Using Models to

Estimate the Mass of Dinosaurs

Introduction

Whether you know it or not, you deal with models every day. Role models, for example, are the people who help us understand how we should act. Fashion models help us understand how clothes will look when they are worn. Behavior models help us to understand why someone behaves the way they do.

Models are very important in science as well. Watson and Crick used paper cutouts and ball and stick models to understand the structure of DNA. Bohr used a model of the planets orbiting around the sun to help understand how the electrons in an atom orbit the nucleus. Einstein imagined a model of a person in a sealed elevator traveling through space in order to understand the implications of relativity. Almost all great scientific discoveries were preceded by a scientist who used a model to form a hypothesis.

Models come in many different forms. Some models don't really look like what they represent: instead they simply act like what they are supposed to represent. (Electrons in an atom don't really look like planets orbiting the sun). Other models, like cars, airplanes, and dinosaurs, look like what they are supposed to represent, but they are built on a smaller scale and are made out of less expensive materials than their real counterparts.

Objectives

* Students will use Archimedes' principle to determine the volume of a scale model of a Dinosaur.

* Students will use the volume of a scale model to determine the volume of a real dinosaur.

* Students will use the concept of density to determine the mass of a real dinosaur.

* Students will explain how models are used to further scientific understanding.

Materials

1. Scale model dinosaurs

2. One gallon plastic bucket with a tube attached

3. 100 or 250 ml graduated cylinder

4. 250 ml beaker

Fig. 1. Bucket, beaker set-up.

Procedure

1. Place the 250 ml beaker under the plastic tube which will act as a spout.

2. Pour water into the bucket until the water begins to pour out of the spout.

3. Wait until the water stops dripping out of the spout.

4. Remove the beaker, pour the water into a waste container, dry the beaker, and replace it under the overflow tube. See Fig. 1.

5. Pick your favorite dinosaur from the sample box. Be sure it will completely fit into the one gallon bucket.

6. With the beaker under the overflow tube, place the dinosaur into the bucket until it is completely submerged.

7. Wait until the water stops dripping out of the spout.

8. While you are waiting, record the name of the dinosaur in the table below. Also record its scale.

9. Remove the beaker and pour the water into the graduated cylinder.

10. Record the volume of water displaced by the dinosaur in the table.

11. Repeat with another dinosaur model.

Data

 Trial    Name of Dinosaur      Scale     Volume of Water    Actual Volume  of   
                                           Displaced (ml)    Real Dinosaur (ml)  
   1                                                                             
   2                                                                             

Analysis

1. Determine the scale of the model. To do this, look at the bottom of your model. It will be labled with the actual length of the dinosuar. Measure the dinosaur and determine its scale. If the dinosuar measures 15 cm and the length labled on the bottom is 6 meters then the scale is 6/.15 = 40:1.

Calculate the actual volume of a real dinosaur.Since you are working with volumes, which are in cubic dimensions, you have to multiply the volume determined in this experiment by the scale of the dinosaur cubed. Thus, if the scale if 40 you will have to multiply your volume by 40 X 40 X 40 = 64,000.

Show your work below, and record your answer in the data table.

2. Since most of a dinosaur was made up of skin, guts, blood and stuff, we will assume the density of a dinosaur was 1.0 g/ml. This is probably a good approximation, because this is also the approximate density of water, crocodiles and mammals. Find the mass of the real dinosaur using its density of 1.0 g/ml and its volume from the data table. Show your work below. (Remember that density = mass/volume.)

3. Convert the answer you found in Question 2 to kilograms.

4. Convert the answer you found in Question 3 to metric tons. (There are 1000 kilograms in a metric ton.)

5. Convert the answer you found in Question 4 to pounds. (There are 2,205 pounds in a metric ton.)

6. If a full grown African male elephant weighs about 5 metric tons, how many elephants would it take to equal the mass of your dinosaur.

7. Using your body weight, how many times heavier was a dinosaur than you are?

Conclusion

1. List some advantages to using scale models in this experiment, as opposed to the real thing.

2. Assume dinosaurs were still alive, list some disadvantages to using a model as opposed to the real dinosaur in order to determine its mass.

3. What assumptions were made in this lab which were not verified?

4. What information was necessary before the model we used could be built? How was this information gathered?

5. What are some similarities and differences between scientific models and non-scientific models?