Changes in States of Matter

Transcription

1 TEKS predict, observe, and record changes in the state of matter caused by heating or cooling Changes in States of Matter What Is Matter? Anything that has mass and takes up space is matter. All physical objects are made of matter. If you could view an object through the most powerful microscope, you would see that matter is made of tiny particles called atoms. Different types of matter are made of different arrangements of atoms. Each type of matter has physical properties that you can see, smell, touch, taste, measure, and study. States of Matter You know that different kinds of matter have different properties. Helium, water, and aluminum, for example, are very easy to tell apart. At room temperature, each of these kinds of matter exists in a different state. One is a solid, one is a liquid, and one is a gas. Do you know which is which? At room temperature, helium is a gas. A gas is the state of matter that expands to fill its container. A gas does not have a definite shape or volume. Helium gas is used to fill balloons. Water is a liquid at room temperature. A liquid is the state of matter that has a fixed volume but not a definite shape. A liquid takes the shape of its container. You can pour liquid water from a pitcher to a glass. Aluminum is a solid at room temperature. A solid is the state of matter that holds its own shape and has a fixed volume. You can bend and tear a sheet of aluminum foil, but the total volume of aluminum does not change. Solids keep their shapes. Liquids flow. Gases fill their containers. Why? You can answer this question by thinking of matter as being made of tiny particles that are in motion. The state of matter is dependent upon the amount of energy the matter contains. The particles in a solid are packed very close together. They vibrate in place, but they can t slide past one another. This gives a solid its definite volume and shape. The particles in a liquid are not as close together. They have more energy and can move past one another. This enables a liquid to flow. The particles in a gas have a lot of energy. They are not very close together and move the fastest. They spread out to fill their container. The particles are so far apart that they can be squeezed together. That s what you do when you pump up a ball or a tire. You squeeze more gas into the ball or tire, which gives it pressure. solid liquid gas and Assessment TEKS Page 1 of 6

2 Changes in Matter Matter can go through physical and chemical changes. A physical change does not change what a substance is. When paper is cut, shredded, or torn, it is still paper. This is a physical change. A chemical change results in a new substance being formed, and energy is either given off or absorbed. When paper is burned, it turns new forms of matter hot gases and ash. Changes in State You learned that some kinds of matter are solid at room temperature. Other kinds of matter are liquid or gas at room temperature. Did you know that each kind of matter can exist as a solid, a liquid, or a gas? The temperature of matter determines its state. As heat is added, the particles of matter begin to move faster. As heat is taken away, the particles move slower. When enough heat is added or taken away, matter can change state. For example, aluminum foil will turn into a liquid if its temperature reaches 660 C (1,220 F). It is still aluminum, but it is no longer a solid. This is a change in state. Changes in state are physical changes. Let s take a closer look at water. Water is a liquid at room temperature. If you put it in a freezer, its temperature decreases. The particles of water begin to slow down. At temperatures below 0 C (32 F), water freezes. Freezing is the change from a liquid to a solid. Solid water is called ice. If you remove an ice cube from the freezer, it slowly warms. The particles of water begin to move faster and slide past one another. At temperatures above 0 C, ice melts. Melting is the change from a solid to a liquid. Ice is solid water. It melts and becomes liquid water. Place a pot of liquid water on a hot stove, and the water gets warmer. When it reaches 100 C (212 F), it boils. Boiling is the rapid change from a liquid to a gas. Sometimes, particles near the surface of a liquid move fast enough to become a gas, even if the temperature is not at the boiling point. This is called evaporation, which occurs slowly and only at the surface of a liquid. To form a seal between two metal pipes, a welder heats metal so it turns into a liquid that can be formed into a certain shape. The boiling point of water is 100 C. and Assessment TEKS Page 2 of 6

3 When a gas turns to a liquid, the process is called condensation. You have seen this process occur when water drops form on the outside of a cold glass. It might look like the glass is leaking, but that s not the case. Water in the form of a gas is called water vapor. It s in the air all around you, but you can t see it. The water vapor s temperature is cooled by the cold glass. The decrease in temperature causes the water vapor to condense and form droplets of liquid water. Condensation is the process of turning a gas into a liquid. We also call the physical drops of liquid that form condensation. Hands-On Activity Observing States of Matter The state of matter can change based on the amount of energy in the substance. Matter can exist as a solid, a liquid, or a gas. In this activity, you will examine water in each of these states. Procedure: Materials ice cubes water hot plate freezer-strength zip-top bags 1. Place a few ice cubes in a zip-top bag. Pass the bag around. Squeeze and press the bag. What happens? In a small group, discuss the properties of the ice. Include temperature, texture, shape, and color in your discussion. 2. Pour some water into a zip-top bag, and seal it. Pass the bag around. Gently squeeze and press the bag. What happens? Discuss the properties of the water. Include temperature, texture, shape, and color in your discussion. 3. Watch as your teacher holds a zip-top bag over boiling water to capture some water vapor. The water vapor is mixing with the air around you. Pass the sealed bag around the classroom. Gently squeeze and press the bag. What happens? Discuss the properties of the water vapor and other gases in the bag. Include temperature, shape, and color in your discussion. Discussion Questions: 1. What differences did you notice in the different states of water? 2. What are other examples of solids, liquids, and gases? and Assessment TEKS Page 3 of 6

4 Changes in States of Matter Write a definition for each term below. freeze boil condense Suppose an ice cube is taken out of the freezer. Predict how it will change over several hours. Complete the cause-and-effect graphic organizer below. Cause Effect The liquid evaporates. Complete the Venn diagram below to compare and contrast melting and boiling. Melting Both Boiling and Assessment TEKS Page 4 of 6

5 TEKS Assessment Fill in the letter of the best choice. Which is the process by which a gas becomes a liquid? evaporation condensation melting boiling What happens to the particles of matter when a liquid changes to a gas? They stop moving. They vibrate in place. They move faster and spread out. They slow down and begin bumping into one another. Which of the following is correct? Only water can exist as a solid, a liquid, and a gas. The solid form of water is called water vapor. A change of state is a chemical change because a new kind of matter is formed. At the right temperature, any kind of matter can exist as a solid, a liquid, or a gas. Look at the thermometer below. Look at the drawing below. Which prediction is correct? The ice will melt, and condensation will form on outside of the glass. The ice will evaporate before it finishes melting. The ice will boil, and water will spill on the outside of the glass. The ice will condense and stick to the outside of the glass. What properties does water have at this temperature? It would fill its container. It would hold its own shape. It would not have a shape. It would take the shape of its container. and Assessment TEKS Page 5 of 6

6 Answer Key Hands-On Activity (p. 3) 1. Students should note that the ice (solid water) had a definite shape, was hard, and was cold. The liquid water was not cold, changed shape when the shape of the bag was changed, and did not fill the bag completely. The water vapor filled the entire space inside the bag. It was not possible to see the water vapor. 2. Answers will vary. Sample answers: Helium in a balloon, the air we breathe, propane in a stove, and natural gas that heats a home are examples of gases. Examples of liquids include honey, vinegar, soda, juice, and gasoline. Most of the objects used in the classroom are solids, including desks, books, pencils, paper, and backpacks. Student Response Activity (p. 4) 1. To freeze is to change from a liquid to a solid. To boil is to turn rapidly from a liquid to a gas. To condense is to change from a gas to a liquid. 2. When an ice cube is taken out of the freezer, heat energy will move into the ice cube and the ice cube will begin to get warmer. As the temperature gets above 0 C (32 F), the ice will melt. Liquid water on the surface may evaporate, or turn in to a gas. The puddle of water formed will eventually dry up if given enough time to evaporate completely. 3. The particles on the surface of a liquid get enough energy and move fast enough to escape from the other liquid particles. 4. Melting changing from a solid to a liquid; Boiling changing from a liquid to a gas; Both changes in state, require addition of energy TEKS Assessment (p. 5) 1. B 2. C 3. A 4. D 5. D and Assessment TEKS Page 6 of 6