What Is The Unit Of Heat – Average kinetic energy Measuring device Calorimeter Thermometer Units Joule, calories °C, °F, K The omission of the “degree” symbol for the Kelvin scale indicates that it is not related to an arbitrary reference point such as the Celsius and Fahrenheit scales .
13 Accuracy refers to how close the measurement is to the true or correct value for the quantity. Precision refers to how close a set of measurements are to a given quantity, whether the measurements are correct or not.
What Is The Unit Of Heat
Larry, Carly and Mo are given the same type of metal and are asked to measure its density. The actual density of the metal is 3.0 g/ml, but they are not told this. They take four sets of measurements and use them to calculate the density of the metal for each set of measurements. Their results are shown below. Larry Curly Moe 2.5 g/ml 4.0 g/ml 2.7 g/ml 2.0 g/ml 4.1 g/ml 3.1 g/ml 1.0 g/ml 3.3 g/ ml 5.0 g/ml 4.2 g/ml Which is most accurate? Who is the most accurate? What is the percent error (experimental error) of Larry’s reported density measurement?
How Does A Heat Pump Work?
Larry, Carly and Mo are given the same type of metal and are asked to measure its density. The actual density of the metal is 3.0 g/ml, but they are not told this. They take four sets of measurements and use them to calculate the density of the metal for each set of measurements. Their results are shown below. Larry Curly Moe 2.5 g/ml 4.0 g/ml 2.7 g/ml 2.0 g/ml 4.1 g/ml 3.1 g/ml 1.0 g/ml 3.3 g/ ml 5.0 g/ml 4.2 g/ml Which is most accurate? My, it has the smallest range (0.2). 2. Which is the most accurate? Curly, his average is closest to 3.0 (the accepted value). 3. What is the percent error (experimental error) of Larry’s reported density measurement (2.9 g/ml)?
In order for this website to function, we log user data and share it with processors. To use this website, you must agree to our privacy policy, including our cookie policy. Part 3 Thermodynamics Chapter 20: Heat and the first law of thermodynamics Reading assignment: Chapter 20.1 to 20.5, 20.7 Homework: (due in by Monday, June 30, 2003) : Assignments: Chapter 19: 1, 14, 17, 28, 30 Chapter 20 : 3, 5, 13, 20, 28 Chapter 20 Heat, specific heat Internal energy The first law of thermodynamics
Microscopically, energy flows in both directions On average, energy flows in one direction Temperature predicts the direction of energy flow Energy flows from hotter to colder No flow thermal equilibrium same temperature Heat: transfer of energy across the boundary of a system due to a temperature difference between system and its environment.
3 units of heat Because heat is a transfer of energy, it has units of energy: Joule (SI unit) Also used: 1 calorie (1cal) amount of energy to raise the temperature of 1 g of water from 14.4°C to 15°C 1 calorie = 1000 calories This unit is often used in food (a slice of cheesecake has 500 calories). 1 kcal = J
The Unit Of Thermal Conductivity Is :
When energy (heat Q) is added to the substance (and no work is done and no phase transition) the temperature increases with DT. How much the temperature rises depends on: – the mass of the substance, m – the type of substance c… specific heat (depending on the material) see Table 20.1) C… heat capacity
5 Blackboard Example 20.1 Problem 20. 3 21977 J of heat is transferred to kg of water to raise the temperature by 10°C. What is the specific heat of water? 1230 J of heat is transferred to kg of silver to raise the temperature by 10°C. What is the specific heat of silver?
The amount of heat flowing out of one body is the same as the amount of heat flowing into the other body. Qcold = – Qwarm plate Example 20.2 (Problem 20.5): A 1.5 kg iron horseshoe (T = 600°C) is thrown into 20 liters (20 kg) of water (T = 25°C). What is the final temperature of the water (plus horseshoe)?
Whenever a substance undergoes a phase transition, energy is transferred into or out of the substance WITHOUT causing a change in temperature. Common phase transitions: liquid to solid: freezing, latent heat of solidification Solid to liquid: melting, latent heat of fusion Liquid to gas: boiling, latent heat of vaporization Gas to liquid: condensation, latent heat of condensation Solid to gas: sublimation, latent heat of sublimation Gaseous to solid: sublimation, latent sublimation heat
Before Using The Clinical Thermometer Mercury Level Should Be Below:
The heat required to change the phase of a given mass m of a pure substance is: L… latent heat (see table 20.2 in the book) Table example (exercise 20.13): How much energy (heat) is needed to to evaporate 100 grams of water? How much energy (heat) is needed to melt 100 g of water? A 3.00 g bullet at 30°C is fired at a velocity of 240 m/s into ice at 0°C and embedded. How much ice melts?
If the volume decreases, the work is negative. If the volume increases, the work is positive. To evaluate this integral we need: The initial and final volumes Vi, Vf P as a function of V (P is often not constant). Work depends on the path followed!!
Expand the gas from Vi to Vf at constant pressure. Expand the gas from Vi to Vf at constant pressure. Reduce the pressure from Pi to Pf at constant volume by cooling. Pressure and volume are constantly changing at a constant temperature.
13 Table example 20. 4 Problem 20.20 The gas in a container has a pressure of 1.50 atm and a volume of 4.00 m3. What is the work done on a gas if it expands to twice its original volume at constant pressure. If it is compressed to a quarter of its original volume at constant pressure?
Heat Energy And Water
(Generalization of Conservation of Energy) There are two ways of transferring energy between a system and its environment: Heat, Q & Work W. The change in internal energy of a system is given by: The internal energy of an ISOLATED system remains constantly! Note: The work done according to the system is positive; The work done on the system is negative. Heat in the system is positive, heat out of the system is negative.
15 Special process: Closed loop (the start point is the same as the end point). DEint = 0 W = Q In such a process, the work W done on the system is converted into heat Q.
16 Special process: Adiabatic process (no energy enters or leaves the system as heat) Q = 0 DEint = – W Examples: Thermally insulated systems Very fast processes, so no heat is exchanged with the environment. Internal combustion engine (cars). Diesel engines (trucks). fire extinguisher demo.
Special process: iso-volumetric process (process takes place at constant volume). DV = 0 W = 0 DEint = Q P i Energy is added by heat to a system held at a constant volume. Example: Sealed barrel on fire. f Vi Vf V DEint = Q
Match The Following Quantities With Theirunitsquantityunitp) Si Unit Of Heat ( ) X) Kelvinq) Cgs Unit Of
Special process: Isobaric process (the process takes place at constant pressure). DP=0; W, Q and DEint are usually swapped. P i f The gas expands from Vi to Vf at constant pressure P. Vi Vf V Work done by the gas:
19 Special process: Isothermal process (The process takes place at a constant temperature). DT = 0 The internal energy of an IDEAL gas is only a function of temperature. So if DT = 0 DU = 0 Work done on the system leaves the system as heat.
20 Table Example 20.28 Problem 20.28 A gas is compressed from 9.00 L to 2.00 L at a constant pressure of atm. In that process, 400 J of energy leaves the gas with heat. What is the work of the gas? What is the change in its internal energy?
All three transfer heat from hot to cold. Conduction – heat flow through materials 2. Convection – heat flow through moving fluids (air) 3. Radiation – heat flow through light waves
Solution: Heat And Energy
In an insulator, neighboring atoms shake each other through microscopic energy exchanges; atoms act on average, heat flows from hot to cold atoms In a conductor, mobile electrons help transfer heat over long distances, heat flows quickly from hot to cold through electrons
Liquid heats up near a hot object Liquid flows away, taking heat energy with it Liquid cools down near a cold object In general, heat flows from hot to cold Natural buoyancy creates convection Warm liquid rises away from a hot object Cool liquid sinks away from a cold object
27 Examples of radiation: ___________________ Heat transferred by electromagnetic waves (radio waves, microwaves, light,…) It doesn’t need a medium to travel!
28 Radiation Heat transferred by electromagnetic waves (radio waves, microwaves, light,…) Wave types depend on temperature cold: radio waves, microwaves, infrared light warm: infrared, visible and ultraviolet light Higher temperature more radiated heat Black transmits and absorbs light best
Define The Specific Heat.
In order for this website to function, we log user data and share it with processors. To use this website, you must agree to our privacy policy, including our cookie policy. Heat and temperature Essential question: What is the relationship between heat and temperature? Liquid oxygen – 183C liquid
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