Unit 3: Kinetics and Thermodynamics

The capacity to do work or produce heat Makes objects move Makes things stop Energy from sun plants foods we eat energy to live We need energy to “do work”

Go up stairs Play soccer Lift a bag of groceries Ride a bicycle Breathe Heart pumps blood Water goes over a dam

Mechanical – opening a door, moving an object Electrical Thermal (heat) Chemical – food energy, gasoline energy Radiant (light)

Is energy due to position or composition Examples Water behind a dam Compressed spring Chemical bonds in gasoline or coal Chemical bonds in Food

Is energy of motion Examples Hammering a nail Water flowing over a dam Working out Boxing Burning gasoline ( A car moving)

Energy can neither be created nor destroyed, but can be converted between forms The Joule The unit of heat energy used in modern thermochemistry 4.18 Joules = 1 calorie

Energy (Heat) is measured in calories or joules 1 calorie = 4.18 Joules 1 kcal or 1 Calorie = 1000 cal 1 kJ = 1000 J

The amount of heat released or absorbed during a chemical reaction. Endothermic: Exothermic: Reactions in which energy is absorbed as the reaction proceeds. Reactions in which energy is released as the reaction proceeds.

Specific heat is the a mount of heat needed to raise the temperature of 1 g of a substance by 1°C. cal/g°CJ/g°C water aluminum copper silver gold

Q = Amount of Energy (J) m = Mass (g) c = Specific Heat (J/g°C) Δt = Change in Temperature = Final Temperature – Initial Temperature (°C)

1.How many joules of energy are absorbed by a pot of water with a mass of 350g in order to raise the temperature from 25°C to 30°C? (Specific heat of water = 4.18 J/g°C) 2. If it takes 850 J of energy to warm 200g of aluminum from 30°C to 35°C, what is the specific heat (c) of aluminum? 3. How much copper in grams would be needed if 900 J of energy were added and changed the temperature from 60°C to 95°C? (Specific heat of copper = J/g°C) 4. If it takes 38,200 J of heat to warm 275 g of zinc, what was the temperature change? (Specific heat of zinc = 0.387J/g°C) 7,315 J 0.85 J/g°C g °C

The quantity of thermal energy (heat) released when a substance burns. HydrocarbonFormulaHeat of Combustion (kJ/g) MethaneCH EthaneC2H6C2H PropaneC3H8C3H ButaneC 4 H PentaneC 5 H HexaneC 6 H HeptaneC 7 H OctaneC 8 H

Endothermic Reactions Activation Energy: Energy required to start a chemical reaction

Exothermic Reactions

Average Kinetic Energy of moving particles. When you heat water, the water molecules move faster. More KE When molecules move faster, the substance gets hotter. When a substance gets hotter, its temperature goes up.

Energy that flows from something warm to something cooler A hotter substance gives KE to a cooler one. NEVER COLD TO HOT. When heat is transferred (lost or gained), there is a change in the energy within the substance

Heating Curve for Water 120 °C steam Boiling 100 °C 50°C liquid water 0 °C Melting Ice -10 °C Heat added 

Latent Heat of Phase Change The energy that must be absorbed or removed in order to convert one mole of a solid to liquid at its melting point. Heat of Fusion of Water = 334 J/g

The energy that must be absorbed or removed in order to convert one mole of a liquid to gas at its boiling point. Latent Heat of Phase Change #2 Heat of Vaporization of Water = 2,260 J/g

1.How much energy is required to raise 345g of water from -2°C to 20°C? 2.How much energy is required to raise 588g of water from 95°C to 110°C? 3. How much energy is required to raise 115g of water from -5°C to 125°C?