Chem rx 1.pdf - NAME SECTION PARTNER(S DATE AN...

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Exploring the Chemical World, PGCC, 2003 41 NAME__________________________________ SECTION____________ PARTNER(S)____________________________ DATE_______________ AN INVESTIGATION OF CHEMICAL REACTIONS I This laboratory activity will give you some experience with different chemical reactions. You will use your observational skills to describe physical properties of the reactants (starting materials) and products (substances formed as a result of a chemical change). You will practice writing formulas, naming elements and compounds, and balancing equations. As you become familiar with the types of reactions, it will be easier for you to make reasonable predictions about what will happen when unfamiliar substances chemically change PRE-LAB QUERIES 1. You are about to perform a number of chemical reactions. How will you know that a reaction is taking place? List and explain some of the things you expect to observe as chemical changes occur. 2. Let's suppose that you mixed two colorless, clear solutions and there was no visible change. Could a chemical reaction have occurred? Explain how you might know. .
Exploring the Chemical World, PGCC, 2003 42 BACKGROUND Here are some important things to remember or refer to as you do this activity: ; Chemical changes are rearrangements of atoms. New substances with different properties are formed. ; Chemical equations represent chemical changes. All formulas for reactants and products must be accurate. ; Matter is neither created nor destroyed during chemical or physical changes. All atoms must be accounted for. Balancing an equation means making the number of atoms of a particular element equal on both sides of the equation. You can never change a subscript to balance the equation. You add or change numbers in front of substances to achieve the equality. These added values are called coefficients . ; The diatomic elements (hydrogen, oxygen, nitrogen, fluorine, chlorine, bromine, iodine) must be written with a subscript of 2 when they are not combined with another element. ; If one metal is more reactive than another metal (hydrogen included) it will replace the less active metal in a compound. ; Many reactions take place in solution, that is, the reactants are dissolved in water. In some cases, one of the products is a gas or solid that does not dissolve in water. When this occurs it is easy to tell that a reaction has taken place because you can see bubbles or a solid (cloudiness) appear suddenly. The formation of a solid through a chemical reaction is called precipitation . In certain reactions, however, the product(s) dissolve instantly so that it is not

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