Student Chemical Equations – Fill Out and Use

Name: ______________________________________

Date: ________________________

Student Exploration: Chemical Equations

Vocabulary: Avogadro’s number, chemical equation, chemical formula, chemical reaction, coefficient, combination, combustion, conservation of matter, decomposition, double replacement, molar mass, mole, molecule, product, reactant, single replacement, subscript

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

1.A candle is placed on one pan of a balance, and an equal weight is placed on the other pan. What would happen if you lit up the candle and waited for a while? ____________________

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2.Suppose the candle was placed in a large, sealed jar that allowed it to burn for several minutes before running out of oxygen. The candle and jar are balanced by an equal weight.

In this situation, what would happen if you lit up the candle and waited? ________________

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Gizmo Warm-up

Burning is an example of a chemical reaction. The law of conservation of matter states that no atoms are created or destroyed in a chemical reaction. Therefore, a balanced chemical equation will show the same number of each type of atom on each side of the equation.

To set up an equation in the Chemical Equations Gizmo™, type the chemical formulas into the text boxes of the Gizmo. First, type in “H2+O2” in the Reactants box and “H2O” in the Products box. This represents the reaction of hydrogen and oxygen gas to form water.

1. Check that the Visual display is chosen on each side of the Gizmo, and count the atoms.

A. How many hydrogen atoms are on the Reactants side? ____ Products side? ____

B. How many oxygen atoms are on the Reactants side? ____ Products side? ____

2. Based on what you see, is this equation currently balanced? _________________________

Activity A:	Get the Gizmo ready:
Interpreting	•	Erase the chemical formulas in each text box.
chemical formulas	•	Check that the Visual displays are selected.

Introduction: To balance a chemical equation, you first need to be able to count how many atoms of each element are on each side of the equation. In this activity, you will practice counting the atoms that are represented in chemical formulas.

Question: How do we read chemical formulas?

1.Observe: Type “H2” into the Reactants box and hit Enter on your keyboard. Note that the formula is shown as H2 below. The small “2” in H2 is a subscript.

A.What does the “2” in H2 represent? _______________________________________

B.In general, what do you think a subscript in a chemical formula tells you? _________

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C.Try typing in other subscripts next to the H, such as 3, 4, and 5. Is your answer to question B still true? Explain. ____________________________________________

2.Count: Clear the Reactants box, and type in a more complex chemical formula: “Ca(OH)2.” Look at the number of atoms shown.

A. How many of each type of atom do you see? Ca: _____ O: _____ H: _____

B.In general, what happens when a subscript is found outside of parentheses?

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C.Try typing in other subscripts next to the (OH), such as 3, 4, and 5. Is your answer to question B still true? Explain. ____________________________________________

3.Practice: For each of the real chemical formulas below, calculate how many of each element there are. Check your answers for the first three formulas using the Gizmo.

AgCl3Cu2	Ag: _____	Cl: _____	Cu: _____
Ba(AsO4)2	Ba: _____	As: _____	O: _____
(NH4)3PO4	N: _____	H: _____	P: _____	O: _____
MnPb8(Si2O7)3	Mn: _____	Pb: _____	Si: _____	O: _____

Activity B (continued from previous page)

4.Practice: Chemical reactions are generally classified into five groups, defined below. Balance each equation, using the Gizmo for help.

Combination (or synthesis) – two or more elements combine to form a compound.

• Na + O2 Na2O			_________________________________________
• La2O3 + H2O La(OH)3			_________________________________________
• N2O5 + H2O HNO3			_________________________________________
Decomposition		– a compound breaks down into elements and/or simpler compounds.
• KNO3 KNO2 + O2			_________________________________________
• NaN3 Na + N2			_________________________________________
• NH4NO3 N2O + H2O			_________________________________________
Combustion	– a fuel reacts with oxygen to release carbon dioxide, water, and heat.
• CH4 + O2 CO2 + H2O			_________________________________________
• C3H8 + O2 CO2 + H2O			_________________________________________

•C6H12O6 + O2 CO2 + H2O _________________________________________

Single replacement – an element replaces another element in a compound.

•	KCl + F2 KF + Cl2		_________________________________________
•	Mg + HCl MgCl2 + H2		_________________________________________
•	Cu + AgNO3 Cu(NO3)2 + Ag		_________________________________________
Double replacement		– two compounds switch parts with one another.
•	AgNO3 + K2SO4 Ag2SO4 + KNO3			___________________________________
•	Mg(OH)2 + HCl MgCl2 + H2O			___________________________________

•Al(OH)3 + H2SO4 Al2(SO4)3 + H2O ___________________________________