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Energy • Energy is the capacity to do work or produce heat or change • The study of energy and its transformations is known as thermodynamics • Objects, from baseballs to molecules, can produce energy energy • Chemical energy of substances is due to the potential energy stored in the arrangements of their atoms…coal, gasoline, hydrogen • Thermal energy the total amount of energy from the movement of particles in matter; the atoms in matter are always moving; the more motion, the more thermal energy; heat and thermal energy are not the same…heat is transferred, thermal energy is a quantity • Mechanical Energy: energy that moves objects; mechanical energy is the sum of kinetic and potential energy • Sound Energy vibrations of states of matter • Electromagnetic Energy: Energy that can travel through empty space in waves…light falls under this • Nuclear Energy: energy that has its source in the nucleus of an atom…can result from fusion or fission • **Other forms of energy, like electricity, will fall under these** Energy: Mechanical(Kinetic and Potential) • • • • • • • • Kinetic energy is energy in motion Kinetic energy increases as the speed of an object increases…also increases with increasing mass (Ek = ½ mv2): mass x (velosity)2 Potential energy is stored energy that results from the attraction and repulsions an object experiences in relation to other objects Potential energy can be gravitational, chemical, nuclear, or elastic Potential energy due to gravity is GPE = mgh (mass x gravitational acceleration (9.8 m/s2) x height) Potential energy can be converted into kinetic energy Mechanical energy = Potential energy + Kinetic energy Units of Energy • The unit for energy is the joule (“jool”) • A mass of 2 kg moving at a speed of 1 m / s possesses a kinetic energy of 1 Joule (1 J) • A joule is not a large amount of energy and is often expressed in kJ • Energy changes in chemical reactions will sometimes be expressed in calories (cal) • 1 calorie = 4.184 J EXACTLY and is the amount of energy needed to raise 1 g of water 10 C • The specific heat of an object is the amount of energy it takes to raise the temperature of the substance one degree Celsius…the greater the specific heat, the more energy required to raise its temperature • Like matter, Energy Law of Conservation of Energy can neither be created nor destroyed, it can only change form…This is the LAW OF CONSERVATION OF ENERGY • Energy is conserved, it changes form!!! • Energy will be transferred from high to low • No energy transfer is 100% efficient Renewable vs. Non renewable To Flipchart • Non-renewable energy sources cannot be replenished (made again) in a short period of time. Examples include: coal, petroleum, natural gas, propane, nuclear, and oil • Renewable energy sources can be replenished naturally in a relatively short period of time. Examples include: water, geothermal, wind, solar, and biomass • Secondary energy sources are those that come from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. Energy • • • • • • Energy is transferred in two general ways: to cause motion of an object against a force, or to cause a temperature change…pg 81 of your book A force is any kind of push or pull on an object Work is energy used to cause an object to move against a force; work = force x distance moved W = fd; units are Joules Heat is the energy transferred from a hotter object to a colder one; thermal energy and heat are not the same! The transfer of heat results in an increase in thermal energy! Energy Efficiency is a measurement of how much energy is converted in to a desirable form than is released into the surroundings; energy Energy Efficiency = output input TEMPERATURE AND PARTICLE MOVEMENT • Everything around you has kinetic energy even if it is not in motion…the atoms are moving • The Kinetic theory of matter states that all of the molecules that make up matter are constantly in motion • Remember how particles behave in the states of matter!!! • Temperature is a measure of the average kinetic energy of all molecules in an object…it is not possible to know the kinetic energy of each individual molecule • If something is said to have a high temp. that means its molecules are moving fast and have a high average kinetic energy • When something warms, its molecules speed up; when something cools, they slow down…soup cools when its molecules collide with the air molecules above it • Remember that kinetic energy = (½ mass x velocity2); it goes for molecules too!!!! KE = mv2…doorknobs don’t have to move as fast as air Direction of heat transfer • Heat is the flow of energy from an object of high temperature to one of low temperature…when an object gives off heat, that means it is transferring energy!! Heat is energy in transit • Thermal energy is the total kinetic energy of molecules in an object…all the kinetic energy is added together! • Thermal energy and temperature are different, why? • As heat is transferred, thermal energy can go up or down, how? • When a system absorbs heat, it is said to be endothermic (endo = into) • Ice melting is an endothermic process • Ice feels cold because it is absorbing heat from our hand, the surroundings • The release of heat is called an exothermic process (exo = out of) • Heat flows out of the system and into the surroundings Energy / Heat transfer • Conduction is the direct transfer of heat through touching of solid objects…objects that transfer heat easily are good conductors • Insulators do not transfer energy easily, there are spaces between their molecules • Convection is the transfer of energy through the movement of particles in a liquid or an gas • Radiation is energy that travels as electromagnetic waves…it is unique in that it can travel through empty space • Heat can be transferred by conduction, radiation, and convection Temperature Scales o F = (9/5C) + 32 o • The choice of a temperature scale is arbitrary, meaning it is not bound by rules • A scientist who made especially good thermometers was Gabriel Fahrenheit (1686-1736)…he devised his own temperature scale • Celsius, named after its inventor Anders Celsius (1701-1744) a Swedish Astronomer. It has the freezing point of water at sea level being 0 degrees Celsius, and the boiling point at sea level 100 degrees C • Thermometers measure temp. by a variation of physical properties of the liquid inside…the liquid will expand with a rise in temperature (thermal expansion) C = 5/9(F – 32) The Kelvin Scale K = oC + 273 • SI unit for temperature is Kelvin • Named after an English physicist and mathematician, Lord Kelvin (William Thomson) (1824-1907) • The degree symbol (o) is not used • However, one degree Kelvin is the same size as one degree Celsius • The difference between Kelvin and Celsius is the location of the zero point (0C +273.15 K) • 0 K, or absolute zero, is the point at which the motion of particles of matter, their kinetic energy, is gone!!