ENERGY Energy Changes Temperature Chemical Energy

Energy and Work A. Energy is the ability to do work or cause a change. –Ex. The wind has energy B. Work occurs when a force is exerted on an object that causes the object to move. 1. Work = force (N) x distance (m) 2. Unit of measure is the Joule (J).

Energy and Work 3. One Joule is when 1 N of force is exerted to move an object 1 meter. 4. Named after James Prescott Joule a physicist in the 1800’s who did a great deal of study on work.

Energy Transformations Energy changes from one form to another without any being lost or gained Chemical energy in wood – use to cook, stay warm, and provide light Electrical energy converted into heat by blow dryer Lightbulb converts electrical energy into heat and light energy

Kinetic Energy Energy due to motion An object’s kinetic energy depends on its mass and speed When objects collide, kinetic energy can be transferred

Potential Energy Stored energy due to an object’s position Potential energy can be transformed to kinetic energy and kinetic energy can be transformed to potential energy The higher an object is lifted above Earth, the greater its potential energy

Potential Energy

Law of Conservation Energy cannot be created or destroyed; it can only change form Total amount of energy in the universe NEVER changes Kinetic energy can be converted to heat energy, as happens when two objects rub against each other, such as a book sliding across a tabletop

Other Forms of Energy A. Mechanical Energy is the energy of motion. B. Thermal Energy is the total energy of the particles in an object. –1. Warm = fast moving particles –2. Cool = slow moving particles C. Chemical energy is potential energy stored in chemical bonds. –1. Found in foods or a match

Other Forms of Energy D. Electrical energy is moving electrical charges that produce electricity. E. Electromagnetic energy is energy that travels in waves. –1. Light, ultraviolet radiation, microwaves, infrared radiation. F. Nuclear energy is a potential energy stored in the nucleus of an atom. –1. When the nucleus is broken apart energy is released.

Temperature Measure of the average kinetic energy of an object’s atoms Temperature is measured with a thermometer Fahrenheit scale – freezing point of water is 32 degrees and boiling point is 212 degrees Celsius scale – freezing point of water is 0 degrees and boiling point is 100 degrees

Heat Transfer of energy from one object to another due to a difference in temperature –Heat flows from warmer object to cooler ones –Flow of heat stops when the temperature of two objects is the same –Water is unusual because it takes a large amount of heat to raise its temperature; water’s temperature does not change as much as surrounding air or land

Heat on the Move Heat can be transferred in THREE ways –Conduction: transfer of energy by collisions between the atoms in a material, e.g., metal spoon in boiling water; usually occurs in solids Insulators: blankets, clothes, plastic, wood, rubber, and ceramic materials

Heat on the Move Heat can be transferred in THREE ways –Convection: transfers heat when particles move between objects or areas that differ in temperatures; most common in gases and liquids

Heat on the Move Heat can be transferred in THREE ways –Radiation: energy transferred by waves

Chemical Energy Chemical reactions release energy Compounds are broken down or new compounds are formed in chemical reactions Energy in chemical bonds is a form of potential energy called chemical energy In every chemical reaction, transformations in energy occur

Chemical Energy To break chemical bonds, energy must be added; when chemical bonds form, energy is released –Endothermic reactions: chemical reactions that absorb energy –Exothermic reactions: chemical reactions that release energy –Chemical reactions occur at different rates; a catalyst changes the rate of chemical reaction without its own structure being changed

Exothermic processesEndothermic processes making ice cubesmelting ice cubes formation of snow in cloudsconversion of frost to water vapor condensation of rain from water vaporevaporation of water a candle flameforming a cation from an atom in the gas phase mixing sodium sulfite and bleachbaking bread rusting ironcooking an egg burning sugarproducing sugar by photosynthesis forming ion pairsseparating ion pairs Combining atoms to make a molecule in the gas phase splitting a gas molecule apart mixing water and strong acids mixing water and ammonium nitrate making an anhydrous salt from a hydrate crystallizing liquid saltsmelting solid salts nuclear fissionreaction of barium hydroxide octahydrate crystals with dry ammonium chloride mixing water with calcium chloride