Ch 5 Thermochemistry Flashcards
5.1 Energy Basics - Define energy, distinguish types of energy, and describe the nature of energy changes that accompany chemical and physical changes - Distinguish the related properties of heat, thermal energy, and temperature - Define and distinguish specific heat and heat capacity, and describe the physical implications of both - Perform calculations involving heat, specific heat, and temperature change
Energy
Capacity to supply heat or do work
Work (w)
Process of causing matter to move against an opposing force
Potential Energy
The energy an object has
Kinetic Energy
The energy an object has while in motion
Law of Conservation Of Energy
Energy cannot be created or destroyed during chemical or physical changes, but it can be changed in form
Thermal Energy
Kinetic energy is associated with the motion of atoms
At ________temperatures, the kinetic energy _______, so the atoms move quickly. Meanwhile, at low ________, the kinetic energy ________, so atoms move slower.
a. higher
b. increases
c. temperatures
d. decreases
________ (q) is the transfer of thermal energy between two bodies at different temperatures. Heat flow increases the thermal energy of one body, but ______ the thermal energy of another
a. Heat
b. decreases
Sample A has a higher temperature than Sample B. If these samples were to make contact with one another what would happen?
Consider the temperature, kinetic energy, & heat transfer.
Since Sample A has a higher temperature, so the atoms have greater kinetic energy. Meanwhile, Sample B would have less kinetic energy because of its low temperature.
When these samples come in contact with each other, there will be a transfer of heat. Sample A would lose heat & kinetic energy, and transfer it to Sample B. Heat flow will transfer until both samples reach the same temperature. This is known as thermal equilibrium.
Exothermic
A change that releases heat
Endothermic
A change that gains heat
What units are used to measure energy?
Calories (cal) & Joules (J)
Heat Capacity (C)
Quantity of heat absorbed or released during a temperature change
Formula: C = q/delta T
Extensive Property
Specific Heat Capacity (c)
Quantity of heat required to raise temperature
Formula for Heat (q)
q = mcAT
m = mass in grams
c = specific heat capacity
AT = change in temperature
How do you know if Heat was gained or lost using the formula q=mcAT?
If q is positive, then heat was gained.
If q is negative, then heat was lost.
A flask containing 8.0 × 102 g of water is heated, and the temperature of the water increases from 21 °C to 85 °C. How much heat did the water absorb?
Specific heat of water: 4.184 J/g °C
5.07 × 104 J
_________ is used to measure amounts of heat transferred to or from a substance.
Calorimetry
Chemical Thermodynamics
The science that deals with the relationships between heat, work, and other forms of energy in the context of chemical and physical processes.
System vs Surroundings
Intensive vs Extensive Property
