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Mind Map by Alexia Charlize, updated more than 1 year ago
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Created by Alexia Charlize
about 9 years ago
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Unit 5: Thermochemistry
- Thermochemistry
- the study of the transfers of energy as heat that accompany
chemical reactions and physical changes
- the study of the transfers of energy as heat that accompany
chemical reactions and physical changes
- Temperature and heat are related but not idential
- Calorimeter
- The energy absorbed or released as heat in a chemical
or physical change is measured in a calorimeter
- The energy absorbed or released as heat in a chemical
or physical change is measured in a calorimeter
- Therefore, the energy given off (or absorbed) during the reaction
is equal to the energy absorbed (or given off) by the known
quantity of water.
- The amount of energy is determined from the temperature
change of the known mass of surrounding water.
- The amount of energy is determined from the temperature
change of the known mass of surrounding water.
- The data collected from calorimetry experiments are temperature changes because
energy cannot be measured directly; but temperature, which is affected by the
transfer of energy as heat, is directly measurable.
- For calculations in thermochemistry, we use the Celsius and
Kelvin scales. Celsius and Kelvin temperatures are related by
the following equation.
- K = 273.15 + °C
- For most calculations in this book, 273.15 is
rounded to 273.
- K = 273.15 + °C
- Heat
- energy transferred between samples of matter because of
a difference in their temperatures.
- energy transferred between samples of matter because of
a difference in their temperatures.
- Energy transferred as heat always moves spontaneously from matter
at a higher temperature to matter at a lower temperature.
- Calorimeter
- Temperature
- a measure of the average kinetic energy of the particles
in a sample of matter
- The greater the kinetic energy of the particles in a sample, the
higher the temperature is and the hotter it feels
- a measure of the average kinetic energy of the particles
in a sample of matter
- Joule
- the SI unit of heat as well as all other forms of energy.
- The joule, abbreviated J, is derived from the
units for force and length.
- N x m = kg x m^2 / s^2
- the SI unit of heat as well as all other forms of energy.
- Specific heat
- amount of energy required to raise the temperature of one gram of a substance by
one Celsius degree (1°C) or one kelvin (1 K) (because the sizes of the degree divisions
on both scales are equal).
- amount of energy required to raise the temperature of one gram of a substance by
one Celsius degree (1°C) or one kelvin (1 K) (because the sizes of the degree divisions
on both scales are equal).
- enthalpy change
- the amount of energy absorbed by a system as heat during a process at
constant pressure.
- the amount of energy absorbed by a system as heat during a process at
constant pressure.
- The enthalpy of reaction
- the quantity of energy transferred as heat during a
chemical reaction.
- the quantity of energy transferred as heat during a
chemical reaction.
- thermochemical equation
- an equation that includes the quantity of energy released or absorbed
as heat during the reaction as written.
- In any thermochemical equation, we must always interpret the
coefficients as numbers of moles and never as numbers of
molecules.
- an equation that includes the quantity of energy released or absorbed
as heat during the reaction as written.
- in an endothermic reaction—products have a larger enthalpy
than reactants.
- Thermochemical equations are usually written by designating the value of ∆H,
rather than by writing the energy as a reactant or product. For an exothermic
reaction, ∆H is always negative because the system loses energy
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