section 10.2 the flow of energy 1.to understand how energy flow affects internal energy how much...
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Section 10.2 The Flow of Energy Internal Energy, E – sum of kinetic and potential energies of all the “particles” in a system A. Thermodynamics –Internal energy can be changed by two types of energy flow: Heat (q) Work (w) – a force acting over a distance E = q + w I can warm a beaker of water with my hands or I can push it across the bench – which is q and which is w?TRANSCRIPT
Section 10.2
The Flow of Energy
1. To understand how energy flow affects internal energy• How much energy is there in a substance?
2. To understand how heat is measured• What are the units of energy?
3. To understand how the flow of heat changes temperature • How does an amount of heat gained or lost relate to a
change in temperature?
Objectives
Section 10.2
The Flow of Energy
A. Thermodynamics • Thermodynamics – the study of energy • First law of thermodynamics
– Energy of the universe is constant or
– Energy can neither be created nor destroyed
Where does the energy come from and go to in a basketball game?
Section 10.2
The Flow of Energy
• Internal Energy, E – sum of kinetic and potential energies of all the “particles” in a system
A. Thermodynamics
– Internal energy can be changed by two types of energy flow: • Heat (q) • Work (w) – a force acting over a distance
E = q + w
I can warm a beaker of water with my hands or I can push it across the bench – which is q and which is w?
Section 10.2
The Flow of Energy
• Thermodynamic quantities always consist of 3 parts:
A. Thermodynamics
– A number (magnitude of the change)– A unit of energy– A sign (indicates the direction of flow in or out of
the system)
ΔE = -145kJ Heat is given off - exothermic
ΔE = + 377kJ Heat is absorbed - endothermic
Section 10.2
The Flow of Energy
Section 10.2
The Flow of Energy
B. Measuring Energy Changes
• The common energy units for heat are the calorie and the joule.
– calorie : the amount of energy (heat) required to raise the temperature of one gram of water by 1oC.
– Joule : 1 calorie = 4.184 joules
How many Joules does it take to raise the temperature of 1 gram of water by 1oC?
1000 calories = 1kcal = 1 Calorie
Section 10.2
The Flow of Energy
B. Measuring Energy Changes
Section 10.2
The Flow of Energy
B. Measuring Energy Changes
• Specific heat capacity is the energy required to change the temperature of a mass of one gram of a substance by one Celsius degree.
High Specific Heat Capacity of Water
Section 10.2
The Flow of Energy
B. Measuring Energy Changes
• To calculate the energy required to raise the temperature of a substance:
Q = s x m x t