Freezing, Melting, and Evaporation Science Lesson 17 TCAP Coach

Objectives SPI 0507.9.2 Describe the differences among freezing, melting, and evaporation SPI 0507.9.3 Describe factors that influence the rate at which different types of material freeze, melt, or evaporate

Freezing, Melting, and Evaporation Most matter on Earth exists in three states: solid, liquid, and gas. Matter can change from one state to another. Ice can melt into liquid water. Liquid water can turn into a gas. In this lesson, you will explore how these changes happen and learn what makes them happen faster or slower.

States of Matter States of matter are the forms that matter can take, such as solid, liquid, and gas. To understand this better, you need to understand what makes one state different from another state. All matter is made up of tiny particles called atoms and molecules. You can think of atoms as tiny spheres and molecules as two or more tiny balls stuck together. These particles are always in motion.

States of Matter The particles in a solid move a little bit. They vibrate in place and do not have much energy. The particles in a liquid move more than those in a solid. They have more energy. The particles in a gas move the most. They have the most energy.

States of Matter The result is that the particles in a solid are usually very close together. The particles in a liquid are normally a bit farther apart. The particles in a gas are much more spread out.

States of Matter

Changing State-How does an ice cube turn into a small puddle of water? Melting is the process by which a solid changes to a liquid. To melt a solid you must add energy to it. This makes the particles in a solid move faster. As this continues, the solid turns into a liquid. Heat energy makes this change take place.

Changing State-How does a puddle of water change from a liquid to a gas? It can evaporate and also boil. Evaporation is the process by which a liquid changes to a gas as the liquid’s surface. Boiling is the process by which bubbles of gas from throughout a liquid and rise to the surface. In both evaporation and boiling, energy makes the particles move faster and farther apart. As this continues, the liquid changes to a gas. Heat energy makes this change take place.

Changing State A gas can also change back into a liquid. Example: Water vapor can rise and then form droplets on the lid over a boiling pot of water. This process is called condensation. For a gas to condense into a liquid, the particles in the gas must have less energy and move closer together. This takes place when heat energy is removed. When the gas cools, the particles move more slowly. They also get closer together. As this continues, the gas turns into a liquid.

Changing State Now think about changing a liquid into a solid, such as making ice cubes in a tray. The change in state from a liquid to a solid is a process called freezing. When energy is taken away from the particles in a liquid, they move more slowly. As this continues, the particles get so close together that the liquid turns into a solid.

Speeding Up or Slowing Down Changes in State Different materials change state at different temperatures. But the same factors affect how quickly or slowly the changes take place. Heat, volume, pressure, and surface area are some of these factors.

Speeding Up or Slowing Down Changes in State Heat-Adding or removing heat can affect the rate of change. Imagine two matching pots holding the same amount of water. One pot is on a burner set on high heat. The other pot is on a burner set on low heat. The pot on the high heat will boil first. The greater the heat, the faster the change in state will be from a solid to a liquid, or from a liquid to a gas. This works in the opposite direction, as well. If you want to increase the rate of change from a gas to a liquid or liquid to a solid, you take away heat faster. In other words, you cool the material faster.

Speeding Up or Slowing Down Changes in State Volume-Now think about the experiment in a different way. This time the pots are on burners that are giving off the same amount of heat. But there is less water in the second pot. Its volume is smaller. Remember that volume is the amount of space matter takes up. The water with the smaller volume will boil first. The smaller the volume of the material, the faster it will change state. The same idea works in the opposite direction. The less volume a substance has, the faster you can cool it.

Speeding Up or Slowing Down Changes in State Pressure- Air has weight. It presses down on the surface of a liquid. This pressure keeps particles of a substance from moving faster and spreading out. So, the less pressure on the substance, the faster it will change state from a solid to a liquid or from a liquid to a gas. If you want to increase the rate of change in the opposite direction, you can increase the pressure.

Speeding Up or Slowing Down Changes in State Surface Area- The total area that the surface of a substance takes up it its surface area. Which will melt faster, a large block of ice or the same amount of ice crushed into a pile of tiny ice chips? The tiny ice chips have a much larger surface area compared to the ice block. In the pile of ice chips, many more particles touch the warmer air. The greater the surface area, the faster a substance changes from a solid to a liquid. The ice ships will melt faster than the ice block.

1. In which state of matter are particles usually closest together? A. solid B. liquid C. gas D. water

1. In which state of matter are particles usually closest together? A. solid

2. What kind of energy makes a substance change state? A. electricity B. light C. heat D. sound

2. What kind of energy makes a substance change state? C. heat

3. You increase the pressure on a liquid 3. You increase the pressure on a liquid. How will that affect its change to a gas? A. It will change more quickly. B. It will change more slowly. C. It will not change at all. D. It will disappear.

3. You increase the pressure on a liquid 3. You increase the pressure on a liquid. How will that affect its change to a gas? B. It will change more slowly.

4. You pour the same amount of water into an open soft drink bottle, a cup, a salad bowl, and a dinner plate. In which container will the water evaporate first? A. the bottle B. the cup C. the saucer D. the dinner plate

4. You pour the same amount of water into an open soft drink bottle, a cup, a salad bowl, and a dinner plate. In which container will the water evaporate first? D. the dinner plate