# The First Law of Thermodynamics

• rico22
In summary, the question is asking for the amount of natural gas needed to be burned daily to maintain a temperature of 23.5°C inside a house with walls and roof that have an average thermal conductivity of 0.480 W/m · °C and an average thickness of 24.7 cm. Disregarding radiation and energy lost through the ground, the calculation involves finding the rate of heat transfer for each wall and the roof, adding them together, and converting it to kcal. Finally, this value is divided by the heat of combustion of natural gas (9300 kcal/m3) to determine the required amount of gas to be burned daily. It is recommended to calculate the total area of the walls and roof and use that for
rico22

## Homework Statement

The average thermal conductivity of the walls (including the windows) and roof of a house is 0.480 W/m · °C, and their average thickness is 24.7 cm. The house is heated with natural gas having a heat of combustion (that is, the energy provided per cubic meter of gas burned) of 9 300 kcal/m3. How many cubic meters of gas must be burned each day to maintain an inside temperature of 23.5°C if the outside temperature is 0.0°C? Disregard radiation and the energy lost by heat through the ground.

the Side walls are 5m x 8 m and the front and back walls are 5m x 10 m respectively. The roof has an incline of 37 degrees between the roof and the side of the house.

## Homework Equations

rate of heat transfer P = (k(thermal conductivity)A ΔT)/Δx

## The Attempt at a Solution

I tried finding the rate of heat transfer for the house. side wall, front wall and the roof and I added them up. then I found how many total joules were transferred for the day as this give me Joules/ sec. After I got this I converted it into cal by multiplying it by .239 and then kcal. finally I divided the total amount of kcal by the 9300 kcal/m3 given. I just want to know if I am on the right track or am I way off? Thanks in advance.

Yes, that's the right procedure. For the first step, I would have just added the areas rather than calculating the rates separately then adding them up. Can't check the details without seeing your working.

## 1. What is the First Law of Thermodynamics?

The First Law of Thermodynamics states that energy cannot be created or destroyed, only transferred or converted from one form to another.

## 2. How does the First Law of Thermodynamics relate to the conservation of energy?

The First Law of Thermodynamics is essentially the scientific way of stating the law of conservation of energy. It acknowledges that energy cannot be created or destroyed, but can only change forms.

## 3. What are some examples of the First Law of Thermodynamics in action?

Some common examples of the First Law of Thermodynamics include a car engine converting the chemical energy in gasoline into mechanical energy to power the car, a person eating food and converting it into energy for their body to use, and a light bulb converting electrical energy into light and heat energy.

## 4. How does the First Law of Thermodynamics apply to living organisms?

In living organisms, the First Law of Thermodynamics is evident in the way that energy is constantly being transferred and converted within the body. For example, plants use sunlight to convert water and carbon dioxide into glucose (chemical energy) through photosynthesis, which is then used by animals for energy through the process of cellular respiration.

## 5. Can the First Law of Thermodynamics be violated?

No, the First Law of Thermodynamics is a fundamental law of physics and has never been observed to be violated. However, it is important to note that although energy cannot be created or destroyed, it can be wasted or lost as heat energy in some processes.

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