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Chemical Reactions

Investigation 1 – PreLab









Everything in the environment, whether naturally occurring or man-made, is composed of chemicals, and research of chemicals has led to the discovery and development of new and improved paints, medicines, cosmetics, electronic components, and thousands of other products. 


Chemical engineers design and develop chemically based products such as rubber, plastic, soaps, and gasoline. They also test these products to make sure they are safe for consumers and the environment.


This Investigation is designed to help you to answer the following Focus Question:

  • In a chemical reaction, what is the relationship between the amount of reactants and the amount of products? 

Note: This question is located in your SDR at the beginning and end of the Investigation.


As a class, read the Background(s) in the Investigation. When finished, discuss the following concepts as a class:

  • Chemical reactions usually have two or more chemicals called reactants that are different from one another.
  • The reactants interact during the chemical reaction to form one or more products.
  • Products are substances that are different from the reactants and from each other.
  • All chemical reactions can be written as equations that are like sentences.
  • The reactant and product formulas are like words in a sentence.
  •  In an equation, the reactants and products are separated by an arrow, which represents the word “yield.”
  • Sometimes chemical reactions produce heat.
  • A calorimeter is a device that prevents the heat of a reaction from being lost to the surroundings.



The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

  • chemical reaction
  • reactant
  • product
  • formula
  • chemical equation
  • yield
  • calorimeter

Note: Definitions to these terms can be found on the Introduction page to the CELL.



  • The following chemical equation is a chemical “sentence” that uses chemical “words” to describe what occurs during the reaction. 


  • In a chemical reaction, chemical bonds between atoms are broken and reformed converting reactant chemical compounds into product chemical compounds.
  • In breaking and reforming chemical bonds, energy in the form of heat can be released or consumed in a chemical reaction. Consider the following examples to illustrate this concept.
    • When “ice melt” or calcium chloride (CaCl2) is spread on icy roads in the winter, the ice melts due to the release of heat. The solid calcium chloride (CaCl2) gradually dissolves releasing heat energy as bonds are formed between the calcium (Ca), the chloride (Cl), and the water molecules.
    • Chemical cold packs contain solid ammonium nitrate (NH4NO3) and water in separate bags. When the inner bag of water is broken by squeezing, the solid and the water come in contact. The formation of bonds between the ammonium (NH4), nitrate (NO3), and the water molecules requires that heat is absorbed by the reaction. The cold pack feels cold to the touch because heat leaves our hand and is absorbed by the reaction.
  • Can you predict the answers to the following questions?
    • What happens to the reacting chemicals in a chemical reaction?
    • What is produced in a chemical reaction?
    • How do you know that a chemical reaction has occurred?


  • Play the video below. Remember to follow along with your SDR and make any notes that you think might be helpful in the lab.
  • After the video, divide into your lab group to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video. 


Be sure that you review the Investigation and video in preparation for the Lab.