Characteristic Properties of Matter

Transcription

1 Characteristic Properties of Matter Overview Number of instructional days: 20 (1 day = 45 minutes) Content to be learned Differentiate among the characteristics of solids, liquids, and gases. Predict the effects of heating and cooling on the physical state, volume, and mass of a substance. Recognize that different substances have properties that allow them to be identified, regardless of the size of the sample. Classify and compare substances (solids, liquids, and gases) using characteristic properties. Explain that regardless of how parts of an object are arranged, the mass of the whole is always the same as the sum of the masses of its parts. Compare the masses of objects of equal volume made of different substances. Essential questions How do the characteristic properties of solids, liquids, and gases compare? How does heating and cooling affect the physical state, volume, and mass of substances? Science processes to be integrated Make observations and collect data in order to identify, compare, differentiate, and classify using characteristic properties of matter. Conduct investigations in order to predict the effect of heating and cooling on physical state, volume, and mass. Use science tools to demonstrate an understanding of conservation of mass, and the relationship between mass and volume. What is the relationship between the mass of an object and the sum of the masses of its parts? How do the masses of objects compare when the objects are made of different substances but are of equal volume? Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-1

2 Written Curriculum Grade-Span Expectations PS1 - All living and nonliving things are composed of matter having characteristic properties that distinguish one substance from another (independent of size or amount of substance). PS1 (5-8) SAE+MAS 4 Represent or explain the relationship between or among energy, molecular motion, temperature, and states of matter. PS1 (5-6) 4 Students demonstrate an understanding of states of matter by 4a differentiating among the characteristics of solids, liquids, and gases. 4b predicting the effects of heating and cooling on the physical state, volume and mass of a substance. PS1 (5-8) INQ+POC 2 Given data about characteristic properties of matter (e.g., melting and boiling points, density, solubility) identify, compare, or classify different substances. PS1 (5-6) 2 Students demonstrate an understanding of characteristic properties of matter by 2a recognizing that different substances have properties, which allow them to be identified regardless of the size of the sample. 2b classifying and comparing substances using characteristic properties (e.g., solid, liquid, gas). PS1 (5-8) INQ+ SAE 3 Collect data or use data provided to infer or predict that the total amount of mass in a closed system stays the same, regardless of how substances interact (conservation of matter). PS1 (5-6) 3 Students demonstrate an understanding of conservation of matter by 3a explaining that regardless of how parts of an object are arranged, the mass of the whole is always the same as the sum of the masses of its parts. PS1 (5-8) INQ-1 Investigate the relationships among mass, volume and density. PS1 (5-6)-1 Students demonstrate an understanding of characteristic properties of matter by 1a comparing the masses of objects of equal volume made of different substances. Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-2

3 Clarifying the Standards Prior Learning In grades K 2, students identified, compared, and sorted objects by similar or different physical properties, and recorded observations/data about physical properties. They used attributes of properties to state why objects are grouped together, and used simple tools to explore the property of weight. Students described properties of and identified and compared solids and liquids, and they made logical predictions about the changes in the state of matter when adding or taking away heat. In grades 3 4, students identified, compared, and sorted objects by similar or different physical properties, such as size, shape, color, texture, smell, weight, temperature, and flexibility, and they cited evidence to support conclusions about why objects are grouped/not grouped together. Students described properties of, and identified and compared solids, liquids, and gases, and they made logical predictions about the changes in the state of matter when adding or taking away heat. They observed and described physical changes, and used tools to measure weight in order to prove that all matter has weight. Students also used measures of weight to prove that the whole equals the sum of its parts, and they showed that the weight of an object remains the same despite the change in its shape. Current Learning In grade 5, students demonstrate an understanding of states of matter by differentiating among the characteristics of solids, liquids, and gases, and predicting the effects of heating and cooling on the physical state, volume, and mass of a substance. They demonstrate an understanding of characteristic properties of matter by recognizing that different substances have characteristic properties that allow them to be identified regardless of the size of the sample. Furthermore, students classify and compare substances using these characteristic properties, and they compare the masses of objects of equal volume made of different substances. These concepts are new to grade 5, and should be taught at the developmental level to the reinforcement level of instruction. In addition, students demonstrate an understanding of conservation of matter by explaining that regardless of how parts of an object are arranged, the mass of the whole is always the same as the sum of the masses of its parts. This concept has been addressed in previous grade levels, and should be taught at the reinforcement level of instruction. Great care should be taken when introducing fifth grade students to the relationship between energy, temperature, and changes in state, as well as to characteristic properties, such as density, melting point, and boiling point. These concepts are very abstract, and students have time to explore these concepts since they are taught throughout grades 5 8. Students have difficulty understanding the difference between heat and temperature, so the focus in grade 5 should be on observing and describing how adding and taking away heat produces changes in state. This provides the perfect opportunity to also explore the characteristic properties of freezing point, melting point, and boiling point. As students observe changes in state, they can use thermometers to observe and record the occurrence of constant temperatures at the freezing point, melting point, and boiling point of a substance, such as water. In addition, students can measure the mass of a given volume of the substance (water, for example) as a liquid and again when it changes state to a solid. The mass remains the same. This is also true when the solid melts back to a liquid, and when the liquid evaporates into a gas, as long as the substance is measured and changes state in a closed container. This gives students an opportunity to again observe that matter is conserved. When addressing the characteristic property of density in grade 5, the focus of instruction should be on comparing the masses of objects of equal volume but made of different substances. Students will use balances to measure mass, and can determine volume using water displacement in graduated cylinders. Then students can measure out a volume of water that is equal to the volume of each of the solids, and Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-3

4 mass the water. Students should then order the objects, including the water, from least to greatest mass. The objects can then be placed in a tub of water to observe whether they sink or float. Since the volume of all the objects, including the measured amount of water, is equal, those with less mass than water will float, while those with a greater mass than water will sink. Then students can explore with objects of varying sizes but made of the same materials in order to observe that density does not change, despite a change in mass and volume. This will help students develop a conceptual understanding of the relationship between mass and volume. In grades 7 8, students will develop a more abstract understanding of the proportional relationship between mass and volume by learning to calculate density using the equation D = m/v. Future Learning In grade 6, students will continue to differentiate among the characteristics of solids, liquids, and gases. They will predict the effects of heating and cooling on the volume and mass of substances, and will distinguish between solutions, mixtures, and pure substances, including compounds and elements. In grades 7 8, students will measure mass and volume of both regular and irregular objects, and will use those values and the relationship D = m/v to calculate density. They will identify an unknown substance given its characteristic properties, and will classify and compare substances using these characteristic properties. They will demonstrate an understanding of conservation of matter by citing evidence to conclude that the amount of matter before and after undergoing a physical or chemical change in a closed system remains the same. Students will create diagrams or models that represent the states of matter at the molecular level, and will explain the effect of increased and decreased heat energy on the motion and arrangement of molecules. They will also observe the physical processes of evaporation and condensation, or freezing and melting, and describe these changes in terms of molecular motion and conservation of mass. Students will use models or diagrams to show the difference between atoms and molecules, and will classify common elements and compounds using symbols and simple chemical formulas. They will interpret the symbols and formulas of simple chemical equations, and will use symbols and chemical formulas to show simple chemical rearrangements that produce new substances. Students will explain that when substances undergo physical changes, the appearance may change, but the chemical makeup and chemical properties do not. They will also explain that when substances undergo chemical changes to form new substances, the properties of the new combinations may be very different from those of the old. Additional Findings During grades 3 5, the study of materials should become more systematic and quantitative. Objects and materials can be described by more sophisticated properties, and students should measure, estimate, and calculate sizes, capacities, and weights. Many experiences of weighing including weighing piles of small things and dividing to find the weight of each will help. It is not obvious to elementary students that wholes weigh the same as the sum of their parts. That idea is preliminary to the conservation principle to be learned later (grades 7 8) that mass does not change in spite of striking changes in other properties as long as all the parts, including invisible gases, are accounted for (Benchmarks for Science Literacy, p. 76). By the end of fifth grade, students should know that heating and cooling cause changes in the properties of materials. Many kinds of changes occur faster under hotter conditions. No matter how parts of an object are assembled, the weight of the whole object made is always the same as the sum of the parts; and when the object is broken down into pieces, the parts have the same total weight as the original object (Benchmarks, p. 77). In grades 5 8, the focus in physical science shifts from properties of objects and materials to the characteristic properties of the substances from which the materials are made. In this grade span, students Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-4

5 observe and measure characteristic properties, such as boiling point, melting point, solubility, and density, all of which are independent of the amount of the sample. Students usually bring some vocabulary and simplistic understanding of the particulate model of matter, and it can be tempting to introduce atoms and molecules or improve student understanding of them. However, use of such terminology is premature for these students and can distract from the understanding that can be gained from focusing on the observation and description of the visible features of substances and of physical and chemical reactions (National Science Education Standards, pp. 149, 154). Researchers have found that, from an early age, children notice how objects differ in the way they appear to press down on the hands as they learn to feel the weight of objects. Children compare objects by their felt weight, and over time, generate the idea that felt weight is a characteristic property of an object. The concept of mass develops slowly, and is often associated with size or volume. In these cases, students often estimate the mass of a material from its bulk appearance (Making Sense of Secondary Science, pp ). Piaget found that at ages 9 to 10, students begin to relate density of one material to that of another. For example, children say that a material floats because it is lighter than water (Making Sense, p. 78). At grade 5, students are generally at the concrete operational level of cognitive development; therefore, the abstract nature of these concepts may be difficult for students to conceptualize. Students will benefit from many hands-on experiences. Bristol-Warren, Little Compton, Portsmouth, Tiverton Public Schools, C-5