In this lesson, students will use a PhET simulation in combination with Safety Data Sheets in order to analyze specific ionic and covalent substances. Students will then use the collected data in order to identify trends in the properties of similar substances.
This lesson will help prepare your students to meet the performance expectations in the following standards:
- 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.
- Scientific and Engineering Practices:
- Analyzing and Interpreting Data
- Engaging in Argument from Evidence
By the end of this lesson, students should be able to
- Determine if a substance is ionic or covalent, based on its formula.
- Identify the properties of ionic and covalent substances, including appearance, conductivity, melting point, and state of matter at room temperature.
This lesson supports students’ understanding of
- Ionic Bonding
- Covalent Bonding
- Chemical Formulas
- Physical Properties
Teacher Preparation: 15 minutes
Lesson: 90 minutes
- Student Handout
- Computers with internet access
- Teacher can demo of simulation and provide hard copies of SDS if computer access if unavailable
- Digital access to Flinn Safety Data Sheet database
- PhET Simulation: Sugar and Salt Solutions
- A common high school chemistry lab is one in which students are provided a set of unknown substances, and perform tests to identify if the substances are ionic or covalent. For example:
- This lesson is designed to precede these types of activities.
- Part 1 asks students to use the Sugar and Salt Solutions PhET.
- This is one of the older simulations that runs on Java Script, so may need to be done as a teacher demo if student electronic devices do not support Java.
- Students should see that the salt breaks down into individual ions when dissolved in water, while sugar molecules remain intact, just separate from each other. They will use this later to help explain why ionic compounds conduct electricity.
- Part 2: After using the simulation, they will access Flinn Safety Data Sheets to collect information on a variety of ionic and covalent substances. If computers are not available, the Safety Data Sheets can be printed and students can work in small groups to collect data. The hazards are not necessary for determining if a substance is ionic or covalent, but students are often interested in them, and this is a good opportunity to help them learn how to identify hazards of any substances that they use (ex. cleaning solutions).
- Once they have completed the table in Part 2, they will analyze properties of ionic and covalent compounds. Most of these questions require students to respond to a “Claim” and “Evidence”, but not “Reasoning”, as they may not have knowledge to respond to that quite yet.
- After this activity, it would be helpful to have students will work on an unknown substances lab, where they will use these properties in the lab to determine if the unknown is ionic or covalent. There are several labs on the AACT website that could be used after this, including:
For the Student
An ionic bond is formed by the attraction between oppositely charged ions. Ionic bonds are formed between metals and nonmetals. Remember that metal atoms lose one or more valence electrons in order to achieve a stable electron arrangement. When a metal atom loses electrons it forms a positive ion, known as a cation. When nonmetals react they gain one or more electrons to reach a stable electron arrangement. When a nonmetal atom gains one or more electrons it forms a negative ion or anion. The metal cations lose electrons to the nonmetal anions so they “stick” together in an ionic compound. This means that ionic bonds are formed by the attraction of these two oppositely charged particles.
A covalent bond is formed between nonmetal atoms. The nonmetals are connected by a shared pair of valence electrons. Remember, nonmetals need to gain valence electrons to reach a stable arrangement. Nonmetal atoms share their valence electrons with other nonmetal atoms. Since the two atoms are using the same electrons they are stuck to each other in a neutral particle called a molecule. A molecule is a neutral particle of two or more atoms bonded to each other. Molecules may contain atoms of the same element such as N2, O2, and Cl2 or they may contain atoms of different elements like H2O, NH3, or C6H12O6. Therefore, covalent bonding is found in nonmetallic elements and in nonmetallic compounds.
- Define ionic bond:
Define covalent bond:
- What types of elements compose ionic compounds (only metals, only nonmetals, or a metal and a non-metal?)
- What types of elements compose covalent compounds?
- Look at the formulas below,
and determine whether it is ionic or covalent.
- sodium iodide (NaI)
- nitrogen monoxide (NO)
- glucose (C6H12O6)
- magnesium selenide (MgSe)
- calcium chloride (CaCl2)
Part 1: PhET Sugar and Salt Solutions
- Go to the PhET simulation “Sugar and Salt Solutions”. https://phet.colorado.edu/en/simulation/sugar-and-salt-solutions
- Select the “Micro” tab, and shake some salt (sodium chloride) into the water. Watch what happens as salt dissolves, and record your observations below.
- Reset the simulation, and repeat with sugar (sucrose). Pay careful attention to the difference in dissolving, and again, record your observations below.
- Now select the “Macro” tab, and test the conductivity of sugar and salt. Record your observations in the data table provided in Part 2 of the activity.
|Salt in water||Sugar in water|
Part 2: Safety Data Sheets
- You will use the Flinn Safety Data Sheets (SDS) to search for properties of the substances listed in the table below.
- Safety Data Sheets are provided with each chemical that we purchase, and they include instructions for the safe use and potential hazards associated with a particular material or product.
- The SDS should be available for reference in the area where the chemicals are being stored or in use. They can be found online at: https://www.flinnsci.com/sds/, with the exception of oxygen, which can be found at: https://www.airgas.com/msds/001043.pdf
|State of matter at 20°||Melting Point||Solubility in Water||Hazards||
- Using the data you gathered today, compare and contrast ionic and covalent compounds in terms of phase at room temperature (what trends do you notice?) Be sure to provide EVIDENCE from your data table to support your answer.
- Using the data you gathered today, write a CLAIM to describe the melting point of ionic and covalent substances—what trends do you notice (a trend is a general pattern)? In general, are the melting points high or low? Be sure to provide EVIDENCE from your data table to support your answer.
- Using the data you gathered today, write a CLAIM to describe the conductivity of ionic compounds (what trend do you notice?) Be sure to provide EVIDENCE from your data table to support your answer.
- Look back at your observations from the PhET activity. Electricity can be simply defined as the “presence and flow of electric charge.” Based on your observations, and knowledge of ionic and covalent compounds, why do ionic compound conduct electricity when dissolved in water, while covalent compounds do not?
- Using the data you gathered today, write a CLAIM to describe the solubility (do they dissolve in water?) of ionic compounds—what trend do you notice? Be sure to provide EVIDENCE from your data table to support your answer.
- Describe whether the
following compounds are likely to be ionic or covalent based on the properties
given. Explain your reasoning.
- Compound 1 has a melting point of 545 degrees Celsius and dissolves well in water.
- Compound 2 is a brittle solid that conducts electricity when dissolved in water.
- Compound 3 melts at 85 degrees Celsius and catches fire when heated to 570 degrees Celsius.