1. Review  Endothermic reactions _________________ energy causing the q and ∆H to be ______________.  Exothermic reactions ___________________ energy causing the q and ∆H to be _____________________. absorb positive release negative

2. Energy – the ability to do work or produce heat  Exists in 2 forms:  Kinetic energy – energy of ___________  Potential energy – energy at rest or energy of ____________ HEAT -- the energy that transfers from one object to another because of a temperature difference between them  Heat always flows from a ___________ object to a _______________ object motion position warmer cooler

3. Energy  Kinetic energy – in a chemical reaction temperature is the determining factor  The higher the temperature…the faster the particles move…the higher the average kinetic energy  Therefore, the lower the temperature the ________ the kinetic energy.  Temperature is a measure of the average kinetic energy  Kelvin scale : 0 K = -273 °C, °C + 273 = K lower

4. Law of Conservation of Energy  Law of Conservation of Energy – Energy is neither created nor destroyed  What else have we seen conserved in a chemical reaction? Mass

5. Units for Measuring Heat Flow  Heat or energy can be in joules, calories, kilocalories, or kilojoules  The SI unit is the joule  1000 cal = 1 kcal  1 cal = 4.186 J  1kcal = 4186J  1 J = 0.239 cal

6. Heat Capacity  The amount of heat it takes to change an object’s temperature by 1ºC  Depends on an object’s mass and chemical composition  Ex. A cup of water has a greater heat capacity than a drop of water.

7. Specific Heat (C)  Specific Heat (C) – the amount of heat required to raise the temperature of 1 gram of a substance by 1  C  Specific heat is an intensive property, and therefore does not depend on size  Every substance has its own specific heat (look at your CRM)  Ex. Water = 4.184 J/(gºC) Glass = 0.500 J/(gºC) *The higher the specific heat, the greater amount of energy! The lower the specific heat, the larger the increase in temperature!

8. Specific Heat  Units for C = J/gºC (joules per gram degree Celsius)  Equation for Specific Heat: C = q / (m Δ T)  C = specific heat;  q = heat;  m = mass  ΔT = change in temperature  This equation can be rearranged to solve for heat (q) q= mCΔT

9. Specific Heat  A 10.0 g sample of iron changes temperature from 25.0  C to 50.4  C while releasing 114 joules of heat. Calculate the specific heat of iron.

10. Example  C= q/ (m∆T)  C=114 J/ (10.0 g x 25.4°C)  C = 0.45 J/g  C

11. Yet another example  4.50 g of a gold nugget absorbs 276 J of heat. What is the final temperature of the gold if the initial temperature was 25.0  C & the specific heat of the gold is 0.129J/g  C

12. Yet another example  C= q/ (m∆T); rearrange to find  ∆T = q / (C x m)  ∆T = 276 J / (.129 J/g°C x 4.50 g)   T = 475.45  C   T = Tf-Ti  475.45 = Tf-25  Tf = 500.45  C