Chapter 2 Complete with density

Chapter 2 Complete with density - Lecture 5: Energy Goal:...

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Lecture 5: Energy Goal: Identify energy as potential or kinetic energy and understand the units of energy. Be able to convert temperature from one scale to another. Use specific heat to calculate heat loss or gain, temperature change or mass of a sample. Outline (Timberlake Chapter 2.1-2.3): Energy (2.1) Temperature (2.2) Specific Heat (2.3) Problems for Extra Practice: 2.3, 2.5, 2.9, 2.11, 2.13, 2.15, 2.17, 2.19, 2.21
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Significant Figures – Combined Operations
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Energy Energy – makes objects move – makes things stop – is needed to “do work” Work is done when – you climb – you lift a bag of groceries – you ride a bicycle – you breathe – your heart pumps blood – water goes over a dam
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Potential Energy Potential energy is energy stored for use at a later time. Examples: • water behind a dam • a compressed spring • chemical bonds in gasoline, coal, or food
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Kinetic Energy Kinetic energy is the energy of matter in motion. Examples: • swimming • water flowing over a dam • working out • burning gasoline
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Energy Conversion • Some examples of energy interconversion. .. sunlight : radiant (electromagnetic) energy. ..plants harvest sunlight and convert it to sugars (chemical energy) food : the sugars (chemical energy content) from plants are metabolized by animals (different chemical energy content), allowing them to move around and stay alive (kinetic energy) gas : long-dead plants and animals (chemical energy) are distilled and refined and delivered to your car where they are burned up and converted to kinetic energy and heat.
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Potential and Kinetic Energy Ball at the top of the hill has potential energy Falling ball has kinetic energy
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Learning Check Identify each of the following as potential energy or kinetic energy. A) A slice of pizza B) Jogging C) A gallon of gas in a gas tank D) An car speeding down the road Potential Kinetic Potential Kinetic
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Heat Defined • Heat is defined as energy the flows from a warmer object to a cooler one • Heat is associated with the motion of particles
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Heat and Units of Energy • Heat is measured in joules or calories. – 4.184 joules (J) = 1 calorie (cal) (exact) – 1 kJ = 1000 J – 1 kilocalorie (kcal) = 1000 calories (cal)
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Learning Check A person uses 750 kcal to run a race. Convert the energy used for the race to joules. 1) 3.1 x 10 3 J 2) 3.1 x 10 6 J 3) 7.5 x 10 5 J
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Setting Up a Problem A person uses 750 kcal to run a race. Convert the energy used for the race to joules. – Step 1: Given unit: 750 kcal Need: J – Step 2: Plan: kcal cal J – Step 3: Conversion factors: 1 cal = 4.184 J 1000 cal = 1 kcal – Step 4: Set up problem
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Temperature Temperature • is a measure of how hot or cold an object is compared to another object • is an indication of the kinetic energy of the particles in a substance • indicates that heat flows from the object with a higher temperature to the object with a lower temperature
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Temperature Scales
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A. What is the temperature of freezing water?
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This note was uploaded on 01/18/2012 for the course CHEM 120A taught by Professor Leahmiller during the Fall '11 term at University of Washington.

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Chapter 2 Complete with density - Lecture 5: Energy Goal:...

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