An Investigation of Colligative Properties Created by: Amy Taylor Hazelwood Central High School To Teacher PageTo Teacher Page To ActivityTo Activity

Teacher Page Grade Level: 10 MAP Content Standards: –The learner will be able to comprehend that the properties of solutions are dependant on the solutes and solvents involved. This activity is recommended for use in the chemistry classroom after solutions and colligative properties have been introduced. This activity does not involve the calculations associated with boiling point elevation and freezing point depression.

Tips for Classroom Use: –Preview the activity before using it with your class. –Buttons are present on each page that will enable you to move forward and back within the activity. Journaling: –This activity is intended to be used in conjunction with journaling. –The notebook icon will prompt the students when to journal in their notebooks.

Focus on the process of problem-solving with your students…they need to understand not only the facts, but the reasoning behind them. Have them write their thoughts on paper and then discuss them as a class.

Colligative Properties A Brief Review… All matter has physical and chemical properties that determine its behavior. One physical property is that matter has a particulate nature (is made up of smaller particles such as atoms, molecules, and ions). The arrangement of these particles determines such other properties as state, density, polarity, and crystalline structure.

The arrangement of these particles is not the only thing that affects the behavior of matter…the number of particles present can also play a role. COLLIGATIVE PROPERTIES are physical properties of a solution that depend solely on the number of particles of solute and solvent present in a solution. Examples of colligative properties are vapor pressure, boiling point, freezing point, and osmotic pressure.

How do colligative properties affect everyday life? Ethylene glycol is the chemical name for a product found in any garage--antifreeze. Most people are aware of the importance of antifreeze when added to the water in the radiator of their cars… –it prevents the water in the radiator from boiling over and –it prevents that same water from freezing in the winter.

Study the graph below... What information does this graph give us? Concentration of Antifreeze vs. Melting Time Melting Time (min) % Antifreeze Solution

The preceding graph was a representation of data collected when various concentrations of antifreeze were frozen with dry ice and then allowed to melt. The concentrations that took longer to melt had a higher melting point …thus a higher freezing point.

Look a little closer... Describe the data obtained from the experiment. At which concentration is the antifreeze most valuable for preventing freezing? Concentration of Antifreeze vs. Melting Time Melting Time (min) % Antifreeze Solution

Now, study this graph carefully... What information does this graph give us? Concentration of Antifreeze vs. Boiling Point % Antifreeze Solution Boiling Point (°C)

This graph was of the data obtained when those same antifreeze solutions were brought to a boil. The data graphed is of the boiling points in degrees Celsius of the various concentrations of antifreeze solutions.

Look at this same data again... Describe the data obtained from the experiment. At which concentration is the antifreeze most valuable for preventing boiling? Concentration of Antifreeze vs. Boiling Point Boiling Point (°C) % Antifreeze Solution

When looking at the back of any antifreeze container, the manufacturer recommends using a 50% antifreeze solution in your car. Why is this recommended over a 100% antifreeze solution?

Does the experimental data support the manufacturer’s recommendations? Discuss why or why not with your class.