M6 Phy 1stSem Finals Heat and Gases Section 3 and 4

Objectives

• Perform calculations with a specific heat capacity.

• Interpret the various sections of a heating curve.

​A 0.050 kg metal bolt is heated to an unknown initial temperature. It is then dropped into a calorimeter containing 0.15 kg of water with an initial temperature of 21.0°C. The bolt and the water then reach a final temperature of 25.0°C. If the metal has a specific heat capacity of 899 J/kg•°C, find the initial temperature of the metal.

​A 0.050 kg metal bolt is heated to an unknown initial temperature. It is then dropped into a calorimeter containing 0.15 kg of water with an initial temperature of 21.0°C. The bolt and the water then reach a final temperature of 25.0°C. If the metal has a specific heat capacity of 899 J/kg•°C, find the initial temperature of the metal.

​A 0.050 kg metal bolt is heated to an unknown initial temperature. It is then dropped into a calorimeter containing 0.15 kg of water with an initial temperature of 21.0°C. The bolt and the water then reach a final temperature of 25.0°C. If the metal has a specific heat capacity of 899 J/kg•°C, find the initial temperature of the metal.

Because phase and temperature can't change at the same time, latent heat accounts for the extra energy that's added or removed during phase change.

​Two points where phase changes occur latent heat will come into play in both of these locations In the first, it's known as the heat of fusion, which is the energy needed to transfer between the solid and liquid phases. When the water transitions to steam, we use the heat of vaporization. This is also called latent heat, but it's defined as the energy needed to transfer between the liquid and gas phases.

​During melting, the energy added to a substance equals the difference in potential energy between its solid and liquid phases, known as the heat of fusion (L_f). During vaporization, the energy added equals the difference in potential energy between its liquid and gas phases, called the heat of vaporization (L_v). These latent heats are specific to each substance.

Summary

• Specific heat capacity is a measure of the energy needed to change a substance’s temperature.

• By convention, the energy that is gained by a substance is positive, and the energy that is released by a substance is negative.

• Latent heat is the amount of energy required to change the phase of a substance.

Objectives

• Calculate heat, work, and the change in internal energy by applying the first law of thermodynamics.

• Apply the first law of thermodynamics to describe cyclic processes.

​The first law of thermodynamics, or the principle of energy conservation, includes a system’s internal energy, work, and heat. For a rapidly compressed balloon, work is done on the system, increasing its internal energy and temperature (W is negative). If the process is adiabatic, no heat is exchanged (Q = 0), and the change in internal energy equals the negative of the work done (∆U = −W). Later, heat is transferred out of the system, decreasing its internal energy (∆U = Q). Visualizing energy flow with arrows into or out of a system can help understand changes in internal energy.