SCIENCE 3rd quarter exam (reviewer)

• Physical Properties


  Properties of matter that can be observed or measured without changing the identity of the matter
• Examples of Physical Properties

  • Density
  • Malleability
  • Ductility
  • Solubility
  • State
  • Thermal Conductivity
• Density


  Amount of mass in a given volume
• A substance is always the same density at a given pressure and temperature regardless of the size of the sample of the substance
• The density of one substance is usually different from that of another substance
• Density formula

  Density = mass / volume
• Calculating Density

  D = m / v
• Calculating Density

  • A bar of copper has a mass of 216 g and a volume of 24 cm³. What is the density of copper?
  • The volume of a candy bar is 55 cm³. The mass of the candy bar is 70 g. What is the density of the candy bar?
• Malleability


  The ability to be pounded into thin sheets
• Malleability


  • Aluminum can be rolled or pounded into sheets to make foil
• Ductility


  The ability to be drawn or pulled into a wire
• Ductility

  • Copper in wiring - soldering wires or joints
• Solubility


  The ability to dissolve in another substance
• Solubility


  • Sugar or salt dissolve in water
• Ways to increase solubility

  • Heat or make warmer
  • Grind or smash
  • Stir or mix
• State of Matter


  The physical form in which a substance exists at room temperature
• States of Matter

  • Solid - matter has a definite shape and volume
  • Liquid - matter takes the shape of its container and has a definite volume
  • Gas - matter changes in both shape and volume
• Thermal Conductivity


  The ability to transfer thermal energy from one area to another
• Thermal Conductivity


  • Plastic foam is a poor conductor, so a hot drink won't burn your hand
  • The inside of the toaster (hot coils)
• Chemical Property


  A property of matter that describes a substance based on its ability to change into a new substance with different properties
• Examples of Chemical Properties

  • Combustibility
  • Flammability
  • Reactivity
  • Acids
  • Bases
  • Oxidation
• Chemical properties are not as easy to observe as physical properties
• Chemical Properties

  • Flammability - Only when wood burns
  • Combustibility - Only when fireworks explode
  • Reactivity - Only when iron oxidizes (rust)
• Physical Change


  A change that affects one or more physical properties of a substance without forming new substances
• Physical Change

  • Change of state - Solid to Liquid, Liquid to Gas
• Chemical Change


  A change that occurs when one or more substances are changed into entirely new substances with different properties
• Chemical Change

  • Reactivity - Oxidation (rust) on a bicycle
  • pH (Acid / Base) - Effervescent tablets
  • Flammability - Burnt wood
  • Combustibility - Fireworks
• 5 Signs of a Chemical Change

  • Odor Production
  • Change in Temperature
  • Change in Color
  • Formation of Bubbles
  • Formation of a Precipitate
• Democritus


  Greek Philosopher who suggested the world was made of two things - empty space and "atomos" (Greek word for uncuttable)
• Democritus' two main ideas


  • Atoms are the smallest possible particle of matter
  • There are different types of atoms for each material
• John Dalton's Atomic Theory


  1. All matter is made of atoms

  2. Atoms of one element are all the same

  3. Atoms cannot be broken down into smaller parts

  4. Compounds form by combining atoms
• Dalton's Early Atomic Model


  Envisioned atoms as solid, hard spheres, like billiard (pool) balls, so he used wooden balls to model them
• J.J. Thomson


  Discovered the electron and was the first scientist to show the atom was made of even smaller things
• Thomson's Experiment

  1. Voltage source

  2. Vacuum tube

  3. Metal Disks
• Eugen Goldstein


  Using a cathode ray tube he discovered canal rays which are beams of positively charged particles, credited with the discovery of protons in an atom
• Millikan's Oil Drop Experiment


  Determined the charge on an electron

  Used Thomson's charge to mass ratio to calculate the mass of an electron
• Ernest Rutherford


  Discovered the nucleus of a gold atom with his "gold foil" experiment
• Most alpha particles go straight through the gold foil, but a few are sharply deflected
• Rutherford's Conclusion


  The atom is mostly empty space
• Rutherford's Contribution to the Atomic Theory

  The atom is mostly empty space

  The nucleus is a small, dense core with a positive charge