Forms of Energy

1. Forms of Energy • Kinetic Energy – due to the movement of an object. As the blocks move they lose potential energy but it is converted to kinetic Kinetic Energy vs. Attractive Force - as particles gain kinetic energy there is less force holding them together – energy overcomes the force so it changes from a solid to a liquid and gas • Potential Energy – energy stored due to the position of an object. • Radiant Energy – also called light energy • Electrical Energy – energy associated with moving charges, usually electrons. • Thermal Energy – also called heat energy. Thermal energy is related to the movement of particles. Thermal energy always moves from the higher temperature to the lower temperature. Is temperature energy? NO! Temperature is a measure of the average kinetic energy of the particles in a substance. • Nuclear Energy – energy stored within the nucleus of an atom.

2. Law of Conservation of Energy • Energy cannot be created or destroyed. It can be transformed from one form to another. • Ex) When natural gas, CH4, is burned to heat your home the chemical energy in the CH4 molecule is converted to thermal and radiant energy. The products from the combustion reaction, H2O and CO2, also contain some products from the chemical energy. If we were to total up the energy of the system before and after we would find that the total energy before=total energy after.

3. Heat and Temperature • Heat (J or calories) – a transfer of energy from a body of higher temperature to a body of lower temperature. Thermal energy is associated with the random motion of atoms and molecules. • Ex) steam v water • Temperature – a measure of the average kinetic energy of the particles of a substance. Temperature is not a form of energy. • Question: What state of matter has the most energy? GAS • Absolute Zero – 0 K = -273 C the point at which the motion of particles of matter ceases.

4. Change of State (review) • A change of state, also called a phase change, is the conversion of a substance from one of the 3 states of matter to another. A change of state always involves a change in energy.

5. Heating and Cooling Curves • Shows how a substance changes states at each temperature increase over time.

6. Heat Calculations • Specific Heat Capacity – the amount of energy required to raise the temperature of a substance one degree. • Ex: Takes more energy to heat a swimming pool that a cup of water • Specific heat Capacity of H2O (l) = 4.18 J/g X C • Fusion – melting • Heat of Fusion – the amount of heat needed to convert unit mass of a substance from a solid to a liquid at constant temperature. • - when ice is melting the kinetic energy stays the same • Heat of Fusion of H2O = 334 J/g

7. Calculations con • Heat of Vaporization – the amount of heat needed to convert a unit mass of a substance from a liquid to a gas at constant temperature. • - when ice is boiling the kinetic energy stays the same • Heat of V of H2O = 2260 J/g • TABLE B in Reference Table

8. Calculations con. • Q = mC∆T • Q = mHf • Q = mHv

9. Vapor Pressure • In every liquid, some particles are far enough away from each other to be considered gas but are pushed down by atmospheric pressure. When in liquid, some particles are far enough apart to escape their neighboring molecules and enter the gas phase (vapor). As temperature increases, particles gain more energy and more particles escape from the surface. The pressure these gaseous particles exert is called vapor pressure. As temp increases, vapor pressure increases.

10. Vapor Pressure con. • Vapor pressure eventually builds up enough to equal atmospheric pressure. When it surpasses atmospheric pressure, the liquid boils and allows the gaseous particles to escape. • Vapor Pressure – pressure gaseous particles exert upward