Elements are the simplest form of substances. This means that
whatever you do with an element, it remains to be the same element. Its
physical state may change but the identity of the element will not. It
may form compounds with other elements but the element will never form
anything simpler than it already is.
There are already more than a
hundred elements and are organized in a Periodic Table. Some of them are
naturally occurring and some were produced in a laboratory.
In this module, you will find out more about the elements. You will see
that majority of them are metals, and almost the rest are nonmetals.
How are metals different from nonmetals?
How are they similar?
In the earlier grades, you segregated objects according to the material
they are made of. You did this when you were starting the habit of 5Rs —
recycle, reuse, recover, repair or reduce. Look around you. Which
objects are made of metals? What made you say that they are metals?
Perhaps, you have been identifying a metal based on its appearance.
Most of the time, metals are shiny. They exhibit a certain luster.
Other properties exhibited by some metals
Some metals are ductile. This means that metals can be drawn into
wires. An example is copper. Refer to the figure on the right. Note the
form at which copper is mined. However, due to its ductility, copper may
assume a form similar to a wire, just like the image in the cover of
this module. Gold is also a metal that is ductile; however, it is rarely
used as an electrical wire. What could be the reason for this?
Some metals are malleable. This means that they can be hammered or
rolled into thin sheets without breaking. An example is aluminum. It is
mined deep from the ground in the form of blocks. They are passed into
mills and rolled thinly. One common form is the aluminum foil that you
use to wrap food to keep it hot. Most soda cans are made of aluminum
too. Find a soda can and strike it with a hammer. What happened with the
soda can?
Some metals are magnetic. This means
that they are attracted by a magnet. The common ones are iron, nickel
and cobalt. Get a magnet. Try them in different metals in your home or
school. Were they all attracted to the magnet? What metals are these?
Metals are known to possess luster, ductility, malleability and
magnetic properties. However not all metals exhibit all of these
properties. For instance, the metals sodium and potassium are not
ductile at ordinary conditions. They are very soft that even a kitchen
knife can cut them into slices as what you can see in the image on the
right. Note though that only experts are allowed to do this. Recall what
you have learned in module 4 about sodium when it comes in contact with
water. Zinc at room temperature is not malleable. Most of the metals
are not attracted by a magnet. Nevertheless, a material is still
considered a metal as long as it possesses any of these properties. A
material that does not possess any of these properties is known as a
nonmetal.
Properties exhibited by all metals
But are there properties that are common to all metals?
Electrical conductivity is property of metals that allows electricity to pass through a material.
The metallic probe in the figure on the right is the one that comes in
contact with the sample. It will measure then display the electrical
conductivity value in the liquid crystal display (LCD) screen. Refer to
the periodic table found at the back page of this module. The electrical
conductivity values are written at the bottom line of each box. It is
expressed in x106 Ohm-1cm-1. What do you notice about the elements with
electrical conductivity values? Where are they located in the periodic
table?
One amazing feature of the periodic table is that all the metals are
placed in one side. Those that are on the other side (grayish shade)
are the nonmetals.
Notice that there is a stair step line which somewhat divides
the metals and nonmetals. These elements are the metalloids. They are
elements exhibiting properties that are intermediate to metals and
nonmetals. Name the metalloids. Name some metals. Name some nonmetals.
Which are electrically conductive, metals or nonmetals? Which element
has the highest electrical conductivity value? Is it higher than copper?
If so, what could be the reason for using copper as an electrical wire
more than this element?
You might wonder why some
metals do not have electrical conductivity values when supposedly all of
them possess such property. Notice that these metals are the ones
mostly found at the last rows of the periodic table. Elements in those
rows are mostly radioactive. This means that the element is very
unstable and exists in a very short period of time. In effect, it would
be difficult to test for their properties. In the higher grade levels,
you will learn that there are ways to infer the electrical
conductivities of these elements.
Electrical conductivity clearly
distinguishes metals from nonmetals but there is one exception. Refer to
the periodic table. Which element is electrically conductive even if it
is a nonmetal?
One form of carbon is graphite. It
is commonly available as the black rod in your pencils. Get your
sharpened pencil. Place the black rod in between the end tips of your
improvised conductivity tester. Make sure that the black rod is in
contact with the tips of the tester. What happened?
In the higher grade levels, you will learn why carbon (graphite) though a nonmetal is electrically conductive.
Look for other objects and test if they are made up of metal or
nonmetal. Write down these objects in the appropriate box of the diagram
below.
Were you able to find a cooking pot as one of your test objects? What element is it mainly made of?
Refer
to Table 2. This table shows the thermal conductivity values of some
elements expressed in Watt/centimeter-Kelvin (W/cmK). Thermal
conductivity is the ability of an element to allow heat to pass through
it. The higher the value, the better heat conductor an element is. Find
the element that was mainly used for the cooking pot you have. What can
you say about the thermal conductivity of this element compared with the
other elements? Is this element, a metal or nonmetal? In general, which
are better heat conductors, metals or nonmetals? Based on Table 2, what
other elements can be used as cooking pots?
Table 2. Thermal conductivities of some elements
Element Symbol Thermal Conductivity* (W/cmK)
Copper Cu 2.37
Iron Fe 0.802
Selenium Se 0.0204
Sulfur S 0.00269
Phosphorus P 0.00235
Metals and Nonmetals In and Around You
In the figure below, you will find the elements that
your body is made up of. What element are you made up of the most? Is it
a metal or a nonmetal? Of all the elements reported in the graph, how
many are metals? How about nonmetals?
Refer to the figure below. The figure shows how much of one element is
present in the Earth’s crust relative to the other elements. What
element is the most abundant in the Earth’s crust? What comes second?
Are these metals or nonmetals?
Refer to the periodic table. What constitutes majority of the elements, metals or nonmetals?
Interestingly, even with the fewer number of nonmetals, their abundance
is higher than metals. As you have seen above from the two graphs, both
living and nonliving systems are mainly composed of nonmetals.
As you learned in module 4, elements form compounds. The
percentage abundance of the elements reported in the graphs above
accounts some elements that are present in compounds, much like the food
ingredients you encountered in the last module. For instance, sodium is
present in sodium chloride. The 18.0% carbon that makes up the human
body is mostly compounds of carbon such as the DNA that carries your
genetic code.
Oxides of Metals and Nonmetals
Similarly, oxygen accounted in the graphs may also be in
compounds. Some of these compounds are called oxides. These oxides may
be formed when an element is burned. These oxides exhibit different
acidities.
In module 2, you learned that there
are indicators that you can use to determine such. One of these acid
indicators is the litmus paper. What color does the litmus paper show
when the sample is acidic? How about when the sample is basic?
In the next activity, you will separately burn a sample of a metal and a
nonmetal. You will test the acidity of the oxide of a metal and that of
the oxide of a nonmetal.
In this module, you learned about the properties
of metals and nonmetals. These properties are the ones that determine
their uses like aluminum’s malleability to become soda cans, and
copper’s ductility to become electrical wires.
Most of the
elements are metals. Some metals are malleable; some are ductile; some
are magnetic but all of them are electrically conductive. Nonmetals are
electrically nonconductive except for some forms of carbon.
It
is important to note though that most objects are made not of a single
material, rather of a combination of materials so they become fitter for
a purpose. This is where your knowledge on the properties of materials
comes in. Which materials do you combine to make it fit for a purpose?
As you can see from the image in this module cover, the electrical wire
made of copper was covered with rubber. Rubber is mainly made of
compounds of nonmetals such as carbon, hydrogen and chlorine. As you
have learned, nonmetals are nonconductors of electricity. Using a
nonmetal to cover a metal makes it safer to use as an electrical wire.
As you advance to another grade level, there are more properties of
matter that you will encounter. It is hoped that you will be able to
maximize the properties of different materials to create new beneficial
products or find other uses for them.
Problem 2: Two tennis ball launchers shoot balls at the same time, angle and initial
speed from different floors of a tall building. The balls land in the street
below. Ignore air resistance. 
