s8pe-20704-ca
12/19/05
4:45 PM
MAZER
Page 227
Conductivity and Melting Temperature
Some elements conduct heat and electric current very easily. Others
are poor conductors of heat and electric current. Elements on the
right side of the periodic table tend to be poor conductors. They are
nonmetals. The best conductors of both heat and electric current are
the metals, which are on the left side and in the middle of the periodic
table. The measure of how well a substance conducts thermal energy
is called thermal conductivity. The measure of how well a substance
conducts electric current is electrical conductivity.
Recall that the melting point of a substance is the temperature at
which the solid form of the substance becomes a liquid. The boiling
point of a substance is the temperature at which the liquid form of the
substances becomes a gas. A substance with a high melting point will
also have a high boiling point. And a substance with a low melting
point will also have a low boiling point.
The periodic table shows broad patterns for melting and boiling
points. For example, the nonmetals, which are on the right side of the
periodic table, tend to have lower melting and boiling points than the
metals, which make up the left and central parts of the table. This helps
explain a general pattern in melting points and boiling points across
the periods. Also, on the left side of the periodic table, melting points
tend to fall as you read down a group. On the right side of the periodic
table, melting points rise as you read down a group.
Heat
Heat Conductivity
Conductivity
How well do different materials conduct heat?
SKILL FOCUS
Inferring (8.7.c)
PROCEDURE
1
Obtain a beaker of hot water from your teacher.
2 Place a metal spoon, a plastic spoon, a craft stick, and a glass
MATERIALS
stirring rod in the water.
3 After one minute, take each item out of the water.
4 Record how warm each item feels in order from warmest
to coolest.
WHAT DO YOU THINK?
•
•
•
•
•
•
beaker
craft stick
metal spoon
glass stirring rod
plastic spoon
clock
TIME
• Which item felt the warmest? the coolest?
• What do you think determined how warm or cool each item
felt to the touch?
25 minutes
CHALLENGE Do you think shape affects conductivity?
Design an experiment to test your hypothesis.
Chapter 7: Atomic Structure and the Periodic Table 227
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