Energy and Chemical Processes

Energy

The ability to do work that can be quantified by different types of units.

Joule

The SI unit of energy.

Calorie

Unit of energy used in health professions and everyday life.

Law of Conservation of Energy

Energy cannot be created or destroyed by any physical process.

System

An experiment or observation.

Surrounding

Everything not a part of the system.

Kinetic Energy

Energy in motion.

Potential Energy

Stagnant/Standing energy.

Electrical Energy

Flow of electrical charge.

Thermal Energy

Random motions of atoms and molecules in matter.

Chemical Energy

Potential energy, positions of the particles that compose a chemical system.

Units

1,000 Joules (J) = 1 Kilojoule, 1,000 calories (Cal) = 1 kilocalorie (kcal) = 1 Calorie (Cal), 1 cal = 4.184J, 1 Cal = 4.184 kJ.

Dimensional Analysis w/ Energy Units

How many Joules are in 70.0 Calories? 4.184 J/1 cal * 1000 cal/1 Cal * 70.0 = 293,000.

Temperature

Measure of thermal energy of matter and can be measured using 3 scales.

Fahrenheit Scale

Water freezes at 32 degrees Fahrenheit, water boils at 212 degrees Fahrenheit.

Celsius Scale

Water freezes at 0 degrees Celsius, water boils at 100 degrees Celsius.

Kelvin Scale

Avoids negative temperatures by assigning 0 Kelvin to absolute zero, molecular motion virtually stops.

Conversions

K = C + 273.15, C = (F - 32)/1.8, F = (C x 1.8) + 32. Degree symbol is only used with Celsius and Fahrenheit.

Heat

The transfer of energy, proportional to the mass of a substance and can be measured by a change in temperature.

Energy Changes in Chemical Reactions

Chemical reactions are always accompanied by an energy change. Broken bonds use energy, forming bonds release energy.

Exothermic

Energy of bonds in the products is lower than the energy of the bonds in the reactants. Heat is released.

Endothermic

Energy of bonds in the products is higher than the energy of the bonds in the reactants. Heat is absorbed.

Heat Formula

Heat = MCΔT. M = mass of a substance in grams, C = specific heat of a substance (proportionality constant), ΔT = change in temperature (final temp - initial temp). Measured in Celcius