Next Generation Science Standards (NGSS) and Middle

American Chemical Society

Next Generation Science Standards (NGSS) and Middle School Chemistry Middle School Structure and Properties of Matter: MS-PS1-4 Jim Kessler Office of K-8 Science

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.

This is a Performance Expectation so at the end of middle school, students should be able to do this.

How do you, as a teacher, help them to get there? Where do you start?

The Performance Expectation is based on information in the foundation boxes so first look at the foundation boxes. American Chemical Society

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Solids, Liquids, and Gasses Let’s look at the Disciplinary Core Ideas first:

• Gases and liquids are made of molecules or inert atoms that are moving about relative to each other. • In a liquid, the molecules are constantly in contact with others; in a gas, they are widely spaced except when they happen to collide. In a solid, atoms are closely spaced and may vibrate in position but do not change relative locations. • The changes of state that occur with variations in temperature or pressure can be described and predicted using these models of matter.


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Definitions of Energy also Addressed • The term “heat” as used in science refers to the energy transferred due to the temperature difference between two objects. • Temperature is a measure of the average kinetic energy of particles of matter. (From MS Energy)

• It is “secondary” because it is dealt with more directly in the middle school topic Energy.


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The Main Ideas for this PE •

Solids, liquids, and gases are made up of atoms and molecules.

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The arrangement and motion of atoms and molecules are different in solids, liquids, and gases.

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Adding or removing energy affects the motion and arrangement of atoms and molecules and can result in a change of state.

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Temperature is a measure of the average kinetic energy of molecules.

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Heat is energy that is transferred from one substance to another due to a difference in temperature.


These are topics that you probably already teach!

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The Science and Engineering Practice and Crosscutting Concept For MS-PS1-4: Science and Engineering Practice •

Develop a model to predict and/or describe phenomena.

Crosscutting Concept •

Cause and effect relationships may be used to predict phenomena in natural or designed systems.


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So What Do You Do? There are lots of ways for students to model the arrangement and motion of atoms and molecules that make up solids, liquids, and gases. •

For the purpose of the NGSS, developing and using the model should be to predict or describe phenomena.

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You don’t want students to jump in and start building models of molecules without any context.

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The idea is to start with and investigate phenomena in order to develop a model to understand and explain that phenomena.

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This way, students will be engaged in a science practice and learning the disciplinary core idea while also becoming proficient in the practice.


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Here Comes a Phenomena! Lesson 1.1 – Molecules Matter

Students begin to develop a particle-level model of water by observing 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 attracted? Why?


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Thinking about Molecules Students observe another familiar phenomena. Guide them to think about it on the molecular level. 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 Introduce the idea of a model. The spheres are used to represent water molecules. Molecules are in constant motion. Attractions keep molecules close together.

Students use the activity sheet to make their own drawings with captions.


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Plan and Carry Out an Investigation Lesson 1.2 - Heating and Cooling Water Further develop the model by doing an investigation.

Ask students: If you wanted water molecules to move faster, what could you do?

If you wanted to test whether heating or cooling water affects the motion of the molecules, how could they do it?


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Heating and Cooling Water Does heating or cooling water affect the motion of water molecules?

Planning and Carrying Out an Investigation Ask students how they would design the experiment. Use the same amount of water? Use the same type of cup? Use the same color food coloring? Put it in the water at the same time and in the same way?


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Heating and Cooling Molecules Continue Developing the Model Ask students and discuss what the experiment showed. Show a molecular model animation to help students visualize on the molecular level.

Have students draw and describe what happens to the molecules in the model as they are heated and cooled


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Investigate a Phenomenon and Use the Model to Describe and Predict

Lesson 1.3 – The Ups and Downs of 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 the thermometer is placed in hot water? •Why the liquid goes down when the thermometer is placed in cold water?


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How Thermometers Work on the Molecular Level • Hot: faster, further apart, move up • Cold: slower, closer together, move down • Students draw their model and add captions to explain


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Heating and Cooling a Solid

Lesson 1.4 – Moving Molecules in a Solid

Do the ball-and-ring demonstration or show the video. Ask students: If solids are also made of atoms and molecules, explain why this happens on the molecular level. Discuss student ideas.


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Molecular Motion in Solids • Show the molecular model animation. • Discuss how the model relates to the ball-and-ring demonstration. • Students draw their own model and use captions to explain.


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Modeling the Molecules of a Gas Lesson 1.5 – Air, It’s Really There

Show students that air is made up of molecules that have mass and take up space. The molecules of a gas are matter.


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Molecular Motion in Gases

• Discuss the differences between the arrangement and motion of molecules in solids, liquids, and gases.


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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. Ask students: On the molecular level, why does this happen?


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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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Modeling heating and cooling a gas

Heating: • The faster-moving molecules in the heated sample push harder against the detergent film and the outside air pressure and expand the detergent into a bubble. • Cooling: • The slower-moving molecules in the cooled sample push less hard against the detergent film and the outside air pressure. This outside air pressure causes the bubble to contract and go into the bottle.


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NGSS MS-PS1-4 and Chapter 1 Summary •

Students investigated heating and cooling a solid, liquid and gas.

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Students participated in developing a particle model of a solid, liquid, and gas.

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The model described and predicted the motion of the particles when thermal energy was added (heated) and when thermal energy was removed (cooled).

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This is a good start to 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.

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Chapter 2 lessons will focus on a definition of temperature and state changes. American Chemical Society

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Questions?


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Lesson 2.1 Heat, Temperature, and Conduction

Room temperature washers placed in hot water. The temperature of the water decreases. The temperature of the washers increases. (not shown)

Ask students: Why do you think this happens?


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Heat Transfer by Conduction Energy is transferred from faster moving molecules in the soup to slower moving atoms in the spoon. This process of energy transfer by contact is called conduction. Students use the activity sheet to draw and describe their own particlelevel model.

In science, heat is the energy transferred due to a difference in temperature. So what is temperature?


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What is Temperature? Remind and discuss with students that in any substance, whether solid, liquid, or gas, the particles are in motion. Since the particles are moving, they have a type of energy called kinetic energy.

MS Energy PS3.A •

Temperature is a measure of the average kinetic energy of the atoms or molecules of a substance.


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Changes of State Chapter 2, Lesson 2: Evaporation Show students a moist brown paper towel. What are some common examples of evaporation? What are some factors that affect how fast or slow water evaporates? How could we design a test to see if temperature affects the rate of evaporation?

Room Temp. Hot


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Heating and the Rate of Evaporation

Adding energy increases molecular motion. More molecules will be moving fast enough to overcome their attractions and break away to become a gas.

Students interpret and describe the molecular-level model.


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Different Models of Water While students wait for evidence from their experiment: Introduce the more detailed model of a water molecule.

The water molecule is composed of two hydrogen atoms bonded to an oxygen atom. Decide how much detail you want to get into with students.


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Why are Water Molecules Attracted to One Another? You could tell students that because of the way the oxygen and hydrogen atoms are bonded to each other, a water molecule is more negative near the oxygen and more positive near the hydrogen. The negative area of the oxygen atom of one water molecule attracts the positive area of the hydrogen atom of another. This is why water molecules attract each other.


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Water Vapor As a result of evaporation, liquid water becomes water vapor, a gas.

During evaporation, water molecules separate from one another but the bonds between the atoms within the molecules do not come apart.

Students make 3-D Styrofoam models of water molecules. They use the molecules to model increased molecular motion and increased rate of evaporation.


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Chapter 2, Lesson 3: Condensation Hot water is placed in the bottom cup. Empty tall cup turned upside down and placed on top. Students see that the inside of the top cup turns from clear to cloudy.

On close examination they see that the cloudiness is actually tiny water droplets. How could this happen?


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The Process of Condensation Condensation using hot water and two cups

• Water evaporated from the hot water in the bottom cup and became water vapor. • Molecules of water vapor touched the inside of the cooler top cup. • These molecules transferred some energy to this cooler cup and slowed down. • Since they were moving slower, their attractions were able to bring them together and form liquid water. American Chemical Society

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Designing a Test to See if Temperature Affects Condensation? What test could we do to see if cooling water vapor increases the rate of condensation? Identify and control variables

• • • •

Amount of water placed in lower cups Initial temperature of hot water placed in cups Type of upper cup used When upper cups are placed on lower cup

The cup that had the ice has larger drops of water. This suggests that more water vapor condensed to liquid water in the cup that was cooled.


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NGSS MS-PS1-4 and Chapter 2 Summary 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. Students explored the meaning of heat , temperature, energy transfer, and change of state. Liquid to gas (Evaporation): •Molecules gain enough energy and move fast enough to overcome the attractions of other water molecules. •Adding energy (heating) increases the rate of evaporation. Gas to liquid (Condensation): •Molecules lose enough energy and move slow enough for their attractions to keep them together as a liquid. •Removing energy (cooling) increases the rate of condensation. American Chemical Society

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Chapter 2, Lesson 4: Freezing How does ice form on the outside of an ice cream container or cold can? Based on what students know so far, they can attempt an explanation: • There are water molecules in the air. • These molecules contact the cold can. • These faster-moving molecules transfer some of their energy to the colder can. • This causes the molecules slow down. • Attractions cause the molecules to condense to form liquid on the can. • The liquid then freezes to form ice.


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Water Molecules in Ice Water molecules arrange themselves into a repeating crystal pattern as solid ice. The six sides of the crystal are Reflected in the six-sided symmetry of snowflakes.


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Molecular Motion in Ice Although the molecules in ice are in fixed positions at 0 °C or lower, and do not move past each other, they still vibrate. There is molecular motion at any temperature.


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Ice Melting

• As energy is added, the motion of molecules increases. • Motion eventually overcomes attractions and molecules begin to move past each other as the crystal structure collapses.

• Molecules are closer together as liquid water than they were as solid ice.


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When Things Get Too Cold

Liquid water freezes and expands as it becomes solid ice. The force of the expanding ice on the metal container is so great that it shatters.


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Putting It All Together Changing state is about the attractions and motions of the molecules that make up a substance.

Adding energy: •Increases molecular motion enough to overcome attractions •Changes a solid to a liquid and a liquid to a gas.

Removing energy: •

Decreases molecular motion enough for attractions to hold molecules closer together

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Changes a gas to a liquid and a liquid to a solid.

How is water the same or different from other substances when it comes to changing states?


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Questions?

Next Generation Science Standards (NGSS) and Middle

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