Chemical Bonds Lab

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Objective

Students will be able to discover what type of bond (ionic, covalent, polar covalent, metallic) holds atoms together by experimenting with three substances (epson salt, sugar, iron filings).

Big Idea

Learning about bond types is more engaging when students can experiment for themselves.

NGSS Background

This lesson is based on California's Middle School Integrated Model of NGSS.

NGSS Performance Expectation (PE): (MS-PS1-2) Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occured.

Science and Engineering Practice (SP) 4: Analyzing and Interpreting Data

Disciplinary Core Ideas (DCI): PS1.B: Substances react chemically in characteristic ways.

Crosscutting Concept (CCC): Energy and Matter

With this lesson the students test three substances (epson salt, sugar, iron filings) in order to determine which type of bond is holding the atoms together (ionic, covalent, polar covalent, metallic) (MS-PS1-1). The students collect data and analyze their observations to make a scientific conclusion (SP4). Based on their collected evidence, students prove what type of bond is present in the material. They discus the evidence with their peers to prove which type of bond corresponds to each substance.

Set-up (Prelab)

25 minutes

In this lab investigation, students test three materials (epson salt, sugar, iron filings) to determine which type of bond (ionic, covalent, polar covalent, metallic) holds their atoms together.

Materials Needed

  1. Goggles (student safety)
  2. Small light bulb
  3. 9v battery
  4. 9v battery connection
  5. Electrical wire with alligator clips
  6. Copper strips (2)
  7. Test tubes (3)
  8. Test tube rack
  9. Test tube clamp
  10. Candle
  11. Spoon
  12. Hand lens
  13. 200mL beaker
  14. Black construction paper (5"x5")
  15. Epson salt (Magnesium sulfate – MgSO4)
  16. Sugar (C12H22O11)
  17. Iron filings (Fe)
  18. Distilled water (H20)

TIP: The quality of your iron filings greatly determines the success in determining metallic bonds. in the past I have sent students to the elementary sand box with a magnet and zip lock bags to collect iron filings. Purchasing from a science catalog provides high quality iron filings.

Four tests will be conducted on three materials (epson salt, sugar, iron filings).

  1. Observe with a hand lens (looking for a crystalline structure - property of an ionic bond)
  2. place the material between the electrical testing kit (testing electrical conductivity - property of a metallic bond)
  3. dissolving the material in distilled water and using the electrical testing kit (testing electrical conductivity dissolved in a polar liquid [water] - property of a polar covalent bond)
  4. burning over a open flame (low melting point - property of covalent bond)

A tool the students will need is an electrical testing kit. If you have a class set of volt meters this will work fine or you can build your own with a 9v battery, 9v battery connection, small light build, wires with alligator clips, and two strips of copper (see photo).

Student Activity (Lab)

45 minutes

To begin, students:

  1. Complete the Chemical Bond Properties Chart - BLANK document. TIP: I project the Chemical Bond Properties Chart and have the students copy down the properties of bonds before they perform the lab.
  2. Assemble and test the electrical testing kit.

Pass out a copy of Chemical Bonds Lab to each student. This document has directions/procedures, space for the students to record their observations, and answer questions. 

Laboratory Procedures (students record their observations after each test):

Epson salt (MgSO4)

  1. Place dry Epson salt (MgSO4) on dark paper and observe with the hand lens if the material has a crystal structure. 
  2. Put the Epson salt (MgSO4) between the copper strips. 
  3. Add a small amount (pinch) of Epson salt (MgSO4) to the beaker and stir well. Place the copper strips in the water. 
  4. Put a small amount of Epson salt (MgSO4) into its own clean test tube. Call the teacher over to light the candle. Hold this test tube over a candle for two minutes

 

Sugar (C12H22O11)

  1. Place dry sugar (C12H22O11) on dark paper and observe with the hand lens if the material has a crystal structure. 
  2. Put the sugar (C12H22O11) between the metal strips. 
  3. Add a small amount (pinch) of sugar (C12H22O11) to the beaker and stir well. Place the copper strips in the water. 
  4. Put a small amount of sugar (C12H22O11) into its own clean test tube. Call the teacher over to light the candle. Hold this test tube over a candle for two minutes

 

Iron filings (Fe)

  1. Place dry iron filings (Fe) on dark paper and observe with the hand lens if the material has a crystal structure.
  2. Put the iron filing (Fe) between the metal strips. 
  3. Add a small amount (pinch) of iron filings (Fe) to the beaker and stir well. Place the copper strips in the water. 
  4. Put a small amount of iron filing (Fe) into its own clean test tube. Call the teacher over to light the candle. Hold this test tube over a candle for two minutes

 

Publish Results (Postlab)

20 minutes

As a final assessment of what they learned I have my students draw four pictures on a graphic organizer representing the four types of chemical bonds we learned during this investigation. The pictures must have a title, labels, minimum of three colors, and provide a simple explanation of the type of bond.

The students will build a graphic organizer from an envelope and present their display stands to their shoulder partner. This Notebook Foldable was inspired by Dinah Zike Graphic Design Foldables for Science. The graphic organizer is stored within a sleeve of their Interactive Science Notebook.

A simple sleeve can be glued into the Interactive Notebook with white glue (see video below). TIP: Your students must be taught to use as little glue as possible - I tell my students that "ozzers are losers".

To build this particular graphic organizer seal a 9"x12' manilla envelope and shave the two longest edges from the envelope. Fold the envelope in half and crease this fold. Open up the envelope and you have a 9" tall square column. Each side is decorated with one of the four types of chemical bonds.

TIP: Be careful to set a firm deadline of completion. I have found that having it due at the end of a class period is better than letting is go home as homework. I have not had success with assignments like this being done as homework.

 

Extensions

60 minutes

To help my students learn about chemical bonds I have created a mnemonic sentence to remember the four types of bonds

I can play music.

Ionic

Covalent

Polar Covalent

Metalic

I have also included Chemical Bonds - a powerpoint that teaches the four types of bonds.

As the students are watching and taking notes on the lesson they are also filling in the Chemical Bond Properties Chart - BLANK. This chart is glued into their Interactive Notebook. If any student needs a completed chart, I included the Chemical Bond Properties Chart - a completed version.