2 Ch 3 Lesson 1 Energy What is energy? Energy – is the ability to cause changes in matter.Changing states of matter is a good example.Solid Liquid GasActivity
3 Kinetic Energy Kinetic energy – the energy of motion. Any matter in motion has kinetic energy.Look at this ping pong ball, when does it have kinetic energy?
4 Potential energyPotential energy – is the energy an object has because of where it or because of its position.Lets look again at the ping pong ball. Where does the ball have potential energy?
5 energyThe change in energy from potential to kinetic is called the Transformation of Energy.Even though energy can transform from one form to another, it cannot be created or destroyed. This is called the: Law of Conservation of Energy.
6 Forms of Energy Types of Kinetic Energy: Types of Potential Energy: Mechanical – energy moving objects have.Thermal – movement of molecules of matter.Electric – movement of electronsLight – pictures that move to your eyes in waves.Sound – vibrations heard through the ear that also move in waves.Types of Potential Energy:Elastic – energy found in compressed springs or rubber bands.Gravitational – energy an object has in an elevated positionChemical – stored energy in the food we eat.Is changed into thermal or mechanical energy by our bodies for energy and heat.
8 Review Questions What is energy? What is kinetic energy? You use mechanical energy to walk around. What form did this energy have before your body changed it to mechanical energy?If you toss a ball in the air, at what point does it have the most potential energy?What law states that energy can’t be created or destroyed?The law of mechanical energyThe law of conservation of energyThe law of kinetic energyThe law of potential energy
9 Ch 3 Lesson 2 Electric energy How has ever received a shock when touching a metal object?How many of your have every shocked someone or been shocked yourself?What causes the shock to occur?
10 Electric ChargesElectric energy is produced by the movement of electrons.Electricity is all around us; in lights televisions and the radio.Within an atom are electrons with a negative charge. Protons have a positive charge. They attract to each other.
11 Electric charges continued.. When an object gains or loses electrons it has an electric charge.If the object gains electrons is has a negative charge.If it loses electrons it has a positive charge.
12 Electric forceElectric force is the attraction or repulsion of charges.Like charges repelUnlike charges attract.Electric force depends on distance. The charge will be greater the closer two objects are.Charged objects have potential electric energy.AKA static electricityThe electrons aren’t moving until the charged objects are close enough to each other that the potential energy is changed into kinetic.Electrons flow from negatively charged objects to positively charged objects.
13 Electric current & Circuits Electric current – is the flow of electrons.Electric Circuits – is any path along which electrons can flow.Conductor – material that conducts electrons easily.Insulator – is a material that doesn’t carry electrons easily.Resistor – Don’t stop the flow of electrons completely, but resist the flow in some way.Examples of ConductorsMetalsExamples of InsulatorsRubberPlasticGlassAirExamples of ResistorsFilament (light bulbs)
15 Magnets and electricity Electromagnet – a current carrying wire is wrapped around a magnet.Only magnetized when electricity is flowing through it.
16 Review questions How do like electric charges react to each other? Why are insulators placed around electric conductors?What are resistors, and why are they important?Are the lights in your school connected in a series circuits or parallel circuit? Explain.Clue: Does on burned out light, turn off every other light?A coil that is magnetized only when an electric current flows through it is ?BatteryGeneratorConductorElectromagnet
17 CH 3 Lesson 3 Light Energy Light Energy Reflection vs. Refraction Light rays are a form of energy that can travel through empty space or through some kinds of matter.Reflection vs. RefractionReflection – other colors bounce off objects.Refraction – the bending of light rays.
18 lenses Convex Is thicker in the middle than at the edges. When light passes through the light rays bend toward each other.Magnifying glass is an example.Farsighted.
19 Lenses Concave This lens is thicker around the edges than the middle. When light rays pass through this lens they bend away from each other.They make objects nearer seem smallerCameras are an example.Nearsighted
20 Light Waves Light energy is also called electromagnetic waves. Visible light waves are those we can see, but they are just a small part of the electromagnets waves produced.Other examples: Radio waves, x-rays, microwaves.Does not need matter to move through; it can move through space.
21 Light You SeeVisible light waves are different color wavelengths.The human eye senses different wavelengths as different colors of light.Long wavelengths appear red, were as short wavelengths appear violet. Between red and violet are all the colors of the rainbow.ROYGBV is an acronym to help you remember visible wavelength colors.R – redO – orangeY – yellowG – greenB – blueV - violet
22 Inside the human eye Lens – light passes through the clear lens. Iris – is the colored part of the eye. It narrows in bright light and narrows in darkness.Cornea – light enters through the cornea and bends light raysRetina – an upside-down image falls here where cells change light energy to electric and chemical energy in the form of nerve impulses. This is were the blind spot in the eye is located, because there are no photoreceptors were the optic nerve is located.
23 Review questions What is refraction? What type of lens would you use to magnify your view of a butterfly?If a bright explosion took place in space, would it be seen on Earth?Which part of the eye has cells that change light energy into nerve impulses?The irisThe blind spotThe lensThe retina
24 Ch 3 Lesson 4 Thermal & chemical energy Thermal energy – is the kinetic energy of molecules.Temperature – is the average kinetic energy of all the molecules in an object. The higher the average kinetic energy, the faster the molecules, the higher the temperature.Heat – is the transfer of thermal energy from one substance to another.It always flows in the same direction.Warmer Colder
25 Transferring thermal energy Conduction – is the DIRECT transfer of thermal energy between objects that touch.Conductors and Insulators are important when using conduction.
26 Transferring thermal energy Convection – is thermal energy transfer as the result of the mixing of a liquid and a gas.
27 Transferring thermal energy Radiation – is the transfer of thermal energy by electromagnetic waves.Only radiation can transfer thermal energy through space. An example is the heat you feel from the sun.
28 Thermal Energy Transfer 3 ways Thermal Energy can be transferredConductionConvectionRadiation
29 Chemical energyChemical energy – energy that is stored as a form of potential energy.Chemical energy can be transferred into kinetic energy.Our body uses this chemical energy to carry out daily activities and maintain our body temperature.
30 Review questions What is convection? What type of heat transfer takes place when you burn your hand on a stove?Two atoms absorb thermal energy when joining together to form a molecule. What happens to the thermal energy?Suppose you drop an ice cube into a warm drink, and it melts. How is thermal energy transferred?Which form of energy transfer allow you to feel the warmth of the sun on your face?RadiationConductionConvectionChemical energy