Name: __________________________________________________________Period: _______    Date: _________

 

Ionic and Covalent Compound Lab

Background:

The two types of bonds that hold atoms together in a compound are ionic and covalent.  Ionic bonds form when electrons are transferred between atoms creating positive and negative ions.  The force of attraction between the positive and negative ion is an ionic bond.  Covalent bonds result when atoms share pairs of electrons.  This means the electrons move freely between both outer electron shells.  Ionic and covalent compounds have different properties as a result of this exchange verses sharing of electrons.  These differences are so distinct they can be used to distinguish between the two types of compounds.

 

In this lab we will be using two properties to distinguish between ionic and covalent compounds; melting point and ability to conduct electricity when dissolved in water.  The ionic compound you will be testing is sodium chlorideThe covalent compound is sucrose.  Melting point refers to the temperature required for a substance to change from a solid to liquid state.  In ionic compounds, melting points are frequently over 300C where in covalent compounds they are much lower.  When ionic compounds are dissolved in water they conduct electricity.  This occurs because water molecules break ionic bonds by separating the positive and negative ions within the compound.  This is called dissociation.  As a result of dissociation, positive and negative ions are floating freely in the water.  These allow electricity to be conducted.  When covalent compounds are dissolved in water they will not conduct.  Water molecules do not disrupt covalent bonds.  The bonds remain in tact. 

 

Purpose: In this lab, students will identify the different properties of ionic and covalent compounds and use these to identify an unknown as an ionic or covalent compound.

 

Data

Data Table A:

Melting Point of Ionic and Covalent Compounds

Compound

Time to Melt (seconds)

Qualitative Observations

Sucrose

 

 

 

 

Sodium Chloride

 

 

 

Unknown A

 

 

 

 

Unknown B

 

 

 

 

Data Table B:

Conductivity of Ionic and Covalent Compounds in Water

Type of Solution

Conductivity (Yes or No)

Qualitative Observations about the solution

Distilled Water

 

 

 

Sucrose

 

 

 

 

Sodium Chloride

 

 

 

Unknown A

 

 

 

 

Unknown B

 

 

 

 

 

 

 

 

Analysis:

 

1.       What type of bond holds the atoms in a sucrose (sugar) molecule together?  What about salt?

 

 

 

 

2.       Distinguish between ionic and covalent compounds in terms of their melting points and ability to conduct electricity when dissolved in water.

 

 

 

 

 

 

3.       Was Unknown Substance A an ionic or covalent compound?  Provide two pieces of evidence to support your conclusion.

 

 

 

 

 

 

4.  Was Unknown Substance B an ionic or covalent compound?  Provide two pieces to evidence to support your conclusion.

 

 

 

 

 

 

 

5.  Why do ionic compounds conduct electricity when dissolved in water while covalent compounds do not?

 

 

 

 

 

 

 

 

 

6.  In aqueous (water) solutions, covalent bonds are stronger than ionic bonds.  The water molecules can disrupt the ionic bonds but not the covalent bonds.  Which type of bond is stronger outside of solution?  Explain.