Thermodynamics Energy Basics Chapter 5.1 Flashcards
Thermochemistry
area of science concerned with the amount of heat absorbed or released during chemical and physical changes
Energy
capacity to supply heat or do work
potential energy
the energy an object has because of its relative position, composition, or condition
Kinectic energy
the energy that an object possesses because of its motion
The law of conservation of energy:
during a chemical or physical change, energy can be neither created nor destroyed, although it can be changed in form
The law of conservation of matter
During any physical or chemical change, the total mass of the products remains equal to the total mass of the reactants.
Thermal energy
kinetic energy associated with the random motion of atoms and molecules
Temperature
Hotness or coldness of an object
When the atoms and molecules in an object are moving or
vibrating quickly, they have a …. and we say that the object is ___
higher average kinetic energy (KE),
hot
When the atoms and molecules are moving slowly, they have …, and we say that the object is “___”
lower average KE
cold
Assuming that no chemical reaction or phase change (such as melting or vaporizing) occurs, increasing/decreasing the amount of thermal energy in a sample of matter …..
will cause its temperature to increase. And, assuming that no chemical reaction or phase change (such as condensation or freezing) occurs, decreasing the amount of thermal energy in a sample of matter will cause its temperature to decrease.
Heat
The transfer of thermal energy between two bodies at different temperatures
What does Heat flow do
+when does it stop?
Increases the thermal energy of one body and decreases the thermal energy of the other. Heat flow will continue until the two substances are at the same temperature
Exothermic process
A chemical reaction that RELEASES heat (has a negative ΔH).
Endothermic process
A reaction or change that absorbs heat
Thermal equilibrium (3)
Both substances are at the
- same temp
- their molecules have same average kinectic energy.
No net flow of thermal energy between them when they are connected by a path permeable to heat.
Calories+why its not used as a unit for energy (3)
The amount of energy required to raise one gram of water by 1 degree C (1 kelvin).
However, this quantity depends on the atmospheric pressure and the starting temperature of the water.
The SI unit of heat, work, and energy
Joule
Joule
the amount of energy used when a force of 1 newton moves an object 1 meter.
heat capacity (C)
the quantity of heat (q) it absorbs or releases when it experiences a temperature change (ΔT) of 1 degree Celsius (or equivalently, 1 kelvin):
heat capacity (C)
(3)
+formula+ trait+what it is
the quantity of heat (q) it absorbs or releases when it experiences a temperature change (ΔT) of 1 degree Celsius (or equivalently, 1 kelvin)
extensive property
What is heat capacty determined by?
Heat capacity is determined by both the type and amount of substance that absorbs or releases heat.
extensive property
its value is proportional to the amount of the substance.
Why is heat capacity dependent on mass? (2)
Use pan as the compared example +what’s the relationship with mass and HC?
More mass means more atoms are present in the larger pan, so it takes more energy to make all of those atoms vibrate faster.
The larger pan has a (proportionally) larger heat capacity because the larger amount of material requires a (proportionally) larger amount of energy to yield the same temperature change
heat capacity and mass relationship
They are directly porportional
The specific heat capacity (c)
(4)
+formula+what it depends on+the property vocab
- the quantity of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius (or 1 kelvin)
- depends only on the kind of substance absorbing or releasing heat
- intensive property
Intensive property
a physical quantity whose value does not depend on the amount of substance which was measured.
ex: specific heat capacity. The mass doesnt change the SPH value
Specific heat capacity is derived from
hint: 2 extensive properties
being derived from a ratio of two extensive properties (heat and mass).
Heat is an extensive property, and is proportional to the total energy of all atoms in an object.
specific heat capacity/ heat capacity value of large and small pan example exaplanation:
*same diff?
Because of its larger mass, a large frying pan has a larger heat capacity than a small frying pan. Because they are made of the same material, both frying pans have the same specific heat.
Enthalpy change is the heat change when
Enthalpy change equals Heat change at constant pressure.
