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Introduction
Temperature and Heat
All particles have kinetic energy, which is the energy derived from their motion. Temperature measures the average kinetic energy of particles within a substance. Meanwhile, heat is simply the transfer of kinetic energy between particles.
In an isolated system (information down below), if two substances with varying temperatures make contact, the kinetic energy would eventually become evenly dispersed throughout the system, resulting in a thermodynamic equilibrium.
What is Calorimetry?
Calorimetry studies the change in heat energy of a system by measuring the variation in the potential energy of the system's reactants and products.
System: Site of heat transfer. (Reactants, products, etc.)
Surrounding: Water, beaker, flask, calorimeter, etc.
Open vs. Closed vs. Isolated System
Open System - A system where mass and heat energy can escape.
Closed System - A system where only heat energy can escape.
Isolated System - A system where mass and heat energy cannot escape.
Ideally, we would like to achieve an isolated system for calorimetry, as it would provide the most accurate information.
Specific Heat Capacity
The specific heat capacity of a substance tells us how much energy (J) it takes to heat a gram of the substance by 1°C.
The unit for specific heat is J/g°C.
Because calorimetry usually involves water, it is useful to remember that the specific heat of liquid water is 4.184 J/g°C.
Specific Heat Capacity Formula:
q = mcΔT
q: Heat Energy (J)
m: Mass of Substance (g)
c: Specific Heat of Substance (J/g°C)
ΔT: Change in Temperature, Tf - Ti (°C)
This formula ties the relationships of energy, mass, specific heat capacity, and temperature together.
Concept of Heat Transfer with q = mcΔT
First Law of Thermodynamics: Energy cannot be created or destroyed, only transferred.
In a perfectly isolated system, the energy lost from the hotter material gets transferred to the cooler material, eventually reaching an equilibrium in temperature throughout the system. This relationship could be expressed as -q = q, or -(mcΔT) = (mcΔT).
For example... suppose you heat up a piece of metal and dump it in water to cool. As the energy lost by the piece of metal transfers to the water, the system's temperature will eventually reach equilibrium. According to the first law of thermodynamics, in a perfectly isolated system, the heat energy lost by the metal must equal the negative of the heat energy gained by the water.
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