Irregular Shaped Object Lab Test

Richard D. Smith, Glencoe-Silver Lake High School, Glencoe, MN, 55336
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This activity is a lab test based on previous lab experiences. The student teams will each be given a sample of an 'unknown' substance. This container for this substance is marked on the outside with a number (the atomic number of the substance). The students are to only be told that the number is for reference in grading. The students are given lab equipment including the required items to perform the lab test along with several extra items. The students are given a worksheet (attached to this activity) to be filled out, this makes grading easier and more consistent. To increase the difficulty one could eliminate the worksheet and have the students write up their own report in the standardized format for the classroom. Once the students have found the density of the unknown object (given in BB form works great), they are to use a bar graph provided by the instructor to compare against their results (average) to determine the identity of their substance. The x-axis displays the elements symbols while the y-axis gives the densities, a sample graph is attached to this activity.

Learning Goals

The concepts/skills the students are to display in this activity include ones that were to be learned in previous activities. These include, but are not limited to; mass, volume, displacement, density, reading a graph, interpreting data, calculating average, and recording of findings.

Context for Use

This activity is a culminating test of multiple skills that have built upon one another and then tie several of the different skills together showing an extension of the knowledge/skills learned. The substances used are in basic elemental form either in shot or slag shapes, the 'easiest' ones to obtain and use are; Copper, Iron, Glass (Silicon), Zinc, Aluminum, Lead – any of the scientific supply companies will have these in shot or similar format. Each group should receive between 5 and 20 mL (estimate) of the samples. NOTE: Be careful with the Zn and Al, sometimes their shapes are very similar and after some surface oxidation has occurred their color becomes very similar also. To adapt this for lower level students a 'fill in the blank' type of test sheet may be helpful, for the advanced level students simply having them write a lab report as for any other lab in the class would work well.

Description and Teaching Materials

This activity should be preceded with discussions and lab experiences covering the following topics, (but is not limited to); mass, volume by displacement, density, calculating average, graphing (creating and interpreting), recording data, and working with data.
The students get into teams (however many you in a team that you are comfortable with), once into teams note the ability levels of the members, have one member from each team come to the front and receive their substance (do not say element, leave that for the student to figure out) and the test sheet (if you desire to give them one). Giving the students a worksheet to fill out helps to keep the lab test to one class period (approx. 35-50 minutes is what I have found). Make sure the students write their sample number on the test paper.
In the lab the students are provided with a balance (electronic or manual), graduated cylinders (usually I give them two, 2, different sizes), water (remind them where the water comes from and is to be put when they are done with it). I also provide an assortment of other lab equipment that may include, but is not limited to; beakers (makes for interesting questions to the students during the test), tongs, buret clamp, scoopula.
The students are to do five trials with different amounts of the substance; they are then to find the average. Take the new found data and compare it to the bar graph provided – I usually post 3-4 around the room (remember to tell the students that all of the graphs are identical or they will be looking at all of them trying to figure out what is different).
Once the teams have completed the lab test, answered all of the follow up questions, they are to hand in their written work along with the sample provided to them. Test paper created by Richard Smith (Acrobat (PDF) 178kB Nov21 08)

Teaching Notes and Tips

*If the students are using the beaker to measure volume, discuss with them accuracy and precision during the test – they will catch on quickly and realize their error.
*Many teams will try to use the entire sample that was given to them in one trial and then the graduated cylinder overflow and they are confused. Ask why they believe they need to use the entire sample at once, discuss what different trials means.
*It never fails, every year there is a team that gets the glass marbles and can not figure out how to get them to fit into the 10mL graduated cylinder – this can lead to interesting conversations about why they are not trying the other graduated cylinder provided.
*This is the best!!! Once the test is done, corrected, handed back and you are all most done going over the test – Ask, "Who had sample number 82?" (or whichever sample you choose to use as an example). That team will raise their hands, you then look at the periodic table hanging in the room (I presume all science teachers have one hanging in their room) and say, "You had lead." Ask about a couple other sample numbers, confidently replying with the correct element name. Suddenly students will begin to realize the answer to the test was on the wall the entire time. This leads into a great discussion about observations, previous knowledge (especially with those that had copper and found the incorrect answer).
Feel free to adjust as you need for your situation.


I have traditionally graded this lab test as team scores, looking at the correct number of significant figures (especially when I tell them measure to the hundredths place), correct math (accommodate for being off on measurements), correct identification of the substance, correct and complete answers on the associated questions in the conclusion area of their lab report.


9-12.I.B.1 – The student will design and complete a scientific experiment . . .
9-12.I.B.2 - The student will distinguish between . . .
9-12.I.B.3 - The student will apply mathematics . . .
9-12.I.B.4 - The student will identify possible sources of error . . .

References and Resources