Instructional Time: 1 Hour s. Keywords: Solid, liquid, gas, particles. This resource requires special permission and only certain users have access to it at this time. Aligned Standards This vetted resource aligns to concepts or skills in these benchmarks. Display options. Show Clarifications Show Color. Aligned Access Points This vetted resource aligns to concepts or skills in these access points. Related Resources Other vetted resources related to this resource.
Congratulations You have successfully created an account. Did you enter an incorrect email address? Explain that the little balls represent the particles of a solid, in this case the atoms in a metal. Although atoms and molecules are different, this same simple model of balls is used for both. Let students know that for now, they will use circles or spheres to represent atoms and molecules, but eventually they will use a more detailed model.
Tell students that they should focus on the motion of the molecules, how they interact, and their distance from one another. Show the molecular model animation Particles of a Solid. Show the molecular model animation Comparing Solid and Liquid. Click on both tabs and make sure students notice the differences in the movement of the atoms and molecules.
Students will record their observations and answer questions about the animation on the activity sheet. Look at the teacher version of the activity sheet to find the questions and answers. It is harder to show that the molecules of a solid move faster when heated than it is to show the same thing with a liquid like in Lesson 2.
But you can do it if you have a special ball and ring apparatus that shows the expansion of a metal when heated. This inexpensive device, available through science education equipment companies, consists of a rod with a metal ball on the end and another rod with a metal ring. At room temperature, the ball just barely fits through the ring. But when the ball is heated sufficiently, it will not pass through the ring. If you do not have this equipment, you can show students a video of this demonstration titled Heating and Cooling Metal Ball.
Hold the ball in one hand and the ring in the other. Show students how the ball fits through the ring. When students see that the ball expands, they may wonder if the atoms themselves expanded.
Tell students that the atoms do not expland. Instead, the atoms in a solid follow the same rules as the molecules in a liquid.
Heating increases molecular motion, causing the atoms to spread a little further apart. Show the molecular model animation Heating and Cooling Metal Ball. Point out that when metal is heated, the atoms move faster and move slightly further apart. The gas particles have big distances between them. Solid — In a solid, the attractive forces keep the particles together tightly enough so that the particles do not move past each other.
Their vibration is related to their kinetic energy. In the solid the particles vibrate in place. Liquid — In a liquid, particles will flow or glide over one another, but stay toward the bottom of the container. In gases the particles move rapidly in all directions, frequently colliding with each other and the side of the container.
With an increase in temperature, the particles gain kinetic energy and move faster. The actual average speed of the particles depends on their mass as well as the temperature — heavier particles move more slowly than lighter ones at the same temperature. The oxygen and nitrogen molecules in air at normal room temperature are moving rapidly at between to metres per second. Unlike collisions between macroscopic objects, collisions between particles are perfectly elastic with no loss of kinetic energy.
This is very different to most other collisions where some kinetic energy is transformed into other forms such as heat and sound. It is the perfectly elastic nature of the collisions that enables the gas particles to continue rebounding after each collision with no loss of speed. Particles are still subject to gravity and hit the bottom of a container with greater force than the top, thus giving gases weight.
If the vertical motion of gas molecules did not slow under gravity, the atmosphere would have long since escaped from the Earth. In liquids, particles are quite close together and move with random motion throughout the container. Particles move rapidly in all directions but collide with each other more frequently than in gases due to shorter distances between particles. With an increase in temperature, the particles move faster as they gain kinetic energy, resulting in increased collision rates and an increased rate of diffusion.
In a solid, the particles pack together as tightly as possible in a neat and ordered arrangement. The particles are held together too strongly to allow movement from place to place but the particles do vibrate about their position in the structure.
With an increase in temperature, the particles gain kinetic energy and vibrate faster and more strongly. The attractive force in solids need not be stronger than in liquids or gases. For example the forces between solid helium particles at degrees C are still very weak. By comparison, the forces between iron vapour particles requires very high temperatures are very strong.
If you compare different substances that are at the same temperature, then the average kinetic energy of the particles will be the same i. Attractive forces don't get weaker when a substance moves from the solid to the liquid to the gas state, rather the kinetic energy of the particles increases implying faster motion , allowing them to overcome the attractive forces.
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