers between them while keeping the total energy constant, influenced by the reaction being endothermic or exothermic.
What is the difference between heat and temperature in thermodynamics?
Heat is energy transferred between regions due to temperature differences, measured in joules (J). Temperature measures the average kinetic energy of particles, shown in degrees Celsius (°C) or Kelvin (K). Temperature indicates particle energy level; heat indicates energy flow.
Exothermic
Describes a reaction in which energy is transferred to the surroundings.
Endothermic
Describes a reaction in which energy is transferred from the surroundings.
What temperature change occurs in the surroundings during an endothermic reaction?
There is a temperature decrease in the surroundings as energy is absorbed.
What temperature change occurs in the surroundings during an exothermic reaction?
There is a temperature increase in the surroundings as energy is released.
How do energy profiles indicate an endothermic reaction?
Reactants have lower energy than products, indicating energy absorption.
How do energy profiles indicate an exothermic reaction?
Reactants have higher energy than products, indicating energy release.
Enthalpy
Measurement of heat energy within a system. It is symbolised in expressions by H.
Standard enthalpy change
The heat energy transferred within a reaction under standard conditions with all substances present in their standard states.
Thermochemical equation
A chemical equation that shows the enthalpy change (∆H) of a reaction.
Calorimetry
The study of heat transfer during a physical or chemical process.
Calorimeter
The apparatus used to measure temperature changes associated with a physical process or chemical reaction.
