Toxins 5E Lab

Two important topics in APES are combined for this 5E–Serial dilution Lab and LC50 Lab. The lab papers needed for this lab can be found on these google doc links.
Engage, Explore, Explain
Elaborate, Evaluate
How Toxic is Toxic
LD50 of Substances

Engage: Flint, Michigan

This Engage is a short case study about lead exposure for students. Most students have heard of Flint, Michigan and its water quality problems so this adds to previous knowledge (a key component of Engage). The video piques their interest and then we discuss our own drinking water and how this problem would not occur here, because we are a newer community that does not have lead pipes. We also discuss how older cities with lead pipes can prevent lead leaching by using an additive in the water. Click to read this article explaining more about how lead gets into drinking water.

Explore: Serial Dilution

Students in AP® Environmental Science need to understand how toxins can still be prevalent in very small amounts. The best way to do this is for students to do a serial dilution. (Note: This activity is courtesy of Dan Hyke from the APSI, I attended in 2006. I have altered it and combined with LD-50 for this 5E)

Materials needed for serial dilution

As students walk through the procedure, fill in their data charts and answer the guiding questions, they hopefully will come up with the concept on their own–toxins can still be present even in very small amounts such as parts per million (ppm), parts per billion (ppb) and parts per trillion (ppt). Materials needed are: (Click on an underlined item for a link to the product)

  • Well plate
  • Plastic Pipet
  • Beaker for tap water
  • Toothpicks
  • Dropper bottle of a dye/stain/coloring such as a Food Grade Dye like FD&C Red Dye #40 Do not use regular food coloring as it dilutes much too quickly

Students use 3-4 drops of the red dye solution in the first well.  Then they fill the other wells with 9 drops of tap water. After that, they drop one drop from the previous well and stir.

Well Tray at the end of the lab

Students are often concerned when their solution is clear by well 7. I tell them that’s normal and they are to still make the transfers. They need to move the molecules in order to understand the point of the lab.

Students creatively identify shades of red and pink and learn about ppm, ppb, and ppt on their data sheet. Some students will need help with these circles. I tell them that “their brains will hurt” today.

Sample serial dilution data
Students using an online thesaurus to get creative on shades of red

Explain: Student Sense-Making

In a good 5E, students should be able to develop the concept you want them to on their own. Developing good guiding questions is your job as the teacher to lead them to it.  For this lab, students should make a CLAIM or a STATEMENT that “Substances can be in water even if you cannot see it, smell it or taste it.

Elaborate: LC50 Lab

We use the results from the salinization Lab to do LC-50. Students bring their salinization labs back to class and we collect class data. (Students save all work in their APES binder) This time, however, we want “opposite” data–the number of seeds that DIED, instead of the number that germinated.

Students fill in the chart for their group’s data and then all students copy class data. From there, using a document camera or on the board, teach students how to find the LC-50 by drawing a line from 50% on the y axis to where it hits the dose-response curve and then down to the x axis. Read the concentration that kills 50% of seeds. If you need help with this, I made this video for absent kids that may help you understand how to do this lab:


This 5E does not have its own Evaluate–rather students are assessed for these skills and knowledge on their next exam.

* 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.

Everything Ecocolumns

My students’ favorite lab is building and taking care of Ecocolumns.  This lab gives them practice in long-term data collection and a myriad of other essential topics in APES. Here are the posts you can click on to learn how to build, buy supplies and assess ecocolumns.

Prepping Ecocolumns

Buying Supplies for Ecocolumns

Ecocolumns with a Small Budget and a Big Budget

Making Ecocolumns

The following posts are the order in which students should build ecocolumns. The fish doesn’t come for 2 weeks!

  1. Cutting and Filling Ecocolumns
  2. Planting Seeds, Setting up Data Charts, Taking Soil Data
  3. Adding Bugs, Worms and Leaf Litter
  4. Building the Aquatic Chamber
  5. Adding fish

When things go wrong

Things go wrong in ecocolumns and its okay!

Data and Assessment

Group Data Analysis
Scientific Concepts Kids Should Learn in Ecocolumns

Finishing EcoColumns

Biomagnification Activity from the Monterey Bay Aquarium

I really like this biomagnification activity from the Monterey Bay Aquarium. I discovered this activity in a Monterey Bay Aquarium workshop at a conference I attended a couple of years ago.  Its accessible for different levels of learners in regular NGSS Biology and regular Environmental science and has enough technical science for AP® kids.

The materials are easy to use and cheap. My school laminates for me to make the items durable for many years.

This activity focuses on POPs-Persistent Organic Pollutants and then plastic pollution in the ocean, but we discuss mercury pollution in top predatory fish as well.

How to do the Biomagnification Activity

The instructions from the Monterey Bay Aquarium are easy to follow,  but here are some pictures that may also help.

Each student gets a card. The instructions tell you the correct proportions for your class size. Each trophic level hunts at the same time.

These are ocean “molecule” cards.

I use the center lab table in my lab, but you can do this outside or inside on the floor. I spread them out and don’t worry about turning them all over. I tell students they can only “hunt” with one hand and place the molecules in the other hand.

A sample of molecules that were picked up and counted,

Students need to tally their POPs only. Then, they write their POP total on a mini post-it note.

The first round is all the phytoplankton–about (15-20 students). The second round is all the zooplankton (about 8-9 students), then the sardines (5-6 students), salmon (2-3 students) and finally 1 human. After the phytoplankton hunt, the other hunters during their round take the tally of POPs on the mini post-it-note from the previous trophic level and then continue to hunt on the table.

Sample data from a “Salmon”

After the simulation, students answer questions, read and annotate/highlight.

A nice leveled reading for students

I make copies of pages 8-10 of the document for my students. This is nice, easy and meaningful biomagnification activity for my students and leads well into Water Quality. 

Math Differentiation in Science

Students in science classes often have differing math abilities and its difficult to cover math without boring some kids and losing other kids. One way to approach  is to allow student to have choices on how to approach the math problems. This is a form of differentiation and allows kids to take ownership of their own learning. To do this method, you will need videos of your math lessons. This is not a onerous task. I usually record a worksheet in just 15 minutes on the Explain Everything app. I upload to Youtube, or Google Drive and share the links on Google Classroom.

Since videos are recorded, students can go at their own pace and direct their learning.

Introducing Differentiation to Students

Kids do well when they understand “why”. I go over the Immediate Goal with them:

  • To practice how to do various energy word problems in order to get a good grade on Exams, the Final Exam and the AP® Exam.

And the Ultimate Goal:

  • Life is made of word problems. You can use these skills as you analyze household bills, your car’s fuel efficiency, purchasing decisions, etc.  Some of you will also need these skills in your career.

Directions for Students

  • Skim your paper/s
  • Make a choice on how to proceed 


A. Work through problems on own–persevering through difficult ones until your brain clicks and you have an “Aha” moment.  Check answers with key when finished. Sample Answer Key:

Review papers with keys.

B. Work through problems on own, when stuck for longer than 1-2 minutes on a problem, check solution and answer on key.  Then, go onto the next problem without the key.

C. Work through the easier problems on own, skip the harder ones. Then, watch the video to check answers on the easier ones and to learn how to solve the harder ones. Fast forward the video to the problems you need help with. Example Video Below:

D. Watch the videos in their entirely to learn how to solve the problems.

NOT an Acceptable Choice: Copy the solutions and answers from the key or from a friend. You will earn a bad grade on your next exam, the final exam and the AP® Exam.

  • Tell your elbow part which one you are going to choose and why
  • Can you switch later?  Absolutely
  • Can you start one way and then change?  Absolutely


Grade your students not only on completion, but also for following one of the choices. Rotate around the room to make sure they are on task. Accountability comes when students take an exam and know or don’t know how to do the problems.