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Magic Salt, Melting Snow

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Author: Muriel Gerhard

Grade Level: 9th; Type: Chemistry

Objective:

To determine which salt, magic salt or regular salt is most effective in melting snow?

Research Questions:

  • What are the states of matter?
  • How do scientists explain the change of state on a molecular level?
  • What do we mean by the freezing point of water or the melting point of ice? Are they the same?
  • What is an ion? What is the colligative property of matter?
  • Why should we use sand instead of salt when the temperature is lower than 15 degrees F?
  • What is ice? How is it formed?
  • What is snow? How is it formed?
  • Should you try both ice and snow, what is your hypothesis as to the results? Will they be the same or different? Why do you think so?
  • How the melting might salts impact on our drinking water?

On the information level, the student will acquire some basic and some practical information on the chemistry and physics of water, its melting an d freezing points and how various differing chemical compounds   are utilized to promote a change of state. For example, just plain salt can be used to raise the melting point of water or lower the freezing point. Salt lowers the temperature at which water freezes. Salt absorbs moisture and forms ions when dissolved in water. In the case of snow or ice, when salt lowers the melting or freezing point of water, it serves as a freezing point depressor.  Other substances that dissolve in water also lower the freezing point of the solution. The amount by which the freezing point is lowered depends only on the number of molecules dissolved, not on their chemical nature. This so called freezing point depression is described as a colligative property of water. This property is one that depends on the number of ions that a substance produces when placed in solution. The more ions a substance produces when in solution in water, the more effective it is in lowering the freezing point of water. Salts such as sodium chloride and calcium chloride which ionize are useful in de-icing. However there are other variables to be considered such as the effects of these salts on grass, pavements, cars, concrete and living animals in the area.

As for the methodology of this project, this science fair experiment also serves to acquaint students with the essential processes of sciencing such as the importance of the use of a control, of identifying dependent and independent variables, of data collection, of pictorial and or graphic presentation of data and of being able to make better judgments as to the validity and reliability of their findings. They take on the role of scientists and in the process behave as one.

Materials:

  • Salt (sodium chloride)
  • Magic Salt
  • Snow balls (kept in the freezer)
  • Ice cubes (if snow is not available)
  • Timer
  • Tablespoon
  • Measuring cup
  • Paper towels
  • Balance

Experimental Procedure:

  1. Gather all the materials you will need for this experiment which include salt (sodium chloride) , Magic Salt(rock salt plus magnesium chloride plus a liquid ,a byproduct of the distillation of vodka), snow balls (kept in the freezer) or ice cubes (if snow is not available, susbstituteice cubes, or you may test both by repeating the steps given below on your second choice), two bowls, a timer, a thermometer  a tablespoon,  a measuring cup , paper towels, labels and a pen.
  2. Reproduce the Data Charts provided below. Chart #1 is for testing with just one preferably ice cubes since they are readily available from your freezer can be replicated to use with snow balls and  chart #2 is for synthesizing the data on both ice and snow and comparing the outcomes.  You may wish to expand the experiment to determine if there were any differences in the results. Did the salts work equally as well on both ice and snow or were there variations?  Your choice! If you test both, what is your hypothesis? Will the results be the same or different? Why?
  3. Start by labeling each of the three bowls, #1Control, #2 Salt and #3 Magic Salt.
  4. Start by removing the ice cubes and dividing them equally into three bowls. Use your thermometer and take the temperature of the ice cubes in one of the bowls. Record the temperature. (It should be the same in all three.)
  5. Label one bowl the control and let it stand. Take one ounce or 28 grams of salt and pour it over the ice cubes in bowl #2 and take one ounce or 28 grams of Magic Salt and pour it over the contents of bowl #3. Note the starting time. The race has begun.
  6. Wait and watch! Note when the melting has begun. At three five minute intervals, pour off the liquid water and measure the amount of water in each of the three bowls each time. Record the amounts.
  7. Record the temperature of each bowl at the end of the fifteen minute period.
  8. Compare the melt downs. What was left in each bowl? Where was the least? What were the results of the action of the table salt, of the Magic Salt? How did they compare with each other and with the control? Which won the race?
  9. Write up your report. Include your responses to the research questions as well as your bibliography. You may wish to include your reactions to the experiment and how you might want to pursue the topic further.

Data Chart: Ice and for Snow Experiments 

Melting Agents

Initial Temp.

Final Temp.

Am`t of H2O 5minutes

Am`t of H2O 10minutes

Am`t of H2O 15minutes

Salt

 

 

 

 

 

Magic Salt

 

 

 

 

 

Control

 

 

 

 

 

 

Data Chart: Summaries

Melting Agents

Initial Temp.

Am’t of H2O

Final Temp.

Final Am’t of H2O

Salt

 

 

 

 

Magic Salt

 

 

 

 

Control

 

 

 

 

 

Terms/Concepts: States of matter; Water vapor; Liquid water; Ice freezing point; Melting point; Change of state; Ions; Ionization; Property; Colligative property

References:

  •  VanCleaves., A+ Project in Chemistry, John Wiley & Sons New York, 1993
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