Factors That Affect the Rate of Dissolving Solutes Lab

Factors that Affect the Rate of Dissolving Solutes Lab

The purpose of this lab is to observe factors that affect the rate a solute dissolves in a specific solvent. The process of forming a solution can be affected by a number of variables. Larger pieces of material versus smaller pieces may dissolve in a shorter or longer period of time. The temperature of the solvent may affect the rate at which a material dissolves. Finally, the amount that the solvent is stirred may also change the rate at which a solution forms.

In this lab you will design experiments to explore the effects of these variables and answer the following questions.

Be prepared to make graphs for all of these objectives. In each case the rate of dissolving is your dependent variable and belongs on the y-axis. The variable you are testing is your independent variable and belongs on the x-axis.

3 Variables to Be Tested:

1. How does the size of the pieces of material you start with affect the rate at which it dissolves? Can you formulate a general rule for rate of dissolving as a function of the size of a chunk? 2. How does the amount of agitation affect the rate at which a material dissolves? Can you formulate a general rule for rate of dissolving as a function of amount of agitation? Measure the rate the same way. Measure the amount of agitation in a logical, repeatable, and quantifiable way. (Creativity may be required). 3. How does the temperature affect the rate at which a material dissolves? Can you formulate a general rule for rate of dissolution as a function of temperature? Measure the rate as before and measure the temperature with a thermometer. Try to gather data for several different temperatures.

Materials: sugar cubes, granulated white sugar, glass cups, spoon to stir, tap water, timer, microwave or stove to heat up water

Procedure

The procedure for this lab is mostly up to you. For each variable to be tested you must design and carry out experiments to answer the objective question(s). Keep the following in mind as you plan your work:

 What experiments are you going to perform?  Before you set up the experiments try to decide what you think is going to happen. Write this down and refer back to it once you are done.  In your experiments, what are you going to hold constant?  What are you going to change?  Set up data tables to before doing your experiments.  How are you going to decide whether you have answered the questions? 3 Variables:  Size of the solute o Procedure:

o Data Table:

o Graph:

 Amount of Agitation o Procedure:

o Data Table:

o Graph:

 Temperature o Procedure:

o Data Table:

o Graph:

Analysis:

1. What is happening at the molecular level when a sugar cube dissolves? 2. How is dissolving different from melting? 3. What effect does the size of the chunks of sugar have on the rate at which it dissolves? What evidence do you have to support the effect you report? 4. Why does the size of a chunk of sugar have an effect on the rate of dissolution? Explain what’s happening at the molecular level. 5. What effect does the amount of agitation of the water have on the rate at which the sugar dissolves? What evidence do you have to support the effect you report? 6. Why does agitation have an effect on the rate of dissolving? Explain what’s happening at the molecular level. 7. What effect does the temperature of the water have on the rate at which the sugar dissolves? What evidence do you have to support the effect you report? 8. Why does temperature have an effect on the rate of dissolution? Explain what’s happening at the molecular level.

Conclusion:

In the conclusion paragraph, apply what you have learned to the following question: If you have room temperature water, ice cubes, and powdered lemonade mix in what order would you mix them to dissolve the powder the quickest to make a cold drink? Why? Also discuss what you have learned by conducting these procedures.

Conclusion Paragraph: Lab Created by Aaron Keller: http://kaffee.50webs.com/Science/labs/Chem/Lab-Dissolving.Sugar--Check-in.htm