Name: Section: Activity S: Thermodynamics in the Kitchen (25 pts Directions: To

Question

Name: Section: Activity S: Thermodynamics in the Kitchen (25 pts Directions: To compkete this activity, answee the corresponding questions completely The Law of Conseration of Enerye states that: "Energy cannot be created or destroyed. It can only be transformed into another form, with the total amount of energy remaining the same. The Ist Law of Thermodynamics is an extension of the Law of Energy Conservation when a ied to thermodynamic systems T ank, how energy conserved when you eat broskEast in the morning? The chemical energy in food will be converted into mechanical energy that enables you to do work, lloe walking, running, and lnbing stairs. But, not all cheenical energy in the food you eat will be tranformed nto mechanical energy. Some of it will le released from your body its leat, that is, when you sweat and feel warm. So you see, the Law of Conservation of Energy, we talk here of energy, work and heat How are these three quantities rlated when we spenk of theruolynamie systeus? In thermodynamics, a system is any region completely enelosed within a well-defined boundary and ev- erything outskle this system is considered its sundings. The system might be a iological orgaaisn, a meclanical device, or the whole of the earths atmosphere It is important that we define what is contained inside the system as well as what exists outside it system The first law is all about the relationship between internal energy, heat, and work. To find out how these three quantities are related, perform this simple activity. You will need: What to do: 1. Put a marshimallow in the microwave for a maxin of 10 seconds (PLEASE do not let the marshmallow explode or catch fire! Response Questions (25 pts.): I. In order to conduct any type of analysis, what is and is not included in the system must first be clearly defined. In the case of the marshmallow, what type of thermodynamic system shoukd we consider here 2. What happens to the marshmallow while its in the mierowave? What changes take place?

Explanation / Answer

1) The thermodynamic system here is an open system (Marshmallows) which is allowed to interact with it surrounding the (Microwave) and the rest of the universe is not our concern.

2) Marshmallows are mostly sugar, water, and air bubbles, the microwave heats the water molecules by vibrating them and as a consequence, this softens the sugar and making the air bubbles warmer, therefore, the marshmallows expand in size. This as a thermodynamic system is an exchange of heat energy from the microwave to the marshmallow.

3) Marshmallow before going into the microwave was soft and elastic, in the microwave the water heats up which changes the state of the marshmallows. A change in state has occurred in increasing the temperature, volume and the pressure in marshmallows.

4) Energy transfer took place into the system from the surrounding. The reason that caused this energy transfer is is the heat that went in from the microwave to the marshmallow.

5)There is work in the marshmallow system since the microwave caused a change of pressure, volume and temperature of the marshmallow all of this are stored as work (internal energy).

6) Change in internal energy of the marshmallow = heat went into the marshmallow - Work done by microwave to change the state of marshmallow.

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