Where Do Chemicals Come From?

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Objective

SWBAT obtain, evaluate and communicate Information about the origin of elements found on the periodic table.

Big Idea

A great article from ChemMatters that answers students questions about elements, the periodic table and their origin.

Introduction

This lesson is aligned with NGSS HS-PS1-1, "use the periodic table as a model to predict the relative properties of elements based on the patterns of electrons in the outermost energy level of atoms" and aligned with PS1.A: The periodic table orders elements horizontally by the number of protons in the atom’s nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states.

The lesson answers the questions that many of my students ask:  How are all the elements made, and are there any more?  

In this lesson students explore the periodic table using the Science and Engineering Practice (SEP):  Obtaining, evaluating and communicating information.  In this lesson my students read a ChemMatters article that details how elements were formed billions of years ago and how they relate to everyday chemistry.  The origin of elements is not explicitly stated in HS-PS-1-1. However, the lesson does provide students with answers to the common question about where elements come from and furthers their understanding of the distinguishing features of elements, in addition to adding a reading and writing literacy component to the class.

 

Review/Homework check-in

10 minutes

In lesson three of this unit my students colored the periodic table and answered questions about the major characteristic of the periodic table (PT).  I start this class by checking in the lesson three assignment (available in lesson three) and giving them credit based on completion: 10 points for coloring and 10 points for answered questions. This takes a few minutes as I walk around the room.  While I am doing this I have a copy of what their periodic table and answer sheet should look like on the document cam, so they check their work for accuracy. 

After checking in their work I formally go over the periods, families, metals and nonmetals, and the summary questions from the previous day's lesson. A complete understanding of this information is   important as we progress through the unit learning about ions, bonding and forces of attraction.  They need to know that:  1. metals and nonmetals have certain properties, 2. whether an element is metal or nonmetal will determine whether its atoms gain or lose electrons to form ions, and 3. families (columns or groups) of elements have common properties based on number of valence electrons.

 

Explore

15 minutes

The purpose for this lesson is to answer some of the questions that have been posed about the origin of elements, but also to introduce to the Science Practice of Obtaining, evaluating and communicating information through discourse.  The hope is that students will think about where they are getting their information -- whether it is a fact, opinion or just a guess.

As students came into class they picked up a copy of the ChemMatters article, Where Do Chemical Elements Come From?  I cannot post this lesson due to copyright laws, but it is freely available at ChemMatters.com by searching Where do Chemical Elements Come From?

I start this part of the lesson by asking the question, does anyone know how many elements there are? Most students say 117 based on the periodic table that they have. 

I follow it up by asking, does anyone knows where they came from? Common responses are: The Earth, the sky and man. 

I then ask if they can justify their responses.  Many struggle with this question because at the high school level children are still developing the necessary critical-thinking skills needed for this type of communication. As the semester progresses, the hope is that their ability to justify and communicate thoughts will allow them to engage in higher-order thinking--one of the Science and Engineering Practices, and goals of this lesson.

 

Individual Exploration

After engaging in the brief discussion I introduce the article and tell them that they are going to explore the origin of elements as a group. I then place students into groups of 4 students based on the six sections the article will be broken down into:  Introduction, Stellar Ovens, How Stars Make Elements Heavier, Exploding and cooking Elements at the Same Time, Our Stellar Origin and Find Chemicals Inside of Stars.  If there are more than 24 students in class I will create an extra group to read the longer section, Stellar Ovens.

Prior to reading, I assign each group a heading and encourage them to highlight, underline or annotate the important part of the section they are reading to help them organize their thoughts. I also provide roles for each student, 1-4: 1 is the leader, 2 is the recorder, 3 is the time keeper and 4 the presenter.  See my role reflection for more explanation of my rationale for this structure.

At this point I instruct each person in the group to take 7-10 minutes to read their section silently and each individual in a group is responsible for reading the section silently first.

While they are reading I monitor their progress and gage how much time to give them. Typically 10 minutes is enough time even for the longest passage (Stellar Ovens). 

Group Exploration

After reading the article I ask them to take 5 minutes to organize their collective thoughts about their selected passage on paper into a 1 minute summary.  This is where I remind them it is key that all people participate and follow their roles.

As they are summarizing, I walk around and listen to what is being said because a teaching challenge that is encountered during a jigsaw is students sometimes struggle with context that is fragmented into separate sections. This is easily addressed by asking them to write down what they’ve learned, and attaching the reading to prior knowledge. 

After 5 minutes I make sure all recorders have written down their group information so they can share it with the class

Explanation

20 minutes

This part of the jigsaw is where the SEP around communication (SEP 7) is truly established because most groups have developed a curiosity about the information other groups have read.  This stimulates a great deal of conversation and questioning that make the information more authentic, and really drives the conversation to a deeper understanding of the periodic table.

As my students are sharing their section summaries, I ensure that the key points are covered in each of the sections: 

  • Introduction-26 elements were formed in the stars and these elements traveled through space and ended up in planets
  • Stellar Ovens-Protons and electrons can combine to form heavier elements like helium, but not heavier than iron.
  • How Stars Make Elements Heavier-Neutron combination is responsible for elements heavier than iron.
  • Exploding and cooking Elements at the Same Time-As stars get heavier they explode and create heavier atoms through neutron absorption and beta decay.
  • Our Stellar Origin-The Big Bang is responsible for matter being spread out throughout the universe, and we are all made of cosmic dust (formed in stars) from the Big Bang.
  • Find Chemicals Inside of Stars-Elements can be identified from the light that is emitted from gases, and associated with electrons.

After about 20 minutes of sharing, we move on to the evaluation portion of the lesson.

  

Evaluation

5 minutes

After we are done with the "jigsaw", I have students share about how their understanding of matter and the periodic table has changed after reading this article. 

I call this activity One Big Idea which is a quick summary that gives a general idea of how their thoughts about a topic have changed from beginning to end.  I do this because it ties into the Big Bang Theory and the idea that all things originate from an beginning thought.  

I have students share their Big Ideas for the last five minutes. I typically do this randomly or by asking for volunteers, but this time, instead of taking volunteers for this part, I picked students who were in the time keeper roles.   I picked the time keepers since their roles were fairly insignificant and I wanted to assess what they learned. Also I wanted to remind all my students that they will be responsible for their thoughts during group discussion regardless of the role they have.