Physical Science 9 Lab #1
Simple Measurement
You can find an example of how one is to write up a lab on the course web page under the heading sample lab.
Theory
Density = Mass / Volume
Volume of a cylinder = height of cylinder x area of base
Area of a circle = pi x radius2
1 mL = 1 cm3
1.0 x 10 6 mL = 1 m3
Procedure
The order in which you perform sections 1, 2 and 3 is unimportant, so feel free to proceed to another section if the equipment you need is unavailable. Section 4 must follow 1 and 2.
Part #1 Cylinder Dimensions/Volume
Compare two methods of determining the volume of the cylinder.
- Use the meter stick to find the height and diameter of the metal cylinder and calculate the volume via the formula above. (Remember that diameter and radius are different.) For extra credit you can learn to use the vernier calipers or the micrometer to do more accurate measurements. If you do this you should compare your results and discuss why they are not the same. Which do you think is better? How?
- Use the displacement method to find the volume of the wooden ball. I will show the method. If you cannot get access to the apparatus move on to another part of the lab.
- Discuss which method you think is more precise and why. Also discuss when the displacement method would work where the first method would not.
Part #2 Cylinder Mass
Use two balances to determine the mass of the cylinder.
- Use the triple beam balance to mass the cylinder.
- Use the electronic balance to get the mass of the cylinder.
- Which of the two balances gives the more precise results? What is the limitation of the electronic balance?
Part #3 Timing Error
Use the digital timers to develop techniques to minimize reaction and other timing errors. Reaction time is the difference in time between receiving a stimulus and your brain sending a message to your body to act. It can be as large as half a second.
- Have one person start two stop watches at the same time by having one in each hand. The other partner should take one of the stop watches and watch the first partner to see if he or she clicks the watch stopped. When this occurs the second partner should try to stop his or her watch as quickly as possible. The difference between the two times will be the reaction time of the second partner.
- Now repeat the process from above but have the first person count down rhythmically prior to clicking the stop button. Calculate and compare reaction times here to those above. What are the limitations ot this method?
- Now repeat the process with the second person starting their own watch by watching the first person to see when they start their watch. (The same for stopping.) Why does this reduce the effect of reaction time? What are the limitations ot this method?
- If you have the time and interest you can ask me how to do a pendulum experiment for extra credit. Wait until you have finished the rest of the lab, however.
Part #4 Calculating Density
Using the most precise results from part one and two calculate the density of your sample. You should give the results in kg/m3 so you must first convert your measurements from grams to kilograms and mL or cm3 to m3. Use the table of densities below to figure out from what material your cylinder is most likely composed.
Densities of Metals
Magnesium 1,700 kg/m3
Aluminum 2,700 kg/m3
Copper 8,700 kg/m3
Gold 19,300 kg/m3
Iron 7,800 kg/m3
Lead 11,300 kg/m3
Platinum 21,400 kg/m3