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Bellwork

Bellwork. Chapter Pre-test: 1. What instrument would you use to measure temperature? Thermometer 2. Which of the following is a unit of volume? A. atmosphere B. gram C. meter D. liter D. 3. What characteristic of matter can you measure using a graduated cylinder? Volume

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Bellwork

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  1. Bellwork • Chapter Pre-test: • 1. What instrument would you use to measure temperature? Thermometer • 2. Which of the following is a unit of volume? • A. atmosphere • B. gram • C. meter • D. liter D. • 3. What characteristic of matter can you measure using a graduated cylinder? Volume • 4. The sides of a cube are 2 cm by 2 cm. What is the volume of the cube? 8 cm3 • 5. What additional quantity would you need to calculate the density of the cube in question 4? Mass • 6. Which of the following topics is not studied in chemistry? • A. Composition of matter • B. reactions of substances • C. properties of materials • D. motion of large objects. D.

  2. Physical science Chapter 2 Properties of Matter

  3. Lab • Groups of three-four will be made • Each group will be provided 5 materials, a rubber band, a steel paper clip, a copper prong, wooden pencil or toothpick, and a graphite pencil filler. • Determine the properties or characteristics of the materials by touching, smelling, and looking at them. • Record these properties in a table/chart. • After you record these properties, write a description of each material that could be used to clearly identify it.

  4. Bellwork • Finish the lab quickly so we can discuss your descriptions.

  5. Possibilities • Rubber’s elasticity • Copper’s color • Steel’s shininess • Wood’s brittleness • Graphite’s ability to leave a mark • Description: • Copper is a gold-ish solid that is flexible enough to be shaped and bent

  6. Section objectives • 1. Classify pure substances as elements or compounds. • 2. Understand why are elements and compounds are classified as pure substances • 3. Understand how mixtures differ from pure substances. • 4. Know what the main difference is among solutions, suspensions, and colloids.

  7. Intro • Your book uses the example of a care label on your clothes. • Why is it there? • A tendency to wrinkle is a property of cotton, the tendency to not wrinkle is a tendency of polyester, the tendency to shrink when washed is a property of wool. • They all have different properties because they have different compositions. • These compositions can be broken into pure substances and mixtures

  8. Pure substances • Matter that always has the same composition is classified as a pure substance, or substance • Every sample of a given substance has the same properties because a substance has a fixed, uniform composition. • Salt is a composition of sodium and chloride • Substances can be classified into two categories, elements and compounds

  9. Elements • There are only about 100 elements • Element: a substance that cannot be broken down into simpler substances • An atom is the smallest particle of an atom • An element has a fixed composition because it contains only one type of atom.

  10. Elements • No two elements contain the same type of atom. • Most elements are solids at room temperature (20 C, 68 F)

  11. Examples • Aluminum

  12. Example • Carbon

  13. Elements • Some elements are gas at room temperature • Oxygen and nitrogen are the main gases we breathe

  14. Bellwork • Draw the diagram classifying the different types of matter • What are elements made of? • What form are most elements in at room temperature?

  15. Liquid Elements • Only two elements that are liquid at room temperature: Bromine and mercury, both are very poisonous

  16. Symbols • The symbols for elements are similar to why scientists use the SI system of measurement. • Many symbols are based on the Latin name for the element and all scientists agree on the symbol for each element • *project!: Choose an element you are unfamiliar with. Research the origin of the symbol. Then, research the application or use of the element. Write at least a paragraph detailing this information and turn it in on Thursday

  17. Compounds • Someone read the first paragraph under Compounds on pg. 40 • A compound is a substance that is made from two or more simpler substances. The simpler substances are either elements or other compounds

  18. Compounds continued • THE PROPERTIES OF A COMPOUND DIFFER FROM THOSE OF THE SUBSTANCES FROM WHICH IT IS MADE • Water is a compound made up of the elements hydrogen (H) and oxygen (O) • Both of these elements are gases at room temperature, but water is a liquid • Hydrogen can fuel a fire and oxygen is needed to keep it going, but water is used to put it out

  19. COMPOUNDS • COMPOUNDS ALWAYS CONTAIN TWO OR MORE ELEMENTS JOINED IN A FIXED PORTION • Silicon dioxide, for example, is the compound found in most light colored sand • It is made from the elements silicon ( a gray solid) and oxygen. • It is always made with two oxygen atoms for each silicon atom. (di means 2) Same for water

  20. Mixtures • Mixtures tend to retain some of the properties of their individual substances • But the properties of a mixture are less constant than the properties of a substance • The properties of a mixture can vary because the composition of a mixture is not fixed.

  21. On your own • Read pages 41-44 • Create a chart with descriptive visuals and examples to help you classify the different types of mixtures • Heterogeneous • Homogeneous • Solutions • Suspension • Colloid • When you finish, complete section 1 in your workbook

  22. Types of mixtures • Mixtures are combinations of substances • The composition of the substances (unlike compounds) are not constant • Example: salsa • Heterogeneous mixtures: the parts that make up the mixture are noticeably different • Example: sand

  23. Bellwork • Think of a homogeneous and a hetergeneous mixture

  24. Heterogeneous MixturesHetero (different) genus (kind)

  25. Homogeneous mixtures • Homogeneous mixtures: the substances are so evenly distributed that it is difficult to distinguish one substance from another • Example: a stainless steel spoon is a homogeneous mixture of iron, chromium and nickel

  26. Homogeneous Mixtures

  27. Solutions, Suspensions, Colloids • Based on the size of its largest particles, a mixture can be classified as a solution, suspension, or a colloid

  28. Solution • Solution: when substances dissolve and form a homogeneous mixture • Example: sugar dissolved in water • Characteristics: • Particles are too small to settle out of the solution • Particles cannot be trapped by a filter • Particles are too small to scatter light

  29. Solution

  30. Suspension • “Shake Well” • Suspension: a heterogeneous mixture that separates into layers over time • Example: Sand and water • Characteristics: • Particles will settle • Particles can be filtered • Particles are large enough to scatter light

  31. Suspension

  32. Colloid • Colloid: contains some particles that are intermediate in size between the small particles in a solution and the larger particles in a suspension. • Example: homogeneous milk • Characteristics: • Particles do not separate into layers • You cannot filter to separate parts of a colloid • Particles are large enough to scatter light

  33. Colloid

  34. Bellwork 8-29 • Give an example of a solution, suspension, and a colloid

  35. Examples of physical properties • Physical property: any characteristic of a material that can be observed or measured without changing the composition of the substances in the material. • Viscosity • Conductivity • Malleability • Hardness • Melting point • Boiling point • Density

  36. Viscosity • Viscosity: the tendency of a liquid to keep from flowing-its resistance to flowing • The greater the viscosity the slower the liquid flows

  37. Viscosity • Viscosity usually decreases when heated • Importance? Think motor oil…

  38. Conductivity • Conductivity: a material’s ability to allow heat to flow • Materials with high conductivity (metals) are conductors • If a material is a good conductor of heat it will usually do the same for electricity • So why do we stir soup with a wooden spoon?

  39. Conductive materials

  40. Malleability • Malleability: the ability of a solid to be hammered without shattering. • Most metals are malleable • Solids that shatter when struck are brittle • Give an example of a malleable and brittle material.

  41. Malleability

  42. Hardness • Hardness: how hard a material is • To compare hardness you can try to scratch one object with another • Diamond is the hardest material known

  43. Hardness

  44. Melting and boiling points • Melting Point: The temperature at which a substance changes from a solid to liquid • Boiling Point: The temperature at which a substance boils • What are the melting and boiling points of water in Celsius? • Are there any factors that can affect boiling point?

  45. Melting/Boiling Points

  46. Density • Density: can be used to test the purity of a substance • Examples include methanol for bike racing

  47. Using Physical Properties to Identify Materials • 1. Decide which properties to test • 2. Perform tests on unknown samples • 3. Compare data results with data reported for known materials • Example: crime investigation

  48. Using Properties to Choose Materials • Properties determine which materials are chosen for which uses. • Wood shoelaces?

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