Transcript Physical Properties Quiz

Physical Properties Quiz
 List three physical properties of water.
 Why does a golf ball feel heavier than a tabletennis ball?
 Which of the following statements about density
is true?
a. Density depends on mass and volume.
b. Density is weight per unit volume.
c. Density is measured in milliliters.
d. Density is a chemical property.
Chemical Properties
 Chemical Properties describe a substance
based on its ability to change into a new
substance with different properties.
– For example a piece of wood can be burned to
create a new substance (ash and smoke)
– Think of our CSI unit. When we burned the wool
and cotton we were investigating their chemical
properties.
Observing Chemical Properties
 Not as easy to observe as physical
properties.
 You can only observe the flammability of
wood while the wood is burning.
 A substance always has its chemical
properties.
– A piece of wood is flammable even when it is
not burning!
Car Properties
 Chemical Properties of
Iron:
– Non-reactive with oil
and gasoline
– Reactive oxygen which
can cause cars to rust!
 Physical Properties of Iron
– Strength
– Malleability
– High melting point
Physical vs. Chemical Properties
 You can observe physical properties without
changing the identity of the substance.
 You can observe chemical properties only in
situations in which the identity of the
substance could change.
Physical Changes
 A physical change is one that affects one or
more physical properties of a substance.
– For example if you took a piece of chalk and
broke it into pieces you have changed the
physical property of the size of the chalk.
– However the chemical properties of the chalk
still remain the same.
– Chalk will still produce bubbles if placed in
vinegar.
Examples of Physical Change
 Melting (for example butter), turns from a
solid to a liquid, but the identity of the
butter did not change
 Freezing water for ice cubes
 Sanding a piece of wood
 Cutting your hair
 Crushing an aluminum can
 Bending a paper clip
 Mixing oil and vinegar
Can Physical Changes be undone?
 They do not change the identity of
substances, and are therefore usually easy
to undo.
– For example: leaving butter on the counter
where it melts. Later if you put the butter into
the refrigerator it will reverse the change.
Chemical Changes
 Chemical changes form NEW substances!
– Chemical change occurs when one or more
substances are changed into entirely new
substances with different properties.
 A chemical property describes a
substance’s ability to go through a
chemical change.
 A chemical change is the actual process in
which that substance changes into another
substance.
Examples of Chemical Change
 Sour milk smells bad
because bacteria have
formed new substances
in the milk.
 Statue of Liberty: should
be shiny orange-brown
copper, but the metals
interaction with carbon
dioxide and water has
formed a new substance:
copper carbonate!
Clues to Chemical Change
 Chemical changes often cause
color changes, fizzing or foaming
heat, or the production of sound,
light, or odor.
 Can chemical changes be undone?
 Answer: No, you cannot reverse chemical
changes using physical means.
– For example: you cannot un-crumple or iron
out a chemical change.
– Imagine trying to un-bake a cake?
– Chemical changes are difficult to reverse,
however under the right conditions by other
chemical changes sometimes they can be
reversed.
Think about it…
 A hot gas formed when
hydrogen and oxygen join
to make water helps to
blast this space shuttle into
orbit.
 The water formed can be
split back into hydrogen
and oxygen by using an
electric current.
 A lot of work, but the
chemical change can be
undone.
Quiz #3
 Classify each of the following properties as
either physical or chemical:
– Reacts with water
– Dissolves in acetone
– Is blue
– Does not react with hydrogen
 List 3 clues that indicate a chemical change
might be taking place.
 http://www.youtube.com/watch?v=qqqmFFC
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 http://www.youtube.com/watch?v=pmHxYE_
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 http://www.youtube.com/watch?v=xYFAj50c
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