Question to investigate Is the speed of water molecules different in hot and cold water? Teacher preparation This activity works best if there is a big difference between the temperatures of the hot and cold water. Squirt 4—5 drops of blue food coloring into a small cup for each group. Squirt 4—5 drops of yellow food coloring into another small cup for each group.
Add ice to about 6 cups of tap water to make it sufficiently cold. Allow the colors to mix on their own as you watch them for a couple of minutes. Record and discuss student observations. Describe what the colors looked like and how they moved and mixed in the cold water. Describe what the colors looked like and how they moved and mixed in the hot water. What does the speed of the mixing colors tell you about the speed of the molecules in hot and cold water?
Expected Results The yellow and blue food coloring will spread faster in hot water than in cold. Explain Show an animation of water molecules at different temperatures. Ask students: Are the molecules moving faster in cold or hot water? Students should realize that the molecules of hot water are moving faster.
The molecules of cold water are moving slower. How does this match with your observations with the food coloring? The food coloring in the hot water mixed faster than the coloring in the cold water did. Look closely at the space between the molecules in cold and hot water.
Is there more space in between the molecules in hot water or in cold water? Is it a lot of space? Point out to students that molecules of hot water are moving faster and are slightly further apart.
The molecules of cold water are moving slower and are a little closer together. If students do not notice a difference, move the slider all the way to the left again and then quickly to the right.
Show the animation a few times to give students a chance to notice the differences. Have students answer questions about the animation and draw a model of water molecules on their activity sheet. It is the motion of particles that creates a form of energy called heat or thermal energy that is present in all matter. The particles in solids are tightly packed and can only vibrate. The particles in liquids also vibrate but are able to move around by rolling over each other and sliding around.
In gases, the particles move freely with rapid, random motion. At higher temperatures, particles have more energy. Some of this energy can be transmitted to other particles that are at a lower temperature. For example, in the gas state, when a fast moving particle collides with a slower moving particle, it transfers some of its energy to the slower moving particle, increasing the speed of that particle.
With billions of moving particles colliding into each other, an area of high energy will slowly transfer across the material until thermal equilibrium is reached the temperature is the same across the material.
If heated sufficiently, the movement of particles in a solid increases and overcomes the bonds that hold the particles together. The substance changes its state from a solid to a liquid melting. If the movement of the particles increases further in the liquid, then a stage is reached where the substance changes into a gas evaporation.
Convection transfers heat energy through gases and liquids. As air is heated, the particles gain heat energy allowing them to move faster and further apart, carrying the heat energy with them.
Warm air is less dense than cold air and will rise. Cooler air moves in below to replace the air that has risen. To begin the lab, I have students record the temperature of the room temperature water and begin recording data for that beaker. As I am doing this, I am heating up water in the lab microwave. The water temperature should be hotter than room temperature, but not hot enough to cause injury.
I have also done this lab while teaching in a math classroom and have had a coffeemaker on hand to heat the water. If you do not have enough glass beakers for every group, make sure the hot water beaker is glass, and the rest can be made of plastic. Stars are so far apart from each other, that if we were to put two grains of sand into a cathedral, that would be about the correct scale to represent the sizes and distances of stars in our part of the Universe.
Javascript must be enabled to use Cool Cosmos. Learn how. Purpose The purpose of this lab is for students to determine the relationship between temperature and speed of molecules in a liquid. Students should know how to convert between Celsius, Fahrenheit, and Kelvin. Students should know the difference between heat and temperature. Students may ask why the temperature of the water went down by a different amount than the temperature of the washers went up.
The same amount of energy left the water as went into the washers, but it takes a different amount of energy to change the temperature of different substances.
Pour about 30 milliliters of room-temperature water into the control cup. Place a thermometer in the cup and tell students the temperature of the water. Show the molecular model animation Heated Spoon. Point out to students that the water molecules in the hot water are moving faster than the atoms in the spoon. The water molecules strike the atoms of the spoon and transfer some of their energy to these atoms. This is how the energy from the water is transferred to the spoon. This increases the motion of the atoms in the spoon.
Since the motion of the atoms in the spoon increases, the temperature of the spoon increases. It is not easy to notice, but when the fast-moving water molecules hit the spoon and speed up the atoms in the spoon, the water molecules slow down a little. So when energy is transferred from the water to the spoon, the spoon gets warmer and the water gets cooler.
Explain to students that when fast-moving atoms or molecules hit slower-moving atoms or molecules and increase their speed, energy is transferred. The energy that is transferred is called heat. This energy transfer process is called conduction. Show the molecular model animation Cooled Spoon. Point out to students that in this case, the atoms in the spoon are moving faster than the water molecules in the cold water. The faster-moving atoms in the spoon transfer some of their energy to the water molecules.
This causes the water molecules to move a little faster and the temperature of the water to increase. Since the atoms in the spoon transfer some of their energy to the water molecules, the atoms in the spoon slow down a little.
This causes the temperature of the spoon to decrease. Describe how the process of conduction caused the temperature of the washers and water to change in the activity. Students tend to understand heating but often have a misconception about how things are cooled. Just like heating a substance, cooling a substance also works by conduction. But instead of focusing on the slower-moving molecules speeding up, you focus on the faster-moving molecules slowing down.
The faster-moving atoms or molecules of the hotter substance contact slower-moving atoms or molecules of the cooler substance. The faster-moving atoms and molecules transfer some of their energy to the slower-moving atoms and molecules. The atoms and molecules of the hotter substance slow down, and its temperature decreases.
Something can only get colder by having its atoms and molecules transfer their energy to something that is colder. Note : In the model you will show students, the change in speed of both the water molecules and the atoms in the spoon is represented with different numbers of motion lines.
Students may remember that when atoms or molecules move faster, they get further apart, and when they move slower, they get closer together. For this activity, the change in distance between water molecules or between atoms in the spoon is not the focus, and therefore it is not shown in the model.
You could tell students that models can emphasize one feature over another, in order to help focus on the main point being represented. The following simulation shows that at any temperature, the atoms or molecules of a substance are moving at a variety of speeds.
Some molecules are moving faster than others, some slower, but most are in-between. Show the simulation Temperature. Tell students that anything that has mass and is moving, no matter how big or small, has a certain amount of energy, called kinetic energy.
The temperature of a substance gives you information about the kinetic energy of its molecules. The faster the molecules of a substance move, the higher the kinetic energy, and the higher the temperature. The slower the molecules move, the lower the kinetic energy, and the lower the temperature. But at any temperature, the molecules don't all move at the same speed so temperature is actually a measure of the average kinetic energy of the molecules of a substance. Show the animation Conducting Energy to help answer the question about why metal feels colder than cardboard.
Explain that the molecules in your finger are moving faster than the molecules in the room-temperature metal. Therefore the energy from your finger is transferred to the metal.
Because metal is a good conductor, the energy is transferred away from the surface through the metal. The molecules in your skin slow down as your finger continues to lose energy to the metal, so your finger feels cooler.
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