Summary

In this lab, students will investigate trends of the periodic table by examining samples of six elements. Students will use observations about the elements’ appearance, conductivity, and malleability to determine whether they are metals, nonmetals, or metalloids. They will also see how these elements, as well as two more in a teacher demo, react with water and use this information to make claims about reactivity patterns in the periodic table.

Grade Level

Middle School, High School

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

• 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 occurred.
• 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.
• HS-PS1-2: Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.
• Scientific and Engineering Practices:
  • Analyzing and Interpreting Data
  • Engaging in Argument from Evidence

Objectives

By the end of this lab, students will:

• Better understand trends of the periodic table.
• See the difference between metals, nonmetals, and metalloids firsthand.

Chemistry Topics

This lab supports students’ understanding of:

• Trends of the periodic table

Time

Teacher Preparation: 20-30 minutes

Lesson: 45-60 minutes

Materials

Part I & II

• Element samples: silicon, magnesium, aluminum, sulfur, calcium, carbon
• Well plate
• Water
• Conductivity meter (such as Flinn’s conductivity meter or similar)
  

Teacher demo

• Small (approximately pea-sized or smaller) samples of lithium and sodium (these metals shouldn’t be mixed, and when adding them to water, add them to separate beakers)
• Large beakers (2)
• Watch glass (2)
• Cutting device (2)
• Water

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

• Students should have some understanding of the properties of metals, nonmetals, and metalloids before doing this lab.
• Students are asked to design their own data tables for both parts of the procedures in this lab. This provides students with good practice in identifying what information is important to record and figuring out how to present it in a well-organized fashion. However, if students are younger or less advanced, you may want to discuss as a class what should be included on their data tables, or provide data tables for them (see answer key for examples).
• Students can use the same six elements for both parts of the procedure. Which element corresponds with which unknown doesn’t really matter, but the answer key provides sample data for the unknowns identified as follows:
• Unknown 1: Aluminum
• Unknown 2: Calcium
• Unknown 3: Carbon
• Unknown 4: Magnesium
• Unknown 5: Sulfur
• Unknown 6: Silicon
• Another test you could do in Part I of the procedures is have students put a few drops of acid (dilute HCl, for example) on each sample. Most metals will react with acid (including all of the examples in this lab), and most non-metals and metalloids will not.
• In Part II, students see how each sample behaves when it is added to water. At room temperature, they will only see a reaction with calcium, but if magnesium is put in hot water (as seen in this video), it will react with water as well.
• The final part of this lab involves a teacher demonstration of the reaction between group 1 elements and water. These reactions should be demonstrated by the teacher only, adding small amounts (pea-sized or smaller) of lithium and sodium to large beakers half-filled with water, with students observing from a safe distance. The lithium and sodium release a lot of heat when they react with water and it may splatter. Perform in a fume hood.
• Do not add lithium and sodium to the same beaker of water. Before putting them in water, cut a small piece of metal off a larger sample on the watch glass. This also gives students an opportunity to see the shinier, unoxidized metal before adding it to water. You could also use a conductivity meter on these unoxidized metal pieces to show students that they are good conductors.
• Be sure to practice the demo before showing it to students so you know what to expect and can point things out to students. Some things that might surprise them include that lithium and sodium are both soft enough to be cut with a knife, both are less dense than water and float, and sometimes the hydrogen gas produced by the reactions will get hot enough to ignite, making the small piece of metal appear to be on fire as it floats on the surface of the water.
• If you do not feel comfortable doing the demonstration of the group 1 elements’ reactions with water, the demo can be substituted with (or supplemented by) a video, such as this one, which also includes potassium. (Potassium is not included as part of the teacher demo as even a relatively small amount of potassium can produce a violent reaction and there is more risk involved than with lithium or sodium.)
  • You can have students record observations of the potassium reaction on the video if you show it, as they did with the lithium and sodium demos.
  • As it shows in the video linked above, you could also put phenolphthalein in the beakers of water before you add the group 1 elements, which will make the contents of the beaker turn pink (indicating the presence of a base) as the reaction occurs, since lithium hydroxide and sodium hydroxide are products of the reaction. Trapping the hydrogen gas produced by the reactions in a test tube and then holding it near a candle flame (also in the video) is another option.