American Chemical Society Middleschoolchemistry.com Big Ideas about the Very Small Chapter 1: Matter – Solids, Liquids, and Gases

American Chemical Society

Middleschoolchemistry.comBig Ideas about the Very Small

Chapter 1:

Matter – Solids, Liquids, and Gases

American Chemical Society 2

WelcomeWelcomeSix 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:

•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.

What is middleschoolchemistry.com?


What’s in a Chapter?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


Goals of the WebinarGoals 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.


Who are You and Why are You Here?Who are You and Why are You Here?A PollA 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?

A Quick Look at the Website

Let’s take a quick look at the website to see a few of the main features.



Lesson 1.1Lesson 1.1Molecules MatterMolecules Matter

What are some examples of matter?A chairA hatA mustacheA 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?

Engage Explore Explain Evaluate Extend


A Close Look at WaterA 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?


The Motion of Water MoleculesThe Motion of Water Molecules

ExploreEngage 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?


Molecular Model Animation - LiquidMolecular Model Animation - LiquidExploreEngage Explain Evaluate Extend

Attractions keep molecules close together

Molecules are in motion and move past each other


Drawing a Model of a LiquidDrawing a Model of a Liquid

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.


Effects of the Attractions of Water Effects of the Attractions of Water MoleculesMolecules


Why do you think the water keeps its shape the moment the balloon is popped?


Play a Water GamePlay a Water Game

Let’s play “Water Drops Unite” & “Race Drop Raceway”



Why are Water Molecules Attracted to Each Why are Water Molecules Attracted to Each Other? (Covered in Chapter 2 and 5)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.


Water Molecules Attract Each OtherWater 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.


Lesson 1.2Lesson 1.2Heating and Cooling WaterHeating and Cooling Water

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?

Ask students: What do you think you could do to the water to make the water molecules move faster?


Heating and Cooling WaterHeating 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


Moving MoleculesMoving Molecules

Aside from moving faster or slower, what else changes about water molecules as the temperature changes?

Add energy

• Further apart

• Faster motion competes with attractions

Remove energy

• Closer together

• Slower motion competes with attraction


LiquidLiquid

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.

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, …


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)



Lesson 1.3Lesson 1.3An Application of Molecular Motion An Application of Molecular Motion in Liquids: Thermometersin 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?


How Thermometers WorkHow Thermometers Work

• Hot: faster, further apart, move up

• Cold: slower, closer together, move down


Lesson 1.4Lesson 1.4Molecular Motion in SolidsMolecular Motion in Solids

Do the same principles that apply to liquids also apply to solids?


Heating and Cooling a SolidHeating 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.


How are the Atoms of a Metal How are the Atoms of a Metal Attracted to Each Other?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.


Solids vs. LiquidsSolids vs. Liquids

Assume that the solid and liquid are both at room temperature.

•Vibrate

•Attracted to each other

•Don’t move past each other


Heating and Cooling a SolidHeating 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.


SolidSolid

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.

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.


Lesson 1.5 Lesson 1.5 Molecular Motion in GasesMolecular Motion in Gases

• Very far apart

• Very weak attractions


Heating and Cooling a GasHeating 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?

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.


Heating and Cooling a GasHeating 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.

Why are the Molecules of the Gases in Air Not Attracted to Each Other?


Nitrogen gas (N2)

Oxygen gas (O2)

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.


GasGasCharacteristics 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.

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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American Chemical Society Middleschoolchemistry.com Big Ideas about the Very Small Chapter 1: Matter – Solids, Liquids, and Gases