Presentation on theme: "Energy Notes What is Energy?"— Presentation transcript:
1Energy Notes What is Energy? Energy makes change. Energy moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. Energy makes our bodies grow and allows our minds to think. Scientists define energy as the ability to do work. People have learned how to change energy from one form to another so that we can do work more easily and live more comfortably.
2KINETIC ENERGY POTENTIAL ENERGY Forms of EnergyEnergy is found in different forms, such as light, heat, sound and motion. There are many forms of energy, but they can all be put into two categories: kinetic and potential.KINETIC ENERGYPOTENTIAL ENERGYKinetic energy is motion—of waves, electrons, atoms, molecules, substances, and objects.Potential energy is stored energy and the energy of position (gravitational energy).
3Electrical energy is the movement of electrical charges Electrical energy is the movement of electrical charges. Everything is made of tiny particles called atoms. Atoms are made of even smaller particles called electrons, protons, and neutrons. Applying a force can make some of the electrons move. Electrical charges moving through a wire is called electricity. Lightning is another example of electrical energy.
4Radiant energy is electromagnetic energy that travels in transverse waves. Radiant energy includes visible light, x-rays, gamma rays and radio waves. Light is one type of radiant energy. Solar (sun) energy is an example of radiant energy.
5Thermal energy, or heat, is the internal energy in substances––the vibration and movement of the atoms and molecules within substances. Geo-thermal energy is an example of thermal energy.
6Motion energy is the movement of objects and substances from one place to another. Objects and substances move when a force is applied according to Newton’s Laws of Motion. Wind is an example of motion energy.
7Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves. Sound is produced when a force causes an object or substance to vibrate––the energy is transferred through the substance in a wave.To sum up what happens to energy when you use a phone to call a friend:1. The sound energy in your voice makes the air vibrate. Vibrating air carries the sound energy into the phone. 2. The diaphragm in the mouthpiece microphone converts sound energy into electrical energy. 3. The electrical energy travels from the phone, via exchanges, to your friend's phone. 4. A diaphragm in the earpiece loudspeaker of your friend's phone converts the incoming electrical energy back to sound energy. 5. The sound energy travels out from the earpiece into your friend's ear.
8Chemical energy is energy stored in the bonds of atoms and molecules Chemical energy is energy stored in the bonds of atoms and molecules. It is the energy that holds these particles together. Biomass, petroleum, natural gas, and propane are examples of stored chemical energy. Ex. H-O-H
9Elastic (Mechanical) energy is energy stored in objects by the application of a force. Compressed springs and stretched rubber bands are examples of stored mechanical energy.
10Nuclear energy is energy stored in the nucleus of an atom––the energy that holds the nucleus together. The energy can be released when the nuclei are combined or split apart. Nuclear power plants split the nuclei of uranium atoms in a process called fission. The sun combines the nuclei of hydrogen atoms in a process called fusion. Scientists are working on creating fusion energy on earth, so that someday there might be fusion power plants.
11Gravitational energy is the energy of position or place Gravitational energy is the energy of position or place. A rock resting at the top of a hill contains gravitational potential energy. Hydropower, such as water in a reservoir behind a dam, is an example of gravitational potential energy.
13Law of Conservation of Energy Conservation of energy is NOT saving energy. The law of conservation of energy says that energy is neither created nor destroyed. When we use energy, it doesn’t disappear. We change it from one form of energy into another.
15A car engine burns gasoline, converting the chemical energy in gasoline into mechanical energy. Solar cells change radiant energy into electrical energy. Energy changes form, but the total amount of energy in the universe stays the same.
17Energy EfficiencyEnergy efficiency is the amount of useful energy you get from a system. A perfect, energy-efficient machine would change all the energy put in it into useful work—an impossible dream. Converting one form of energy into another form always involves a loss of usable energy.
18In fact, most energy transformations are NOT very efficient. The human body is a good example.Your body is like a machine, and the fuel for your machine is food. Food gives you the energy to move, breathe, and think. But your body isn’t very efficient at converting food into useful work. Your body is less than five percent efficient most of the time. The rest of the energy is lost as heat. You can really feel that heat when you exercise!
19What Does Energy Mean to Us? All organisms must have energy to survive. Photosynthesis is the chemical process that provides that energy! During photosynthesis, the sun’s energy is trapped in the chemical bonds of glucose. Plants (producers) provide us with ENERGY!PHOTOSYNTHESISEnergy Conversion: RADIANT ENERGY is CONVERTED TO CHEMICAL ENERGY!6CO H2O ENERGY C6H12O O2carbon dioxide water from sunlight glucose oxygenCELLULAR RESPIRATIONC6H12O O CO H2O + ENERGYglucose oxygen carbon dioxide water ATP
21CHEMICAL ENERGY IS CONVERTED INTO ATP – bioCHEMICAL ENERGY!
22RESPIRATIONDuring cellular RESPIRATION the energy is released from it’s chemical bonds for use by the cells. The usable energy form is called ADENSOSINE TRIPHOSPHATE (ATP).Conversions efficiencies are always much less than 100%. At each link in a food chain, a substantial portion of the sun's energy - originally trapped by a photosynthesizing autotroph - is dispersed back into the environment (ultimately as heat). Our bodies convert only about 35% of the energy that it takes in. This may seem inefficient, but our cars are even less efficient. Cars convert about 25% of its energy intake into motion.
23Sources of EnergyWe use many different energy sources to do work for us. Energy sources are classified into two groups—renewable and nonrenewable. Renewable and nonrenewable energy can be converted into secondary energy sources like electricity and hydrogen.
24In the United States, most of our energy comes from nonrenewable energy sources. Coal, petroleum, natural gas, propane, and uranium are nonrenewable energy sources. They are used to make electricity, to heat our homes, to move our cars, and to manufacture all kinds of products.These energy sources are called nonrenewable because their supplies are limited. Petroleum, for example, was formed millions of years ago from the remains of ancient sea plants and animals. We can’t make more petroleum in a short time.
25Renewable energy sources include biomass, geothermal energy, hydropower, solar energy, and wind energy. They are called renewable energy sources because they are replenished in a short time. Day after day, the sun shines, the wind blows, and the rivers flow. We use renewable energy sources mainly to make electricity.
26Energy Calculations KE = mv2/ 2 The S.I. unit for energy is Joules, J. Kinetic Energy = 1/2 mass X velocity2KE = mv2/ 2Example Problem:A 15 kg bicycle carrying a 50 kg boy is traveling at a speed of 5 m/s. What is the kinetic energy of the bicycle (including the boy)?
27PE = mgh Example Problem: Gravitational Potential Energy = mass X acceleration due to gravity X heightPE = mghExample Problem:A 0.06 kg tennis ball starts to fall from a height of 2.9 m. How much gravitational potential energy does the ball have at that height?
28Example Problem:Thomas is holding a tennis ball outside a second floor window (3.5 m from the ground) and Dustin is holding one outside a third floor window (6.25 m from the ground). How much more gravitational potential energy does Dustin’s tennis ball have? (Each tennis ball has a mass of 0.06 kg.)
29Mechanical Energy = potential energy + kinetic energy
32Thermal EnergyAll matter is made of tiny particles—atoms and molecules. In all materials—solids, liquids, and gases—these particles are in constant motion. Like all objects that are moving, these moving particles have kinetic energy. The faster these particles move, the more kinetic energy they have.
33The temperature of an object is related to the average kinetic energy of the atoms or molecules. The faster these particles are moving, the more kinetic energy they have, and the higher the temperature of the object is. The SI unit for temperature is Kelvin (K).The sum of the kinetic and potential energy of all the molecules in an object is the thermal energy of the object.
34***Heat is thermal energy that flows from something at a higher temperature to something at a lower temperature. Heat is a form of energy, so it is measured in joules—the same units that energy is measured in. Heat always flows from warmer to cooler materials.
35c = specific heat of substance ∆T = change in temperature The amount of heat that is needed to raise the temperature of 1 kg of some material by 1°C or 1 K is called the specific heat of the material. Specific heat is measured in joules per kilogram Kelvin [J/(kg K)].Q = mc∆TQ = thermal energym = massc = specific heat of substance∆T = change in temperature
37SPECIFIC HEAT CALCULATIONS Q = mc∆T If 150 kilograms of water is heated from 30oC to 40oC, the number of joules of heat energy absorbed is…If a 2.0 kg sample of water at 5.0oC absorbs 26 J of heat energy, the temperature of the sample will be…Q = mc∆T
38HEAT TRANSFERS BY:Conduction—the movement of thermal energy from one object to another when they are in direct contact (touching). Molecules can transfer energy to a neighboring one within an object.Examples:Bare feet touching the cement on a hot summer dayWarming up with a hot cup of coffeeCar seat warmersCan you think of any other examples???
39Convection—the movement of thermal energy from one area to another in a liquid or gas. Heat transfers by currents.Examples:Wind CurrentsHot Air BalloonCan you think of any other examples?
41Radiation—when warm or hot matter emits electromagnetic radiation – especially infrared radiation – that is then absorbed by an object at a distance. The absorption heats the second object. This energy transfer does NOT require matter.Examples:A microwave ovenThe SunUV lightCan you think of any other examples?
45Controlling Heat FlowAlmost all living things have special features that help them control the flow of heat. For example, the Antarctic fur seal’s thick coat and the emperor penguin’s thick layer of blubber help keep them from losing heat. This helps them survive in a climate in which the temperature is often below freezing. In the desert, however, the scaly skin of the desert spiny lizard has just the opposite effect. It reflects the Sun’s rays and keeps the animal from becoming too hot. An animal’s color also can play a role in keeping it warm or cool. The black feathers on the penguin’s back, for example, allow it to absorb as much radiant energy as possible. How do you think humans control body heat flow?
46Insulators—a material that does NOT allow heat to flow through it easily. Materials such as wood, plastic, fiberglass, and air are good insulators. Gases are usually much better insulators than solids or liquids.
47Conductors—a material that allows heat to flow through it easily Conductors—a material that allows heat to flow through it easily. Although conduction can occur in solids, liquids, and gases, solids usually conduct heat much more effectively. Metals such as silver, copper, and aluminum are among the best heat conductors.
48A material that is a good conductor of heat, such as a metal, is a poor insulator. Likewise, good insulators are poor conductors of heat. Why do you think most cooking pots are made of metal but the handles usually are not?
50Heat Movers—a device that removes thermal energy from one location and transfers it to another location at a different temperature such as a refrigerator and air conditioner.
51Change in Energy :Endergonic Reaction—energy is absorbed; requires more energy to break bonds than is given off when new bonds are formedEndothermic Reaction—absorb heat from surroundingsEx: Commercial cold packs usually consist of two compounds- urea and ammonium chloride in separate containers within a plastic bag. When the bag is bent and the inside containers are broken, the two compounds mix together and begin to react. Because the reaction is endothermic, it absorbs heat from the surrounding environment and the bag gets cold.
53Exergonic Reaction—energy is released; less energy is required to break the original bonds than is released when new bonds formExothermic Reaction—giving off heat or light release energy to the surroundings (usually in the form of heat)Ex: sodium and chlorine react so violently that flames can be seen as the exothermic reaction gives off heat.