Phase Change Facilitator Guide States of Matter


Phase Change
Physical Science
Grade Level
Activity Names
States of Matter
Being Prepared
Please check that the computers you plan to use with students run properly ahead of time. Try the activities in advance.

States of Matter. Once again this activity uses a model, so, individual or pair work is possible. Plan ahead to reserve computers and arrange a layout in the classroom for computers and cords.
Getting Started
States of Matter
Share how the models work and how to create a snapshot and use the drawing tools before students begin working, if you think your students will struggle with the directions. Limit the time at each section, if needed. Students MUST read the directions to be successful.

Suggested Timeline
Each activity can be completed in a 45 minutes class period if students are familiar with the models and how to use the sensors. If this is not the case, allow another class period. A pre-lab day could be done before the unit to introduce students to the site, look at models, practice with the sensor, and how to take snapshots. Students can go back to the site the next day and finish the activity.
Thinking about the Discovery Questions
In this unit, students will investigate the three primary states or phases of matter -- solid, liquid, and gas -- at the atomic or molecular level, and how matter changes from one phase to another. In "States of Matter", students use models to investigate forces and attractions at the molecular level in each state.

Misconceptions about phase change still exist at the middle school level.  For the transition from liquid to gas, students may continue have trouble identifying the air as the final location of evaporating water. They may also be challenged by the idea that all materials behave in the same manor, passing through the same phases, though the amount of energy required for phase change varies for different materials.  For example, they may have seen solid iron and liquid iron, but not accept the idea that with enough energy (heat) the iron will become a gas.

Students of all ages show a wide range of beliefs about the nature and behavior or particles. They may lack an appreciation of the very small size of particles; believe there must be something in the space between particles; have difficulty in appreciating the intrinsic motion of particles in solids, liquids and gases; and have problems in conceptualizing forces between particles.  
Learning Objectives
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-PS3-4.	Plan an investigation to determine the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample.

Physical Science – Transfer of Energy
Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei and the nature of a chemical. Energy is transferred in many ways.

Physical Science – Properties and Changes of Matter
Heat moves in predictable ways, flowing from warmer objects to cooler ones, until both reach the same temperature.

Physical Science – Properties and Changes of Matter
A substance has characteristic properties, such as density, a boiling point, and solubility, all of which are independent of the amount of the sample. A mixture of substances often can be separated into the original substances using one or more of the characteristic properties.
Discussion: Setting the Stage
Q: What is kinetic energy?
A: Kinetic energy is the energy of motion that depends on the objects speed and mass. The faster an object moves, the more kinetic energy it has. For a given speed, the more massive an object is, the more kinetic energy it has.

Q: What are the three common (primary) states of matter?
A: The three common states are solid, liquid and gas (plasma and BEC discussed in additional background).

Q: What is the freezing point of water?
A: The freezing point of water is 0° C (32° F).

Q: What are the different scales used to measure temperature?
A: Celsius which most of the world uses and that we usually use in science, Fahrenheit which is commonly used in the US, Kelvin is a scale that starts at absolute zero or 0° K where all atomic movement would stop (for comparison 0° C = 32° F =273.16° K, the model mentions 300 K which is room temperature).
Discussion: Formative Questions
Q: For a single material, in which state of matter are the molecules moving the fastest?
A: In the gas phase molecules have enough energy to completely break away from each other and move further apart.
Discussion: Wrapping Up
Q: Why do the molecules move faster as the temperature increases?
A: Temperature is a measure of the motion of the molecules, as the temperature increases so does the movement of particles. This represents an increase in kinetic energy. As the temperature increase the atoms jiggle around more vigorously. The higher the temperature, the more thermal energy atoms have and the faster they move around. Thermal energy is transferred to kinetic energy.
Additional Background
There are 4 common states of matter. Plasma is ionized gas that has enough energy that some of the electrons are free to travel and is the most common state in the universe (an example is the sun), though when introducing states of matter to students we usually focus on solids, liquids, and gases. Solids are formed when the attractive forces between individual molecules are greater than the energy causing them to move apart. Individual molecules are locked in position, and cannot move past one another. The atoms or molecules of solids are always in motion. When the temperature of a solid is increased,the solid retains its shape. In liquids, molecules can move past one another and bump into other molecules; however, they remain relatively close to each other like solids. As the temperature of a liquid is increased, movement of individual molecules increases. As a result, liquids can “flow” to take the shape of their container. Thus liquids have an undefined shape, but a defined volume.  Gases are formed when the energy in the system exceeds all of the attractive forces between molecules. Thus gas molecules have little interaction with each other beyond occasionally bumping into one another. In the gas state, molecules move quickly and are free to move in any direction. As the temperature of a gas increases, the amount of movement of individual molecules increases.

In a gas, particles are not bound together, and are free to move. Particles are far apart and there is free space between them with no real arrangement of particles. The particles assume the shape of a container. The particles vibrate, rotate, are move at high speeds.

In a liquid, particles are free to move relative to each other, have no arrangement of particles have little free space between them, and assume the shape of a container; liquid particles vibrate, rotate, bump, and slide past each other.

In a solid, particles form an ordered arrangement, and do not flow. They have little free space between them, and vibrate in position.

from the American Chemical Society
"There are five main states of matter. Solids, liquids, gases, plasmas, and Bose-Einstein condensates (BEC) are all different states of matter. Each of these states is also known as a phase. Elements and compounds can move from one phase to another when specific physical conditions are present. One example is temperature. When the temperature of a system goes up, the matter in the system becomes more excited and active. Scientists say that it moves to a higher energy state. Generally, as the temperature rises, matter moves to a more active state." 

States of Matter
Q: Describe the motion of atoms and molecules in a gas.
A: Particles are free to move and move faster than in liquids or solids of the same material. There is little interaction between particles.

Q. How far did the atoms in a liquid appear to travel?
A: Not very far apart compared to a gas's particles, but further than in a solid.

Q: How would you describe the movement and arrangement of atoms and molecules in a solid?
A: A solid's particles are always in motion; they vibrate and bump into each other, but always stay with the same neighbors nearby.
Further Investigation
Students can test different liquids' evaporation rates. Place a cotton ball on a thermometer or temperature probe and moisten with several drops of different liquids (water, nail polish remover, perfume, rubbing alcohol). Collect temperature data at regular intervals for for 5 minutes. Throw out the cotton ball and repeat with another liquid. Compare graphs.

Students can design and conduct investigations with a heat or cold pack.