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[CHEM 1000] - Midterm Exam Guide - Comprehensive Notes for the exam (16 pages long!)


Department
Chemistry
Course Code
CHEM 1000
Professor
Sylvie Morin
Study Guide
Midterm

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York
CHEM 1000
MIDTERM EXAM
STUDY GUIDE

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Thermochemistry- Chapter 7
The study of energy in Chemical reactions
A sub- discipline of thermodynamics
Thermodynamics studies the bulk properties of matter and deduces a few general laws
It does not require any knowledge/ assumptions of molecules
Definitions
System
The part of the universe we choose to study
Surroundings
The rest of the universe (normally we only worry about the immediate surroundings)
Process
A physical occurrence (usually involving energy flow)
Additional definitions
Open System
If a system is open, energy and matter can be exchanged with the surroundings
Closed system
A system where the energy but no matter can be exchanged with the surroundings.
Isolated system
A system where neither energy nor matter can be exchanged with the surroundings
Systems and Energy
All systems will contain energy
In thermodynamics, we are interested in the flow of energy, particularly in the forms of heat
and work.
Note that heat and work occur when there is a process. They only exist when something
happens.
The system has energy, (often described as the capacity to do work), it does not have heat or
work.
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Heat
Energy that is transferred between a system and its surroundings because of temperature
differences
Heat transfers can change the temperature of something but it does not always do (only) that.
Heat transfer can melt or vaporize material
In the case of a material that does not change phase, the increase in temperature of a system is
delta T due to the input of a given amount of heat q.
The heat apait is a ostat that depeds o the sste. So, it’s o partiularl useful.
It is better to be able to define heat capacity in terms of a amount of compound.
Units
The SI unit of heat is a Joule(since it is an energy)
The older unit is the calorie which is defined as the heat required to raise the temperature of 1g of
water to 1 C
1 Cal = 4.184 J
Sign convention and conservation of energy
When heat flows between a system and its surroundings, we define:
- q to be positive if heat is supplied to the system
- q to be negative if heat is withdrawn from the system
If there are no phase changes, conservation of energy requires that
Work
Often when a chemical reaction occurs, work is done. (this is the principle of an engine)
Since work and heat are both forms of energy we must consider both.
Work is done when a force acts through a distance. For example, when a mass is moved.
W is positive if work is done on the system
W is negative if work is done by the system
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