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Energy—Day 4 Materials Needed: • Writing Utensil • Folder • Notebook Please pick up the handout on the front table! 1. Give an example in which one form of energy changes to another form of energy. 2. Give an example in which PE changes to KE. 3. Give an example in which KE changes to PE. 4. What is the unit for energy? Agenda BLAM Notes over different forms of energy. Discuss the Law of Conservation of Energy. Q1: WHY IS DENSITY USEFUL FOR IDENTIFYING ELEMENTS? A. Density predicts whether objects float. B. Density varies at different temperatures. C. Density is often unique to each element. D. Different elements have the same densities. SC8.2.1.g DOK 2 Q2: WHAT IS THE MOST DENSE SOLID SHOWN ON THE TABLE? A. B. C. D. mercury pyrite silver zinc SC8.2.1.g DOK 2 MATH BOOSTER DAY 4 A shop owner increased the selling price of a shirt from $20 to $27. By what percentage was the price increased? GREEK AND LATIN DAY 4 Greek /Latin Picture dynam-erggravkilo- kine- OBJECTIVE DAY 4 1. I will know (knowledge): the different forms of energy and the law of conservation of energy. 2. I will be able to (skill): apply the law of conservation of energy. 1. Give an example in which one form of energy changes to another form of energy. Answer: A light bulb, in which the electrical energy changes to light energy or sound energy or both. 2. Give an example in which potential energy changes to kinetic energy. Answer: A marker falling off a desk. 3. Give an example in which kinetic energy changes to potential energy. Answer: When you throw a ball up in the air. 4. What is the unit for energy? Answer: joules A1: WHY IS DENSITY USEFUL FOR IDENTIFYING ELEMENTS? A. Density predicts whether objects float. Objects of various densities will float, but do not identify elements. B. Density varies at different temperatures. Density does not vary with temperature. C. Density is often unique to each element. Different elements tend to have different densities. D. Different elements have the same densities. Different elements tend to have different densities. SC8.2.1.g DOK 2 A2: WHAT IS THE MOST DENSE SOLID SHOWN ON THE TABLE? A. mercury 13.55 g/cm3 is the most dense liquid, not solid. B. pyrite 5.02 g/cm3 is not the most dense solid. C. silver 10.50 g/cm3 is the most dense solid. D. zinc 7.13 g/cm3 is not the most dense solid. SC8.2.1.g DOK 2 MATH BOOSTER DAY 4 -- ANSWER A shop owner increased the selling price of a shirt from $20 to $27. By what percentage was the price increased? Increase in the price = $27 - $20 = $7 Percentage increase in the price = × 100 = (7 ÷ 20) × 100 = 35 % Energy classifications: 1. kinetic energy 2. potential energy 3. energy in fields such as those produced by electromagnetic waves Each of these forms of energy can be converted into other forms of energy. What are the major forms of energy? What are the major forms of energy? The major forms of energy are: mechanical energy thermal energy chemical energy electrical energy electromagnetic energy nuclear energy Mechanical Energy The energy associated with the motion and position of everyday objects is mechanical energy. Mechanical energy is the sum of an object’s potential energy and kinetic energy. What does sum mean? ADDITION Thermal Energy The total potential energy and kinetic energy of all the microscopic particles in an object make up its thermal energy. When an object’s atoms move faster, its thermal energy increases, and the object becomes warmer. This molten metal is extremely hot. It contains a great deal of thermal energy. Electrical Energy Electrical energy is the energy associated with electric charges. CHEMICAL ENERGY: Chemical Energy: The energy stored in chemical bonds. Electromagnetic Energy Electromagnetic energy is a form of energy that travels through space in the form of waves. Visible light and X-rays are examples of electromagnetic energy. Nuclear Energy The energy stored in atomic nuclei is known as nuclear energy. Turn to a partner: Discuss what fission and fusion are. Do you remember??????? • • Nuclear fission releases energy by splitting nuclei apart. Nuclear fusion releases energy when less massive nuclei combine to form a more massive nucleus. The Law of Conservation of Energy states that energy cannot be created or destroyed, it can only change form. An example: As you light a match energy is converted from one form to another. The work done by friction changes kinetic energy into thermal energy. • • Friction within machinery reduces efficiency. Friction is a major cause of energy consumption in cars and factories. In many cases, most of a falling object’s potential energy is converted into thermal energy because of air resistance. Explain why speed skaters are slowed down, even though they slide quickly over smooth ice. They are slowed down by friction with the air and the surface of the ice. The gravitational potential energy of an object is converted to the kinetic energy of motion as the object falls. • An avalanche brings tons of snow from the top of a mountain to the valley floor. • The elastic potential energy of a compressed spring is converted into kinetic energy as the spring expands. Some gulls use energy conversion to obtain food by dropping oysters onto rocks. Kinetic energy causes the shell to break on collision with the rock. Energy Conversion in Pendulums A pendulum consists of a weight swinging back and forth from a rope or string. AT THIS POINT THE ENERGY OF POSITION IS FULL, SO IT HAS PE! WHILE IT IS MOVING IT HAS KINETIC ENERGY, BUT IT ALSO HAS ENERGY OF POSITION. THERE IS NO LONGER ANY PE BUT THERE IS KE! FINALLY, THERE IS NO MOVEMENT SO THERE IS ONLY ENERGY OF POSITION. THE TOTAL AMOUNT OF ENERGY IS CONSERVED! Summary: Energy Conversion in Pendulums • • • At the highest point in its swing, the pendulum has zero KE and maximum PE. As the pendulum swings downward, PE is converted to KE. At the bottom of the swing, the pendulum has maximum KE and zero PE. Energy Conversion and the Pole Vault In the pole vault, an athlete uses a flexible pole to propel it over a high bar. 1. Some of the pole-vaulter’s kinetic energy is converted into elastic potential energy as the pole bends. 2. The pole springs back into shape, propelling the pole-vaulter upward. 3. As the pole-vaulter rises, the kinetic energy decreases while the gravitational potential energy increases. 4. Once the highest point has been reached, the gravitational potential energy begins to convert back to kinetic energy. Equation: Mechanical energy =KE +PE PE = 10 J KE = ? ME = ? KE = 0 J WHY? GROUP PRACTICE NO MOVEMENT ME = 10 J ½ WAY DOWN KE = ? KE = 5 J PE = ? PE = 5 J ME = ? ME = 10 J NANOSECOND BEFORE IT HITS THE GROUND KE = ? PE = ? KE = 10 J PE = 0 ME = ? ME = 10 J SMALL GROUP: Explain: 1. What you observed about the mechanical energy (ME) as the ball dropped. 2. What you observed happened to KE and PE as the ball dropped? SMALL GROUP -- ANSWER 1. The Mechanical Energy stayed the same at the top, ½ way down, and at the bottom. (ME is the total energy!) The ME was always 10 J. 2. The KE & PE switched places! At the top: KE = 0 PE = 10 J At the bottom KE = 10 J PE = 0 The PE was converted to KE as it fell! Nonrenewable Energy Resources Nonrenewable energy resources exist in limited quantities and, once used, cannot be replaced except over the course of millions of years. Nonrenewable Energy Resources Small Group: Discuss the major nonrenewable sources of energy. Nonrenewable energy resources include oil, natural gas, coal, and uranium. Fossil fuels Oil, natural gas, and coal are known as fossil fuels. • They were formed underground from the remains of once-living organisms. • Fossil fuels account for the great majority of the world’s energy use. • These fuels are not distributed evenly throughout the world. Crude oil is pumped out of the ground, refined, and turned into gasoline, fuel oil, and other oil products. Renewable Energy Resources Renewable energy resources are resources that can be replaced in a relatively short period of time. Renewable Energy Resources Small group: Discuss the major renewable sources of energy. Renewable energy resources include hydroelectric, solar, geothermal, wind, biomass, and, possibly in the future, nuclear fusion. 1. A 2 kg heavy ball falls from a 3 m shelf. Just before hitting the floor, what is its kinetic energy? Answer : According to the Law of Conservation of Energy, total energy at the top will be equal to the total energy at the bottom. Total energy at top = Total energy at bottom PE = mgh = (2 kg)(9.8 m/s2)(3 m) PE = 58.8 J (We know that the KE & PE are switched. ) Therefore, KE = 58.8 J 1. Can you think of any example in which you can create something out of nothing or destroy something completely? 2. What types of energy are converted when you use a cell phone? 1. Can you think of any example in which you can create something out of nothing or destroy something completely? Answer: We cannot create something out of nothing or destroy something completely. 2. What types of energy are converted when you use a cell phone? Answer : the electrical energy from the battery changes sound energy & light energy. Physical Science Text Book 1. Students will read pages 450 – 457 2. Students will create and complete the Thinking Visually Chart on page 468. 3. Students will answer questions #8; #10; #17; and #19 on page 469. Give examples of renewable and nonrenewable resources.