energy – the ability to do work or produce heat ◦ kinetic energy – energy of motion ◦...

Energy – the ability to do work or produce heat◦ Kinetic energy – energy of motion◦ Potential energy – stored energy

Chemical potential energy – stored energy because of composition

Heat – energy process of flowing from a warmer object to a cooler object◦ Calorie – the amount of heat required to raise the

temperature one degree Celsius◦ Joule – SI unit of heat and energy

When your body breaks down sugars and fats to form carbon dioxide and water, these exothermic reactions generate heat that can be measured in Calories

Specific heat – amount of heat required to raise the temperature of one gram of that substance by one degree Celsius

Units - J/g ⁰ C Large specific heats = Large amount of

energy to change temperature (water) Small specific heats = Small amounts of

energy to change temperature (gold)

q = m x c x ∆Tq = mc∆Tq (heat)c (specific heat)m (mass of sample) ∆T (change in temperature)

The temperature of a sample of iron with a mass of 10.0g changed from 50.4⁰C to 25.0 ⁰ C with the release of 114J heat. What is the specific heat of iron?

q = mc∆T Heat (q)

◦ 114J Mass (m)

◦ 10.0g Specific Heat (c)

◦ X Change in temperature (∆T)

◦ 50.4⁰C - 25.0 ⁰ C = 25.4 ⁰ C 114 = 10.0(x)25.4 114 = 254(x) X=.44881 Final answer 0.449J/g ⁰ C (3 significant figures and units)

Calorimeter – insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process

Thermochemistry is the study of heat changes that accompany chemical reactions and phase changes

Enthalpy (H) is the heat content of a system at constant pressure

Enthalpy of reaction◦ ∆Hrxn=Hproducts – Hreactants

Endothermic = absorbs heat giving the ∆Hrxn a positive number

Exothermic = releases heat giving the ∆Hrxn a negative number