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Ch 5: Thermochemistry The relationship between chemical reactions and energy changes involving heat is called thermochemistry.

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Presentation on theme: "Ch 5: Thermochemistry The relationship between chemical reactions and energy changes involving heat is called thermochemistry."— Presentation transcript:

1 Ch 5: Thermochemistry The relationship between chemical reactions and energy changes involving heat is called thermochemistry.

2 Types of Energy Potential energy: energy objects posses as a result to position to other objects Kinetic energy: energy posses by virtue of motion (E=1/2mv 2 )

3 Units of Energy Joule = 1kg-m 2 /s 2 1 calorie = 4.184 J 1 Cal = 1000 cal = 1 kcal

4 System: the focus of study Surroundings: everything else

5 Energy used to cause an object to move against a force is called work. W = F x d

6 Heat is the energy transferred from a hotter object to a colder one.(q) Energy is the capacity to do work or transfer heat.(E)

7 First law of thermodynamics Energy is conserved.  E = E final - E initial

8  E = q + w Anytime work or heat acts on the system it is a positive value. (Vice-versa)

9 When a process occurs in which the system absorbs heat, it is called endothermic. A process in which the system evolves heat is called exothermic.

10 Calculate  E The system absorbs 77.5 kJ of heat while doing 63.5 kJ of work on the surroundings.

11  E = 14 kJ Endothermic

12 How to solve for q q = mc  t c = the specific heat of the material. H 2 O = 4.18 J/gK

13 If a 3.0 g metal is heated to 95 o C and added to a cup of water (50g) at 23 o C, and the water raises to 30 o C, what is the specific heat of the metal?

14 If 125 mL of water at 88 o C is added to 50 mL of water at 30 o C, what is the new temperature of the water?


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