ENERGY

Energy ChangesTemperatureChemical Energy

Energy and Work

A. Energy is the ability to do work orcause a change.

– Ex. The wind has energy

B. Work occurs when a force is exertedon 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 isexerted 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 gainedChemical energy in wood – use to cook, stay warm, and provide lightElectrical energy converted into heat by blow dryerLightbulb converts electrical energy into heat and light energy

Kinetic Energy

Energy due to motionAn object’s kinetic energy depends on its mass and speedWhen objects collide, kinetic energy can be transferred

Potential Energy

Stored energy due to an object’s positionPotential energy can be transformed to kinetic energy and kinetic energy can be transformed to potential energyThe 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 formTotal amount of energy in the universe NEVER changesKinetic 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 storedin chemical bonds.

– 1. Found in foods or a match

Other Forms of Energy

D. Electrical energy is moving electrical chargesthat 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 atomsTemperature is measured with a thermometerFahrenheit scale – freezing point of water is 32 degrees and boiling point is 212 degreesCelsius 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 energyCompounds are broken down or new compounds are formed in chemical reactionsEnergy in chemical bonds is a form of potential energy called chemical energyIn 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 processes Endothermic processes

making ice cubes melting ice cubes

formation of snow in clouds conversion of frost to water vapor

condensation of rain from water vapor evaporation of water

a candle flame forming a cation from an atom in the gas phase

mixing sodium sulfite and bleach baking bread

rusting iron cooking an egg

burning sugar producing sugar by photosynthesis

forming ion pairs separating ion pairs

Combining atoms to make a molecule in the gas phase

splitting a gas molecule apart

mixing water and strong acidsmixing water and ammonium nitrate

making an anhydrous salt from a hydrate

crystallizing liquid salts melting solid salts

nuclear fission reaction of barium hydroxide octahydrate crystals with dry ammonium chloridemixing water with calcium chloride