Canimals borrowed, with thanks, from Malaspina University College/Kwantlen University College http://ommons.wikimedia.org/wiki/file:ursus_maritimus_steve_amstrup.jpg Purpose Investigate the rate of heat loss of animals using an models and investigate how the heat-loss rate is related to the size of the animal; and/or the animals fur and fat; and/or the environmental onditions: outside temperature, wind. Introdution Maintaining a normal temperature is very important for animals. It has a large impat on animals habitats, their behaviour patterns and food intake. In this lab, we look at heat loss due to radiation from the skin. To model small warm-blooded animals, we use metal ans filled with warm ( animals ); the ans are different sizes, have different surfae overs, and are plaed in different environmental onditions. The temperature is reorded at uniform time intervals and a ooling urve is plotted. Theory In this lab, we look at heat loss due to radiation from the skin. If a warm of mass m is plaed in a ool environment, it will lose energy to the environment in the form of heat Q, whih is related to a temperature hange Δ T : ΔQ m ΔT (1) Here is the speifi heat apaity of the, whih is similar to the speifi heat apaity of for animals, therefore, 1101 Canimals 1 Saved: 7/7/17, printed: 7/7/17
ΔQ m ΔT (2) For the heat loss, Q and are in fat both negative, but we will neglet the negative sign here to fous on the magnitudes of the hanges in these two terms. We will be using metal ans filled with warm to model animals, thus we all this lab animals. As the animal is made of both the metal an and, we need to find the equivalent mass, m, of equation (2). The atual heat loss will be ΔQ ( m m ΔT (3) an an ) Therefore, m m m an an (4) where man is the mass of the empty an, m is the mass of the inside the an, an is the speifi heat apaity of the an (use an = 0.452 J/gC ), and is the speifi heat apaity of (4.186 J/gC ). We ignore the masses of fur or fat. Without any heat input, the temperature of the will drop with time, reating a urve that Δ T we all the ooling urve. The slope of the ooling urve is the ooling rate. It depends Δt on many fators for a real animal suh as the differene between the temperatures of the to the outside, the size and the skin struture of the animal, the presene of fur, and onditions like shelter, wind, rain et. The rate of heat loss is given by Q R ( manan m ) m (5) Normally the ooling urve is not a straight line, but if the temperature drop is small, the urve will be approximately linear and the slope of the graph will give an estimate of / at that average temperature. Therefore, we an alulate R, the rate of heat loss. Apparatus set of animals with lids and bases, thermometer, stopwath, fan, fat, fur. Data Note: In this lab, the results of the entire lass are pooled. Eah desk measures one animal, makes one / graph, and alulates the rate of heat loss R. But you will use the entire lass s data to write your Conlusion and Disussion. 1101 Canimals 2 Saved: 7/7/17, printed: 7/7/17
Desribe your setup of the experiment: Reord your animal number, its mass (without lid), outer diameter, and height. Remember to reord unertainties for eah measurement. State whether you are using fat, fur, wind or ie, and briefly desribe what they are and where you put them. Reord the room temperature. If ie is part of the environment, also measure the temperature between the animal and the ie pakage. Set up the temperature measurement: Put the lid and the base of the animal on. Put the thermometer to an appropriate height with a rubber band so that you an read the temperature from 30 C and above. Put on the fur or fat if required. If you will be using a fan, plae the fan so that it is blowing straight toward the animal. The air path must be unobstruted, both behind and in front of the fan. Fill the animal with warm (Around 40-42 C), leaving room for the lid. Measure and reord the temperature one every minute to find a ooling urve. You should start somewhat higher than 40 C and keep reording until you have 15 data points below 40 C. Gently stir the a few times after eah reading with the thermometer, but make sure you do not touh the an with your hand. Again, remember to reord unertainties for time and temperature. On a rough graph, plot eah temperature you reord after eah minute to observe your ooling urve in real-time to hek for any issues. Measure the mass of the an full of. Subtrat the mass of the an to find the mass of the. Calulate the equivalent mass, m, of the animal. Ignore the masses of fur or fat. Reord the following data in the olletive-data table, inluding unertainties where appropriate (Eah desk fills one row): Can # Conditions (Fur/fat/wind,et.) empty an an + Equivalent mass, m Diameter D (m) Height H (m) Calulations Plot the ooling urve (i.e. the graph of temperature versus time) starting from 40 C for 15 minutes. Assuming it is linear (see Note below), find the slope of the graph (you an handgraph, use LoggerPro, or Exel). This slope will be referred to as the ooling rate of the animal at temperature. Express the ooling rate in C/min. 1101 Canimals 3 Saved: 7/7/17, printed: 7/7/17
Note: this slope an be different if the experiment was performed at a signifiantly different temperature beause the ooling urve is in fat a urve. For our small range in temperature, we assume that the slope hanges slowly enough that we an take it as a onstant. Calulate A, the area of the blak radiating surfae of the animal. Find the area to mass ratio, A/m. Add the following alulated results into the olletive-data table. For alulated results, always reord at least 5 signifiant digits. Ignore unertainties in alulated results for now. Can # Blak area, A (m 2 ) A/m ratio (m 2 /kg) Cooling rate, ΔT/Δt (C/min) Heat loss rate, R (W) Report By now, you have a lot of experiene writing lab reports so you know that your report should be a omplete, logial and understandable artile for a general reader (not the marker!). Keep the readers in mind when you write! For example, your title should not be Canimals. It is an interesting word, but it is made up, and people will not know what it means. Something like Investigating Heat Loss in Animals using Can Models is muh more desriptive. You are the author and have the privilege of titling your own artile! For Data inlude data from your desk, inluding the data used to generate the ooling urve. Remember to inlude unertainties on all data. For Calulations, show how you arrived at all the numbers you entered into the olletivedata sheet. Inlude a opy of your ooling urve graph and show your slope alulations. Introdue and insert the olletive-data sheet. For Unertainty Analysis alulate δr, the unertainty in R. Reall equation (5): R Q m Here the relative unertainties in m and are negligible ompared to the relative unertainty in ΔT/ Δt, whih omes from the unertainty from the slope of your ooling urve graph. For Conlusion/Disussion setions, hoose one or both from the topis below. The topi(s) you hoose should be onsistent with the title and the purpose of your report. Do not limit your disussion to the suggestions below introdue your own thoughts. 1101 Canimals 4 Saved: 7/7/17, printed: 7/7/17
Topi 1: Size of animals. Pik three or more bare animals that are very different in size and ompare the ooling rate and the rate of heat loss R. For eah animal you pik, assume that the animal s diet onsists solely of Planters dry-roasted peanuts (listed on the jar as 790 kj per 30 g serving). What fration (%) of its mass would it have to onsume eah day in order to maintain its temperature? From these results, explain why there exists a lower limit to the size of warm-blooded animals. What shape should a resting animal take in old weather? In hot weather? Why? Topi 2: The effet of fat/fur How effetive is dry fur in reduing the heat-loss rate in still air? In the wind? Hint: Compare R of a furry animal with that of a bare animal. How effetive is wet fur in reduing the heat loss rate in still air? In the wind? What does the above say about the severity of heat loss by aidental drenhing in old windy weather? What does it say about the effetiveness of sweating as a heat removal mehanism in warm weather? Compare the heat loss rates of animals with and without fat. What does this suggest about the neessity of the blubber layer beneath the skin of sea mammals? What is the differene between fur and fat? Please note that your Conlusion/Disussion should appear like a small essay, rather than a series of answers to questions from the lab manual. If you are using a subset of olletive data for a speifi omparison, make a smaller table showing only the data used. 1101 Canimals 5 Saved: 7/7/17, printed: 7/7/17