Objective:◦ Today I will be able to:

Determine the percent composition for each element in a compound

Determine the percent composition of sugar in gum Evaluation/Assessment:

◦ Informal assessment – monitoring student interactions as they complete the gum lab and the practice

◦ Formal assessment – analyzing student responses to the gum lab, the practice and the exit ticket

Common Core Connection◦ Make sense of problem and persevere in solving them ◦ Look for and express regularity in repeated reasoning ◦ Attend to precision ◦ Use appropriate tools strategically

Evaluate: Warm – Up Engage and Explore: Percent Composition

of Gum Lab Explain: Percent Composition Notes Elaborate: Percent Composition Practice Evaluate: Exit Ticket

An organic compound with a molecular mass of 140 g/mol is 68.54% carbon, 8.63% hydrogen, and 22.83% oxygen.

What is the molecular formula of the compound?

Today I will be able to:◦ Determine the percent composition for each

element in a compound◦ Determine the percent composition of sugar in

gum

Finish Percent Composition Practice

Start studying for quiz on Monday 3/17!!!

Warm-Up Percent Composition Notes Percent Composition of Gum Lab Percent Composition Practice Exit Ticket

To calculate the percent composition of sugar in gum

First you need the mass of your gum before you chew it◦ Take the mass◦ Chew the gum as we take notes◦ DO NOT THROW AWAY THE WRAPPER

Percent Composition – is the mass of each element in a compound compared to the entire mass of the compound x 100

Example: What is the % composition of oxygen and

hydrogen in water? Water = H2O = 18 g/mol

2 g H2

18 g H2O

x 100 =

11.1 % Hydrogen

16 g O18 g H2O

x 100 = 88.9 % Oxygen

Q: Find the % composition of a compound that contains 2.30 g sodium, 1.60 g oxygen, and .100 g hydrogen in a 4.00 g sample of the compound?

2.30 g Na

4.00 g

x 100 = 57.5 %1.60 g O4.00 g

.100 g H4.00 g

x 100 =

x 100 = 40.0 %

2.50 %

A sample of an unknown compound with a mass of .562 g has the following % composition: 13.0% carbon, 2.20% hydrogen, and 84.8% fluorine. When this compound is decomposed into its elements, what mass of each element would be recovered?

13.0% C

100

x .562 g = .0731 g C

2.20 % H

100

84.8 % F100

x .562 g =

x .562 g = .0124 g H

.477 g F

Mass your chewed gum. Be sure to put the wrapper down on the balance first

Complete the calculations and the questions

When you finish, you may begin working on the percent composition practice worksheet

Complete the practice at your desk. Problems not completed in class will become your

homework.

Write your percent composition of sugar in gum on the board.

We will discuss the results as a class