LESSON 6: Dew Drops ESTIMATED TIME Setup: 5 10 minutes Procedure: 15 20 minutes DESCRIPTION Use jars of hot and cold water to demonstrate how water changes states. OBJECTIVE This lesson demonstrates the physical change of a gas to a liquid and the conditions under which it occurs. Students place hot and ice-cold water in different jars to observe condensation. This lesson can be extended to address elements, compounds, energy, and energy transfer. CONTENT TOPICS Scientific inquiry; states of matter; physical changes (condensation, vaporization); atomic structure; energy MATERIALS o Clear glass jars with lids o Ice o Hot and cold water Always remember to use the appropriate safety equipment when conducting your experiment. Refer to the Safety First section in the Resource Guide on pages 391 393 for more detailed information about safety in the classroom. Jump ahead to page 80 to view the Experimental Procedure. NATIONAL SCIENCE EDUCATION STANDARDS SUBJECT MATTER This lesson applies both Dimension 1: Scientific and Engineering Practices and Dimension 2: Crosscutting Concepts from A Framework for K 12 Science Education, established as a guide for the updated National Science Education Standards. In addition, this lesson covers the following Disciplinary Core Ideas from that framework: PS1.A: Structure and Properties of Matter PS3.A: Definitions of Energy PS3.B: Conversion of Energy and Energy Transfer PS3.D: Energy in Chemical Processes and Everyday Life OBSERVATION & RESEARCH BACKGROUND Scientists use the term matter to describe the things around you. Matter is anything that has mass and takes up space, such as paper, food, cups, and water. Matter exists primarily in three states on the earth solid, liquid, and gas. Solids have a definite volume and a definite shape. Examples of solids are chairs, books, and cups. Liquids have a definite volume but no definite shape. Therefore, they will take the shape of the vessel that contains them, filling the bottom of the container first. Examples of liquids are water and orange juice. Gases have no definite volume and no definite shape. If a gas is put into a container, it will take the shape of the container, filling that container completely. An example of a gas is the air around you! In addition to differences in shape and volume, solids, liquids, and gases have other unique properties. Changes between these states of matter are physical changes. A physical change is any change in a substance s form that does not change its chemical makeup. The chemical formula of the substance stays the same before and after the change. For example, ice, water, and water vapor are all H2O in different physical states. The chemical formula remains H2O regardless of whether it is in the solid, liquid, or gaseous state. Matter can change from one state to another, generally as a result of a change in temperature. Melting is a change in state from a solid to a liquid. The opposite change is You Be The LESSON Chemist 1: Activity Goofy Guides Putty page 77 77
LESSON 6: Dew Drops freezing. Freezing is a change in state from a liquid to a solid. A change in state from a liquid to a gas is known as vaporization, while a change in state from a gas to a liquid is known as condensation. Changes directly between the solid and gaseous states that do not go through the liquid state first are less common. Sublimation is a change in state from a solid directly to a gas. The opposite is deposition, in which a gas changes directly into a solid. In this experiment, water is used to demonstrate the physical changes between a liquid and a gas. The gas is water vapor, which occurs naturally in the air. When the water vapor comes in contact with the cool glass, the water vapor cools and changes into liquid water. The jar with ice water makes the glass jar very cold. Because there is water vapor in the outside air, as the water vapor in the outside air touches the cold glass, the vapor becomes a liquid. As a result, you can see droplets of water form on the outside of the glass jar. The jar holding the hot water acts in a similar way; however, the vapor inside the jar comes in contact with the cooler glass. Therefore, the water droplets will form inside the jar. (If the water is hot enough, students may also be able to first observe vaporization.) FORMULAS & EQUATIONS Tap water is actually a mixture of pure water, minerals, and other substances. Keep in mind, enough energy has to be added to cause this change. The temperature of the liquid substance must reach its boiling point. The boiling point is the temperature at which a substance begins changing its state from a liquid to a gas. On the other hand, when energy is removed from a gas, the gas changes into liquid form, and it condenses. CONNECT TO THE YOU BE THE CHEMIST CHALLENGE For additional background information, please review CEF s Challenge study materials online at http://www.chemed.org/ybtc/challenge/study.aspx. Additional information on physical changes and states of matter can be found in the Classification of Matter section of CEF s Passport to Science Exploration: The Core of Chemistry. HYPOTHESIS uwater droplets will form on the inside of a glass jar filled with hot water, and water droplets will form on the outside of a glass jar filled with ice water because of temperature differences. The chemical formula for pure water, in any state of matter, is H2O. During a physical change, the structure or chemical formula of the substance does not change. As energy (in the form of thermal energy) is added to or removed from the substance, it changes from one state of matter to another. When enough energy is added to liquid water, it becomes a gas. H2O (l) + energy g H2O (g) Fun Fact When you take a hot shower, the mirror or bathroom window usually gets foggy. The fog is actually the condensation of water vapor. You Be The Chemist Activity Guide page 78
LESSON 6: Dew Drops DIFFERENTIATION IN THE CLASSROOM LOWER GRADE LEVELS/BEGINNERS Perform the experiment as described on page 80, but spend more time on states of matter. Show pictures of different things and have the students identify the state of matter. Likewise, show images of matter changing states ice melting, water droplets forming on grass, etc. (You may need to use a series of images to demonstrate the changes.) Again, have the students identify which change they see and how they know. HIGHER GRADE LEVELS/ADVANCED STUDENTS DESCRIPTION Jars of hot and cold water are used to demonstrate the processes of condensation and energy transfer. OBJECTIVE This lesson demonstrates energy transfer, condensation, and the conditions under which condensation occurs. OBSERVATION & RESEARCH Matter can be classified into pure substances and mixtures. Elements are pure substances that cannot be broken down further by normal chemical means. All matter is made up of basic elements. They are known as the building blocks of matter. A compound is a pure substance made up of two or more elements joined in a defined ratio. For example, water is a compound made up of the elements hydrogen and oxygen in a 2:1 ratio. Two hydrogen atoms and one oxygen atom join together, giving water the chemical formula H2O. However, the water that comes out of a sink is not a pure substance. It is a mixture of pure water, minerals, and other substances. It is generally called tap water. Matter exists primarily in three states on the earth solid, liquid, or gas. Solids, such as books and cups, have a definite volume and a definite shape. Liquids, such as water and orange juice, have a definite volume but no definite shape. Gases, such as the air around you, have no definite volume and no definite shape. Changes between these states of matter are physical changes. A physical change is any change in a substance s form that does not change its chemical makeup. For example, ice, water, and water vapor are all H2O in different physical states. The chemical formula remains H2O regardless of whether it is in the solid, liquid, or gaseous state. Matter changes states whenever energy is added or taken away. Energy is a measure of the ability to do work or generate heat. During a change in state, energy is transferred between a substance and its surroundings. These changes are often the result of changes in temperature. When a solid gains enough energy, it melts into liquid form. Likewise, when a liquid gains enough energy, it vaporizes to become a gas. If a gas loses enough energy, it will condense and become a liquid. If a liquid loses enough energy, it will freeze into solid form. In this experiment, water is used to demonstrate the physical changes between a liquid and a gas as energy is transferred between the water (H2O) and its surroundings. The gaseous form of H2O is water vapor, which occurs naturally in the air. When the water vapor comes in contact with the cool glass, the water vapor cools and changes into liquid water. The jar with ice water makes the glass jar very cold. Because there is water vapor in the outside air, as water vapor in the outside air touches the cold glass, the vapor becomes a liquid. As a result, you can see droplets of water form on the outside of the glass jar. The jar holding the hot water acts in a similar way; however, the vapor inside the jar comes in contact with the cooler glass. Therefore, the water droplets will form inside the jar. (If the water is hot enough, students may also be able to first observe vaporization.) CONNECT TO THE YOU BE THE CHEMIST CHALLENGE For additional background information, please review CEF s Challenge study materials online at http://www.chemed.org/ybtc/challenge/study.aspx. Additional information on states of matter, physical changes, and energy changes can be found in the Classification of Matter section of CEF s Passport to Science Exploration: The Core of Chemistry. Additional information on energy can be found in the Measurement section of CEF s Passport to Science Exploration: The Core of Chemistry. Additional information on elements and compounds can be found in the Atomic Structure section of CEF s Passport to Science Exploration: The Core of Chemistry. You Be The Chemist Activity Guide page 79
EXPERIMENTATION LESSON 6: Dew Drops As the students perform the experiment, challenge them to identify the independent, dependent, and controlled variables, as well as whether there is a control setup for the experiment. (Hint: If the temperature of the water in the jar changes, will the water droplets form in a different location?) Review the information in the Scientific Inquiry section on pages 14 16 to discuss variables. NOTES EXPERIMENTAL PROCEDURE Part One 1. Add hot tap water to a jar until it is half full. 2. Put the lid on the jar, and place it on a table. Observe. 3. Pour the water out of the jar, and dry the inside and outside of the jar completely. Part Two 1. Add cold tap water to a jar until it is half full. Then, add a few ice cubes to make the water very cold. 2. Put the lid on the jar, and place the jar on a table. Observe. In the cold water setup, if you do not see any water droplets forming on the jar, try the experiment in a bathroom, kitchen, or another humid room where the outside air may have more water molecules in it. DATA COLLECTION Have students record data in their science notebooks or on the following activity sheet. What forms on the inside or outside of the jar? Have students answer the questions on the activity sheet (or similar ones of your own) to guide the process. You Be The Chemist Activity Guide page 80
ANALYSIS & CONCLUSION LESSON 6: Dew Drops Use the questions from the activity sheet or your own questions to discuss the experimental data. Ask students to determine whether they should accept or reject their hypotheses. Review the information in the Scientific Inquiry section on pages 14 16 to discuss valid and invalid hypotheses. ASSESSMENT/GOALS Upon completion of this lesson, students should be able to Apply a scientific inquiry process and perform an experiment. Compare and contrast solids, liquids, and gases and give examples of each. Define and identify different physical changes between states of matter, specifically condensation and vaporization. Understand the conditions required for condensation to occur. Define and provide examples of elements and compounds (see Differentiation in the Classroom). Define energy and its relation to physical changes (see Differentiation in the Classroom). MODIFICATIONS/EXTENSIONS Modifications and extensions provide alternate methods for performing the lesson or similar lessons. They also introduce ways to expand on the content topics presented and think beyond those topics. Use the following examples or have a discussion to generate other ideas as a class. K-4 Use two jars to compare the two setups at the same time. Add ice-cold water, room-temperature water, and hot water to different jars, and place them in the same location (outside, in a dry room, in a bathroom, etc.). What processes do you observe? Try another location to see if the processes are different. Tell the students that they can all cause condensation to take place. When they blow their hot breath on a mirror, condensation is occurring. The water vapor in their breath condenses when it hits a cooler mirror. Try it out in class or have them test it out at home with their parents permission. See Lesson 7: The Moving Molecule Stomp for a fun activity to illustrate the motion of particles in solids, liquids, and gases and changes between those states of matter. REAL-WORLD APPLICATIONS A similar process occurs on the windows of buildings. On a cold winter day, water droplets may form on the inside of a window as warm air from inside the building touches the cold window. In contrast, on a hot summer day, water droplets may form on the outside of a window of an airconditioned building as warm water vapor particles in the outside air touch the cool window. COMMUNICATION Discuss the results as a class and review the activity sheet. Review the information in the Scientific Inquiry section on pages 14 16 to discuss the importance of communication to scientific progress. You Be The Chemist Activity Guide page 81
OBSERVE & RESEARCH 1. Write down the materials you see. 2. How might these materials be used? 3. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an image of the example. Term Definition Example (write or add image) Matter Solid Liquid Gas Physical change Melting Freezing Vaporization Condensation You Be The Chemist Activity Guide page 82
4. Consider what will happen to jars filled with water of different temperatures and why. uwrite your hypothesis. PERFORM YOUR EXPERIMENT Part One 1. Add hot tap water to a jar until it is half full. 2. Put the lid on the jar, and place it on a table. Watch what happens. 3. Pour the water out of the jar. Dry the inside and outside of the jar. Part Two 1. Add cold tap water to a jar until it is half full. Then, add a few ice cubes to make the water very cold. 2. Put the lid on the jar, and place the jar on a table. Watch what happens. ANALYZE & CONCLUDE 1. In Part One, do water droplets form on the inside or outside of the jar? 2. How did the water droplets get there? You Be The Chemist Activity Guides page 83
3. In Part Two, do water droplets form on the inside or outside of the jar? 4. How did the water droplets get there? 5. The physical change when a gas becomes a liquid is called. 6. The physical change when a liquid becomes a gas is called. 7. Have you ever seen the processes of condensation and vaporization take place at home? If so, when? If not, provide another example of each change. 8. Is your hypothesis valid? Why or why not? If not, what would be your next steps? You Be The Chemist Activity Guide page 84
EXPAND YOUR KNOWLEDGE ADVANCED 1. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an image of the example. Term Definition Example (write or add image) Element Compound Energy 2. Compare and contrast the three states of H2O (water). 3. Describe how energy causes matter to change states. Give examples. You Be The Chemist Activity Guides page 85
ANSWER KEY Below are suggested answers. Other answers may also be acceptable. OBSERVE & RESEARCH 1. Write down the materials you see. Glass jars, water, ice 2. How might these materials be used? Glass jars may be used to hold a substance. Water may be used to drink, bathe, or clean. Ice may be used to reduce the temperature of a substance. These materials may be used together to show physical changes. 3. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an image of the example. Term Definition Example (write or add image) Matter Any substance that has mass and takes up space; matter is generally found as a solid, liquid, or gas on the earth. Solid A state of matter characterized by a definite volume and a definite shape. Liquid A state of matter that has a definite volume but no definite shape; a liquid will take the shape of the container that holds it, filling the bottom first. Gas A state of matter that has no definite volume or shape; a gas will take the shape of the container that holds it, filling the entire container. Physical change A change that alters the form or appearance of a substance but does not change its chemical makeup or create a new substance. Melting A physical change in which a substance changes states from a solid to a liquid. Freezing A physical change in which a substance changes states from a liquid to a solid. Vaporization A physical change in which a substance changes states from a liquid to a gas. Condensation A physical change in which a substance changes states from a gas to a liquid. You Be The Chemist Activity Guide page 86
ANSWER KEY Below are suggested answers. Other answers may also be acceptable. 4. Consider what will happen to jars filled with water of different temperatures and why. uwrite your hypothesis. Water droplets will form on the inside and outside of a jar because of differences in temperature. As water vapor touches the cooler areas of the glass, it condenses and forms water droplets on that part of the glass. PERFORM YOUR EXPERIMENT Part One 1. Add hot tap water to a jar until it is half full. 2. Put the lid on the jar, and place it on a table. Watch what happens. 3. Pour the water out of the jar. Dry the inside and outside of the jar. Part Two 1. Add cold tap water to a jar until it is half full. Then, add a few ice cubes to make the water very cold. 2. Put the lid on the jar, and place the jar on a table. Watch what happens. ANALYZE & CONCLUDE 1. In Part One, do water droplets form on the inside or outside of the jar? Droplets of water form on the inside of the jar in the first setup. 2. How did the water droplets get there? The hot temperature of the water causes some of the water to vaporize. Then, the vaporized water comes in contact with the sides of the jar. The sides of the jar are cooler and will cause the water vapor to form into droplets along the inside of the jar. You Be The Chemist Activity Guide page 87
ANSWER KEY Below are suggested answers. Other answers may also be acceptable. 3. In Part Two, do water droplets form on the inside or outside of the jar? Droplets of water form on the outside of the jar in the second setup. 4. How did the water droplets get there? The water vapor in the air comes in contact with the outside of the jar. Because the water inside the jar cools the glass, the water vapor in the air will condense on the outside of the jar when it touches the cool glass. 5. The physical change when a gas becomes a liquid is called. condensation 6. The physical change when a liquid becomes a gas is called. vaporization 7. Have you ever seen the processes of condensation and vaporization take place at home? If so, when? If not, provide another example of each change. Yes, when you take a hot shower, condensation will cause water droplets to form on the mirror in your bathroom. Also, when you boil a pot of water to cook spaghetti or boil water for tea, some of the water will vaporize out of the pot. 8. Is your hypothesis valid? Why or why not? If not, what would be your next steps? Answer 1: Valid because the data support my hypothesis. Answer 2: Invalid because the data do not support my hypothesis. I would reject my hypothesis and could form a new one, such as You Be The Chemist Activity Guide page 88
ANSWER KEY Below are suggested answers. Other answers may also be acceptable. EXPAND YOUR KNOWLEDGE ADVANCED Have students complete this section if you used the advanced differentiation information, or challenge them to find the answers to these questions at home and discuss how these terms relate to the experiment in class the next day. 1. Define the following key terms. Then, provide an example of each by writing the example or drawing/pasting an image of the example. Term Definition Example (write or add image) Element A pure substance that cannot be broken down into simpler substances by ordinary chemical or physical means; an element is made up of only one type of atom. Compound A pure substance made up of two or more elements joined in a defined ratio. Energy The ability to do work or produce heat. 2. Compare and contrast the three states of H2O (water). The three states of H2O are ice, water, and water vapor. Ice is a cold and hard solid. Water is a liquid and flows easily. Water vapor is a gas and can be found in the air. 3. Describe how energy causes matter to change states. Give examples. When energy is applied to matter, such as applying heat to ice, it will cause the ice to turn into water. The removal of energy, such as putting water in a freezer, will cause water to turn into a solid ice. You Be The Chemist Activity Guide page 89