Law of conservation of mass

6 December 2011

Catalyst 12.6.2011

RESPOND: Is it possible to make something from nothing? Explain your answer, and give an example to make your opinion stronger.

Agenda

Catalyst (5min)

Alka-Seltzer Demonstration (20min)

Alka-Seltzer Demonstration Debrief (5min)

Law of Conservation of Mass Notes (25min)

Basic Balancing Equations (25min)

Exit Ticket (5min)

Closing (2min)

Objective

Students will analyze an Alka-Seltzer tablet reaction to visualize the Law of Conservation of Mass and review parts of a chemical reaction.

Students will explain why equations must be balanced to satisfy the Law of Conservation of Mass by notes and simple balancing problems.

Alka-Seltzer Demonstration

On your handout for today, there are a series of questions for you to answer as I carry out this demonstration. Please make sure to keep up!

Yesterday in class we discussed the parts of a chemical equation. To refresh, consider the equation below:

2H2 + O2 --> 2H2O

What are the reactants in the equation? Products?

Alka-Seltzer demonstration

Citric acid and sodium bicarbonate are combined with water in a water bottle and a balloon is fixed to the top to provide a sealed cap. Mass of Water Bottle (full, no cap)Mass of Empty Water Bottle (no

cap)Mass of Water

Mass of Alka-Seltzer TabletMass of Balloon

Mass of ReactantsMass of Balloon + Water Bottle +

ProductsMass of Products

Notes

Law of conservation of mass

A chemical reaction occurs when atoms from one or more reactants rearrange to make one or more products.

The Law of Conservation of Mass states that mass (or matter) cannot be created or destroyed, although it can be rearranged in space.

Chemical equations

The Law of Conservation of Mass demands that chemical equations have the same number of atoms of each element on the reactant side as there are on the product side.

BAlancing Chemical equations

When balancing equations, we may only change the coefficients.

Coefficients can only be whole numbers (1, 2, 3, 4, etc.)

BALANCING

On your handout for today, there is a box containing a sample balancing problem. As we work the sample problem, make sure to follow along in the box.

practice problemsWork # 1 - 5 on your handout. you may choose to

work alone or with a partner.

exit ticket

You will have the next 5 minutes to complete the two exit ticket questions on your handout.

You should complete these 2 questions on your own, and you will submit your handout for a grade at the end of class.