...HEAT 4.1 UNDERSTANDING THERMAL EQUILIBRIUM 1. Define: The measure of the degree of hotness of an object. (a) Temperature Measured in SI unit Kelvin, K A hot object is at a higher temperature than a cold object. Form of energy, measured in Joules, J (b) Heat Heat is transferred from hotter object (higher temperature) to colder object (lower temperature) When an object is heated, it will absorb heat energy and the temperature will increase. When an object is cooled, it will release heat energy and the temperature will decrease. (c) Thermal Two objects are in thermal contact when heat energy contact can be transferred between them. (d)Heat transfer When two objects with different degrees of hotness come into thermal contact, heat energy is transferred between the two objects. (e) Mechanism of Thermal Equilibrium Energy is transferred at a faster rate from the hotter object to the colder object. Energy is also transferred from the colder object to the hotter one, but at a slower rate. There is a net flow of energy from the hotter object to the colder object. (f) Thermal When two objects are in thermal equilibrium, there is Equilibrium no net flow of heat between them. Two objects in thermal equilibrium have the same temperature 60 The hotter object cools down while the colder object warms up . After some time, energy is transferred at the same rate between the two objects. There is no net heat transfer between the objects. The two objects are said to be in thermal equilibrium...
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...Ice melting • There are about 5, 614, 000 miles³ (24, 062, 913.678268 km³) of ice on earth. • Some scientists say it would take more than 5,000 years to melt it all. • Sea level would rise by 216 feet. • East Antarctica—the east Antarctica ice sheet is so large that it contains 4/5 of all the ice on earth. Source: www.ngm.nationalgeographic.com/2013/09/rising-seas/if-ice-melted-map) • The current sea-level rise is about 3mm/year Source: en.wikipedia.org/wiki/current_sea_level_rise Some examples of glaciers on Earth • Arctic Sea Ice › Location: Arctic Ocean › has shrunk by 6 percent since 1978 with a 14 percent loss of thicker, year-round ice. Has thinned by 40 percent in less than 30 years. • Greenland Ice Sheets › Location: Greenland › has thinned by more than a meter a year on its southern and eastern edges since 1993. • Columbia Glacier › Location: Alaska, U.S. › has retreated nearly 13 kilometres since 1982. In 1999, retreat rate increased from 25 metres per day to 35 metres. Physics SPECIFIC LATENT HEAT (L) - the specific latent heat of a material is the amount if heat required to chance the state if 1 kilogram of the material without changing its temperature. (Unit: J/kg) • Specific latent heat (L)- 334 kJ/kg • Heat required to change the state of ice to liquid (Q)- 8.037042 x 1024 J Sources: Lf – www.engineeringtoolbox.com/latent-heat-melting-solids-d_96.html Q – I calculated it. In this presentation we will be talking...
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...difference between saturated vapor pressure at water temperature (ew) and actual vapor pressure in air (ea). EL = C (ew – ea), Where, EL is lake evaporation rate, C is a constant of proportionality. Causes of Humidity Molecules of water having sufficient kinetic energy to overcome attractive forces tending to hold them within the body of liquid water are projected through the water surface into the air. The process by which liquid water is converted into vapor is called vaporization or evaporation. Since the kinetic energy increases and surface tension decrease as temperature rises, evaporation rate increases with temperature. Most of the atmospheric vapor is the product of evaporation from water surfaces. The direct transformation from ice to vapor, and vice versa, is called sublimation. The process by which vapor changes to the liquid or solid state is called condensation. Properties of Water Vapor The partial pressure exerted by water vapor is called vapor pressure (e). If all the water vapor in a closed container of moist air with an initial total pressure p were removed, then the final pressure p’ of dry air alone would be less than p. Then, e = p – p’ When the maximum amount of water vapor for a given temperature is contained in a given space, the space is saturated with water vapor. The pressure exerted in a...
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...very good solvent.Charged molecules such as salts, sugars, amino acids dissolve readily in water and are called hydrophilic. Uncharged molecules such as lipids do not dissolve so well in water and are called hydrophobic. * High Specific heat capacity- Water has a specific heat capacity of 4.2 J g-1 oC-1, which means that it takes 4.2 joules of energy to heat 1g of water by 1oC. This is unusually high and it means that water does not change temperature easily. This minimises fluctuations in temperature inside cells and it also means that sea temperature is quite constant. * Latent heat of vaporisation- Water requires a lot of energy to change state from a liquid to a gas, and this is made use of a cooling mechanism in animals (sweating and panting) and plants (transpiration). As water evaporates it extracts heats from the surrounding area, cooling the organism * Latent heat of vaporisation- Water also requires a lot of heat to change state from solid to liquid and must loose a lot of heat to change state from a liquid to a solid. This means it is difficult to freeze water so ice crystals are less likely to from inside cells. * Unique Density Behaviour- Water is its solid state (ice) is less dense than the liquid state, so ice floats on water.As the air...
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...bonds but strong enough to contribute to: – Cohesion – High surface tension Hydrogen Bonding -High solubility of compounds in water -Unusual thermal properties of water -Density of water Water as a solvent • Water molecules attract other polar molecules. • This attraction produces an ionic bond. • Water can dissolve almost anything – universal solvent Water’s thermal properties • Water in all three phases is present at the Earth’s surface. • Water moderates the Earth’s heat budget. Heat, Freezing and Boiling Points • Heat – energy that is transferred • Temperature – average kinetic energy of molecules in a substance • Freezing point (also melting point): 0°C • Boiling point (condensation point): 100°C • Freezing and boiling points of water are unusually high Water’s Heat Capacity and Specific Heat • Heat Capacity – ratio of heat absorbed to the change in temperature • Water has a high heat capacity – can take in or lose much heat without changing...
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...Introduction to Physical Science – SCI110 Assignment #2 Week 4 Melissa Garrett Assignment #2: Paper Due Week Four: In a documented essay of 900 - 1200 words please address the following issues, in your own words: * How does the study of heat relate to the kinetic theory of matter? * What is heat? * What is temperature? * What is the relationship between heat and temperature? * How are they different? * What are the various properties of a substance that determine its heat capacity? * What are the various sources of heat? Conclusions about the structure of matter have been developed by physicists and chemists over the past 150 years. To understand it further let us look at the structure and the processes that occur to determine the state in which it exits. Matter typically exists in 3 common states or phases: solids, liquids, and gases. It is made up of molecules. “A molecule is the smallest particle of a compound or a gaseous element that can exist and still retain the characteristic properties of that substance” (Tillery, B., Enger, E., Ross, F., Integrated Science 2009 Custom Edition, p.98). According to the Kinetic theory of matter, these molecules are in constant, random motion. Through the force of cohesion, molecules interact and attract each other. In the case of solids, which have a definite shape and volume, the molecules vibrate “in a fixed equilibrium position with strong cohesive forces” (Tillery, B., Enger, E., Ross,...
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...Energetics / Thermochemistry 1. A 9.36 g of platinum is heated to 98.6 °C and dropped onto ice. When the metal’s temperature has dropped to 0.0 °C, it is found that 0.37 g of ice has melted. Determine the specific heat capacity of platinum. (Given the latent heat of fusion for ice is 333 J g -1 .) 2. A 72.8 g of copper at 143.2 °C is added to an insulated vessel containing 165 mL of glycerol (density = 1.26 g mL-1 ), at 24.8 °C. The final temperature is 31.1 °C. The specific heat capacity of copper is 0.385 J g-1 °C-1 . (a) Determine the mass of glycerol. (b) Determine the heat released from the copper. (c) Determine the specific heat capacity of glycerol in J g-1 °C-1 . (Ans: 2.4 J g-1 °C-1 ) [Dec 2014] 3. (a) Acetic acid, CH3COOH, is made industrially by the reaction of methanol and carbon monoxide as shown by the following equation: CH3OH(l) + CO(g) → CH3COOH(l) ΔHrxn = 355.9 kJ Determine the amount of heat evolved when 0.5 L of acetic acid is produced. (Given the density of CH3COOH is 1.044 g mL-1 ) (b) The molecule N2O4 is a dimer of the molecule NO2. The enthalpy of formation of N2O4 and NO2 are +9.67 kJ mol-1 and +33.86 kJ mol-1 respectively. Calculate the standard enthalpy of reaction, in kJ mol-1 for the formation of N2O4 from NO2. 4. The combustion of one mole of ethylene (C2H2) gas to form carbon dioxide and water releases 1299.4 kJ of heat energy. (a) Write a balanced thermochemical equation for this reaction. (b) State whether the...
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...point of 78°C at atmospheric pressure, highly flammable Water (along with life) is what sets our planet apart from our neighbors and it is the topic of this chapter. The hydrosphere is the watery part of the Earth, but this is a little misleading since it gives the impression that there is one place where water occurs. Instead, water is everywhere, or nearly so. Water is present in the atmosphere, in the form of vapor, liquid, and solid. It is tied up in rocks, locked away in the crystal lattices of minerals that make up rocks; it occurs in the innumerable small pore spaces of rocks, from the surface to depths greater than 5 km. Water is also tied up in living organisms; humans, for example, contain about 70% water. Water is stored in ice sheets large and small, it occurs in various surface water bodies, and, of course the oceans, the reservoir of the great majority of Earth's water. The hydrosphere, then, is intimately tied up with all of the other spheres that make up our whole Earth system. Inventory of Water Here is a partial breakdown of...
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...Water The chemical formula of water is H2O. This means two hydrogen atoms are joined to one oxygen atom to make up each molecule of water. The two electrons in each oxygen-hydrogen bond are not shared equally. They are more strongly attracted to the oxygen atom, making it a polar molecule. One of the most important results of this charge separation is that water forms hydrogen bonds. The slightly negative oxygen atom of one water molecule will attract to the slightly positive hydrogen atoms of other water molecules in a weak electrostatic attraction called a hydrogen bond. This means that the molecules of water will ‘stick together’ more than you otherwise might expect, because although each individual hydrogen bond is weak, there are a great number of them. Water also has relatively high melting and boiling points compared with other substances that have molecules of a similar size. This is because it takes more energy to overcome the attractive forces of the numerous hydrogen bonds. Water is a liquid and so cannot be compressed. This incompressibility means it is an important factor in many hydraulic mechanisms in living organisms. One of the major functions of water in living organism is its use as a solvent. Water is a Polar solvent and is thus slightly ionised meaning other polar molecules such as salts, sugars and amino acids will dissolve readily in water. This allows water to be used for the transportation of such substances in the bloodstream...
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...movement). However, in construction, such a complete system of heating, ventilation, and air conditioning is referred to as heating, ventilation, and air conditioning (HVAC -as opposed to AC).[2] B. Heater 1. Principles of Air Conditioning BASIC PRINCIPLES OF AIR CONDITIONING You don’t have to be an air-conditioning expert to use Spot Coolers, but understanding the basics of air conditioning will help you understand how Spot Coolerswork. This section highlights some of the basic principles of air conditioning for those who would benefit from additional knowledge in this area. PRINCIPLES OF COOLING Heat Transfer Heat is a form of energy. Every object on earth has some heat energy. The less heat an object has, the colder we say it is. Cooling is the process of transferring heat from one object to another. When an air-conditioning system cools, it is actually removing heat and transferring it somewhere else. This can be demonstrated by turning on a Spot Cooler and placing one hand in front of the cold air nozzle and the other over the warm air exhaust. You will feel the...
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...Impianti chimici II Monographic Thesis ADSORPTION HEAT PUMPS USING THE ZEOLITE-WATER PAIR: Operating principle and applications Author: Federica FURNARI 1 SUMMARY Introduction ___________________________________________________________________ 3 Chapter 1 Why choosing water-zeolite? ____________________________________________________ 5 Chapter 2 Operating principle of water-zeolite heat pump ____________________________________ 8 Chapter 3 Technological applications _____________________________________________________ 11 Solar-powered adsorption icemakers _____________________________________________________ 12 Self chilling beer kegs _________________________________________________________________ 15 Solar-powered adsorption air conditioners ________________________________________________ 16 Chapter 4 Key issues for future development _______________________________________________ 18 The heat/mass transfer issue ___________________________________________________________ 19 Heat recovery _______________________________________________________________________ 21 Bibliography _________________________________________________________________ 24 2 Introduction Although adsorptive processes have been extensively studied for gas separation, catalysis, etc., it is only recently that they have been proposed for heat management. The interest in adsorption systems started to increase, firstly due to the oil crisis in the 1970s that lead to...
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...2. BASICS OF ENERGY AND ITS VARIOUS FORMS Syllabus Basics of Energy and its various forms: Electricity basics - DC & AC currents, Electricity tariff, Load management and Maximum demand control, Power factor. Thermal basics -Fuels, Thermal energy contents of fuel, Temperature & Pressure, Heat capacity, Sensible and Latent heat, Evaporation, Condensation, Steam, Moist air and Humidity & Heat transfer, Units and conversion. 2.1 Definition Energy is the ability to do work and work is the transfer of energy from one form to another. In practical terms, energy is what we use to manipulate the world around us, whether by exciting our muscles, by using electricity, or by using mechanical devices such as automobiles. Energy comes in different forms - heat (thermal), light (radiant), mechanical, electrical, chemical, and nuclear energy. 2.2 Various Forms of Energy There are two types of energy - stored (potential) energy and working (kinetic) energy. For example, the food we eat contains chemical energy, and our body stores this energy until we release it when we work or play. 2.2.1 Potential Energy Potential energy is stored energy and the energy of position (gravitational). It exists in various forms. Chemical Energy Chemical energy is the energy stored in the bonds of atoms and molecules. Biomass, petroleum, natural gas, propane and coal are examples of stored chemical energy. Nuclear Energy Nuclear energy is the energy stored in the nucleus of an atom - the energy that holds...
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...is at its farthest position from equator 23.5 degrees N/S Equinoxes: spring/autumn march 21/22 septemeber 22/23 when the day is equal (day and night) Analemma: Shows path of noon sun angle throughout months Tropic Cancer: 23.5N Tropic Capricorn 23.5S (Farthest the sun can be away from equator that reaches 90 degrees above earth) Solar Radiation Insolation: Incoming solar radiation. Incoming is shortwave and outgoing is long wave. Duration: the longer the sun is out the more heat will be produced Intensity: angle the sun hits the earth. More intense closer to equator. Atmosphere: Constituents- Nitrogen: 78% Oxygen: 21% Carbon Monoxide: most of the remaining Selective screening: reflection- reflects radiation refraction- changes direction of radiation absorption- absorbs radiation Attenuation: absorb, reflect, refract Elements of weather and climate Temperature: degree of heat, measure by thermometer Pressure: 29.92 Hg (mercury) or 1013 mB. Measured either mercury barometer(Hg) or aneroid Barometer (mb) Moisture: presence of liquid, can be related to humidity Winds: H to L Speed- related to pressure differential. The greater difference the greater wind speed Named according to the direction from which they flow Atmospheric layers: troposphere 10km...
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...Explain how the properties of water are important to plants/animals. All living things contain water. Water is the main constitute of all organisms. Mammals consist of around 65% water. Water is the solvent, the medium and the participant in most of the chemical reactions occurring in our environment. The properties of water are extremely important to plants and animals for many reasons. Firstly, water is transparent which allows light to filter into aquatic environments, and therefore aquatic plants can absorb light and perform photosynthesis. Since all plants originated in the ocean, the transparency of water has had a major influence on life as we know it. Secondly, water is also cohesive, meaning it binds to itself, due to the polarity of the water molecule. The positive, hydrogen side of the molecule binds to the negative, oxygen side of another water molecule. This bond is called a hydrogen bond. Water is also adhesive, meaning it binds to other things around it. This property allows for transport of water against gravity in plants. The water clings to the xylem tube of plants and is able to be drawn up in long columns up the stem due to its strong cohesive force. ...
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...coming into the atmosphere is from insolation (short wave solar radiation). The amount of this energy from the sun is determined by: *Solar constant- varies slightly & affects longer term climate rather than short term *Distance from the sun- Earth’s orbit around sun can cause variation in distant *Altitude of the sun in the sky- equator receives more energy as rays are head on. At 60 degrees N or S its at an angle so there’s twice the area to heat up & more atmosphere to pass through *Length of the day & night Some radiation is absorbed by ozone, water vapour, co2, ice particles, and dust reduce the amount reaching Earth. & clouds also reflect radiation back! ALBEDO is the ratio between the amount of incoming and reflected radiation. (Usually at 4%) Short wave radiation is converted to heat and heats the surface of earth, while longer radiation (infrared) is radiated back into atmosphere. Longer wave tends to get trapped while short actually penetrates atmosphere easier. THE ATMOSPHERIC HEAT BUDGET THE HEAT BUDGET The earth is not heating up or cooling down as there is a balance between incoming insolation and outgoing terrestrial radiation. But there are significant variations within the atmosphere. So although energy...
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