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Middleschoolchemistry.com
Big Ideas about the Very Small
Chapter 1:
Matter – Solids, Liquids, and Gases
Welcome
What is
middleschoolchemistry.com?
Six chapters of activity-based lesson plans in
chemistry-related physical science for middle
school.
Lessons align with state standards and the
Next Generation Science Standards (NGSS).
Three main goals:
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Help students understand and be able to
explain basic chemistry concepts on the
molecular level.
•
Help students to design and conduct valid
scientific experiments.
•
Help students see the chemistry in
everyday life.
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What’s in a Chapter?
•
Fully-developed 5-E Lesson Plans
–
Hands-on Activities
–
Student Activity Sheets
–
Multimedia
–
Extra Teacher Background
•
Student Reading
•
Test Bank
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Goals of the Webinar
•
Review some basic beginning-of-the-year
chemistry concepts and lessons you can use
from middleschoolchemistry.com (MSC) to
help students investigate them.
•
See how the philosophy and format of the
MSC lessons offers flexibility in how you might
use it for different teaching situations.
•
See how MSC supports the disciplinary core
ideas, science practices, and crosscutting
concepts in the NGSS and state standards.
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Who are You and Why are You Here?
A Poll
What grade level do you teach?
Have you used Middlescchoolchemistry.com before?
Has your state adopted the NGSS and what is happening to address them?
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A Quick Look at the Website
Let’s take a quick look at the website to see a few of the main features.
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Lesson 1.1
Molecules Matter
Engage
Explore
Explain
Evaluate
Extend
What are some examples of matter?
A chair
A hat
A mustache
A rock
Matter is basically stuff.
How about a liquid, like water? Is water matter?
How about you? Are you matter?
How about a gas, like air? Is air matter?
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A Close Look at Water
Engage
Explore
Explain
Evaluate
Extend
All the lessons in MSC are based on
students observing some common
phenomenon and trying to investigate,
on the molecular level,to figure out why it
happened.
Students observe water on wax paper.
Does the water drop stay together or
come apart easily?
If water was made of tiny particles
(molecules), would you say they are
attracted to each other or not?
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The Motion of Water Molecules
Engage
Explore
Explain
Evaluate
Extend
What else can we learn about the particles that make up water?
Why do you think the
food coloring spread
out?
If the food coloring is also
made of particles, how
could the water molecules
help to spread them out?
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Molecular Model Animation - Liquid
Engage
Explore
Explain
Evaluate
Extend
Attractions keep molecules
close together
Molecules are in motion and
move past each other
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Drawing a Model of a Liquid
Engage
Explore
Explain
Evaluate
Extend
The student activity sheet serves as the “Evaluate” for each lesson
Students draw a model of
water molecules and a
caption to describe what
their model represents.
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Effects of the Attractions of Water
Molecules
Engage
Explore
Explain
Evaluate
Extend
Why do you think the water keeps
its shape the moment the balloon
is popped?
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Play a Water Game
Engage
Explore
Explain
Evaluate
Extend
Let’s play “Water Drops Unite” & “Race Drop Raceway”
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Why are Water Molecules Attracted to Each
Other? (Covered in Chapter 2 and 5)
The water molecule is composed of
two hydrogen atoms bonded to an
oxygen atom.
These are covalent bonds in which
electrons are shared between the
oxygen atom and the hydrogen
atoms.
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Water Molecules Attract Each Other
In the bonds in a water molecule, the
electrons are not shared equally.
The electrons are more attracted to the
oxygen atom than to the hydrogen
atoms. This makes water a “polar”
molecule.
Water molecules attract one another
according the their opposite polar ends.
This accounts for the cohesion between
water molecules and gives water many
of its characteristic properties.
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Lesson 1.2
Heating and Cooling Water
Ask students: What do you think you could do to the water to make the
water molecules move faster?
If you wanted to test whether heating
or cooling water affects the motion of
the molecules, how could you do it?
How would we make sure your test
is fair?
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Heating and Cooling Water
On the molecular level, why does heating the water affect how fast
the food coloring mixes in the water?
Adding or removing energy affects the
speed of molecules
• Heating a liquid increases
molecular motion
• Cooling a liquid decreases
molecular motion
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Moving Molecules
Aside from moving faster or slower, what else changes about water
molecules as the temperature changes?
Add energy
• Faster motion competes
with attractions
• Further apart
Remove energy
• Slower motion competes
with attraction
• Closer together
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Liquid
Characteristics of a liquid on the molecular level
• The molecules of a liquid move at a certain speed at room
temperature.
• The attractions between the molecules are strong enough to
keep them close together at that speed.
• Adding energy (heating) makes molecules move faster causing
them to move a little further apart.
• Removing energy (cooling) makes molecules move slower
causing them to move a little closer together.
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Quick (very) overview of the NGSS
•
Each NGSS standard is written as a performance expectation describing
what students should be able to do at the end of a grade band.
•
Each performance expectation attempts to integrate elements from three
areas:
– Science and Engineering Practices
• Asking questions, developing and using models, planning and conducting
investigations, analyzing and interpreting data,…
– Disciplinary Core Ideas
• Substances are made from different types of atoms, which combine with one another
in various ways. Each pure substance has characteristic physical and chemical
properties that can be used to identify it,….
– Crosscutting Concepts
• Cause and effect, structure and function, …
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Middle School NGSS for Chemistry
MS. Structure and Properties of Matter
Performance Expectations
Students who demonstrate understanding can:
•
MS-PS1-1 Develop models to describe the atomic composition of simple
molecules and extended structures.
•
MS-PS1-4 Develop a model that predicts and describes changes in
particle motion, temperature, and state of a pure substance when thermal
energy is added or removed.
•
MS-PS1-3 Gather and make sense of information to describe that
synthetic materials come from natural resources and impact society.
(Not addressed)
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Lesson 1.3
An Application of Molecular Motion in
Liquids: Thermometers
Students place a thermometer in hot and then in
cold water.
Ask students to explain, on the molecular level:
• Why the liquid goes up when a thermometer is
placed in hot water?
• Why the liquid goes down in cold water?
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How Thermometers Work
• Hot: faster, further apart, move up
• Cold: slower, closer together, move
down
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Lesson 1.4
Molecular Motion in Solids
Do the same principles that apply to liquids also apply to solids?
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Heating and Cooling a Solid
Ask students: If solids are also
made of atoms and molecules,
try to explain why this happens
on the molecular level.
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How are the Atoms of a Metal
Attracted to Each Other?
The atoms of a metal are
attracted to one another in a
way called “metallic bonding”.
The outer electrons move
between the metal atoms
(positive ions).
The attraction between the
positive metal ions and the
negative electrons holds the
metal together as a solid.
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Solids vs. Liquids
•Vibrate
•Attracted to each other
•Don’t move past each other
Assume that the solid and liquid
are both at room temperature.
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Heating and Cooling a Solid
• Hot: faster, further apart
• Cold: slower, closer together
Flexible joints in roads keep the
road from cracking as it expands
and contracts with changes in
temperature.
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Solid
Characteristics of a solid on the molecular level
• The atoms or molecules of a solid move at a certain speed at
room temperature.
• The attractions are strong enough to keep them close together at
that speed and to hold them in fixed positions as a solid.
• Adding energy (heating) increases the motion of the atoms
causing them to move a little further apart.
• Removing energy (cooling) decreases the motion of the atoms
causing them to move a little closer together.
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Gasses are Matter Too
Air is made up of molecules of
different gasses. It is about 78%
nitrogen and about 20% oxygen.
These molecules have mass and
take up space.
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Lesson 1.5
Molecular Motion in Gases
• Very far apart
• Very weak attractions
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Heating and Cooling a Gas
The mouth of an “empty”
bottle is dipped into a
detergent solution.
The bottom of the bottle is
placed in hot water and then
in cold water.
On the molecular level, why
does this happen?
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Modeling heating and cooling a gas
• Outside air pressure is the same on both.
• The faster-moving molecules in the heated
sample push harder against the air pressure and
expand the bubble.
• The slower-moving molecules in the cooled
sample push less hard against the air pressure
which causes the bubble to contract.
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Heating and Cooling a Gas
• Warmer, faster moving
molecules push harder from
the inside against the bubble
film than the air pressure
pushes from the outside.
• Cooler, slower moving
molecules don’t push as hard
as the outside air pressure
which pushes the bubble down.
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Why are the Molecules of the Gases
in Air Not Attracted to Each Other?
Nitrogen gas (N2)
Nitrogen (N2) and oxygen (O2) gas are made
of two identical atoms bonded together. Each
atom attracts the electrons of the other
equally. There is no polarity like in the water
molecule.
Oxygen gas (O2)
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Gas
Characteristics of a gas at the molecular level
• The molecules of a gas move at a certain speed at room temperature.
• The attractions between the molecules are not strong enough at that
speed to keep them close together as a liquid or a solid; therefore,
they move independently as a gas.
• Adding energy (heating) increases the motion of the molecules, and if
they can, they move further apart.
• Removing energy (cooling) decreases the motion of the molecules,
and if pushed on hard enough, they move closer together.
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Solid, Liquid, or Gas – The Big Ideas
Solids, liquids, and gases are all made out of atoms or molecules (particles).
These particles are in motion.
In solids and liquids, the attractions between the particles keep them close
together. - Fixed positions in solids and sliding past one another in liquids.
In gases, the attractions are so weak that the particles do not stay near each
other.
Adding energy (heating) increases molecular motion, competes with
attractions and particles move further apart.
Removing energy (cooling) decreases molecular motion and attractions bring
particles closer together.
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For more resources …
www.middleschoolchemistry.com
For more information, contact us at k8education@acs.org
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