Matter: anything that occupies spaced and has mass



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Matter: anything that occupies spaced and has mass

  • Matter: anything that occupies spaced and has mass

  • Matter can be distinguished by its physical properties

  • Physical property: a property that can be observed/or measured without changing the chemical makeup of the substance

  • What are some physical properties?

  • color

  • melting and boiling point

  • odor



Density: the mass of a material within a given volume

  • Density: the mass of a material within a given volume

    • The density of liquid water is usually given as 1 g/mL, but it’s actually temperature dependent
    • 1 cm3 = 1 mL (this is super useful for the rest of the year so MEMORIZE it now!)
  • Freezing point: the temperature at which a substance changes from a liquid to a solid

    • For water, it is of course, 0°C
  • What others can you think of?



Graphite — layer structure of carbon atoms reflects physical properties.

  • Graphite — layer structure of carbon atoms reflects physical properties.

  • This allows layers to easily be removed.

  • This easy transfer of layers is why we use it in pencils!



Water is the only ordinary liquid found in naturally in our environment

  • Water is the only ordinary liquid found in naturally in our environment

    • Because so many substances dissolve readily in water, quite a few liquids are actually water solutions
    • A water-based solution is an aqueous solution
  • BTW, what’s a chemical property? A property that can only be observed and/or measured if the substance is chemically altered (Example: flammability)



can be observed without changing the identity of the substance

    • can be observed without changing the identity of the substance
  • Some physical changes would be

  • boiling of a liquid

  • melting of a solid

  • dissolving a solid in a liquid to give a homogeneous mixture — a SOLUTION.





Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.

  • Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.



Heat

  • Heat

  • Odor change

  • Gas Produced (not from boiling!)

  • Precipitate – a solid formed by mixing two liquids together

  • Color change



Examples:

  • Examples:

    • melting point
    • flammable
    • density
    • magnetic
    • tarnishes in air


Examples:

  • Examples:

    • rusting iron
    • dissolving in water
    • burning a log
    • melting ice
    • grinding spices


BUT, physical properties & changes are important, too!

  • BUT, physical properties & changes are important, too!

  • ALL mixtures can be separated physically.

  • They can be separated based on their PHYSICAL properties.





Problem A piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).

  • Problem A piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).



Strategy

  • Strategy

  • 1. Get dimensions in common units.

  • 2. Calculate volume in cubic centimeters.

  • 3. Calculate the density.



SOLUTION

  • SOLUTION

  • 1. Get ALL dimensions in common units.

  • 2. Calculate volume in cubic centimeters.

  • 3. Calculate the density.





Strategy



1. Convert volume to mass

  • 1. Convert volume to mass



Osmium is a very dense metal. What is its

  • Osmium is a very dense metal. What is its

  • density in g/cm3 if 50.00 g of the metal occupies

  • a volume of 2.22cm3?

  • 1) 2.25 g/cm3

  • 2) 22.5 g/cm3

  • 3) 111 g/cm3



2) Placing the mass and volume of the osmium metal into the density setup, we obtain

  • 2) Placing the mass and volume of the osmium metal into the density setup, we obtain

  • D = mass = 50.00 g =

  • volume 2.22 cm3

  • = 22.522522 g/cm3 = 22.5 g/cm3



A solid displaces a matching volume of water when the solid is placed in water.

  • A solid displaces a matching volume of water when the solid is placed in water.

  • 33 mL

  • 25 mL



Density is an INTENSIVE property of matter.

  • Density is an INTENSIVE property of matter.

    • does NOT depend on quantity of matter.
    • Temperature is also intensive
  • Contrast with EXTENSIVE



Most density tables are given with a specific temperature because substances expand when heated.

  • Most density tables are given with a specific temperature because substances expand when heated.



Directly proportional – the relationship between two variables can be expressed as y/x = k where k is a constant.

  • Directly proportional – the relationship between two variables can be expressed as y/x = k where k is a constant.

  • Graphs of directly proportional variables are linear.



If mass is your y variable, and volume is your x variable, y/x = k! (m/V = D)

  • If mass is your y variable, and volume is your x variable, y/x = k! (m/V = D)



In inversely proportional relationships, yx = k

  • In inversely proportional relationships, yx = k

  • This type of graph is curved.

  • We will see this a lot more when we get to the gas laws later in the year.



1) What is a physical property?

  • 1) What is a physical property?

  • 2) Identify three physical properties of water.

  • 3) How does the density of solid water compare to the density of liquid water?

  • 4) Describe a setting where you might observe water as a solid, a liquid, and a gas all at the same time.

  • 5) Distinguish between physical changes and chemical changes.

  • 6) A star is estimated to have a mass of 2 x 1036 kg. Assuming it to be a sphere of average radius 7.0 x 105 km, calculate the average density of the star in units of grams per cubic centimeter.

  • CONTINUED…



7) Classify the following as physical or chemical changes.

  • 7) Classify the following as physical or chemical changes.

    • a) Moth balls gradually vaporize in a closet.
    • b) Hydrofluoric acid attacks glass, and is used to etch calibration marks on glass laboratory utensils.
    • c) A French chef making a sauce with brandy is able to burn off the alcohol from the brandy, leaving just the brandy flavoring.
    • d) Chemistry majors sometimes get holes in the cotton jeans they wear to lab because of acid spills.


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