Modeling Chemical Equations

Unit 16: Balancing Equations
Modeling Chemical Equations

By Raven Turner

Multiple Choice

What do the letters s, l, g, and aq indicate in a chemical equation?

• Whether the substance is an atom or a molecule

• The state of matter of the substances in the reaction

• Whether or not the substances will be able to react

• Which substances in the reaction are reactants and which are products

Open Ended

What is the Law of Conservation of Mass?

Open Ended

Why do unbalanced equations not satisfy the law of conservation of mass?

Open Ended

If equations must be balanced, why do you think the reactants and products are separated by an arrow (→) and not an equal sign (=)?

Open Ended

A coefficient represents the number of molecules that are present in a chemical equation. For the example equation in the Data Table, write the coefficients for the balanced equation in the order that they appear. 

Open Ended

Next to some of the chemical symbols in a formula, like Br2, is a small number called a subscript. What does that number indicate?  

Open Ended

How did you use the coefficients and subscripts to determine the number of atoms that were present?

Open Ended

What is the goal of changing coefficients? 

Open Ended

REFELCTIONS & CONCLUSIONS:

What is the difference between an unbalanced equation and a balanced equation?

Match

Which are the Reactants? The products?

• H2

• O2

• H20

Reactant

Reactant

Product

• Reactant

• Reactant

• Product

Open Ended

What is the difference between reactants and products?

Open Ended

When balancing an equation, is it necessary to change coefficients, subscripts, or both? Explain.

Open Ended

How is the law of conservation of mass demonstrated by balanced chemical equations?

Multiple Choice

Why are coefficients necessary in some chemical equations but not in others?

• Some reactions naturally produce more mass than they start with.
  

• Coefficients are only needed when there are more products than reactants

• They ensure the equation obeys the law of conservation of mass by balancing the number of atoms on both sides.

• Some elements do not follow the law of conservation of mass, so coefficients are unnecessary in those cases.

Multiple Choice

Which of the following is true of chemical reactions?

• Chemical reactions may create more atoms.

• Chemical reactions may reduce the number of atoms.

• The products of a chemical reaction must contain the same number of atoms as the compounds at the beginning of the reaction.

• Chemical reactions always build new chemical substances; they never break them down.

Fill in the Blanks

An unbalanced equation is shown here. What coefficients are needed to balance the equation?

_____P2O5   +   _____H2O   →   _____H3PO4