Density and Avogadro’s Law V α n
Name: Kellie Gentile
Class/Subject: Chemistry/Gas Laws
Date: November 11, 2013
Content Standards/Performance expectations
Overall NGSS: “develop and use models to illustrate that energy at the macroscopic scale
can be accounted for as a combination of energy associated with the motions of particles
(objects) and energy associated with the relative positions of particles (objects)”.
Cause and Effect: In a system of constant temperature and pressure, what is the
relationship between volume and molecules of gas? Volume is directly proportional to
molecules of gas.
Student Objectives:
A) Students will derive the relationship between volume and molecules of gas
under fixed pressure and temperature. The relationship students deduce is
volume directly proportional to mols of gas.
B) Students recognize parallels between Avogadro’s Law and density.
Avogadro’s Law is a chemistry perspective of density.
Assessment Criteria
A & B) To assist student’s derivation of the Avogadro’s Gas Law I have created a
scaffold worksheet. The questions also connect the similarities between density
and Avogadro’s Law as well. The worksheet contains three distinct sections to
lead to the derivation of Avogadro’s Law v α n. The first section relates to the
introductory demo “Bubbling Lava Lamp”. Students have to explain how the
“Bubbling Lava Lamp” or lava lamps in general work. The lamp can function
because of varying material densities. Section II builds off section one by
asking for examples of density units. Students will create a web model to
express possible density units. Now to transition from density to an actual
gas law the third section states a real world scenario. The same variable
chart from lesson one appears after. Students have to decipher the varying
gas law variables and provide evidence to support their claim. The students
will write out a predicted gas law for the real world example. Students
should begin to recognize density variables comprise Avogadro’s Law. A
PowerPoint slide and group discussion will highlight the newly found
relationship between mols and volume and how it’s a new perspective on
density.
Where in the lesson is this addressed?
The initial hook for deriving Avogadro’s Law begins with the introductory
“Bubbling Lava Lamp” demo. The informal assignment will be the completion of
the scaffold worksheet. The worksheet includes a web model for density and a
section bridging the parallel relationship between density and Avogadro’s Law. A
final group discussion will finalize the correct interpretations and a PowerPoint
slide will illustrate a mathematical perspective of Avogadro’s law.
Prior Knowledge:
Make observations and measurements to identify materials based on their
5-PS1-3.
properties.
Students should associate density with g/mL or mass/volume. Although not specifically
an identifiable property, the concept is discussed at the fifth grade level.
Materials/Resources/Technology:
Bubbling lava lamp- glass jar, cap, vegetable oil, food coloring, Alka-Seltzer tablets,
flashlight, water (Demonstration of Gas Laws PDF)
Density/ Avogadro’s Law (note) worksheet
Time 50-minute class period. * Before students arrive prep class demonstration
‘Bubbling Lava Lamp’.
5-10 min
5 minutes
Start of Class:
In replacement of a bellringer we will discuss previous night’s
homework. The homework involved students to research real world
examples incorporating the Gay Lussac’s Gas Law. Initially ask for
volunteers. If no one is volunteering randomly ask an array of students to
answer the bellringer. Students need to state their example and explain
how the law applies to the situation.
Introduction of Lesson:
-Before Students arrive, set-up the Bubbling Lava Lamp and turn off
lights. Here is a short version procedure. The formal instruction can be
found at the website
http://www.stevespanglerscience.com/lab/experiments/bubbling-lavalamp
1) Fill the glass jar ¾ full with vegetable oil
2) Fill the rest of the glass jar with water
3) Add about 10 drops of food coloring. Coloring should be fairly dark.
Notice the coloring only affects the water
4) Divide Alka-Seltzer into 8 pieces
Once students have completed the bell ringer collect their examples
written on paper. Then alert the students to focus on the hand-made Lava
Lamp. Turn the lights off and place the gas jar on a flashlight. Briefly
explain the contents and highlight the fact that only the water is colored.
After drop one at a time the eight Alka-Seltzer pieces. Add another one
once the bubbling stops. Once the pieces are all dissolved cap the jar and
tip the bottle back and forth for the students to see. Tiny drops of liquid
join together to make big lava like blob. Pass the jar around the class for
the students to examine more. Also, turn on the lights. Announce the
introductory question how Does the lava lamp works? The students are to
work in lab group pairs. In other words each lab group of 4 will split into
2 individual pairs. Pass out the worksheet and the each pair must fill out
their own personal copy.
20-25
Minutes
Lesson Instruction:
Part I
In pairs of two, students address the question how does it work? What is
the main identifiable property of matter that allows it to float or sink? As
students complete part one, I will conduct an informal assessment. I will
travel from group to group reviewing their answers for part one. If they
oversaw the identifiable property (density) I may pose the question why
the glob of water was able to flow through the oil when tipping the glass
back and forth? Also, have the glass jar handy for students to visually see
the model. Mark part one with initials to keep tally of which pairs have
been checked.
Part II
Students realize density is a major contributor to the function of the lava
lamp. Now students need to start to connect mass to mols and volume to
liters. The students will brainstorm various units of density (Web model)
5-10 examples. Walk around and ask groups what were some of their
examples. Foster the idea of creating a density unit relatable to chemistry.
Ask them to think about mass units and volume units applicable to our
subject area.
Part III
Last students will investigate the relationship between mols of gas and
volume. The worksheet presents the following life example; Lungs
expand as they fill with air then the longs contract as air is released.
Again the gas law variable chart is presented. Students need to identify
which gas related variables varied and stayed constant. If students are
stuck have them write out before and after states of variables (volume and
mols of air should be changing). Once students have identified the
manipulative variables, they will propose a predicted gas law for mols of
gas and volume.
Assessments/Checks for Understanding:
As stated in the lesson instruction part one an initial check will be
conducted pertaining to the bubbling lava lamp question “how does it
work”? Each group should recognize an object’s density determines if it
will float or sink.
The formal assessment will be worksheet scaffolding the relationship
between density and Avogadro’s Law. It will be collected and graded.
Another informal assessment will be a class discussion about the
worksheet. Reviewing appropriate answers for each of the three sections.
A PowerPoint slide will clearly state Avogadro’s Law and illustrate it in a
mathematical viewpoint utilizing proportions.
Lesson Plan two assessment is alternative because the Avogadro’s Lab
presented incorporates the inquiry based 5E model. The lab encourages
student communication. Since this lab involves lab partners instead of
groups it restricts the appearance of some students working and others
messing around. Although there is only one demonstration to explore
students now have other aids such as a web model, and a real world
scenario. The real world scenario allows students to synthesize similarly
to the engineering profession. Again, I will elaborate on the worksheet to
clear any misconceptions after each group has finished. The evaluation of
the lab is the associated worksheet.
15 minutes
Closure/Wrap-Up/Review:
Recollect students and review the main idea that density is similar to
mols per volume and the number of mols is directly proportional to the
volume. A PowerPoint slide will clearly state Avogadro’s Law and
illustrate it in a mathematical viewpoint utilizing proportions
(V1/n1)=(V2/n2).
This is known as Avogadro’s Law
Self-Assessment (optional):
Rationale for the activity, activity structure, planning etc needs to go here
To begin, the students had to research a real world example incorporating the Gay
Lussac’s gas law. Therefore, in place of a bell ringer, I will ask students to share their
examples. I want student to highlight the changes in pressure and temperature. Again the
rationale for this procedure is to see if students can relate these mathematical statements
to functioning systems. From and engineering perspective students should recognize how
gas laws can relate to a given system. After a few students answer aloud, I will collect
their written examples.
Moving on, I will introduce Avogadro’s Law informally with a demo titled
Bubbling Lava Lamp. Many students have seen a lava lamp before, but few have
questioned its workings. In pairs, I want the students to focus on ‘how does it work’? The
materials used in the lava lamp include oil, water, and Alka-Seltzer tablets. From these
materials, I expect students rationalize density as a plausible explanation. The exhibited
water, oil, and the color blobs will float or sink as a result of differing densities. Students
will record their thoughts on an accompany worksheet and I will float between groups
informally checking their rationales. This activity engages student-student relationships
and allows the pairs to question each other’s function explanations. I’m their floating as a
guide to redirect pairs if their tangents are not applicable to the given situation. I would
scaffold struggling groups to alternative explanations allowing students room to explore
why and conclude supporting evidence. I may pose a similar scenario like the lava lamp
that students encounter everyday such as, why does ice float in water? It’s essentially the
same but what makes ice different then water allowing it to float?
Once concluding density, each pair will start to brainstorm various units of
(mass/volume) using a web model. Students need to see that density can be defined in
other units besides g/mL. Students are encouraged to think about the different mass units
incorporated in their chemistry classroom as well. Pairs will be required to write 7-8 units
describing density.
Then students will read a life example referencing human lungs. The students will
have to fill out a similar chart used on the Gay Lussac’s Law worksheet. In this case, the
volume and mols of air are changing, but pressure and temperature is held constant.
Students will take note of the before and after states of p, v, n, and t.
When the groups finish, I will discuss the worksheet, focusing on the Lung
example. The lung example illustrated how volume of gas is proportional to mols of gas,
which is Avogadro’s Law. In additional, Avogadro’s Law can relate to density because it
incorporates mass/volume. Avogadro’s Law is another perspective on the concept of
density. The notes are simply and elaboration on their group work.
To conclude, the students homework will be to review the Boyle’s, Charles, Gay
Lussac’s and Avogadro’s Law because tomorrow we will be working with all four to
derive the Ideal Gas Law.
Name
Date
.
I. Bubbling Lava Lamp
HOW DOES IT WORK?
II. Density Web Model
Brainstorm different units of density (mass/volume). Specifically
think about mass units pertaining to this classroom
III. Real Life Example
Lungs expand as they fill with air, then the lungs contract as air is released.
Variables Held Constant vs. Variables Manipulated
Pressure
Volume
Temperature
Mols of Gas
Constant
Varied
Explain:
RELATED GAS LAW
Discussion)
. ( Class