Soil Salinization Lab

One of the most common (and important!) labs in AP® Environmental Science is the Soil Salinization Lab.

There are many versions of the lab that are great. This is mine.  It has been altered and changed with ideas from lots of teachers over the year.

(Side note:  I am a HUGE fan of inquiry, but I do not do an inquiry lab for this topic for a couple of reasons.  I want kids to do a proper controlled experiment before they do experimental design later on. They can refer to this lab when they are designing their own later in the year. This is part of scaffolding. With each controlled experiment (such as Ocean Acidification), I remove more instructions and parameters. Another reason is that I also want the kids to test specific concentrations of salt, because we use the results for an LD-50 lab later in the year.)


Supplies needed for the Soil Salinization Lab. These are provided for each group of 4 kids.
  1. Seeds
  2. Graduated cylinders with optional pipets to help kids with precise measurements. Mark one graduated cylinder for the 5% solution and one for the distilled water. Same with pipets. This prevents cross-contamination. Train the kids to be careful and prevent cross-contamination. Even a couple of drops of salt left over in a graduated cylinder can influence results.
  3. Overhead markers
  4. Scissors to cut paper towels
  5. 5% salt solution (mix yourself)
  6. Distilled water
  7. Beakers
  8. Petri dishes or ziploc bags. Petri dishes can be reused for an air pollution lab-Airborne Particulates.

Prepare a 5% salt solution by mixing 5g of NaCl (Table salt) with 95ml distilled water. Make enough for your classes.  I make about a liter for my 5 classes of APES.

I like pea seeds and prepare these containers for the groups. Tell the kids to keep covered to prevent fungi contamination. Fungi does ruin the soil salinization lab on occasion. I’ve had it happen once in 12 years. Use very clean petri dishes and keep beakers covered when not in use to prevent this.

Cover the seeds to prevent fungi spores from contaminating the lab

What seeds to use?

I’ve used peas, mung beans and radishes for soil salinization over the years. My favorite is peas, but the others work as well. Radishes tend to have lower tolerance to salt. You can even have students test different seeds in different groups. Mung beans sprout quickly and have a nice tolerance to salt as well.

Radish germinate quickly, but have a lower tolerance to salt
Mung beans are nice, but hard to find sometimes. They need longer than 2 days to get good results.
My favorite is pea seeds. This is after two days, but we usually take data after 3-4 days so the kids can measure a longer sprout.
This is a bit longer than I like to leave the seeds. They begin to degrade and smell. The best time is 3-4 days.

Using Ziploc Bags

I use snack-sized Ziploc bags with my online APES class that I meet with on Saturday mornings a few times a year. The bags are convenient as I don’t need them back when the lab is over and they’re inexpensive.  In my regular classes, I prefer petri dishes as they can be reused from year to year and are easier for the kids to work with the seeds.

The write up using ziploc bags can be found here.  I also use a Flipgrid conclusion so they can film their results and show me at home.

Use a sharpie to mark the bags and create a paper towel “taco”. Wet the paper towels before putting the seeds in or they roll around too much.

Day 1 of the Lab

Go over the first page of the lab together with students.  They have difficulty with the terms (control, variables, constants) if they’re out of practice. Also, teach the students to use words such as “increasing” or “decreasing” in their hypothesis as this is good practice for FRQs.  Its also more of a “collegiate” and precise hypothesis.

Students need to do the math for serial dilution before beginning the lab. I usually go how to do the math and then they can easily solve.

After doing the math, they can prepare the soil salinization dishes.

Make sure they use separate graduated cylinders for 5% NaCl solution and distilled water. Have a “mixing” beaker to mix the solution before pouring over the seeds. This makes sure that the solution is evenly mixed.

Students preparing petri dishes

Best way to prepare the dishes

Make a paper towel taco and place seeds inside
Pour solution over the seeds
Cover with the top of the taco
Tuck in the sides. If towels stick out, they will wick moisture out of the dish and the dish will be ruined. Label with an overhead marker so the ink can be washed off when finished.
Stacks of completed dishes. 9 stacks of 6 dishes for one period.

Day 2 the lab (3-4 days later is optimal)

Students will take data on the # and % of seeds that germinated and measure the sprout length. I tell students to measure the longest sprout in each dish.

Measuring the sprout in mm
Students sometimes have trouble knowing if a seed germinated so I have this drawing to help.

Results take about 15 minutes. Then students wash and dry dishes. I store and use the dishes again for an air pollution lab and again next year.


Electricity 5E using Kill-A-Watt Meters

Updated Spring 2019!

This year, I revised my Kill-A-Watt lab with a lot more math, better leading questions to help students to figure out the concepts, a phenomena that is referenced throughout and an Evaluate with solutions. The lab with an answer key can be found here.

Students always need more math and so this updated version has more calculations based around different strands of Christmas Lights. It brings in the concept that cheaper devices break more often and have more economic consequences as well as being more expensive in the long run. 

The math is challenging for students. They needed some scaffolding and we worked through the first part of #17, 18 and 19 together.

I added an “Evaluate” section which has students find solutions to reducing energy. This is surprisingly tricky for students. The question asks them to find ways to REDUCE energy use. Kids automatically think solar and wind and electric cars. None of these reduce energy–just switches to a more sustainable form. Kids need to learn to answer the prompt carefully.

Bar graph of the wattages of various appliances and electronic devices.

In addition, I added a video at the beginning to engage students as a short phenomena–admittedly its not a great phenomena in the idea NGSS way, but it is really engaging, makes students confused and helps bring together some difficult concepts. I refer to it several times throughout the lab. Note: It is a strange video and a little shocking for students. The link is on the answer key in the lab. Use your own discretion on whether to keep it or not. I found it effective to help students understand a lot of concepts about developing countries, tourism, energy etc.

Original Post

Recently, I received a grant for Kill-A-Watt meters and implemented this new lab.  It teaches students about electricity, watts, math and conservation using Kill-A-Watt meters. The kids were SUPER engaged (so were adults who came by) and it was highly relevant for not only their lives, but the energy concepts they need to know.  My AP® Environmental Science students did the lab, but the AP® Physics B teacher will also use this year.

Click for a copy of the lab.

You will need to alter the copy to reflect the cost of electricity in your town and the specific appliances that you have or want to use in lab.

Supplies Needed

  • Kill-A-Watt Meters:  I had one meter per lab table with two items to test at each table.  I ordered the Kill-A-Watt EZ model from Amazon.  But, I also like the regular model too.   The EZ model lets kids see the cost of electricity more easily, but the regular model is easier to use and find the “watts”setting.  Either are fine for this lab. (But, if you use my write-up, be sure to change some of the instructions if using the regular model).

In order to afford 10 of them, I wrote a grant request on Donors Choose and was funded in a few days by two corporate sponsors.  Here is a post about my favorite ways to find funding for new labs. 

  • Various appliances from your science room or from home.
  • Power Strips (optional).  The plugs in my lab are on the sides of the tables so I found power strips were very helpful. That way all the kids in a group could see the meter when it was plugged in.  I ordered a few of these to have ready next year.  If your’e writing a grant, be sure to add a few of these, if needed in your lab.
    The plugs in my lab are on the sides of the tables which means only 1 person out of 4 could see the meter AND they’d have to turn sideways to do it. Instead, I placed a powerstrip on each table to bring the meter to the top and all kids could read the meter.
  • Christmas lights (optional, but really engaging for the kids) .  I was fortunate to find regular and Energy start Christmas lights at Target in October, but I couldn’t find LED lights so I ordered online.  They were pricey, but I only needed 1 strand and it will last for several years for this lab. (And I can use to decorate my classroom for Christmas!)
    LED, Energy Star, and regular Christmas lights. All were 100 count strands for comparison.

Lab Setup

I had two devices per lab table and meter.  The students rotated from table to table.  I utilized items in the lab whenever possible, like this TV.

The two appliances at this station were the mounted TV and a portable heater.
Large and Small Battery Chargers. The larger one drew more watts, but is also a rapid charger.
Safety warning for the space heater. The heater isn’t dangerous as it has safety mechanisms, but I put a note on just as a precaution.
Apple phone charger and a Micro USB charger. The kids plugged in their own phones. They needed to try two different devices.  Some groups only had iPhones so they had to compare models.
Goggles sterilizer and microwave. It was interesting that the goggles sterilizer (UV light) used the same wattage when plugged it whether it was turned on or off.
A blow dryer on high, low, hot and cold made interesting data.

Data-Explore section

Students took data on a chart and then created a graph.  I had a Kill-A-Watt meter set up at each lab table along with 2-3 appliances and then set a timer for kids to rotate every 4-5 minutes.  I had 9 tables and it took about 45 minutes to rotate to every table.

If kids finished that station before the timer, they worked on the bar graph of their data chart.

The LED desk light only drew 2.8 Watts

Explain-Vampire Power and Conservation

I showed a couple of videos helping explain some of the data that kids see.  I wanted them to notice the appliances that still drew power even when not turned on.  Many students have never heard of this.  I also wanted them to see good examples of energy conservation.

Elaborate–Math Calculations

Kids did A LOT of practice with energy math–which they need for the AP® Exam.  It is also needed in real life.  In addition, they discussed the environmental and human health costs of electricity.

Evaluate-Providing Solutions

Students need a practice in this for the new FRQs in 2020. This is surprisingly tricky for students as they often don’t answer the specific question. 

Students need to think of three ways to conserve electricity or energy in each of the following categories. Remember CONSERVING energy is not replacing it with solar, wind, electric cars etc. Replacing with solar, wind, etc. uses the same amount of watts, but in a more sustainable way.

This video has some ideas (warning, the last few seconds are a little racy)

Students also referenced Disneyland’s energy website:

* AP® is a trademark registered and/or owned by the College Board which was not involved in the production of, and does not endorse this site.


Tragedy of the Commons 5E

A great way to teach Tragedy of the Commons is with a “fishing” activity.  There are many ways to run this simulation that are wonderful. Some teachers use goldfish crackers, some use M&Ms, and some use reusable beads. I use colored marshmallows, because they’re the cheapest “food” option for my large classes.

Colored mini-marshmallows are the cheapest way to do the lab with food items.

This is my “Happy Fishing” 5E. It is taken from many sources and meshed together with questions that help lead the students into learning about resource use and depletion.

In a good 5E, the title of the lab doesn’t give the concept away. Our students are bright and will google the title “Tragedy of the Commons” on their phones to make sure they get the right answers. Our brightest are often the most uncomfortable with inquiry.


In the “Engage” section, students discuss what are resources that we all share.  Ask for volunteers and acknowledge their answers with a “thank you”, but don’t correct them. Tell them that you aren’t going to say if they’re right or wrong right now.  We will go back to the question and make corrections at the end of the 5E. Remember, don’t use the term “Tragedy of the Commons” yet.

Many times, I will have two separate copies.  One with Engage and Explore  and Explain and then the other with Elaborate and Evaluate.  This prevents students from looking ahead to try to get the “right answers”.


Supplies needed per group of 4.

Divide students into groups of 3 or 4.  Write how much each color of “fish” (marshmallow) is worth on the board and have the students copy on their data sheet.  I try to estimate which color I have the most of in the bag and make that color worth the highest amount as students tend to make that color reproduce (if they’re strategic).

Written on the board for students to copy down.

Tell the students that they are competing with each other for extra credit. The winner of each group gets extra credit and the winner (most $ earned) for the class earns more extra credit.  Read over the rules with the kids. You will find that many don’t listen as they’re intent on figuring out how to get the extra credit.

Demonstrate how to make a “net” using tape and straws and a paper towel boat. While they’re making their nets and boats, load up their plates with 5 marshmallows of each color.

Students make a net with a piece of tape between two straws.

A piece of paper towel is their “boat”

Remind them of the rules. Then, “ready, set, fish!”. Time them for 30 seconds and yell “stop”.

You will find that half the groups have depleted their ocean.  I say “now I will come and add babies to your ocean. Two babies for each two of the same color that’s left in the ocean”.

This is when the groups who depleted their ocean go “oops”. I say “for this round only, you may choose to throw some back into the ocean”. They will, but many will have a hard time deciding who gets to throw back fish and they usually won’t throw back very many.

The following video shows my students at the beginning of the lab and how I handle the first year when kids deplete their oceans:

Tell them to fill in their data charts for Year 1.  There are 3 charts to fill in for Year 1.

Remember, this is inquiry so don’t discuss the term “Tragedy of the Commons” yet. Let them figure out the concept about resource depletion before giving them the term. This is called constructivism and is how students best learn and retain information.


Students who left behind some fish


Students who planned well and let their fish reproduce.


Example data


The explain portion is where students work through guided questions in order to discover the scientific concept on their own. Don’t mention the term “Tragedy of the Commons”. Vocabulary and terms come later.

Help the kids with certain questions by asking if any of them fish and what the laws/regulations are.  Most kids have at least a couple of kids who fish and know the answers.

Students will write a Statement/Claim about how shared resources can be depleted and how to sustainably manage them.

This is the time in a learning cycle that you check for understanding. Go around to each group and quickly read the statements. Clear misconceptions.

Students may struggle with this task at first, but will get used to it later with more inquiry or 5Es. Be careful not to give away too much information. The more that they can struggle with and then reason out themselves, the better they retain and understand the information.


Students will watch 3 videos that help them understand Tragedy of the Commons in more detail and how its used in real life.

This video shows how rules and regulations are enforced:

This video reinforces the concept of Tragedy of the Commons and solidifies how people need to work together:

The video discusses other commons beyond just fishing:

After these videos, have students go back to the ENGAGE section and make corrections about commons.  Make sure kids know that a commons is PUBLIC resources, not private. Food, oil, gasoline, and private land do not work. If they say “forests”, make sure they know to write National Forest on an FRQ since much forested land is privately held.

Water is trickier. In some places (like the Eastern US) water is a commons, but in the Western US, there are complicated water rights. But, cities may own water rights but manage the rights for all the cities so the water functions as a commons.  But, privately owned wells or water from streams and rivers aren’t a commons.


The evaluate section here isn’t very long as it doesn’t need to be. Kids need to practice succinctly writing and being able to get the point across with detail without writing too much. This is practice for FRQ writing.



Ocean Acidification Experimental Design Lab

Students learn not only about the effects of increasing acidity in the ocean on marine organisms, but also practice their experimental design skills in this Ocean Acidification Lab.  In addition, the lab helps students practice NGSS Science and Engineering Practice #3: Planning and Carrying Out Investigations.  Click for a copy of the lab.

Materials Needed for Ocean Acidification Experimental Design

A box of donated shells

  1. Shells:  MUST BE MOLLUSCA (Flat shells like clams, mussels, and scallops). NO GASTROPODA (Snails). Too much solution gets stuck way up in the Gastropod shells and will actually cause the mass to increase and not decrease due to water weight.   Ask students to donate shells. Many have boxes in the garage that are no longer wanted. You can also go to a seafood restaurant and ask for their clam, mussel or oyster shells. I like to eat pasta with mussels at home so I save my shells sometimes.  You can also buy at craft stores, but they are usually very small and not the best for the lab, but will do in a pinch.
  2. Soaking cups or small beakers. I use soaking cups since I don’t have enough beakers for multiple classes to soak for several days. I buy small plastic cups at Smart N Final (a restaurant/public supply store). The 5 1/2 oz size is a good size for this lab. Plastic drinking cups are fine as well.  I allow students to have 4 cups per group (I have groups of 4 kids).
  3. Vinegar as the acid.  Some teachers use other acids, but since I don’t teach chemistry, I find vinegar the easiest and it doesn’t have to be specially disposed of.
  4. pH testing: You can use pH paper , but a meter will help the kids with more exact pH measurements.  The other problem with pH paper is that vinegar drops the pH so rapidly that many of the cups will have a similar pH and students need to see the slight different that a pH meter will show. Probes are better, but many cheap ones break over time.
  5. Two graduated cylinders per group. Use one for water and one for vinegar to avoid cross-contamination.
  6. Two plastic disposable pipets per group (optional). Helps students measure precisely using the graduated cylinders.
  7. Water: I use tap water since my tap water is slightly basic which mimics the ocean. Tap water also has minerals which is similar to the ocean. If you can, collect ocean water for more authentic results.
  8. Scale: Any electric scale is good as long as they go to the tenth place in grams. I have a set of pocket scales that I ordered using a Donors Choose grant. If you have some money, pocket scales are inexpensive $10-15 and nice for groups to have their own.  Amazon sells them for cheaper than science supply companies. I have this type of scale in my lab
  9. Sharpie to mark the cups
  10. Hammer (optional) for shells that are too big for the cups.

Need idea for funds to purchase new equipment?  Read about my favorite sources for funding.

Supplies needed

Some shells are too big for soaking cups.

Use a hammer to break into pieces

Each cup gets a piece


Students discuss the design in their groups and fill in the lab paper. I have all the materials they can use in the middle of their table to look at as they brainstorm. The visuals are good for many students such as English Learners and Resource kids. I let them handle the materials also as they figure out how to set up the lab.

Students must get 3 different signatures/initials from me. Most groups need to refine their initial question to make it more “high-school” level. (NGSS SEP #1).  I ask them to use words such as “increasing” and “decreasing”.  This also helps them refine their language in a way that is beneficial on AP® Exam FRQs.

  • One cup must be a control with water and shell only.
  • Students may not use more than 50% vinegar. (You can even make this number smaller)
  • Students need to figure out the total ml of solution in each cup as a constant. They can do this by testing how much solution is needed to cover the shells using a graduated cylinder.
  • Its best to direct the students to use % of vinegar in their cups instead of designing around pH. If students want 4 cups with pH of 7,6,5,4 for example, this is very difficult as it requires a titration and will take students FOREVER in the lab to make their cups. Instead, students should have cups with 0% vinegar, 5%, 10%, 25% etc.  They can decide which ones–that’s the point of experimental design.

A procedure is optional for my students.  I have them outline what’s going in each cup (amount of water and vinegar) and many draw pictures on their paper.  Once they have this information, a procedure is usually not necessary. But that’s up to you.


Students need to find 4 shells that are as identical as they can find (species, thickness etc).  They can also take a larger shells and break into 4 pieces.  The mass of each doesn’t have to be the same, because students are measuring percent change.

Students need to record the mass of the shells before soaking.

Students prepare the four cups using the materials.

After making concentrations, students record pH of the soaking cups.

Students need to rinse pH probes after using each time. Otherwise, trace amounts of vinegar will skew the results of subsequent cups. Make sure the students face the pH meters downwards or water will damage the electronics. (Learned the hard way)

Finished cups labeled with a sharpie

My students store in trays. Use whatever you have for storage.

Shells stay in solution for 3-4 days (or longer)

Three to Four Days Later (or more)

  1. Students remove shells from soaking cups.
  2. Students need to measure the pH again.  This is a great time to talk about buffering!
  3. Students dump solutions in the sink and replace shells in their cups (make sure they don’t mix them up)
  4. Allow shells to dry for 2-4 days.  Shells MUST dry all the way or the students will measure an increase in mass due to water weight.

Buffering (from my chemistry buddy, Laura Solarez)

The pH will rise during the soaking time due to the release of Calcium Carbonate from their shells. The resistance to a pH change with the addition of acid is known as buffering.  This is an important concept when teaching about acid rain or acid mine drainage.

As the calcium carbonate from the shells dissolves, it binds with the acid, neutralizing it.  In this lab, CaCO3 + HC2H3O2 (vinegar) –> CaC2H3O2 + CO2 + H20.  The bubbles seen in the cups are CO2 and H20 as the reaction occurs.

Calcium carbonate is the same component of limestone that is added to reduce the amount of acid in lakes from acid deposition.

In water saturated with CO2, in the oceans, the calcium carbonate can form calcium bicarbonate, but it is still weakened and will degrade the shells.  If the water is acidic, it will try to neutralize the acid, breaking down into CO2 again and adding more CO2 to the oceans.

Three to Four days later (or more) when the shells are completely dry.

Students now measure the mass of their shells and calculate percent change.

After shells have dried for 3-4 days, students take the mass again.

Assessment can follow in many different ways as you prefer.  Graphing, analysis questions, referencing articles about ocean acidification, formal lab write-up, Claims Evidence Reasoning, etc.

I like to do group lab reports for this lab.  You can read about how I do that here.

Owl Pellet Dissection-Trophic Levels and Energy Loss

Owl pellet dissection is used to teach ecology topics such as food webs, biomass pyramids and energy loss.

Buying Pellets and Materials.

Both small and large pellets work with this lab. I’ve used small when my funds are more limited and large when they’re not. Large pellets give more prey per pellet which is fun for the kids.  If you don’t have enough science funds, here’s some suggestions on where to find additional money for your science classroom.

I buy one pellet per team of 4 students due to cost. This is not ideal, but they are only dissecting to count the prey–not to identify all the bones or do anything else with them.

The pellets are sterilized, but I provide gloves for kids who prefer gloves. My pictures show dissection trays, but they’re not necessary. A paper plate or a paper towel works just as well.


Since I try to teach inquiry-style with the 5E learning cycle, I don’t want to pre-load information into the kids’ brains. I do, however, want them to see where owl pellets come from and basic dissecting techniques. I assign these videos the night before on Edpuzzle, but these can also be shown in class prior to the lab.

Phenomena-based video of baby owl regurgitating a pellet.

Basic information and dissection techniques.

Dissecting pellets

There are many variations of the owl pellet lab which are wonderful.  My copy is a 5E learning cycle which was adapted from the original creator.

Kids can use their fingers or tweezers to take the pellet apart. Provide reference sheets. Many can be found for free online.

Bone sorting chart found on Pinterest. I added some more info (like the size of mouse vs. rat skull or “2 per animal”) before copying.

I altered this reference sheet to help kids correctly identify a mouse vs. a rat. I make kids measure as they don’t readily know how large 1 cm is.

Mice skulls are usually 1 cm. Many students tell me they have a mouse and I say “have you measured it?”. When they do, they find out its a small rat.

I combine ecocolumn data along with owl pellets at the same time so 4 kids have more tasks to do. Two kids take ecocolumn data while the other 2 kids in the group dissect the pellet.

After about 20 minutes both pairs are finish and all 4 of them will do calculations and answer questions on their owl pellet papers together.

Calculations and Analysis Questions

(I want to give a shout-out to the original creator of this lab–the famous Dr. E)

Students take their data and fill in a chart. The entire chart is NOT filled in.  Most of the prey will be a rat or mouse. Students always think they found something else like a mole or shrew, because it sounds more interesting, but unless they can ID a skull, it  probably isn’t. (I have some kids who think they have a shrew, because the ribs they find are so skinny….)

Sample data. Point out to students that they will have zeros for some rows animals.

Next, the students create a numbers pyramid and a food web. I draw a pic on the lab white board to help them.

This is in the lab to help them with the numbers pyramid and food web. The food web is partially complete.

For the food web, you can choose to have students create a food web from just the prey found in their pellet or from all the prey the owl could eat.  I choose the first option (but am thinking of switching to the second for next year to give them more practice with a more complicated food web).

Next comes a biomass pyramid which is the crux of this lab in terms of calculating energy loss.  Students need to complete the biomass chart and then draw a pyramid. I have detailed instructions on the lab paper on how to do that since it confuses them.  

Sample paper with biomass chart, biomass pyramid and energy loss calculations.

Working in groups for the questions is helpful so they can hash out what the correct answers should be and learn better. I flipped my class last year so I have the luxury of time to allow an extra day to do this.  Students are often confused that the energy “loss” from the prey to the owl is over 99%. They need to understand that 90% energy “loss” is an average and they will hypothesize why the loss is this lab is so much higher (the owl doesn’t weigh very much for being a top predator).  Its good for them to question their numbers, however, if they seem “off” as that is a good skill for the math is this course.  But, in this case, its correct.

The questions also discuss that energy is not really “lost”, but becomes heat and an unusable form for food in ecosystems–1st and 2nd laws of thermodynamics.

Normally, I have the kids write a conclusion and submit through, but this year, I had them do an oral conclusion on Flipgrid. The results were much stronger in terms of understanding energy loss than if they did the conclusions by themselves.  Much of the AP® Exam is higher level thinking and students can help build these skills by working together.