Explore BrainMass

First Law of Thermodynamics

The first law of thermodynamics is a version of the law of conservation of energy that is adapted for thermodynamic systems. The internal energy of an isolated system is constant and energy can be transformed from one form to another but cannot be created or destroyed. The first law is often formulated by stating that the change in the internal energy of a closed system is equal to the amount of heat supplied to the system, minus the amount of work done by the system on its surroundings.

The first law of thermodynamics states

ΔU = Q – W 

Where ΔU is the change in internal energy, Q is the heat added to the system and W is the work done by the system.

This law makes use of the key concepts of internal energy, heat and system work. It is often used to the discussion of heat engines

Application of Thermodynamics for Heat Transfer Through a Wall

An insulated frame wall of a house has an average thermal conductivity of 0.0318 Btu/h-ft^2-R degrees. The wall is 6 in thick and it has an area of 160 ft^2. The inside air temperature is 70 degrees F and the heat transfer coefficient for convection between the inside air and the wall is 1.5 Btu/h-ft^2-R degrees. On the outside

Thermodynamics Problems

A closed vessel containing 0.06m^3 at air at 40 atmospheres and 40 degrees Celsius is connected with another closed vessel containing 1.35 kg of argon at 7 atmospheres. When the valve separating these vessels is opened, the pressure of the mixture is 18 atmospheres and its temperature is 30 degrees Celsius. Determine the volum

2nd Law of Thermodynamics

Please see attachment for original question format. A combined air filled, spring loaded cylinder has a frictionless piston of area 0.012 m^2 that rests against the spring. The spring loaded end of the cylinder is open to atmosphere. The spring force in terms of piston movement is given by: Spring Force = k X Show that

Calculate the mass of helium in the cylinder.

A piston cylinder assembly whose piston is resting on a stop contains 400 L of helium gas, initially at 200 kPa and 25 degrees celsius. The mass and the atmospheric pressure acting on the piston are such that a pressure of 500 kPa is required to raise it. At the final state, the volume of helium gas is doubled. a) Calculate

Example for Laws of Thermodynamics

During the first oil crisis of the early 1970s, a business entrepreneur placed an expensive full-page advertisement in the New York Times, appealing to "the ingenuity of the American people." He offered a cash reward to any inventor who could "raise the temperature of a metal rod by cooling a second rod" and then "generate power

help with a short essay

I need to write a short paper and am clueless as to where to start. The question is: Divine Personalities verses material objects, what was God thinking? The task is: Identify, then list reasons for a preference for thinking of the stars, moon, and planets as material objects or as divine personalities. Help please!

First Law of Thermodynamics and Acceleration of a Car

The word acceleration means that something is speeding up or slowing down .......its speed (velocity) is changing. If you are driving on the highway at 60 mph then you are going at a constant speed (velocity) there is no acceleration. If you change your speed up or down, then, during the time that the speed was being changed y

Physics: Second Law of Thermodynamics

1. Use the second law of thermodynamics to explain why many poor people in developing countries live on a mostly vegetarian diet? 2. Someone wants you to invest money in an automobile engine that will produce more energy than the energy in the fuel (such as gasoline or electricity) used to run the motor. What is your response

Carnot Heat Engine and Well-Insulated Piston Cylinder Systems

Problem 1 can only be solved per unit mass- eg work per unit mass, volume per unit mass, since there is not enough info to calculate the system mass. Instructions: Solve the following problems. Be sure to include a sketch indicating the system and its interactions with the surroundings and state all necessary assumptions. Ide

Experiment to demonstrate the Ideal Gas Law.

Experiment to demonstrate the Ideal Gas Law. Attached is the directions and data sheet. Here is the link for the data sheet. ================================================== Data and related questions ==========================================

Heat Transfer & Thermodynamics Relative to Water and Wood

In our ChemE lab, we were asked to place a 25 cm x 25 cm x 1 cm (thick) block of wood in a water bath.....the rate of water absorption into the wood block is known to be 8 grams/100 cm^2 at 20 degrees C --- and the wood block is assumed to be at normalized ambient temp as well and completely dry or free of moisture before enteri

Thermodynamics & Newton's law of cooling

(Please see the attachment for detailed problem description) Distinguish between reversible and irreversible processes in thermodynamics. Describe the circumstances under which a) dQ = Tds and dW = -PdV. A long cylinderical rod of radius R is attached to a source of heat at one end and its surroundings are at temperature

Laws of Thermodynamics

As a patent agent, an inventor comes to you claiming that he has invented a self-powered engine that requires no fuel to run. Will you agree or disagree to patent this invention? Why or why not? Use the first law of thermodynamics to help justify.

Thermodynamics - Warm Up Air

You warm 1.75 kg of water at a constant volume from 17.0C to 32.0C in a kettle. For the same amount of heat, how many kilograms of 17.0C air would you be able to warm to 32.0C? Make the simplifying assumption that air is 100% N2. What volume would this air occupy at 17.0C and a pressure of 1.10 atm?

Laws of Thermodynamics

We can say that life on earth is supported by the sun as the ultimate energy source and that life on earth would not exist without this source of energy. How does this statement relate to the two laws of thermodynamics? Please provide examples.

Heat Transfer and Work Done During Polytropic Process

Oxygen at 300 kPa and 100 degrees C is in a piston, cylinder arrangement with an initial volume of 0.1 cubic meters. It is then compressed in a polytrophic process (P*v^n=constant) with n=1.2 to a final temperature of 200 degrees C. a) Calculate the heat transfer for the process. b) Draw a P V diagram for the process.

Applied Heat Thermodynamics

Please help with the problems involving applied heat thermodynamics. 3. Calculate the change in enthalpy during a compression process in which the work done on the working medium is 24 kJ, and the change in internal energy is 36 kJ. Heat added or rejected 4. Derive the numerical ratio ----------------------------

Steady Flow Turbine

Steam at 800 kPa, 600°C enters a steady flow turbine and leaves at 100 kPa. The steam undergoes an expansion process through the turbine, does work in the amount of 600 kJ/kg, and loses 50 kJ/kg of energy by heat transfer to the surroundings. (a) Determine the exit temperature of the steam, in °C. (b) If the surroundings

Rate of heat supplied from a pump

Air from inside a house enters a steady-flow heat exchanger with a volume flow rate of 200 m3/min at 15°C, 100kPa and eaves the heat exchanger at 35°C. This heat exchanger is located inside the sir handler of a house heat pump system and receives heat from the heat pump. The heat pump receives heat from air outside the house

Calculations Regarding a Piston-Cylinder Device

A piston-cylinder device contains 5kg of steam at 100kPa, quality of 50%. This steam undergoes two processes as follows: (Process1-2) Heat is transferred to the steam in a reversible manner while the pressure is held constant until the steam exits as a saturated vapor. (Process 2-3) The steam is compressed in an adiabatic, rev

Kinetic and Ideal Gas Law Questions.

Question 1: The figure below is a plot of Fahrenheit temperature versus Celsius temperature. (a) Is the value of the y-intercept found by setting 1. TF = TC 2. TC = 0 or 3. TF = 0? (b) Compute the value of the y-intercept. (c) What would be the slope and y-intercept if the graph were plotted the opposite way (Celsius ve

Psychrometry-Hot House

3) SOLVE THIS PROBLEM BELOW: Hothouse Problem A hothouse needs to be kept at a constant temperature of 30°C drybulb and 60% relative humidity (state K) throughout the year. The air flowrate out of the hothouse is 5 m 3 /s . 40% of this air must be replaced by outside air. In winter the air is at 8°C and 90% relativ

Free energy equation - The relationship between dG=dH-TdS (d stands for delta)

I'm having trouble understanding the 2nd law of thermodynamics in it's relationship to entropy. This is probably the reason why i can't seem to grasp the components of the free energy equation dG=dH-TdS What i do know is this, that if dG<0 the reaction is spontaneous (exergonic) and if dG>0 the reactions is nonspontaneous

Thermodynamics: Adiabatic process, P-V graph, final P and T

Air containing gasoline vapor is admitted into the cylinder of an internal combustion engine at 1.0 atm pressure and 30 degrees C. The piston very rapidly compresses the gas, which you may pretend is all air, from 500 cc to 50 cc; a compression ratio of 10. Find the final T and P of the gas. The gas gets hot, but why (was it hea

Problems on heat and thermodynamics

1. A cube 10 cm on each edge contains air (equivalent molar mass 28.9 g/mol) at atmospheric pressure and temperature 27 degree C. Find the mass of gas, its weight, and the force it exerts on each face of the cube. Comment on the physical reason why such a small sample can exert such a great force. 2. In a time t, N hailst