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Energy basics • ‘Work’ is done when a force acts on an object to cause it to move, change shape, displace, or do something physical. • Thermal energy is what we call energy that comes from the temperature of matter. The hotter the substance, the more its molecules vibrate, and the therefore the higher its thermal energy. The amount of thermal energy in an object is measured in Joules (J) • For example, a cup of hot tea has thermal energy in the form of kinetic energy from its vibrating particles. When you pour some milk into your hot tea, some of this energy is transferred from the hot tea to the particles in the cold milk. What happens next? The cup of tea is cooler because it lost thermal energy to the milk. Temperature and Heat We cannot discuss thermal energy without touching on Temperature.Temperatu re and heat are NOT THE SAME. Temperature How hot or cold it is. Measured in degrees Celsius. Heat/Thermal The amount of thermal energy, measured in joules or J. A cup of hot tea has heat energy in the form of kinetic energy from its particles. A swimming pool at 30°C is at a lower temperature than a cup of tea at 80°C. BUT the swimming pool contains more water, so it stores more thermal energy or heat. The small beaker of water boils first The large beaker contains more water and needs more thermal energy or heat to reach 100°C. Chemical Energy is energy stored in the bonds of chemical compounds (atoms and molecules). It is released in a chemical reaction. Chemical energy can be stored and then transferred to the surroundings as thermal energy, sound energy and kinetic energy. Sound is produced when a force causes an object or substance to vibrate (eardrum) — the energy is transferred through the substance in a wave. Kinetic energy (movement Electrical energy is energy that's stored in charged particles within an electric field. Electric fields are simply areas surrounding a charged particle. Energy transfer Energy transfer • Example: The battery transfers stored chemical energy as electrical energy. The electrical energy is transferred to the surroundings by the lamp as light energy and thermal energy (heat energy). The Law of Conservation of Energy Energy is always conserved, it is never "lost" or "wasted“. Energy is not created or destroyed! Two Types of Energy: 1) Kinetic Energy 2) Potential Energy Potential Energy •Potential Energy is stored energy. •An object with potential energy has the ability to move or change. •Potential energy depends on an object’s position or condition. • Gravitational Potential energy is only stored in the height of the object. Any time that a heavy object is kept high up, a force or power is likely to be holding it up there. This is the reason why it stays up and does not fall. It is important to note that the heavier the object, the more its potential energy. Examples: Kinetic Energy • Kinetic Energy is the energy of movement. • It depends on the mass and speed of a moving object. Examples: Potential or Kinetic? Potential or Kinetic? Potential or Kinetic? Potential or Kinetic? Potential or Kinetic? Potential or Kinetic? Heat A Form of Energy Molecules and Motion • The motion of molecules produces thermal energy/heat. • The more motion, the more heat is generated. Heat Transfer • Heat is the flow of thermal energy from a warmer object to a colder one. Forms of heat transfer • Three forms of heat transfer: • Conduction • Convection • Radiation Conduction • Conduction involves the transfer of heat through direct contact • Molecules transfer energy as they collide with adjacent molecules. Conductors & Insulators • Conductors allow energy to flow easily. Ex. metals & glass – think of cookware • Insulators are poor conductors. Ex. wood, plastic, fabric – think of the handles on cookware or an oven mitt. Convection • This is the transfer of energy in liquids and gases as molecules move in currents. • Warmer molecules rise and the cooler ones sink. Radiation • Heat is transferred through empty space. Ex. electromagnetic waves and visible light • Energy from the sun radiates to Earth. *Other hot objects can radiate as well. Questions • What are the three types of heat transfer? • How is conduction different from radiation? Answer: What type of heat transfer is involved? • Heating a room with a fireplace Convection • Egg cooking in a frying pan Conduction • Roof of a house becoming hot Radiation Answer: What type of heat transfer? 1. Warm air mass bringing a change in the weather 2. Wire getting hot from an electric appliance Properties of Light • Reflection- when an object or wave bounces back off a surface Electromagnetic Waves waves without a • Transverse medium! • (They can travel through empty space) • Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency RADIO WAVES INFRARED RAYS MICROWAVES ULTRAVIOLET RAYS VISIBLE LIGHT GAMMA RAYS X-RAYS RADIO WAVES • Have the longest wavelengths and lowest frequencies of all the electromagne tic waves. MICROWAVES • Have the shortest wavelengths and the highest frequency of the radio waves. INFRARED RAYS • Infrared= below red • Shorter wavelength and higher frequency than microwaves. VISIBLE LIGHT • Shorter wavelength and higher frequency than infrared rays. • Electromagnetic waves we can see. • Longest wavelength= red light • Shortest wavelength= violet (purple) light ULTRAVIOLET RAYS • Shorter wavelength and higher frequency than visible light • Carry more energy than visible light X- RAYS • Shorter wavelength and higher frequency than UV-rays • Carry a great amount of energy • Can penetrate most matter. GAMMA RAYS • Shorter wavelength and higher frequency than X-rays • Carry the greatest amount of energy and penetrate the most.