Building Materials, Part 2
Grade Level:1
Objectives:
Students will learn that different building materials have different mechanical strength. They examine
how density and flexibility relate to mechanical strength.
Materials
Each group will need:
• set of plastic, ceramic, wood, and metal bars
• 1 gal plastic bottle with handle (milk jug type)
• twine
• ruler
• plastic cup
• bucket of water
• safety glasses for students
Introduction
Last time we looked at the properties of some building materials that people use.
What do you remember about metals?
[Metal are made by taking certain kinds of rock, grinding them up, and heating them to a very
high temperature. Most metals, except mercury, are solids at room temperature. Metals are shiny.
They are strong. Metals can bend without breaking and you can pull out metals into wires.]
What do you remember about ceramics?
[Ceramics are also make from certain kinds of rock. The rock is ground up and heated, but not
heated high enough to take the metal out of it. When water is added to the powder, there is a
chemical change and the material becomes very hard. Ceramics are hard and strong but they
break if you try to bend them.]
What do you remember about plastics?
[Plastics are made out of the stuff in gasoline. The tiny molecules in gasoline are connected
together to make really long chains. Plastics can be melted and formed. They are not very strong
but bend easily without breaking.]
Last time we looked at the properties of bars of the different materials. Each bar took up about the same
amount of space. They had about the same volume. Do you remember which bar was heaviest? lightest?
The weight or mass of bars with the same volume is a property of the material and is called density
Today we’re going to find out how strong each material is.
Research Question
How can we measure mechanical strength of each material?
Procedure
1. Ask the students for their ideas on testing the
strength. They will probably suggest trying to
break the bars. Tell them that we need some way
of measuring the force needed to break the bar.
2. Separate two lab tables by 4 inches. Loop one
end of a twine loop around a metal bar and
balance it between the two tables. Attach the
other end to an empty 1 gallon jug such that the
jug is about 2-3 inches above the floor. Fill a
basin of water and put a cup in it.
3. Ask the students: Using this set-up, could we
figure out how strong each bar is?
4. Divide the students into groups of 2. Each
student must wear safety glasses during the
procedure. Begin with the ceramic bar. Have one
student add water to the gallon jug using the
blue plastic cup and a funnel. The first line on
the cup measures about 100 mL (100 g) of water.
The second student must keep track of the
number of 100 g water units added. At some
point the bar will break. Note the total weight of
water in the jug.
5. Empty the jug and repeat with plastic. Note that the plastic bends before it breaks.
6. Repeat with the metal. The metal bends but doesn’t break.
7. If time permits, repeat with wood.
Summary and Discussion
1. What material has the greatest strength?
2. Would we use this material for building houses, bridges, roads? Why or why not?
3. What other properties of materials are important in building houses?
Exploring Building Material, part 2
Name
Name
Name
Name
Name
Name
Ceramic
What is it like?
How much weight
breaks the bar?
Did the bar bend
before it broke?
Plastic
Metal
Shiny?
Shiny?
Shiny?
See through it?
See through it?
See through it?
Easy to scratch?
Easy to scratch?
Easy to scratch?
Easy to bend?
Easy to bend?
Easy to bend?