(b) Why would a burn produced by 1 g of steam at 100°C do more damage than a burn caused by 1 g of water at 100°C?
(c) In part 1, what is the importance of making sure that the metal sample is not in contact with any surface of the steam generator(step4)
- No Need Vigorous Proof Just Simply Ans Thx B Why Would A Burn Produced By 1 G Of Steam At 100 C Do More Damage Than A 1 (56.04 KiB) Viewed 37 times
- No Need Vigorous Proof Just Simply Ans Thx B Why Would A Burn Produced By 1 G Of Steam At 100 C Do More Damage Than A 2 (56.04 KiB) Viewed 37 times
- No Need Vigorous Proof Just Simply Ans Thx B Why Would A Burn Produced By 1 G Of Steam At 100 C Do More Damage Than A 3 (86.44 KiB) Viewed 37 times
- No Need Vigorous Proof Just Simply Ans Thx B Why Would A Burn Produced By 1 G Of Steam At 100 C Do More Damage Than A 4 (77.14 KiB) Viewed 37 times
Notes on calorimetry A calorimeter is a vessel or device that thermally isolates an experiment from its surroundings. Ideally, this means that the measurement performed in the calorimeter is independent of the temperature of the surroundings, because no heat flows into or out of the calorimeter. However, no calorimeter is perfect, and there is always some unwanted and unaccountable heat flow affecting the results of any calorimetric experiment. To minimize unwanted heat flow, always plan the experiment so that: 1. The time between taking initial and final temperatures is minimal In other words, do the critical portion of the experiment quickly, so that there is minimal time for unwanted heat flow during the measurement. (Don't rush; just plan carefully.) 2. Whenever possible, room temperature is approximately midway between the beginning and ending temperatures of the experiment. When the experimental temperature varies above and below room temperature by equal amounts, the heat gained and lost to the environment will be approximately equal, minimizing the net affect on the experiment. 3. Mass measurements of liquids are made as near the critical temperature measurements as possible. This reduces the effect of mass loss by evaporation. Measuring liquid mass by taking appropriate differences is a useful technique. Part I. Specific heat of metals 1. Measure Mar, the mass of the calorimeter to be used (it should be empty and dry). Record your result in Table 1. 2. Measure the mass Msample of one of the metal samples. Record it in Table I. 3. Fill % full of water to the steam generator and turn it on. Wait until the water boils. 4. Attach a thread to the metal sample and suspend it in boiling water (NOTE: Make sure that the metal sample is not in contact with any surface of the steam generator). Allow a few minutes for the samples to heat thoroughly. 5. Fill the calorimeter approximately y full of cool water-use enough water to easily cover any one of the metal samples. 6. Measure Tcool, the temperature of the cool water, and record your measurement in Table 1. NOTE: A K-type thermocouple is used for the temperature measurement, please make sure that the digital thermometer is set as K-type. 7. Immediately following your temperature measurement, remove the metal sample from the boiling water, quickly wipe it dry, then suspend it in the cool water in the calorimeter (the sample should be completely covered but should not touch the bottom of the calorimeter). 8. Stir the water with a glass rod and record Trinalthe highest temperature attained by the water as it comes into thermal equilibrium with the metal sample. 9. Immediately after taking the temperature, measure and record Motal, the total mass of the calorimeter, water, and metal sample. 10. Repeat steps 1 to 9 for the other two metal samples. 11. Turn off the steam generator after finishing this part of the experiment. Part II. Latent heat of vaporization of water 1. Measure room temperature Troom and record it in Table 2. 2. Set up the steam generator with a water trap as shown in Fig. 1. The tube lengths are also indicated in Fig. 1. NOTE: The bottom of the water trap should be kept higher than the water level in the calorimeter to avoid water being pulled from the calorimeter back into the water trap.
General Physics I Lab H1 Specific Heat and Latent Heat of Vaporization Purpose In this experiment, you will measure the specific heat of aluminum, copper, and lead. In addition, you will measure the latent heat of vaporization of water. Equipment and components Calorimeter (x4), tubing, steam generator, water trap, digital thermometer with K-type thermocouple, cool water, electronic balance, paper towel, metal samples (aluminum, copper and lead) with thread, stand and clamp (x2), glass rod, lab jack (x2). Background The specific heat of a substance, usually indicated by the symbol c is the amount of heat required to raise the temperature of one kilogram of the substance by one degree Centigrade. The specific heat of water is 4,200 J/kg °C. If an object of mass M is made of a substance with specific heat c, then the heat, AQ, required to raise the temperature of that object by an amount AT is: AQ-MCAT if the specific heat e is constant. In Part 1 of the experiment, you will measure the specific heat of aluminum, copper and lead. When a substance undergoes a phase change, i.e., if it evaporates, melts, or freezes, the arrangement of its molecules changes. If the new arrangement has a higher internal energy, the substance must absorb heat in order to make the phase transition. Conversely, if the new arrangement has a lower internal energy, heat will be released as the transition occurs. During the phase transition, the temperature of the substance does not change. The amount of heat absorbed (or released) per unit mass during evaporation is called the latent heat of vaporization, L. We may think of this heat energy as the work required overcoming the molecular forces holding the material together as a liquid. The heat required to evaporate a mass M of the liquid is AQ - ML It is important to note that the specific heat c and latent heat L are different for different materials. Moreover, for a given material, the specific heat may also change with temperature. At room temperature, this variation can often be neglected, but the temperature dependence of c is very important at low temperatures. In Part II of the experiment, you will determine how much more energy is contained in one kilogram of steam at 100 °C, than in one kilogram of water at the same temperature. This value is called the latent heat of vaporization of water. Procedure CAUTION: 1. This experiment uses boiling water, live steam and hot objects. Please wear heat resistant gloves and work carefully. 2. Lead (one of the metal samples) is harmful if it is ingested or absorbed through the skin, so do NOT directly contact the lead sample without wearing the disposable gloves.