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Transformation of Energy Study Guide Learning Target #1 – I can explain that electricity is the movement of electrons. The source of electrical energy lies in the forces between the electric charges found in atoms. In the atom, protons have a positive charge and electrons have a negative charge. If an atom has the same number of electrons and protons it is neutral and has no charge. If an object gains or loses electrons it becomes electrically charged. If two objects are positively charged they repel each other. Two objects that have opposite charges attract. Static charge or electricity occurs when two objects come in contact and electrons get rubbed off one object onto another. When you rub your feet on the carpet electrons are transferred from the carpet to your feet. This causes an imbalance of electrons (static charge). Then when you touch a metal object you may get a small shock. This is a static discharge or movement of electrons which are attracted to the electrons in the doorknob. The movement of electrons is what causes the shock. Lightning is static electricity. Current electricity is the flow of electric charges through a closed path called a circuit. Batteries and other means are used to start charges flowing through circuits. Materials in which electric charges can move easily are called conductors. Metals such as copper are good conductors. Insulators are materials that do not allow charges to move easily. Rubber and plastic are good insulators. Learning Target #2 – I can construct and explain how circuits work. Electric current will flow continually only if the charges can flow in a closed path. A closed path in which electric charges flow is a circuit. Current will flow in this circuit as long as the path between the battery, wires, and light is not broken. If the switch is open, one of the wires is disconnected or cut, or the light bulb is burned out; the path is no longer closed and the current will no longer flow. In a series circuit the electric current has only one path to follow (one light goes out-they all go out). In a parallel circuit there is more than one path for current to follow. In this circuit if one light burns out the current will take another path to keep the other bulbs lit. Most buildings and houses have parallel circuits. Learning Target #3 – I can give examples of energy. The seven major categories of energy are: heat, light, chemical, mechanical, sound, electrical, and nuclear. You are familiar with light, heat, sound, and electrical. Mechanical energy is the energy of motion - either potential or kinetic. Kinetic energy is the energy of motion- a flying football. Potential energy is energy that is stored and could be moving if released – a skier on top of a hill. Chemical energy is contained in any object that could burn. It is also contained in food. Nuclear energy is the energy that is stored within atoms. You will not have any questions about nuclear energy on the test. Learning Target #4 – I can give examples of energy transfer. That means energy is moved from one object to another. During an energy transfer, energy is moved from one object to another. The energy form remains the same, it’s just where the energy is located that is different. Examples of energy transfer would be hitting a baseball, throwing a football, or hitting a golf ball (mechanical energy transferred from one object to another). Other examples would be cooking bacon in a skillet (heat energy is transferred from the burner to the bacon), sticking your hand into hot water (heat transferring from the water to your hand), or a car running into another car(mechanical energy transferring from one car to another). Learning Target #5 – I can give examples of energy transformations. That means energy is changed from one form to another. During energy transformation, energy is changed from one form to a different form. Energy transformations occur around us all the time. We use the chemical energy in food we eat to power our muscles. We change the chemical energy into mechanical energy. Some of the chemical energy gets changed into heat energy also. This explains why we get hot when we run around (we are changing chemical energy into mechanical and heat energy). The chemical energy in a candle is transformed into heat and light energy. The mechanical energy in a car is transformed into heat and light energy (brakes /engine – heat, signal lights). The most common everyday transformation involves electrical energy. We use electrical energy for a variety of purposes. We transform it into sound energy for radios and iPODs. We transform it into heat/mechanical/sound energy for our hairdryers. We transform it into heat and light for our homes. All electrical energy is produced through the transformation of other energy types into electricity. Mechanical energy (moving water, wind, tides) is used to turn turbines that generate electrical energy. The chemical energy in coal and gas are transformed into electrical energy also. Light energy (solar) is transformed into electrical energy through solar panels. Learning Target #6 – I can describe the exchange of energy between hot and cold objects. Heat is exchanged between objects that are different temperatures. Objects with lower temperatures gain heat energy from their surroundings. Objects with higher temperatures lose heat energy. Heat moves from colder objects to warmer objects. For example, heat moves from a cold can of soda to your hand. A block of ice will absorb heat from its surrounding and melt. The transfer of heat will stop when the objects reach the same temperature. Learning Target# 7 – I can explain how heat energy is transferred. Heat is transferred by three methods: conduction, convection, radiation. Conduction occurs in solid objects. The heat travels through the objects by causing their particles to vibrate more, then those particles bounce into their neighbors causing them to bounce, and this continues through the object. Some objects are better conductors then others (metals are better than wood and plastic). Convection occurs in liquids and gasses. During convection, liquids or gasses that are near the heat source gain energy. This causes them to expand and become less dense. The less dense liquid or gas rises, while more dense liquid or gas sinks to take its place. Convection will remove heat from the bottom of a liquid or gas to the top. Radiation occurs when heat energy is transferred without help of sold, liquids, and gasses. Heat energy is transferred as waves (similar to how light is transferred) by radiation. The heat energy from the sun travels this way to earth. Learning Target #8 – I can trace energy flows back to the sun. Almost all energy on the earth can be traced back to the sun. An ecosystem is powered by the sun. Plants transform light energy from the sun into chemical energy (food) by a process called photosynthesis. In photosynthesis, plants use sunlight, water, and carbon dioxide to make food(sugar) and oxygen. Animals eat this chemical energy and transform it into mechanical, sound, and heat energy. Some chemical energy is stored in animals, when we eat foods like hamburger we get the chemical energy. Weather is another system powered by the sun’s energy. The heat energy from the sun warms the earth. This causes water to evaporate, eventually providing precipitation over parts of the earth. The heat energy also warms the atmosphere causing warmer less dense air to rise and cool more dense air to sink producing winds. Without the sun’s energy and energy transformations we would not have precipitation or wind energy. Lab Learning Targets Learning Target #2 – I can construct series and parallel circuits. Learning Target #9 – I can graph heat transfer between hot and cold objects.
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