Penaut Lab Essay
Submitted By dannisphotogra
Words: 1205
Pages: 5
Ionic and Covalent Bonding Lab
Mrs. Rodriguez and Ms. Apang
Benchmarks:
SC.A.2.4.5- The student knows that elements are arranged into groups and families based on similarities in electron structure, and that their physical and chemical properties can be predicted. SC.H.1.4.1- The student knows that investigations are conducted to explore new phenomena, to check on previous results, to test how well a theory predicts, and to compare different theories.
(Also assesses SC.H.1.2.1, SC.H.1.2.2, SC.H.2.4.2, SC.E.2.4.6, and SC.E.2.4.7)
Objective:
• Test different substances for their ability to dissolve and conduct an electric current.
• Predict the bonding nature of each substance on the basis of your results.
Background Information:
Bond types can be predicted on the basis of the ability of substances to dissolve and conduct electricity. Solubility is a physical property of matter that can be defined as the amount of a substance that can be dissolved in a specified amount of solvent. Conductivity, another physical property, describes the ability of a substance to conduct an electric current. An electric current can be produced by the movement of positive or negative particles. In a solid, such as a wire, only the negative charges (free electrons) are able to move. In this lab you will construct a conductivity apparatus which will light up when an electrical circuit is completed.
Ionic bonds occur between metals and nonmetals when valence electrons are transferred from the metal to the nonmetal. Most ionic compounds are soluble in water and conduct electricity once dissolved when the ions are free to move in the water. Ionic compounds exhibit high melting and boiling points. Covalent bonds occur between two nonmetals by a sharing of valence electrons. Molecular compounds (held together by covalent bonds) do not conduct electricity. Some molecular compounds dissolve in water while others do not. Metallic bonds hold metal atoms together by sharing mobile valence electrons that resemble a “sea of electrons.” Metal substances generally do not dissolve in water, but all conduct electricity. Some substances consist of nonmetal atoms joined in a large covalent network (essentially gigantic molecules). The majority of such covalent network molecules do not dissolve in water and none conduct electricity.
Lesson Lead:
How can the properties of substances be used to predict the way atoms are held together?
Materials:
Conductivity Apparatus*:
A) Conductivity Indicator
B) 9-V battery
Other:
• small beakers or cups (100 mL or less)
• distilled water (~100 mL)
• wash bottle filled with distilled water
• stirring rod
• 1 cm2 of Al foil
• copper
• rubbing alcohol (isopropyl alcohol) (10mL)
Gatorade
Sprite
Baby Oil
Lemon Juice
H2O2
Vegetable oil
Hand Soap
Tap Water
Small amount of each of the following:
• sucrose (table sugar)
• NaCl
• SiO2 (sand)
• paraffin wax shavings
• CaCl2 (calcium chloride)
• CuSO4 (copper II sulfate)
MgSO4
Baking Soda
Pedialyte
HCl
H2SO4
HC2H3O2
Safety Precautions:
• Always wear safety goggles.
• Use conductivity tester only for described activities.
Pre-Lab:
• Predict or hypothesize the conductivity and solubility properties of the substances listed in Table 1, filling in columns 2 and 3 of the table with brief explanations.
Procedure:
1. Conductivity- Use the apparatus to test the conductivity of all substances before making any solutions. Be sure to keep the wire test probes apart. Record your results in the second column of Table 2. Rinse the paper clip probes with distilled water between each test.
2. Solubility- Take a small amount of each solid substance, place it in the small beaker or cup and try to dissolve it with distilled water. Record your results in the third column of Table 2.
3. Conducts when dissolved- If the substance dissolves in water, test the solution with the conductivity apparatus. Make sure to keep the probes
