DOCSLIB.ORG

Thermodynamics Heat & Internal Energy Heat Capacity

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Thermodynamics Heat & Internal Energy Heat Capacity Thermodynamics Heat & Internal Energy Heat Capacity Lana Sheridan De Anza College April 23, 2020 Last time • the ideal gas equation • moles and molecules Overview • finish applying the ideal gas equation • thermal energy • heat capacity Ideal Gas Equation The equation of state for an ideal gas: PV = nRT where • P is pressure • V is volume • n is the number of moles (amount of gas) • R = 8.314 J mol-1 K-1 is the universal gas constant • T is temperature The LHS and RHS of this equation both have units of Joules (energy). 588 Chapter 19 Temperature 66. (a) Show that the density of an ideal gas occupying a copper to be 11.0 3 1010 N/m2. At this lower tempera- volume V is given by r 5 PM/RT, where M is the molar ture, find (a) the tension in the wire and (b) the x coor- mass. (b) Determine the density of oxygen gas at atmo- dinate of the junction between the wires. spheric pressure and 20.08C. 73. Review. A steel guitar string with a diameter of 1.00 mm 67. Two concrete spans of Problemis stretched #74 between supports 80.0 cm apart. The tem- a 250-m-long bridge T perature is 0.08C. (a) Find the mass per unit length of A cylinderthis string. is(Use closed the value by 7.86 a piston 3 103 kg/m connected3 for the den to- a spring of constant are placed end to 250 m end so that no room 2.00sity.)× (b)10 3TheN/m. fundamental With the frequency spring relaxed,of transverse the cylinder is filled with is allowed for expan- a oscillations of the string is 200 Hz. What is the tension sion (Fig. P19.67a). If a 5.00in the L ofstring? gas Next, at a the pressure temperature of 1.00is raised atm to 30.0 and8C. a temperature of temperature increase T ϩ 20ЊC 20.0Find◦C. the resulting values of (c) the tension and (d) the of 20.08C occurs, y fundamental frequency. Assume both the Young’s mod- 10 2 2 what is the height y (a)ulus If theof 20.0 piston 3 10 hasN/m a and cross-sectional the average coefficient area ofof 0.0100 m and 26 21 to which the spans negligibleexpansion mass, a 5 11.0 how 3 10 high (8C) will have it riseconstant when values the temperature is b between 0.08C and 30.08C. rise when they buckle raised to 250◦C? (Fig. P19.67b)? Figure P19.67 74. A cylinder is closed by 68. Two concrete spans Problems 67 and 68. W a piston connected to S that form a bridge a spring of constant 3 k of length L are placed end to end so that no room is 2.00 3 10 N/m (see allowed for expansion (Fig. P19.67a). If a temperature Fig. P19.74). With the increase of DT occurs, what is the height y to which the spring relaxed, the spans rise when they buckle (Fig. P19.67b)? cylinder is filled with 5.00 L of gas at a pres- h 69. Review. (a) Derive an expression for the buoyant force sure of 1.00 atm and a S on a spherical balloon, submerged in water, as a func- temperature of 20.08C. tion of the depth h below the surface, the volume Vi of (a) If the piston has a the balloon at the surface, the pressure P0 at the sur- cross- sectional area of 2 face, and the density rw of the water. Assume the water 0.010 0 m and negli- temperature does not change with depth. (b) Does the gible mass, how high buoyant force increase or decrease as the balloon is sub- will it rise when the T ϭ 20.0ЊC T ϭ 250ЊC merged? (c) At what depth is the buoyant force one- temperature is raised 1 Figure P19.74 half the surface value? toSerway 2508C? &(b) Jewett, What pageis 588. 70. Review. Following a collision in outer space, a copper the pressure of the gas at 2508C? AMT disk at 8508C is rotating about its axis with an angular 75. Helium gas is sold in steel tanks that will rupture if sub- Q/C speed of 25.0 rad/s. As the disk radiates infrared light, Q/C jected to tensile stress greater than its yield strength of its temperature falls to 20.08C. No external torque acts 5 3 108 N/m2. If the helium is used to inflate a balloon, on the disk. (a) Does the angular speed change as the could the balloon lift the spherical tank the helium disk cools? Explain how it changes or why it does not. came in? Justify your answer. Suggestion: You may con- (b) What is its angular speed at the lower temperature? sider a spherical steel shell of radius r and thickness t 71. Starting with Equation 19.10, show that the total pres- having the density of iron and on the verge of breaking sure P in a container filled with a mixture of several apart into two hemispheres because it contains helium . at high pressure. ideal gases is P 5 P1 1 P2 1 P3 1 , where P1, P2, are the pressures that each gas would exert if it alone 76. A cylinder that has a 40.0-cm radius and is 50.0 cm filled the container. (These individual pressures are deep is filled with air at 20.08C and 1.00 atm (Fig. called the partial pressures of the respective gases.) This P19.76a). A 20.0-kg piston is now lowered into the cyl- result is known as Dalton’s law of partial pressures. inder, compressing the air trapped inside as it takes equilibrium height hi (Fig. P19.76b). Finally, a 25.0-kg Challenge Problems dog stands on the piston, further compressing the air, 72. Review. A steel wire and a copper wire, each of diameter which remains at 208C (Fig. P19.76c). (a) How far down 2.000 mm, are joined end to end. At 40.08C, each has an unstretched length of 2.000 m. The wires are con- nected between two fixed supports 4.000 m apart on ⌬h a tabletop. The steel wire extends from x 5 22.000 m 50.0 cm to x 5 0, the copper wire extends from x 5 0 to x 5 hi 2.000 m, and the tension is negligible. The temperature is then lowered to 20.08C. Assume the average coeffi- 26 21 cient of linear expansion of steel is 11.0 3 10 (8C) a b c and that of copper is 17.0 3 1026 (8C)21. Take Young’s modulus for steel to be 20.0 3 1010 N/m2 and that for Figure P19.76 Problem #74 (a) Find h. Tf Pf Vf = Pi Vi Ti kh Tf + P0 (Vi + Ah) = P0Vi A Ti 2 kVi Tf kh + + AP0 h + P0Vi 1 - = 0 A Ti Problem #74 (a) Find h. PV = nRT We have enough info to know the number of moles, n, or we can work around that because the amount of gas does not change as it is heated. P V P V f f = i i Tf Ti Also, kh + P0A = Pf A and Pi = P0 and Vf = Vi + Ah. Problem #74 (a) Find h. PV = nRT We have enough info to know the number of moles, n, or we can work around that because the amount of gas does not change as it is heated. P V P V f f = i i Tf Ti Also, kh + P0A = Pf A and Pi = P0 and Vf = Vi + Ah. Tf Pf Vf = Pi Vi Ti kh Tf + P0 (Vi + Ah) = P0Vi A Ti 2 kVi Tf kh + + AP0 h + P0Vi 1 - = 0 A Ti positive solution: h = 0.169 m Problem #74 (a) Find h. Solving quadratic: 2 kVi Tf kh + + AP0 h + P0Vi 1 - = 0 A Ti Remember: Tf = 250 + 273 K, Ti = 20 + 273 K Problem #74 (a) Find h. Solving quadratic: 2 kVi Tf kh + + AP0 h + P0Vi 1 - = 0 A Ti Remember: Tf = 250 + 273 K, Ti = 20 + 273 K positive solution: h = 0.169 m 588 Chapter 19 Temperature 66. (a) Show that the density of an ideal gas occupying a copper to be 11.0 3 1010 N/m2. At this lower tempera- volume V is given by r 5 PM/RT, where M is the molar ture, find (a) the tension in the wire and (b) the x coor- mass. (b) Determine the density of oxygen gas at atmo- dinate of the junction between the wires. spheric pressure and 20.08C. 73. Review. A steel guitar string with a diameter of 1.00 mm 67. Two concrete spans of Problemis stretched #74 between supports 80.0 cm apart. The tem- a 250-m-long bridge T perature is 0.08C. (a) Find the mass per unit length of 3 3 are placed end to A cylinderthis string. is(Use closed the value by 7.86 a piston 3 10 kg/m connected for the den to- a spring of constant 250 m sity.) (b) The fundamental frequency of transverse end so that no room 2.00 × 103 N/m. With the spring relaxed, the cylinder is filled with is allowed for expan- a oscillations of the string is 200 Hz. What is the tension sion (Fig. P19.67a). If a 5.00in the L ofstring? gas Next, at a the pressure temperature of 1.00is raised atm to 30.0 and8C.
Load more

Recommended publications
  • Lecture 4: 09.16.05 Temperature, Heat, and Entropy
    3.012 Fundamentals of Materials Science Fall 2005 Lecture 4: 09.16.05 Temperature, heat, and entropy Today: LAST TIME .........................................................................................................................................................................................2� State functions ..............................................................................................................................................................................2� Path dependent variables: heat and work..................................................................................................................................2� DEFINING TEMPERATURE ...................................................................................................................................................................4� The zeroth law of thermodynamics .............................................................................................................................................4� The absolute temperature scale ..................................................................................................................................................5� CONSEQUENCES OF THE RELATION BETWEEN TEMPERATURE, HEAT, AND ENTROPY: HEAT CAPACITY .......................................6� The difference between heat and temperature ...........................................................................................................................6� Defining heat capacity.................................................................................................................................................................6�
    [Show full text]
  • HEAT and TEMPERATURE Heat Is a Type of ENERGY. When Absorbed
    HEAT AND TEMPERATURE Heat is a type of ENERGY. When absorbed by a substance, heat causes inter-particle bonds to weaken and break which leads to a change of state (solid to liquid for example). Heat causing a phase change is NOT sufficient to cause an increase in temperature. Heat also causes an increase of kinetic energy (motion, friction) of the particles in a substance. This WILL cause an increase in TEMPERATURE. Temperature is NOT energy, only a measure of KINETIC ENERGY The reason why there is no change in temperature at a phase change is because the substance is using the heat only to change the way the particles interact (“stick together”). There is no increase in the particle motion and hence no rise in temperature. THERMAL ENERGY is one type of INTERNAL ENERGY possessed by an object. It is the KINETIC ENERGY component of the object’s internal energy. When thermal energy is transferred from a hot to a cold body, the term HEAT is used to describe the transferred energy. The hot body will decrease in temperature and hence in thermal energy. The cold body will increase in temperature and hence in thermal energy. Temperature Scales: The K scale is the absolute temperature scale. The lowest K temperature, 0 K, is absolute zero, the temperature at which an object possesses no thermal energy. The Celsius scale is based upon the melting point and boiling point of water at 1 atm pressure (0, 100o C) K = oC + 273.13 UNITS OF HEAT ENERGY The unit of heat energy we will use in this lesson is called the JOULE (J).
    [Show full text]
  • A Comprehensive Review of Thermal Energy Storage
    sustainability Review A Comprehensive Review of Thermal Energy Storage Ioan Sarbu * ID and Calin Sebarchievici Department of Building Services Engineering, Polytechnic University of Timisoara, Piata Victoriei, No. 2A, 300006 Timisoara, Romania; [email protected] * Correspondence: [email protected]; Tel.: +40-256-403-991; Fax: +40-256-403-987 Received: 7 December 2017; Accepted: 10 January 2018; Published: 14 January 2018 Abstract: Thermal energy storage (TES) is a technology that stocks thermal energy by heating or cooling a storage medium so that the stored energy can be used at a later time for heating and cooling applications and power generation. TES systems are used particularly in buildings and in industrial processes. This paper is focused on TES technologies that provide a way of valorizing solar heat and reducing the energy demand of buildings. The principles of several energy storage methods and calculation of storage capacities are described. Sensible heat storage technologies, including water tank, underground, and packed-bed storage methods, are briefly reviewed. Additionally, latent-heat storage systems associated with phase-change materials for use in solar heating/cooling of buildings, solar water heating, heat-pump systems, and concentrating solar power plants as well as thermo-chemical storage are discussed. Finally, cool thermal energy storage is also briefly reviewed and outstanding information on the performance and costs of TES systems are included. Keywords: storage system; phase-change materials; chemical storage; cold storage; performance 1. Introduction Recent projections predict that the primary energy consumption will rise by 48% in 2040 [1]. On the other hand, the depletion of fossil resources in addition to their negative impact on the environment has accelerated the shift toward sustainable energy sources.
    [Show full text]
  • Heat Energy a Science A–Z Physical Series Word Count: 1,324 Heat Energy
    Heat Energy A Science A–Z Physical Series Word Count: 1,324 Heat Energy Written by Felicia Brown Visit www.sciencea-z.com www.sciencea-z.com KEY ELEMENTS USED IN THIS BOOK The Big Idea: One of the most important types of energy on Earth is heat energy. A great deal of heat energy comes from the Sun’s light Heat Energy hitting Earth. Other sources include geothermal energy, friction, and even living things. Heat energy is the driving force behind everything we do. This energy gives us the ability to run, dance, sing, and play. We also use heat energy to warm our homes, cook our food, power our vehicles, and create electricity. Key words: cold, conduction, conductor, convection, energy, evaporate, fire, friction, fuel, gas, geothermal heat, geyser, heat energy, hot, insulation, insulator, lightning, liquid, matter, particles, radiate, radiant energy, solid, Sun, temperature, thermometer, transfer, volcano Key comprehension skill: Cause and effect Other suitable comprehension skills: Compare and contrast; classify information; main idea and details; identify facts; elements of a genre; interpret graphs, charts, and diagram Key reading strategy: Connect to prior knowledge Other suitable reading strategies: Ask and answer questions; summarize; visualize; using a table of contents and headings; using a glossary and bold terms Photo Credits: Front cover: © iStockphoto.com/Julien Grondin; back cover, page 5: © iStockphoto.com/ Arpad Benedek; title page, page 20 (top): © iStockphoto.com/Anna Ziska; pages 3, 9, 20 (bottom): © Jupiterimages Corporation;
    [Show full text]
  • IB Questionbank
    Topic 3 Past Paper [94 marks] This question is about thermal energy transfer. A hot piece of iron is placed into a container of cold water. After a time the iron and water reach thermal equilibrium. The heat capacity of the container is negligible. specific heat capacity. [2 marks] 1a. Define Markscheme the energy required to change the temperature (of a substance) by 1K/°C/unit degree; of mass 1 kg / per unit mass; [5 marks] 1b. The following data are available. Mass of water = 0.35 kg Mass of iron = 0.58 kg Specific heat capacity of water = 4200 J kg–1K–1 Initial temperature of water = 20°C Final temperature of water = 44°C Initial temperature of iron = 180°C (i) Determine the specific heat capacity of iron. (ii) Explain why the value calculated in (b)(i) is likely to be different from the accepted value. Markscheme (i) use of mcΔT; 0.58×c×[180-44]=0.35×4200×[44-20]; c=447Jkg-1K-1≈450Jkg-1K-1; (ii) energy would be given off to surroundings/environment / energy would be absorbed by container / energy would be given off through vaporization of water; hence final temperature would be less; hence measured value of (specific) heat capacity (of iron) would be higher; This question is in two parts. Part 1 is about ideal gases and specific heat capacity. Part 2 is about simple harmonic motion and waves. Part 1 Ideal gases and specific heat capacity State assumptions of the kinetic model of an ideal gas. [2 marks] 2a. two Markscheme point molecules / negligible volume; no forces between molecules except during contact; motion/distribution is random; elastic collisions / no energy lost; obey Newton’s laws of motion; collision in zero time; gravity is ignored; [4 marks] 2b.
    [Show full text]
  • Thermal Energy: Using Water to Heat a School
    Thermal Energy: Using Water to Heat a School Investigation Notebook NYC Edition © 2018 by The Regents of the University of California. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage or retrieval system, without permission in writing from the publisher. Teachers purchasing this Investigation Notebook as part of a kit may reproduce the book herein in sufficient quantities for classroom use only and not for resale. These materials are based upon work partially supported by the National Science Foundation under grant numbers DRL-1119584, DRL-1417939, ESI-0242733, ESI-0628272, ESI-0822119. The Federal Government has certain rights in this material. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. These materials are based upon work partially supported by the Institute of Education Sciences, U.S. Department of Education, through Grant R305A130610 to The Regents of the University of California. The opinions expressed are those of the authors and do not represent views of the Institute or the U.S. Department of Education. Developed by the Learning Design Group at the University of California, Berkeley’s Lawrence Hall of Science. Amplify. 55 Washington Street, Suite 800 Brooklyn, NY 11201 1-800-823-1969 www.amplify.com Thermal Energy: Using Water to Heat a School
    [Show full text]
  • Thermal Profiling of Residential Energy Consumption
    1 Thermal profiling of residential energy consumption Adrian Albert and Ram Rajagopal Abstract—Demand Response (DR) programs aim to dynami- the thermal mass of the premise may act as “thermal bat- cally match consumption on the grid with available supply in tery”. Affecting the thermally-sensitive load may be typically real-time. Understanding the patterns in demand of individuals achieved through direct load control of the HVAC system (e.g., is now being facilitated by granular consumption data collected load curtailment or automatic adjustment of the thermostat via smart meter sensors that power utility companies have rolled setpoint), through adjustable rates (e.g., critical peak pricing), out at scale. In this paper we propose a dynamic model that uses or through incentive schemes [4], [5]. hourly electricity and weather readings to characterize residential users’ thermally-sensitive consumption. From this model we Here we propose a simple model of consumption for a extract useful benchmarks to build profiles of individual users residential premise that is driven by unobserved “occupancy for use with DR programs that focus on temperature-dependent states” that have different responses to ambient weather. These consumption such as air conditioning or heating. We present are consumption regimes of a given household that depend on example profiles generated using our model on real consumers, lifestyle (work schedule, familial composition etc.), premise and show its performance on a large sample of residential characteristics (heating/cooling mass, square footage etc.), users. We then compute metrics that allow us to segment the appliance stock, and weather patterns. It is a daunting task population dynamically for the purpose of a thermally-motivated to disentangle how much energy each of these components DR program.
    [Show full text]
  • TEMPERATURE, HEAT, and SPECIFIC HEAT INTRODUCTION Temperature and Heat Are Two Topics That Are Often Confused
    TEMPERATURE, HEAT, AND SPECIFIC HEAT INTRODUCTION Temperature and heat are two topics that are often confused. Temperature measures how hot or cold an object is. Commonly this is measured with the aid of a thermometer even though other devices such as thermocouples and pyrometers are also used. Temperature is an intensive property; it does not depend on the amount of material present. In scientific work, temperature is most commonly expressed in units of degrees Celsius. On this scale the freezing point of water is 0oC and its boiling point is 100oC. Heat is a form of energy and is a phenomenon that has its origin in the motion of particles that make up a substance. Heat is an extensive property. The unit of heat in the metric system is called the calorie (cal). One calorie is defined as the amount of heat necessary to raise 1 gram of water by 1oC. This means that if you wish to raise 7 g of water by 4oC, (4)(7) = 28 cal would be required. A somewhat larger unit than the calorie is the kilocalorie (kcal) which equals 1000 cal. The definition of the calorie was made in reference to a particular substance, namely water. It takes 1 cal to raise the temperature of 1 g of water by 1oC. Does this imply perhaps that the amount of heat energy necessary to raise 1 g of other substances by 1oC is not equal to 1 cal? Experimentally we indeed find this to be true. In the modern system of international units heat is expressed in joules and kilojoules.
    [Show full text]
  • Lecture 6: Entropy
    Matthew Schwartz Statistical Mechanics, Spring 2019 Lecture 6: Entropy 1 Introduction In this lecture, we discuss many ways to think about entropy. The most important and most famous property of entropy is that it never decreases Stot > 0 (1) Here, Stot means the change in entropy of a system plus the change in entropy of the surroundings. This is the second law of thermodynamics that we met in the previous lecture. There's a great quote from Sir Arthur Eddington from 1927 summarizing the importance of the second law: If someone points out to you that your pet theory of the universe is in disagreement with Maxwell's equationsthen so much the worse for Maxwell's equations. If it is found to be contradicted by observationwell these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of ther- modynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation. Another possibly relevant quote, from the introduction to the statistical mechanics book by David Goodstein: Ludwig Boltzmann who spent much of his life studying statistical mechanics, died in 1906, by his own hand. Paul Ehrenfest, carrying on the work, died similarly in 1933. Now it is our turn to study statistical mechanics. There are many ways to dene entropy. All of them are equivalent, although it can be hard to see. In this lecture we will compare and contrast dierent denitions, building up intuition for how to think about entropy in dierent contexts. The original denition of entropy, due to Clausius, was thermodynamic.
    [Show full text]
  • Internal Energy in an Electric Field
    Internal energy in an electric field In an electric field, if the dipole moment is changed, the change of the energy is, U E P Using Einstein notation dU Ek dP k This is part of the total derivative of U dU TdSij d ij E kK dP H l dM l Make a Legendre transformation to the Gibbs potential G(T, H, E, ) GUTSijij EP kK HM l l SGTE data for pure elements http://www.sciencedirect.com/science/article/pii/036459169190030N Gibbs free energy GUTSijij EP kK HM l l dG dU TdS SdTijij d ij d ij E kk dP P kk dE H l dM l M l dH l dU TdSij d ij E kK dP H l dM l dG SdTij d ij P k dE k M l dH l G G G G total derivative: dG dT d dE dH ij k l T ij EH k l G G ij Pk E ij k G G M l S Hl T Direct and reciprocal effects (Maxwell relations) Useful to check for errors in experiments or calculations Maxwell relations Useful to check for errors in experiments or calculations Point Groups Crystals can have symmetries: rotation, reflection, inversion,... x 1 0 0 x y 0 cos sin y z 0 sin cos z Symmetries can be represented by matrices. All such matrices that bring the crystal into itself form the group of the crystal. AB G for A, B G 32 point groups (one point remains fixed during transformation) 230 space groups Cyclic groups C2 C4 http://en.wikipedia.org/wiki/Cyclic_group 2G Pyroelectricity i Ei T Pyroelectricity is described by a rank 1 tensor Pi i T 1 0 0 x x x 0 1 0 y y y 0 0 1 z z 0 1 0 0 x x 0 0 1 0 y y 0 0 0 1 z z 0 Pyroelectricity example Turmalin: point group 3m Quartz, ZnO, LaTaO 3 for T = 1°C, E ~ 7 ·104 V/m Pyroelectrics have a spontaneous polarization.
    [Show full text]
  • Symptoms of Heat- Related Illness How to Protect Your
    BE PREPARED FOR EXTREME HEAT Extreme heat often results in the highest annual number of deaths among all weather-related disasters. FEMA V-1004/June 2018 In most of the U.S., extreme heat is a long period (2 to 3 days) of high heat and humidity with temperatures above 90 degrees. Greater risk Can happen anywhere Humidity increases the feeling of heat as measured by a heat index IF YOU ARE UNDER AN EXTREME HEAT WARNING Check on family members Find air conditioning, if possible. and neighbors. Avoid strenuous activities. Drink plenty of fluids. Watch for heat cramps, heat Watch for heat illness. exhaustion, and heat stroke. Wear light clothing. Never leave people or pets in a closed car. HOW TO STAY SAFE WHEN EXTREME HEAT THREATENS Prepare Be Safe Recognize NOW DURING +RESPOND Find places in your community where Never leave a child, adult, or animal Know the signs and ways to treat you can go to get cool. alone inside a vehicle on a warm day. heat-related illness. Try to keep your home cool: Find places with air conditioning. Heat Cramps Libraries, shopping malls, and • Signs: Muscle pains or spasms in • Cover windows with drapes community centers can provide a cool the stomach, arms, or legs. or shades. place to take a break from the heat. • Actions: Go to a cooler location. • Weather-strip doors and Wear a If you’re outside, find shade. Remove excess clothing. Take windows. hat wide enough to protect your face. sips of cool sports drinks with salt and sugar. Get medical help if • Use window reflectors such as Wear loose, lightweight, light- cramps last more than an hour.
    [Show full text]
  • 3. Energy, Heat, and Work
    3. Energy, Heat, and Work 3.1. Energy 3.2. Potential and Kinetic Energy 3.3. Internal Energy 3.4. Relatively Effects 3.5. Heat 3.6. Work 3.7. Notation and Sign Convention In these Lecture Notes we examine the basis of thermodynamics – fundamental definitions and equations for energy, heat, and work. 3-1. Energy. Two of man's earliest observations was that: 1)useful work could be accomplished by exerting a force through a distance and that the product of force and distance was proportional to the expended effort, and 2)heat could be ‘felt’ in when close or in contact with a warm body. There were many explanations for this second observation including that of invisible particles traveling through space1. It was not until the early beginnings of modern science and molecular theory that scientists discovered a true physical understanding of ‘heat flow’. It was later that a few notable individuals, including James Prescott Joule, discovered through experiment that work and heat were the same phenomenon and that this phenomenon was energy: Energy is the capacity, either latent or apparent, to exert a force through a distance. The presence of energy is indicated by the macroscopic characteristics of the physical or chemical structure of matter such as its pressure, density, or temperature - properties of matter. The concept of hot versus cold arose in the distant past as a consequence of man's sense of touch or feel. Observations show that, when a hot and a cold substance are placed together, the hot substance gets colder as the cold substance gets hotter.
    [Show full text]