Physical and Chemical Properties

Transcription

1 Lesson 2 Physical and Chemical Properties This hot air balloon is big, yet it easily floats in the air above the Red Sea in Egypt. How is this possible? 32 ENGAGE PS.1 Measure a variety of objects in metric system units (PS-M-A1) PS.2 Compare the physical properties of large and small quantities of the same type of matter (PS-M-A1) Identify the physical and chemical properties of various substances and group substances according to their observable and measurable properties (e.g., conduction, magnetism, light transmission) (PS-M-A3)

2 Which has more matter? Materials Form a Hypothesis Which do you think has more matter the balloon or the tennis ball? Does having more matter make an object larger? Does it make it heavier? Write your answer in the form If the amount of matter increases, then an object will... Test Your Hypothesis Measure Place one object under water. Record how high the water rises with some tape, then remove the object. Do not spill any water! Next, place the second object in the water and record the water level; this is your dependent variable. Place the objects on either side of the equal pan balance. Which is heavier? This is your independent variable. Repeat all your measurements to verify your answers. Draw Conclusions Interpret Data Did the heavier object also raise the water higher? Why or why not? Which object has more matter? Did the test support your hypothesis? Explore More Compare the properties of a large bag of popcorn and a small bag of popcorn. Which do you think would have more matter? Form a hypothesis and test it. Then analyze and write a report to explain your results. Step Step inflated balloon tennis ball container of water tape equal pan balance SI.8 Use consistency and precision in data collection, analysis, and reporting (SI-M-A3) SI.12 Use data and information gathered to develop an explanation of experimental results (SI-M-A4) Also covers SI EXPLORE

3 Essential Question What are some properties of matter? PS.1, PS.2, Vocabulary physical property, p. 34 mass, p. 34 conduction, p. 38 magnetism, p. 38 light transmission, p. 39 chemical property, p. 40 Reading Skill Classify Technology e-glossary and e-review online at The sum of all the masses in the backpack, plus the backpack itself, is equal to the mass of the full backpack. What are physical properties? Pretend you have lost your backpack. You want to describe your backpack to your friends so they can help you look for it. How could you describe it? You could say how large it is, or how many things there are inside. You could talk about its color, texture, or hardness. You are describing the physical properties of the backpack. A physical property is something that can be observed about an object without changing the identity of the object. Physical properties that can be observed without having to measure an object, such as color, are called qualitative properties. Properties that can be measured, such as mass, are called quantitative properties. Mass One way to describe the backpack would be by its mass. Mass is the amount of matter in an object. This property compares the amount of matter in a sample to standard amounts. Mass can be measured on an equal pan balance. Gravity pulls on the standard pieces and on the sample. When the balance levels out, the amount of matter in the sample and the standard pieces is the same. Mass is measured in kilograms or grams. One kilogram is equal to 1,000 grams. Adding up the grams of mass in the standard pieces gives the mass of the sample. An object s mass is always equal to the sum of the masses of its parts. 34 EXPLAIN

4 Measuring Matter Read a Photo Weight Try holding a marble in one hand and a basketball in the other they feel different. It is harder to hold up the basketball. You are feeling the weight of each ball. Weight (WAYT) is how strongly gravity pulls on an object. If an object has more mass, it will also have more weight. Weight is measured in newtons (N). One newton is equal to pounds (lbs) in the English system. Gravity is greater on planets with more mass, so an object s weight depends on the planet it is on. An object s mass, in contrast, is the same on different planets. Volume Mass and weight describe the amount of matter in an object, but what about its size? Volume (VAHL yum) measures how much space matter takes up. You can calculate the volume of a regularly shaped object, such as a rectangular solid. Multiply the object s length (L) by its width (W) by its height (H): L W H. What is the volume of the marble? Clue: What is the water level before and after the marble is in the cylinder? How can you measure the volume of an object with an irregular shape? A rock s volume makes the water level rise when you place it in a graduated cylinder or beaker. Matter in the rock takes up space and pushes water out of the way. The change in the water level when an irregular object is placed under water indicates the object s volume. The volume of liquids and irregularly shaped solids is often measured in milliliters (ml). The volume of regularly shaped solids is usually measured in cubic centimeters (cm 3 ). A volume of 1 cm 3 equals 1 ml. Quick Check Classify Which units are used to measure weight, mass, and volume? Critical Thinking How could you change an object s volume without changing its mass? 35 EXPLAIN

5 What is density? Think of a large empty box with a lid. It has a large volume but little mass. If you place a few marbles in it, it has more mass but the same volume. Add more marbles and there is more mass, but the volume stays the same. As you add more marbles, you are increasing the box s density. Density (DEN suh tee) is the amount of mass for each cm 3 (or ml) of a substance. To calculate a sample s density, you divide its mass by its volume. Density = mass volume A marble and a rubber ball can be about the same size. Which do you think is denser? The marble has more particles, or more mass, inside of it than the ball. The ball has air inside. Air is less dense than both glass and rubber. These observations tell you that the marble is denser than the ball. With boxes and other containers you can change density by adding more mass inside. You could also change the density by changing the volume. You could stretch, crush, or bend the container to let air in or out. Most matter, however, acts like the marble. You cannot add more mass to the inside, nor can you stretch it. Its density will always be the same. Read a Diagram Density and Water How would you represent the density of water? Clue: Look at the density of the marble that sinks and the ball that floats. 36 EXPLAIN

6 Floating and Sinking When an object is placed in a liquid, gravity pulls the object down. In order for the object to go down, the liquid must move out of the way. What would happen if the liquid was denser and did not get out of the way? The object would not sink; it would float. Objects can float as a result of buoyancy (BOY un see). Buoyancy is the resistance to sinking. It occurs because the liquid that is being pushed out of the way pushes back on the object. If an object is denser than the liquid, then the object can push harder and it sinks. If the liquid is denser than the object, then the liquid can push harder and the object floats. Buoyancy depends on density. If you change the mass or the volume of an object, you can change whether it will float. If you have a toy boat and keep adding mass to it, it will sink. Buoyancy also depends on shape. A block of aluminum will sink, but an aluminum canoe will float. Why? The canoe s shape holds in air so that it acts like it has a density less than that of water. But if the canoe is full of water, it will sink. Many liquids also have a property called surface tension (SUR fus TEN shun). In water, every particle pulls toward the other particles. This attraction creates a skin on the surface. This skin is what surface tension means. If an object is spread over the surface, it can rest on this skin even if it would not normally float. If an object is not spread out enough, it will break the skin and sink. Too dense to float? Make a Model You need three models. The first is a triangle cut from a paper towel. The second is a plastic cup. The third is a foam cup. SI.7, SI.14 Place all three objects in water. The triangle should lie flat on the water. The two cups should be placed with the open end down. Which ones sink? Record your answers. Add liquid detergent to the water to break up the surface tension. Do any models sink now? Have your teacher poke evenly spaced holes in each model. Do any models sink now? Infer Which models could float simply because of their density? Which models were helped by their shape or were on top of the water due to surface tension? Quick Check Classify Which properties depend on shape, volume, or mass? Critical Thinking How would you design a boat to carry large masses across the ocean? The density of an object depends on the type of material. 37 EXPLAIN

7 What are some other physical properties? Many physical properties, such as color or mass, can be determined by taking simple measurements or making observations. However, some physical properties require testing or investigations to measure. Conduction Have you ever fastened a seat belt on a hot day? The buckle feels hotter than the strap. This is because the metal in the buckle transfers heat to your hand more rapidly than the cloth strap does. Some substances transfer heat more readily than others. Conduction (kuh DUK shun) is the passing of heat through a material while the material itself stays in place. It occurs between objects that are touching. Magnetism Magnetism (MAG nuh ti zum) is another physical property. Magnetism is the ability of an object to push or pull on another object that has the magnetic property. Magnets attract certain metals, such as iron. However, they do not attract nonmetallic substances such as wood, plastic, or water. Conductivity Material How Many Times Better Than Air It Conducts Heat Oak wood 6 Water 23 Brick 25 Glass 42 Stainless steel 534 Aluminum 8,300 Copper 15,300 Silver 16,300 Read a Table Diamond 35,000 or more Which material from the table would be the best insulator? Clue: It has the lowest conductivity. 38 EXPLAIN

8 What happens if you put a metal object, such as a paper clip, near a magnet? The magnet pulls on the object, and then the object sticks to the magnet. You can see magnetism at work in a junkyard or factory. Large magnets can be used to separate certain metals from other objects. Light Transmission The movement of light through a substance such as air or water is called light transmission (trans MIH shun). When light hits an object it may be able to pass through the object. Objects or substances that allow most light to pass through are called transparent (trans PER unt). Air, glass, and water are examples of transparent substances. Some objects or substances, such as waxed paper, ice, or frosted glass, blur light as it passes through. These objects are called translucent (trans LEW sunt). If an object or substance allows little or no light to pass through, it is called opaque (oh PAYK). Wood, rubber, and metal are examples of opaque substances. The ability to transmit light is another physical property that can help to identify an object. Grouping Objects SI.1, SI.6 Observe Gather a variety of objects. Select tools that can be used to measure physical properties. Make a list of questions that you can use to guide your investigation, such as Is this object a good conductor? Record the physical properties of each object. Interpret Data Use your results to group objects according to their physical properties. Magnetism is a physical property that can be used to sort objects. Quick Check Classify What are some physical properties of metals? Critical Thinking Are you transparent, translucent, or opaque? 39 EXPLAIN

9 What are chemical properties? You have learned that substances have many physical properties, such as color, mass, density, and magnetism. Another way to classify a substance is to describe its chemical properties. A chemical property describes the way a substance reacts with other substances. When sodium metal is dropped into water, it reacts strongly, producing hydrogen gas, sodium hydroxide, and a lot of heat. The heat often causes the hydrogen to burn. Hydrogen can be described as being flammable. Flammability is a chemical property of a substance that describes its ability to catch on fire or burn. Methane is another flammable gas. Elements in the same column on the periodic table have similar chemical properties. The other metals in sodium s column are also very reactive with water. Sodium and potassium, for instance, must be stored under oil to keep them from reacting with water vapor in the air. Generally, the closer that metals are to the bottom of the periodic table, the more reactive they are. A chemical property of some elements can be observed when they are placed in a flame. Each element will burn a different color when placed in a flame. lithium copper potassium sodium 40 EXPLAIN

10 Potassium s violent reaction with water is a chemical property. Scientists call elements in the far-left column of the periodic table the alkali metals. These elements easily form compounds with other substances and never exist by themselves in nature. To the right of the alkali metals are the alkaline earth metals. These metals are not as reactive as alkali metals. Some alkaline earth metals, such as calcium and magnesium, are essential to many living organisms. Transition metals are a large block of elements in the center of the periodic table. They include copper, iron, gold, nickel, and zinc. Transition metals react slowly with other substances. When left outside, some metals will corrode. Corrosion (kuh ROH zhun) is when metals combine with nonmetals from the environment. Iron corrodes by rusting, which causes the corroded iron to flake away. Calcium also reacts with water, but not as violently as the alkali metals. The last column on the periodic table contains the most stable elements the noble gases. These elements rarely react with other substances. To the left of the noble gases are the halogens. Halogens, such as fluorine, chlorine, and bromine, are the most reactive nonmetals. The chemical structure of a substance affects how it acts with other substances. For example, potassium and calcium are different chemically. Potassium and calcium both react with water. However, calcium reacts less violently with water. Quick Check Classify Flammability is a chemical property of hydrogen. Does lithium also have that chemical property? Critical Thinking Why are alkali metals unsafe to handle? 41 EXPLAIN

11 How can properties be classified? Properties can be classified into one of two types: extensive properties or intensive properties. Physical properties can be extensive or intensive. However, chemical properties can only be intensive. Extensive properties depend on the amount of substance present. Examples of extensive properties include mass, length, and volume. Intensive properties do not depend on the amount of substance present. Density is an intensive physical property. The density of a substance is the same no matter how much of the substance is present. Increasing the amount of water does not increase the water s density. The density is always the same. A substance s boiling point is a physical property. Boiling point is the temperature at which a substance boils, or changes state from a liquid into a gas. Is a substance s boiling point an extensive or intensive property? To find out, fill a pan with 100 ml of water and bring it to a boil. You will find that the temperature at which water boils is 100 degrees Celsius (212 F). A smaller amount, such as 10 ml, of water also boils at 100 C. The boiling point of any substance does not depend on the mass of the substance, so this is an intensive property. This liquid oxygen is just starting to boil at a frigid 183 C. The same is true for a substance s freezing point. The freezing point of a substance is the temperature at which the substance freezes. For example, water freezes at 0 C (32 F). Quick Check Classify List some extensive properties and some intensive properties of substances. Critical Thinking How could you show that two pieces of wood that are different sizes have the same densities? An object s mass is an extensive property. This type of physical property depends on the amount of substance present. 42 EXPLAIN

12 Visual Summary Some physical properties, such as mass, volume, and weight, are measurable. Think, Talk, and Write Vocabulary The amount of matter in an object is its. Classify What are physical and chemical properties? Give examples. Make a Study Guide Other physical properties, such as magnetism or conductivity, require testing or investigations to observe. Chemical properties describe how a substance interacts with other types of matter. Make a trifold book. Use the titles shown. Fill in each box with the type of information described by the column heading. Critical Thinking Would a balance on the Moon, which has one-sixth the gravity of Earth, still read masses correctly? Why or why not? Test Prep Which property describes the ability of an object to attract another object? A volume B magnetism C conductivity D light transmission Test Prep Which is a chemical property of water? A Its boiling point is 100 C. B Its freezing point is 0 C. C It reacts with sodium. D It is a liquid at room temperature. Essential Question What are some properties of matter? Writing Link SI.10 Math Link Descriptive Writing Pick a piece of matter inside your classroom. Research and then describe it according to its properties and state of matter. Density and Volume You have 80 ml of water. How many hollow cubes that are 2 cm on a side could you fill? -Review Summaries and quizzes online at 43 EVALUATE

13 Inquiry Skill: Measure When scientists are conducting experiments or making observations, they often make measurements. When you measure you find the length, distance, time, volume, mass, or perimeter of an object. When you make measurements, it is important to record the data you collect. One way to record your measurements is in a table. Learn It Scientists use tools, such as rulers, thermometers, balances, and scales, to measure things. Rulers can be used to measure an object s length or perimeter. Temperature is measured using a thermometer. Mass can be measured using a balance. A scale is used to measure weight. Many different objects are around you. How do scientists distinguish one object from another? One way is to measure and compare the objects properties. Try It Materials wooden block, quarter, golf ball, table-tennis ball, sheet of inch paper, marble, plastic spoon, balance with masses, ruler, yarn, spring scale Create a table like the one shown on the next page. Observe the color and the texture of each object. Record this information in the table. Measure and record each object s mass using the balance and masses. Be sure to use the correct metric unit for measuring mass. 44 FOCUS ON SKILLS

14 Find the weight of the objects by tying a piece of yarn to each object and hanging it from a spring scale. Be sure to use the correct metric unit for measuring weight. Record your data. Find the circumference of the quarter, golf ball, table-tennis ball, and marble by wrapping a piece of yarn around each object. Cut the yarn to fit around the object, and then measure the length of the yarn. Record your data. Find the perimeter, or distance around the outside edge, of the piece of paper using a ruler. Trace the wooden block and the plastic spoon onto a piece of paper. To find the perimeter of each object, lay a cut piece of yarn over the lines you traced. Then measure the length of the yarn. Record your data. Apply It Which objects and properties were difficult to measure? Explain. Which object had the smallest mass? Will a small object always have a smaller mass than a large object? Explain. Use a calculator to find the average mass and average weight of the objects. Compare your data table and calculations with those of your classmates. Did your classmates have the same data? Explain why there are differences between the data you collected and your classmates data. PS.1 Measure a variety of objects in metric system units (PS M-A1) SI.9 Use computers and/or calculators to analyze and interpret quantitative data (SI-M-A3) SI.11 Construct, use, and interpret appropriate graphical representations to collect, record, and report data (e.g., tables, charts, circle graphs, bar and line graphs, diagrams, scatter plots, symbols) (SI-M-A4) 45 FOCUS ON SKILLS

15 UNIT 1 Review DOK 1 Visual Summary Fill each blank with the best term from the list. Lesson 1 All matter is made of elements. Each element is made of a different kind of atom. atom, p. 23 chemical property, p. 40 conduction, p. 38 electron, p. 24 mass, p. 34 matter, p. 22 neutron, p. 24 physical properties, p. 34 Make a Study Guide Lesson 2 Matter can be described by many different properties. Assemble your lesson study guides as shown. Use this unit study guide to review what you have learned. element, p. 22 protons, p A particle with no electric charge is called a(n). 2. A(n) describes the way a substance reacts with other substances. 3. The passing of heat through a material is called. 4. The amount of matter in an object is its. 5. A material that cannot be broken down into anything simpler is a(n). 6. A(n) is a particle with a negative charge. 7. The smallest unit of an element that still has the properties of that element is a(n). 8. Anything that has mass and takes up space is made of. PS.2 9. The atomic number of an element is the same as the number of in an atom. 10. An object s color and mass are examples of. 46 -Glossary Words and definitions online at

16 DOK 2 3 Answer each of the following. 11. Which measures an object s mass? A ruler B pan balance C spring scale D graduated cylinder 12. Experiment Gather the following items: a rubber band, a wooden block, a clear glass jar, and a nail. Determine if each object is magnetic, conducts heat, or if light is able to pass through it. Make a table showing your results. How could you group these items based on their properties? 13. In the table below, which terms should be used for the column headings? Elements in the Periodic Table 17. Measure Gather a variety of items from your classroom. Use tools to measure the physical properties of each item. Be sure to use the correct metric units when writing down your measurements. PS Classify What type of structure does the picture show? What is it made of? O O 19. Compare and Contrast You have ten plastic cups in one hand and two plastic cups in the other hand. Are the physical properties of the two sets of cups the same or different? Explain. PS.2 hydrogen silicon sodium oxygen boron copper sulfur arsenic mercury A Elements, Metals, Nonmetals B Nonmetals, Metalloids, Metals C Gases, Liquids, Solids D Metalloids, Solids, Liquids 14. True or False With a simple microscope, you can see atoms. Is this statement true or false? Explain. 15. Expository Writing John Dalton was the scientist who defined atoms. Research his life and write a biography. Include a drawing of the structure of an atom at the end of your report. 16. True or False Magnetism is an example of a chemical property. Is this statement true or false? Explain. 20. How can you classify matter? PS.1, PS.2,, Know Your Elements What to Do DOK 4 1. Research the properties of an element. How many protons and electrons do its atoms have? Is it a metal, a nonmetal, or a metalloid? 2. Research your element s history and uses. When was it discovered, by whom, and how? Where is it found? Analyze Your Results Use your research to create a pamphlet about your element. Include photos, drawings, charts, or other graphics., SI.3, SI.19 -Review Summaries and quizzes online at 47

17 1 Which physical property does this instrument measure? A. weight B. mass C. magnetism D. conductivity 2 Which part of a neutral atom has a negative electrical charge? A. electron B. nucleus C. neutron D. proton 3 Which test could a student do to determine if an object is a conductor? A. Place it in water to see if it sinks. B. Scratch it on glass to see if it leaves a mark. C. Pound it with a hammer to see if it bends. D. Shine a lamp on one end of the object to see if the other end gets hot. 4 Enrique creates a list of chemical properties for baking soda. Which of the following could he include in his list? A. Baking soda is a white powder. B. Baking soda has a density of 2.2g/cm 3. C. Baking soda reacts with vinegar to produce a new substance. D. Baking soda s melting point is about 60 C. 5 The chart below shows a variety of objects and different physical properties for each. Object Physical Property Metric Unit ball wood block rock toy car mass length volume weight What are the correct metric units for each physical property listed in the chart? List in order from top to bottom. A. grams, meters, newtons, cubic centimeters B. grams, meters, cubic centimeters, newtons C. newtons, meters, cubic centimeters, grams D. newtons, cubic centimeters, grams, meters PS.1 48

18 6 The drawing below shows a water molecule. What is the arrow pointing to? A. electron B. atom C. proton D. nucleus 7 Look at the illustration below. How could you demonstrate that the single crayon has different physical properties from the box of crayons? A. Count the number of crayons in the box. B. Measure the mass of the single crayon and the mass of the box of crayons. C. Break each crayon in half. D. Determine if the crayons conduct heat. PS.2 8 Lithium is an element on the left of the periodic table. It is a silvery, white metal that can easily be cut with a knife. Lithium reacts with oxygen and other elements. Lithium has a melting point of 181 C. Which is a chemical property of lithium? A. silvery, white metal B. easily cut with a knife C. reacts with oxygen D. melting point of 181 C 9 Which instrument should a scientist use to view single atoms? A. graduated cylinder B. hand lens C. electron microscope D. laser beam 10 Which physical property would not differ between a large marble and a small marble? A. mass B. density C. weight D. volume PS.2 Question Review Question Review 1 pp pp p pp p pp pp p pp p