Science 10 General Outcome B1/3 Thermodynamics Notes PDF

Science 10 General Outcome B1/3 Thermodynamics Energy can exist in various forms Energy exists in various forms. Some forms are kinetic, potential, or both depending on how it’s being used. Energy can transform Energy can transform from one form to another. Electrical energy → light...

Science 10 General Outcome B1/3 Thermodynamics Energy can exist in various forms Energy exists in various forms. Some forms are kinetic, potential, or both depending on how it’s being used. Energy can transform Energy can transform from one form to another. Electrical energy → light energy and sound when we use a computer Chemical energy (fuel) → kinetic energy when we drive a car Radiant energy (light) → chemical energy (glucose) through photosynthesis Solar panels Solar panels can be used to generate electricity. Identify and describe all of the energy transformations that occurs in a solar panel powered light bulb. For each transformation, categorize it as kinetic or potential energy. Solar panels 1. The sun’s rays (radiant energy, kinetic energy) are captured by solar panels 2. Solar panels convert sunlight in electrical energy (potential energy) 3. Electrical energy is converted to light (radiant energy, kinetic energy) Fossil fuel combustion In Alberta, most of our electrical energy is generated by burning fossil fuels. Use the diagram shown to identify and describe all of the energy transformations that took place. Fossil fuel combustion 1. Fossil fuels (chemical) are burned (thermal) to heat water 2. Water turns to steam (kinetic) which turns a turbine (kinetic) 3. A generator uses magnets to convert the rotational kinetic energy into electrical energy Waste Energy No process can be 100% efficient. Some energy will always remain in the form of thermal energy.(Second Law of Thermodynamics) This “leftover” thermal energy is often said to be “wasted” as heat. The challenge to engineers is to find ways to keep the amount of “wasted heat” as small as possible. The more transformations that occur, the more wasted energy there generally will be Even in food chains, the laws of thermodynamics are present. Plants convert solar energy to chemical potential energy This energy transformation is not 100% efficient – the amount of solar energy going in does not equal the amount of chemical potential energy coming out, some is “lost” Getting More Efficient Development of the steam engine The development of the steam engine, is an example of how trial and error can drive technological advancement and a deeper understanding of the laws of physics. An engine is a machine designed to convert one or more forms of energy into mechanical energy Sources of energy generally comes from potential energy Many generate heat as an intermediate form Usually involves a piston and crankshaft Development of the steam engine Steam engine- Double acting Steam engine- Early version engine and separate used steam to pull water out of condensers further improved a well the efficiency Thomas Savery James Watt 1st Century AD 1698 1712 1796 Hero of Alexandria Thomas Newcomen Aeolipile- a toy that Atmospheric engine- Improved demonstrated that heat energy the efficiency of Savery’s could cause movement design using trial and error Hero of Alexandria (1st Century AD) Hero of Alexandria- developed the aeolipile, an early steam-powered toy. Demonstrated the potential of steam power but wasn't used for practical purposes. Knowledge of steam came from observation that water turns to steam and steam could be controlled No evidence of knowledge of thermal energy at this point Thomas Savery (1698) Savery wanted to solve the problem of water flooding in mines. Developed an engine to create a vacuum that pulled water up through pipes. Initial trials often led to bursts and inefficiencies due to high-pressure steam Tried different materials to handle the high- pressure steam After numerous trials and dangerous failures, he incorporated safety features to prevent boiler explosions Thomas Newcomen (1712) Newcomen aimed to improve the efficiency of steam engines and invented the atmospheric engine. Early designs failed due to issues with sealing the piston, causing significant heat loss Trials with different sealing materials and designs reduced heat loss With every cycle, the piston and the cylinder were heated with steam and then cooled with a spray of water This constant heating and cooling caused rapid wear James Watt (1796) Watt sought to improve the efficiency and power of Newcomen’s engine. Watt’s innovations included the separate condenser. This way, the piston and cylinder remained hot and did not have to cool down. First models incorporated a separate condenser, but faced issues with sealing To prevent heat loss, Watt experimented with various insulating techniques to improving efficiency. Through trial and error, Watt introduced the double-acting engine, which allowed steam to push the piston in both directions, increasing power output. Became highly efficient, playing a crucial role in the Industrial Revolution. Steam Engine- First Law The challenges faced in improving steam engine efficiency led to significant scientific inquiry and discoveries, ultimately contributing to the establishment of thermodynamic principles. First Law Engineers and scientists observed that steam engines convert chemical energy (fuel) into heat (thermal energy) into mechanical work. This realization emphasized that energy was not created but transformed, and the need to account for this energy in all its forms, especially heat loss. Because energy is not created, improvements to the steam engine came from the need to reduce energy losses in order to increase energy for mechanical work (ie. you only have so much energy, so the more you reduce heat loss, the more you have for useful work) Steam Engine- Second Law Second Law Observations of energy losses in Savery and Newcomen engines led to questions about the limits of heat conversion to mechanical work No matter how efficient each design was, not all of the fuel could be converted into useful work Inefficiencies observed, such as heat losses and friction, led to the understanding that not all heat energy can be converted into work. Efficiency Input and output energy Input energy = energy put into a system Output energy = useful energy that the system exerts Based on the second law of thermodynamics, input energy will always be larger than output energy because of heat loss If input energy = output energy, then the system is 100% efficient Efficiency & The Second Law of Thermodynamics The second law of thermodynamics ○ No process can be 100% efficient ○ Some energy will always remain in the form of wasted energy Eg. A light bulb produces useful light and wasted heat Wasted energy ○ Energy that is not used for the intended purpose ○ Often takes the form of: Heat (friction) Sound Light Efficiencies of Common Engines Type of Machine Efficiency (%) Component in the Automobile Energy Consumed (%) automobile internal combustion 12–30 exhaust system engine 33 cooling and heating system electric engine Up to 95 33 drive train steam reciprocal engine 50–75 10 accessories 4 steam turbine engine Up to 40 internal friction 6 useful energy that propels the 14-30% automobile forward  Useful Energy and Efficiency Useful energy ○ The desired energy needed to do work Efficiency ○ A measurement of how effectively a machine converts energy input into useful energy output 𝒖𝒔𝒆𝒇𝒖𝒍 𝒘𝒐𝒓𝒌 𝒐𝒖𝒕𝒑𝒖𝒕 𝒆𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚 = x 100% 𝒕𝒐𝒕𝒂𝒍 𝒘𝒐𝒓𝒌 𝒊𝒏𝒑𝒖𝒕 Efficiency Percent efficiency is a ratio of energy output to energy input. Energy is usually measured in joules or kilojoules Percent efficiency is measured in percentage The energy input and energy output must be the same units (based on unit analysis they will cancel out) 𝒖𝒔𝒆𝒇𝒖𝒍 𝒘𝒐𝒓𝒌 𝒐𝒖𝒕𝒑𝒖𝒕 𝒆𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚 = x 100% 𝒕𝒐𝒕𝒂𝒍 𝒘𝒐𝒓𝒌 𝒊𝒏𝒑𝒖𝒕 You need to know how to manipulate this formula for output and input: Showing your work When solving mathematical problems, make sure you follow appropriate communication of how you arrived at your answer. 1. Show the formula 2. Substitute the variables in the formula with numbers with units 3. Use unit analysis to show how the final units were determined 4. Circle your final answer Teacher demonstration Calculate the percentage efficiency of a machine with the following input/output energies: 1. Input = 58 J, Output = 23 J 2. Input = 261 kJ, Output = 35050 J Solving for output energy- teacher demonstration A machine is 38.5% efficient. If 350 kJ of energy was put into the system, how many joules of useful output energy is expected? Solving for input energy- teacher demonstration LED lightbulbs are approximately 90% efficient. If 492 joules of light was emitted by the lightbulb, how many joules of electricity did it use?  Example: You peddle your bike up a steep hill, gaining 25m of vertical distance, thus gaining gravitational potential energy. You turn around and ride down the hill reaching a top speed of 13m/s at the end. If you have a mass of 60kg and your bike is 8.0kg then what is the efficiency of the transformation ? Practice: Page 227 #1-9, Answers on pg. 485 (chapter 6) Describe the sustainability of fuels used in Alberta in terms of cost, benefits, and efficiency Energy Sources Renewable energy sources ○ Energy sources that are continually and infinitely available Solar, wind, water, geothermal, tidal, biomass YouTube – Renewable 101 – Student Energy Non-renewable energy sources ○ Energy sources that are limited and irreplaceable Nuclear, fossil fuels Efficiency of Sources of Electricity Percentage efficiency of renewable energy sources: Solar = 24% Wind = 45% Hydro = 90% Although solar is not very efficient, this should be weighed against solar energy’s accessibility and sustainability. Fossil Fuel Economy 2017 data: In all of Western Canada (BC, AB, SK, MB), fossil fuels contribute to 41% of exports by value (74 billion dollars), this is comparable to: Disney’s annual revenue Global music industry Global video game industry Fossil Fuel Sustainability Coal releases the most carbon dioxide per joule of electricity produced. Fossil fuels contribute to approximately 75% of greenhouse gas emissions. 1. Alberta is highly reliant on coal and natural gas for energy production 2. Hydroelectric power is the most efficient source of energy, while other sources are comparable 3. Comparing efficiency of energy sources should be weighed against other considerations, including economy and sustainability 4. Fossil fuels are a massive source of income for the Canadian economy 5. Fossil fuel combustion is by far the largest source of global carbon dioxide emissions 6. It is expected that renewable energy will continue to rise, but fossil fuels will continue to be the dominant source of energy Apply thermodynamic laws quantitatively and/or qualitatively to analyze the design of a thermal device. Exemplary Question The images below show the process of generating electricity using hydroelectric power versus fossil fuel combustion: Explain using the laws of thermodynamics, why hydroelectric power is 90% efficient while coal combustion is 32% efficient. Exemplary Question- DV Response Explain using the laws of thermodynamics, why hydroelectric power is 90% efficient while coal combustion is 32% efficient. The first law of thermodynamics states that energy cannot be created or destroyed, but transformed from one form to another The second law of thermodynamics states that no system can be 100% efficient Hydroelectric power is more efficient because it uses water as the source of energy which will turn a turbine. Water is renewable and a type of kinetic energy, while fossil fuel combustion uses chemical potential energy in the form of coal oil, or natural gas to turn a turbine, in both cases, energy is changing forms. Exemplary Question- PR Response Explain using the laws of thermodynamics, why hydroelectric power is 90% efficient while coal combustion is 32% efficient. The first law of thermodynamics states that energy cannot be created or destroyed but transformed from one form to another. The second law of thermodynamics states that no energy transformations can be 100% efficient For hydroelectric power, the movement of water through a penstock will turn a turbine directly, converting the kinetic energy of water movement into electricity. There are fewer energy transformations compared to fossil fuel combustion. For fossil fuel combustion, fossil fuels are burned to heat water into steam. Steam will turn a turbine to generate electrical potential energy. There are significantly more steps and therefore, more heat is lost. Exemplary Question- EX Response (1/2) Explain using the laws of thermodynamics, why hydroelectric power is 90% efficient while coal combustion is 32% efficient. The first law of thermodynamics states that energy cannot be created or destroyed but transformed from one form to another. For hydroelectric power, a dam is built to creating water with high gravitational potential energy. The movement of water through a penstock will turn a turbine directly, converting the kinetic energy of water movement into electrical potential energy. There are fewer energy transformations and would likely lose little energy due to heat loss. For fossil fuel combustion, fossil fuels (chemical energy) are burned, the thermal kinetic energy used to turn water into steam. The kinetic energy from steam movement is used to turn a turbine to generate electrical potential energy. There are significantly more energy transformations involved with turning a turbine compared to hydroelectric power. Exemplary Question- EX Response (2/2) Explain using the laws of thermodynamics, why hydroelectric power is 90% efficient while coal combustion is 32% efficient. The second law of thermodynamics states that no energy transformations can be 100% efficient, therefore, the more energy transformations that occur in a system, the more likely more heat is lost. Based on the first law of thermodynamics, the more heat is lost, the less energy is available for useful work (ie. turning a turbine to generate electricity) because energy is conserved from the initial energy input. Energy Transformations Energy Conversions in Natural Systems Hydrogen-hydrogen fusion in the sun ○ Creates electromagnetic waves that warm the Earth Photosynthesis ○ Solar energy is converted into chemical energy (glucose) Sunlight + 6 CO2(g) + 6 H2O(l)  C6H12O6(aq) + 6 O2(g) Respiration ○ Chemical energy (glucose) is converted into ATP (the energy currency of the human body) C6H12O6(aq) + 6 O2(g)  6 CO2(g) + 6 H2O(l) + ATP  Energy Conversions in Natural Systems All energy on Earth originated from the sun ○ Even fossil fuels 1. Solar energy fuels ancient photosynthesis 2. Life form dies - bacterial decay of organic matter 3. Time/pressure (reorganization of atoms/chemical bonds) 4. Fossil fuels form 5. Fossil fuels harvested/refined 6. Combustion Energy Conversions in Technological Systems Hydroelectric dams – YouTube - Hydropower 101 - Student Energy Gravitational Potential Energy  Kinetic Energy  Kinetic Energy  Electrical Energy (A - elevated water) (B - moving water) (C - moving turbine) (D - generator) Energy Conversions in Technological Systems Coal burning power plant – YouTube – Coal 101 – Student Energy Chemical Potential Energy  Thermal Energy  Kinetic Energy  Electrical Energy (A - coal) (B – heating water) (C - moving turbine) (D - generator) Energy Conversions in Technological Systems Solar cells – YouTube – Solar Photovoltaics 101 – Student Energy Solar energy  electrical energy Energy Conversions in Technological Systems Nuclear power plant – YouTube – Nuclear 101 – Student Energy Nuclear Energy  Thermal Energy  Kinetic Energy  Electrical Energy (Uranium) (heating water) (moving turbine) (generator) Energy Conversions in Technological Systems Wind turbines – YouTube – Wind Power 101 – Student Energy Kinetic Energy  Kinetic Energy  Electrical Energy (Wind) (moving turbine) (generator)