Chemical or physical change?

By Laura Hospitál on May 03, 2015

 
Students are introduced to the concepts of chemical change and physical change in elementary school.  These concepts are covered in greater detail as students progress through middle school and high school.   A chemical change occurs when substances combine (the reactants)  to form new substances (the products) as atoms are rearranged. Common evidences of a chemical change include a change of color, odor, temperature, the formation of a gas, or a precipitate
 
A physical change occurs when there is a change in physical properties of a substance but not chemical compostion.  Common physical changes include melting, change of size, volume, color, density, and crystal form.  
 
The classic baking soda and vinegar reaction provides evidence of a chemical change due to the formation of a gas and a temperature change.  Students tactually experience the formation of a gas as carbon dioxide fills up the balloon and sense a change of temperature.
 
Related Vocaulary:
  • physical change
  • chemical change
  • products
  • reactants
 
As students complete this activity they will immediately notice the production of the gas.  However, it may be necessary to ask the students to observe the temperature of the substance in the bottle after the reaction. It will be colder than before. 
 
Please see the activity at http://www.perkinselearning.org/accessible-science/conservation-mass for a similar experiment with a focus on Conservation of Mass
 

Preparation:

  • The instructor should gather the materials for this lab.  
  • Prepare a station for each group of 2 students by placing the required materials in a cafeteria tray or bin.
  • Prepare the lab procedure (See attached.) for each student in the appropriate reading medium.

 

Materials

  • 10 mL baking soda per group
  • 30 mL vinegar per group
  • several balloons per group (in case one has a hole)  *See variations for latex allergic students
  • 1- 500 mL water bottle per group

 

Procedure

Please note that this worksheet for the lab is available to be downloaded in regular print, large print, and Duxbury (contracted and uncontracted braille) at the bottom of this page under "Attached Files".   Name:  _____________    Class:  ______________   Lab: Baking Soda and Vinegar   Problem:  What will happen if I mix vinegar and baking soda?  Is it a chemical change or a physical change?   Hypothesis:  _______________________________   Procedure:   
  1. Measure 10 ml of baking soda using a measuring spoon.  Pour the baking soda into the balloon using a funnel.
  2. Measure 30 ml of vinegar and pour it into a water bottle.
  3. Put the mouth of the balloon onto the mouth of the water bottle but be careful to keep the baking soda in the balloon.  (The balloon will be flopped to one side.)
  4. Lift the balloon up and pour the baking soda into the bottle of vinegar.
  5. Observe for 1 minute. 
  Results:  __________________________________     Conclusion:  _______________________________  

Variations

Latex Free option:  This activity was recently chosen by a student of mine as the basis for her science project.  However, she is highly latex allergic.   We found latex-free mylar balloons available through mrballoon.com.  Advice from the company's owner proved very useful.  He recommended using wine spouts to connect the balloon to the bottles as he had fielded this question before.    Please see a review of the products sold by Mr. Balloon in the review section.     Science Project :  This activity can be easily turned into a science experiment.  The student should choose the independent variable and design the project.    

NGSS Standards:

2nd Grade - Structure and Properties of Matter

PS1.B: Chemical Reactions
Heating or cooling a substance may cause changes that can be observed. Sometimes these changes are
reversible, and sometimes they are not. (2-PS1-4)

5th Grade - Structure and Properties of Matter

Structure and Properties of Matter

PS1.B: Chemical Reactions
 When two or more different substances are mixed, a new substance with different properties may be formed. (5-PS1-4)
No matter what reaction or change in properties occurs, the total weight of the substances does not change. (Boundary: Mass
and weight are not distinguished at this grade level.) (5-PS1-2)

chemical and physical changes
 
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