Chemistry Test Review

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Chemistry Test Review
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Your test will be

• 10 short answer questions
• Each question is worth 10 points each
• Partial credit will be given

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Hints for doing well on this test

• Read each question carefully
• Answer the question you are asked
• Re-read each answer
• Make sure you have answered the question
  completely
• Make sure your answer relates to the question

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Example Questions

• And how to answer them

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One of your friends stays overnight at your
house. The next morning, your mother cooks him
some fried eggs for breakfast. He says, "I don't
like fried eggs, can you change them to poached
eggs instead?"

• Use what you know about physical and chemical
  changes to explain why it is NOT possible to
  change the fried eggs to poached eggs.

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You MUST discuss changes why in your answer

• It is not possible to change the fried eggs into
  poached eggs because cooking eggs is a chemical
  change
• Chemical changes produce new products that are
  very difficult to reverse

• Answer identifies cooking an egg as a chemical
  change
• Answer describes chemical changes as being
  difficult to reverse because the original
  substance is changed into a new substance

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Scientists used to think electrons moved in
orbits around the nucleus.

• How do scientists currently describe the movement
  of electrons?

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Notice the word movement the question is not
asking about location only

• Electrons move in an electron cloud around the
  outside of the nucleus
• The electrons do not follow a particular path

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Oxygen gas normally exists as O2 molecules. Each
molecule contains two oxygen atoms.

• Is O2 a compound? Explain your answer.

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Make sure you EXPLAIN

• No answer
• A compound must contain atoms from more than one
  element explanation

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Why is the state of matter a physical property
and not a chemical property?
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You must know the meaning of each of these terms
to answer this question

• State of matter
• Physical property
• Chemical property

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Sometimes giving an example helps explain your
thinking

• Changing state does not change the identity of
  the matter.
• Chemical properties can't be observed without
  changing the substance.
• Water is still water whether it is ice, liquid,
  or vapor. example

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Vanadium, with an atomic number of 23, and
bromine, with an atomic number of 35, are both in
the same period as germanium.

• Explain why bromine is most likely a
  non-metal.
• Explain why vanadium is most likely a metal.

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• Vanadium is most likely a metal because it on the
  left side of the same period

• Bromine is most likely a non-metal because it is
  to on right side of the same period.

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The operating system and programs that run on a
computer depend on tiny electrical circuit boards
called chips, which are made of materials called
semi-conductors.

• Based on the label "semi-conductor," which type
  of element would you predict is used to make
  computer chips? Explain.

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Semi-Conductors

• Metalloids because their ability to conduct
  electricity lies somewhere between the good
  metallic conductors and the poor nonmetallic
  conductors.

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In the fall, you rake leaves into a pile, burn
them, and spread the ashes back on the lawn as
fertilizer.

• What are the chemical changes and what are the
  physical changes in this process?

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Think about each part of the question

• Raking the leaves into a pile and spreading the
  ashes are physical changes.

• Burning the leaves and the ashes being broken
  down by the lawn for fertilizer are chemical
  changes.

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Define the law of conservation of mass and
explain how it relates to physical and chemical
changes.
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2 Parts to this question

• Definition
• The law of conservation of mass states that mass
  cannot be created or destroyed.

• Explanation
• This means that the mass of any substances
  present before a physical or chemical change is
  equal to the mass of the substances present after
  the change.