Physical and Chemical Changes

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Physical and Chemical Changes

• Friday, Sept 29

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Physical Changes

• Definition the chemical nature of the material
  remains unchanged.
• Evidence/ examples
• Ripping, molding, or reshaping the material
• Molding clay
• Phase changes
• Solid -gt Liquid -gt Gas
• Dissolution (dissolving) or recrystalization
• For example, formation of rock candy

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Chemical Changes

• Definition The chemical identity of a substance
  is altered
• Evidence/Examples
• A change in the odor or color of a material
• Formation of large amounts of energy
• Heat, light or electrical
• Formation of a new form of matter with a
  different boiling point or melting point
• Formation of gas bubbles from a solid or liquid
• A white or colored solid appearing around the
  shower head (called precipitation)

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Lab Stations General Instructions

• Record all observations and thoughts in your lab
  notebook
• Visit each station. Identify the elements that
  make up the compounds used.
• Describe any and all physical or chemical changes
  that occur at the lab station.
• Record observations
• Suggest an investigation you might like to
  attempt to further your understanding of the
  situation presented at each station.

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Lab Station 1

• Rock Salt 1 scoop
• Crush rock salt crystals (NaCl) using the mortar
  pestle.
• Add the crushed rock salt to the beaker of H2O.
• Describe what happens.
• Where do the crystals go once placed in the H2O?
• Is it a physical or chemical change?
• How do you know?
• How does the stirring device work?
• Propose a further investigation.

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Lab Station 2

• Place a scoop of calcium chloride into a baggie
  and add 10mL of water. Make observations.
• Repeat using the sodium bicarbonate.
• Add a dropper of phenol red to each and observe.
• Place both baggies into a Ziploc bag and seal.
  After sealing mix the contents and observe.
• Attempt to assign responsibility for each
  observation to a chemical involved in this
  station.

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Lab Station 3

• What are the bubbles made up of in the beaker of
  water?
• Describe what you believe is happening to the
  molecules in the beaker.
• Use an illustration to provide another
  description of what is happening to the molecules.

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Lab Station 4

• Add a nail to the copper sulfate solution and
  observe.
• Remove the nail after a length of time and record
  observations.
• Hypothesize as to the cause and nature of the
  change.

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Lab Station 5

• Place 5 kernels of popcorn into a 250mL and cover
  with clear plastic wrap.
• Poke a hole in the middle of the plastic wrap.
• Heat on a hot plate.
• Respond to the questions on page 71 of your text.

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Lab Station 6

• Obtain 3 test tubes that fit into the test tube
  rack provide.
• Add a dropper of the KOH to a test tube and a
  dropper of HCl to a second test tube.
• Add a dropper of both KOH and HCl to the third
  test tube.
• Add one squirt of phenolphthalein to each test
  tube and record observations.