Question

HoMEWORK FOR INTRODUCTION TO HEAT AND TEMPERATURE 1. Approximately what is human body temperature on the Celsius temperature scale? Which is better at transferring heat, water or air? How does this fact explain the length of time it takes the temperature probe to reach thermal equilibrium with the air or water it is in? 2. 3. What effect does the evaporation of water have on the object from which it is evaporating? When has your body experienced this effect? 4. During evaporation, heat flows from something to something? What does it flow from and what does it flow to? 5. If you put a cup of hot chocolate at 80°C on a table in a room at 20°C you already know it will cool down. a. How cool will the hot chocolate get? b. If you put it outside where the temperature is 5 C, how cool will it get? c. Compare the initial rates of cooling in (a) and (b). Are they the same or is one larger? Explain. d. Where does the heat go as the hot chocolate cools down? On the axes, sketch a graph of the temperature of hot chocolate vs. time if the hot chocolate starts at 80°C and is placed T outside on a cold day where the temperature is 0°C 90 80 70 60 m 50 40 ("C) 30 20 10 e. f. Explain the shape of the graph, especially changes in the rate of cooling as the hot chocolate cools down, in terms of your observations in this lab. Time

Answer 1

1. The Human body temperature on the celsius scale is 37^oC.

2.water is a better way to heat transfer in comparison to air ,as the capacity is higher and so is the density about (1000:1.2)

C( liquid water)- 4.187 kJ/kgK

C (Air)- 1.01 KJ/KgK

The concept of temperature probe to their equilibrium point can be easily studied with the help of thermal conductivity concept in which heat is lost due to surroundings.

6.Thermal equilibrium - when the two substances are at the same temperature.and no heat flows from the body.because the temperature of both the substances are same. This is obey first law of thermodynamics.

7. Temperature is the same for two system in thermal equilibrium.