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Chemical changes occur when substances become new or different substances. Fireworks like those in the QuickTime video at the right, that we see on the 4th of July, are actually metals such as magnesium and copper that change chemically as they light up the night skies with their fantastic colors. To identify a chemical change, look for observable signs such as color change, bubbling and fizzing, light production, smoke, or giving off light or heat.
 

Watch a QuickTime video of the reaction of vinegar and baking soda. Remember to click your back button to return to this page.
 

You can observe a chemical change each morning as you fry an egg for breakfast. Watch a short QuickTime video clip of an egg frying! Remember to click the back button to return to this page. The presence of heat can cause a substance to change chemically. Remember that whenever you cause a chemical change, the substance that you begin with cannot be chemically the same as the substance that you end up with. It is true that the egg does not change into an apple but your raw egg is definitely not the same in structure as a cooked egg.

One of the major evidences of a chemical change is that the substance has been altered chemically.

 

Anaylsis:

  1. What is one eaevidence that the egg underwent a chemical change?
  2. Is cracking or breaking the outer shell of the egg a chemical change?
    • Why did you make this decision?
  3. When you eat the egg for breakfast, is the digestion process based on chemical or physical changes?
  4. What evidence do holiday fireworks provide to prove that a chemical change occurred?
 
Try It!
 

Materials:

  • Phenol red Solution
  • Sodium Bicarbonate powder (NaHCO3) (baking soda)
  • Calcium Chloride (CaCl) powder
  • Quart size freezer bags
  • Plastic spoons
  • Eyedropper
 
Safety concerns: icon Be sure to keep all glassware, and chemical safety rules. As with all science lab activities, the most important safety rule is to follow all teacher directions.
 

Procedure:

  1. Using your finger, raise the middle of the bottom of a Ziploc® bag so that you can put the chemicals into the two corners without mixing them. Add 1 level spoonful of Sodium Bicarbonate and 2 level spoonfuls of Calcium Chloride into one corner of the bag.
  2. Add 2 eyedroppers of Phenyl red into the other corner of the bag. Squeeze the air out and close the bag without mixing the chemicals.
  3. Spill the Phenol red solution into the powders. Record your observations.
  4. List the physical properties of the reactants and products in the table below.
 

Data:

Substance
Property
Calcium Chloride  
Sodium Bicarbonate  
Phenol red solution  
Final product  
 

Analysis:

  1. What happens when the Sodium Bicarbonate and Calcium Chloride are mixed together?
  2. What happens when the phenol red solution comes in contact with the Sodium Bicarbonate and Calcium Chloride?
  3. What evidences of a chemical change did you observe?
  4. What is an exothermic reaction? Give 3 examples.
 

Review Science safetey rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The QuickTime plug-in is needed to play sounds and movies correctly.)

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  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 8th grade science core.


Updated October 24, 2008 by: Glen Westbroek

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