Review Questions
• Molasses is warmed it becomes less viscous
P – no new substance created, still molasses.
Chair is painted it has a new colour
P – no new substance, chair is colour of paint.
Sugar is stirred into hot water it dissovles
P – no new substance, sugar and water still present in a solution.
Wood is sawed some of it changes to sawdust.
P – change in form, still wood.
Wood is burned, ashes remain.
C – change in colour (brown to black), heat and light produced in fire.
Vinegar added to baking soda, bubbles seen.
C – formation of new gas.
When a sample of blue crystals is heated, a vapour is given off and a
white powder remains.
P or C?
Chemical Change – new gas created (vapour), colour change from blue
to white.
12. Physical change – the substance returned to the original substance
as it cooled. Therefore it went through a change of state which is a
physical change.
13. Density would allow you to distinguish iron pyrite from real gold.
You would have to measure the mass of the rock using a scale. You
would then measure the volume of the rock using displacement or
an appropriate formula. Once completed, use the formula d= m/v
and solve for density. If the density is 19.3 g/mL the rock is gold. If
it is not, it is not real gold.
• All density problems should be solved using the formula:
• d=m/v v=m/d m=dxv
• Show all work, answer in a therefore statement, make sure units are
correct.
p. 205
#11. Pots and pans must be good conductors of heat. Heat must pass
easily through the pan to cook the food.
They must be malleable so that they can be hammered into a particular
shape without breaking.
p. 204 #13
Temperature is not a characteristic physical property because it is not
unique to the substance. Temperature of the substance will depend on
its surroundings or what is happening to the substance. It cannot be
used to identify a substance. A characteristic physical property is
unique to a substance. For example, melting point, boiling point and
density are unique and can be used to identify a substance.
Solid mixture – Pizza (mechanical)
Steel – (Alloy/solution)
Liquid mixture –
Pop (Mechanical mixture)
Saltwater (Solution)
Gaseous mixture –
Air
24. Copper would float in liquid mercury because its density is less than
Mercury’s density.
26. Carbon fibre’s density is much less than aluminum, therefore when
used in bicycles it makes the bike lighter allowing the cyclist to
move faster.
27. A dented table tennis ball can be repaired by placing it in a cup of
hot water. Use the p. t. to explain how this is possible.
- Particles of air in tennis ball.
- Hot water causes particles to move faster.
- Particles collide more often and with more force, pushing each other
away further.
- The increase in pressure on the dent forces the dent outwards and
repairs the ball.
28. bbq fuel – physical property
• Vapourizes from liquid to gas, moves easily into barbeque.
Chemical property –
• combustible (reacts with oxygen to form heat and light) in order to
cook food.