bellwork
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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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.
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Physical science Chapter 2
Properties of Matter
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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.
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Bellwork
• Finish the lab quickly so we can discuss your descriptions.
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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
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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.
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Matter
Substance
Element Compound
Mixture
Heterogeneous mixture
Homogenous Mixture
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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
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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
Matter
Substance
Elements Compounds
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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.
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Elements
• No two elements contain the same type of atom.
• Most elements are solids at room temperature (20 C, 68 F)
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Examples
• Aluminum
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Example
• Carbon
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Elements
• Some elements are gas at room temperature• Oxygen and nitrogen are the main gases we
breathe
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Bellwork
• Draw the diagram classifying the different types of matter
• What are elements made of?• What form are most elements in at room
temperature?
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Liquid Elements
• Only two elements that are liquid at room temperature: Bromine and mercury, both are very poisonous
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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
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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
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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
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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
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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.
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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
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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
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Bellwork
• Think of a homogeneous and a hetergeneous mixture
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Heterogeneous MixturesHetero (different) genus (kind)
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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
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Homogeneous Mixtures
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Solutions, Suspensions, Colloids
• Based on the size of its largest particles, a mixture can be classified as a solution, suspension, or a colloid
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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
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Solution
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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
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Suspension
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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
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Colloid
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MixtureCombination of substances
SolutionWhen substances dissolve in a
homogeneous mixture, sugar water
SuspensionHeterogeneous mixture that
separates into layers, sand and water
ColloidHomogeneous mixture with
intermediate particles, milk, fog
HeterogeneousParts are noticeably different
, sand
HomogeneousParts are evenly distributed,
stainless steel spoon
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Bellwork 8-29
• Give an example of a solution, suspension, and a colloid
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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
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Viscosity
• Viscosity: the tendency of a liquid to keep from flowing-its resistance to flowing
• The greater the viscosity the slower the liquid flows
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Viscosity
• Viscosity usually decreases when heated• Importance? Think motor oil…
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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?
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Conductive materials
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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.
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Malleability
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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
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Hardness
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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?
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Melting/Boiling Points
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Density
• Density: can be used to test the purity of a substance
• Examples include methanol for bike racing
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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
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Using Properties to Choose Materials
• Properties determine which materials are chosen for which uses.
• Wood shoelaces?
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Using Properties to Separate Mixtures
• Two properties are used to separate:– Filtration– Distillation
• Filtration: a process that separates materials based on the size and of their particles.
• What are some examples of filtration?
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Homework
• Finish section 1 in your work/study book• Finish your research on your symbol
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Chemical Properties
• Chemical property: any ability to produce change in the composition of matter
• Chemical properties can only be observed when the substances in a sample of matter are changing into different substances.
• Example: Paraffin wax in a candle (made of compounds containing hydrogen and carbon).– As the compounds burn they combine with oxygen and
form water and carbon dioxide
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Chemical Properties
• Flammability and Reactivity are two chemical properties of matter.
• Flammability: a material’s ability to burn in the presence of oxygen
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Why does it matter?
• Think of some reasons why the flammability of a material or substance is important?
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Reactivity
• Reactivity: how readily a substance combines with other substances
• Oxygen and iron are highly reactive substances.
• What happens when iron reacts with oxygen and water?
• What are some other materials that rust?
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Rust
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Reactivity• Nitrogen has a low reactivity
• Because of this it is used to displace the reactivity of other substances
• Example: water tanks that stabilize ships are filled with seawater.
• The oxygen in the water reacts with the iron in the steel and creates rust
• Japanese engineers have pumped nitrogen in these tanks to displace the oxygen and decrease rust.
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Recognizing chemical changes
• Chemical change occurs when a substance reacts and forms one or more new substances.
• Can you think of examples of chemical change?
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Recognizing change
• Think of things that change chemically.
• What are some “side effects” of chemical change?
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Recognizing Chemical Change
• 3 types of evidence for chemical change:– 1. Change in Color– 2. Production of gas– 3. Formation of a precipitate
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Change in Color
• A change in color is a clue that a chemical change has produced at least one new substance
• Copper + water+ Oxygen=Patina
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Production of a Gas
• Can you think of an example of a production of gas when compounds or substances are combined?
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Production of Gas
• Many gas reactions include carbon dioxide.• When baking soda and vinegar are combined
they form bubbles of carbon dioxide• Baking soda in a cake combines with an acid
and creates bubbles which make the cake rise
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Formation of a Precipitate
• Any solid that forms and separates from a liquid mixture is called a precipitate
• What are some examples?
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Formation of a Precipitate
• When acid is added to milk the proteins undergo a chemical change that alters their structure, causing them to stick together in clumps
• These clumps are cheese!
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Chemical or Physical Change?
• Always ask, “are different substances present after the change takes place?”
• If not, then it is a physical change• Chemical change= the composition of the matter
changes• Physical change=the composition of the matter
remains the same.• What are some examples of physical change that
have evidence of chemical change?
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Video for Chemical and Physical Change
• http://youtu.be/gCbqjs-pqJo