thermochemistry the basics of heat transfer. the flow of energy thermochemistry - concerned with...
TRANSCRIPT
Thermochemistry The Basics of Heat
Transfer
The Flow of Energy
Thermochemistry - concerned with heat changes that occur during chemical reactions
Cranking up the Heat: Basic ThermodynamicsEnergy - capacity of an object
to do work or produce heat
Kinetic EnergyThe energy an object has due
to its motion
Potential EnergyStored energyEnergy of position
Energy in the universe is constant, though it changes forms.
Law of Conservation of energyLaw of Conservation of energy – energy can neither be created nor destroyed
Heat vs. TemperatureTemperature and heat are not the same thing.
Temperature describes the amount of motion of particles (the higher the temp., the faster the particles move because they have more energy).
Heat describes amount of energy transferred from one object to another
Describing Energy ChangesHeat flow is from the warmer object to
the cooler object
Heat Flow
Heat Flow
Describing Energy ChangesHot day 50°C = 122°F
Beans lost energy, it was transferred to its surroundings. This change of energy would be negative change = ∆
Energy transferred from fire to beans. Change in energy for beans would be positive.
Endothermic reactions – absorbs heat, ∆E is positive, the surroundings cool down
Exothermic reactions – releases heat, ∆E is negative, the surroundings heat up
Heat
Surroundings
Heat
Surroundings
Describing Energy Changes
Feels cold to the touch
Feels warm to the touch
Units used to describe Energy:
calorie – called “little calorie” – (cal)
kilocalorie – called “Big calorie”- (CAL) 1000 calories – same as a food calorie
Joule – the SI unit of heat - (J)
CONVERSION FACTOR
1 cal = 4.184 joules
1 cal 4.184 J
4.184 J 1 cal
Heat Units: Conversion Problems1. Convert 32.7 cal to joules.
2. Convert 6.24 J to cal.
3. Convert 10.2 Cal to cal.
4. Convert 10.2 Cal to joules.
5. Convert 8.16 joules to Cal.