Radiometric Dating

Last week, we learned about Darwin’s voyage and how he collected data to formulate his theory of evolution.  We went on to study biological classification, using the system devised by Linneaus way back in 1735.  Previously, we learned that scientists collecting were able to date common ancestors of humans to over 3 million years ago.  Our work over the next few days will be to learn how scientists use radiometric dating to estimate the age of really old samples.  We will begin an introduction to chemistry, focusing our efforts on understanding the difference between carbon-12 and carbon-14 atoms.  Class notes are pictured below:

Next, we will watch a video introducing radiocarbon dating:

After the video, we will begin the Radioisotopes Activity.  We will read through the first few pages, and then tomorrow students will work with a partner to complete the activity which is anticipated to wrap up by Wednesday.

Acids and Bases

For the first lesson of chapter 16, students were formally introduced to acids and bases via a lab.  We began class with the Lesson 84 PowerPoint which included a starter question helping students connect acid/base chemistry with the biology of heartburn.  After learning about indicators, chemical solutions that change color in response to changes in pH, we reviewed the Lesson 84 worksheet.  For Part 1, students were instructed to number the nine solutions in order, with the number on the worksheet corresponding to one of nine numbered flasks containing the indicated solution. An image of the lab setup is shown below:

After students complete the lab portion of Part 1, they were instructed to return to their seats to complete the Part 1 analysis questions.  We will share out results as a class, and if time permits, conduct Part 2 as a teacher-led demonstration.

Universal Indicator Chart
Universal Indicator Chart

 

Red cabbage indicator chart
Red cabbage indicator chart

Example of student results with indicators – samples are arranged #1-9 in rows A and B, with cabbage juice indicator in row A and universal indicator in row B.

Part 1 Student Results

Results from the teacher-led demonstration for Part 2 are shown below:

Acidic solutions reacted with the calcium carbonate antacid tablets (Tums).