An alternative assessment is another way for your teacher to evaluate your comprehension of the material. You may choose to have this alternative assessment count for a percentage of your overall test grade.
How does the alternative assessment work?
On the day of the test you will turn in a completed alternative assessment along with this cover sheet all stapled together. The box checked will indicate what percent you want the alternative assessment to count. If you do not turn in the alternative assessment your test will be counted as 100% of your grade.
This alternative assessment is composed of a writing component AND a lab component. The lab component will be offered multiple times before and after school 11/13 – 11/15. Specific times will be announced and posted. You must complete the lab component during one of these times.
An example of an alternative assessment grade: You choose option #4 and your alternative assessment is worth 40% of your final grade
You score 45/60 on your test = 75%
You score 55/60 on your alternative assessment = 92%
Writing Component of Bonding Alternative Assessment Directions: You are to write a 5 paragraph essay comparing ionic and covalent bonds. You must have an intro and closing paragraph. This should be typed and doubled spaced. No credit will be given for any other type of format. In your essay you must cover the following topics.
Physical/Chemical differences between ionic and covalent compounds
Differences of how ionic and covalent compounds are formed
Use these words: valence electrons, electronegativity, sharing, gaining, losing, charge, noble gases
Differences in naming/formula writing of ionic and covalent compounds
Use these words: roman numerals, prefixes, change of ending, polyatomic ions, criss-cross, total charge of zero
Bonding Alternative Assessment Lab: Properties of Ionic and Covalent Compounds INTRODUCTION
A compound is a substance that contains two or more atoms. A chemical bond is formed when electrons are shared or transferred between atoms of different elements. Ionic bonding occurs when a positively charged ion transfers electrons to form a negatively charged ion. The resulting bond is a result of the attraction between the positively and negatively charged particles. This is called an electrostatic interaction. Covalent bonding generally occurs when two or more nonmetallic atoms share electrons.
Properties such as melting point, boiling point, solubility, electrical conductivity, color, and odor can help you distinguish ionic and covalent compounds.
Conductivity: An electric current results whenever there is a net movement of electric charge. The movement of electrons (carrying a negative charge) in metal wires supplies the electric power used in our homes and businesses. The movement of positively charged ions (cations) and negatively charged ions (anions) in batteries provides the electric current necessary to start cars and power a variety of cordless electric devices.
Ionic materials are good conductors of electricity in their liquid state or when dissolved in certain solvents. The strength of the electric current is dependent on the quantity of ions moving per unit time. Therefore, the greater the number of ions present or amount of ionic character of the bond, the better the conductor. By contrast, covalently bound substances are good insulators because there are no separate charged particles. If there is no movement of electrical charge, there will be no current. Conductivity of aqueous solutions is measured in microseimens (S).
The melting point of a substance is a characteristic physical property of that substance. If a substance is pure, it will melt at a distinct temperature. Melting involves adding energy to a compound to disrupt the forces between the molecules or ions. The stronger the attraction between particles, the more difficult it will be to separate the particles. When a substance melts, the particles are still close to one another but the forces of attraction that held the particles rigidly together in the solid state have been overcome, allowing them to move. Interactions between ions are much stronger than those between covalently bound molecules; therefore, the melting temperature of an ionic compound will be much higher than that of a covalently bound substance.
In this experiment you will classify substances as containing covalent or ionic bonds based on the properties of conductivity and melting point.
PROCEDURE Testing Conductivity: Use the conductivity probe and lab pro to determine whether the following materials conduct electricity: sodium chloride, sucrose, calcium chloride, salicylic acid, ammonium chloride. Record your data in the data table below.
Data Table 1: Conductivity
Testing Melting Point:
1) Take approximately 0.5g of sodium chloride in a test tube.
2) Heat the test tube over a Bunsen burner and record in Data Table 2 the amount of time required for the solid to melt. If the solid takes longer than 2 minutes to melt in a blue flame, note this.
3) Use the following solids: sodium chloride, sucrose, calcium chloride, salicylic acid, ammonium chloride.
1) Draw conclusions and summarize your data in the table below.
Support from Data
2) Why is pure water a poor conductor of electricity?
3) Of the compounds you determined contained ionic bonds, which one would you predict has the greatest number of ions present in the formula unit. How does your data support your prediction?
4) Why was it important in the conductivity test that all of the solutions be of the same concentration?
5) Look up the chemical formula for sucrose. What are the elements that form sucrose? Where are they found on the periodic table? Based on the elements found in sucrose, what type of compound is sucrose? Does your data agree with this prediction?
6) Based on your data, what conclusions can you draw about ionic compounds? What conclusions can you draw about covalent compounds?