Video Transcript
In this video, we will learn how to
describe and compare the chemical properties of metals and nonmetals.
In the periodic table, the metal
elements are generally located towards the left-hand side. The exception to this statement is
hydrogen, which is a nonmetal located in group one. The nonmetal elements are located
mainly towards the right-hand side of the periodic table. We will see how metals and
nonmetals behave in chemical reactions. This behavior is described as the
chemical properties of these elements.
A chemical property is a
characteristic of a substance that can only be observed by changing the composition
of the substance through a chemical reaction.
In the first section of this video,
we will look at the chemical reactions of metals. One of the most common reactions of
metals is with oxygen gas. If a pile of freshly made, shiny
iron nails is exposed to moist air for a relatively short period of time, the nails
become dull and rusty. The iron reacts with oxygen in the
air, and its chemical composition changes. The orange-to-brown substance that
we call rust is known chemically as iron(III) oxide. We can write this as a chemical
equation where four iron atoms react with three oxygen molecules to form two units
of iron(III) oxide.
A similar reaction happens if we
heat a piece of magnesium ribbon strongly in the presence of oxygen. When the hot magnesium ribbon is
placed into a jar of oxygen gas, a fierce reaction starts. Bright white light is seen, and a
white powder or white smoke is formed. The white smoke or white powder
that is formed during this reaction is magnesium oxide. This reaction is much faster than
the reaction of iron with oxygen during rusting. The chemical equation for this
reaction shows us that two magnesium atoms react with one oxygen molecule to form
two units of magnesium oxide.
In the next section, we will look
at the chemical activity series. The speed or ease with which metals
react with oxygen and other substances can be compared using the chemical activity
series. Metals near the top of the series
are chemically very reactive, whilst metals near the bottom of the series are
chemically unreactive. When we compare metals in this way,
we can see that metals like potassium and sodium react very rapidly, whilst metals
like copper, silver, and gold will react very slowly, if they react at all. This explains why magnesium reacts
very rapidly with oxygen when it is hot enough, whereas iron, which is lower in the
chemical activity series, reacts much more slowly with oxygen.
The chemical activity series can
also be used to predict how metals will react with acids. When metals react with acids, a
salt and hydrogen are produced. In general, nonmetals do not react
with acids. To decide if a metal will react
with a dilute acid, we use the activity series. If the metal is above hydrogen in
the activity series, then a reaction will occur and hydrogen gas will be
produced. The metals copper, silver, and gold
do not react with dilute acids, and no hydrogen gas bubbles are formed. So if magnesium metal is added to
hydrochloric acid, a vigorous reaction will start immediately and bubbles of
hydrogen gas will be seen forming rapidly.
The symbol equation for this
reaction shows us that one atom of magnesium reacts with two molecules of
hydrochloric acid to form one unit of magnesium chloride and one molecule of
hydrogen gas. Magnesium chloride is the salt
produced in this reaction.
Some metals can also react with
water. For a metal to react with water, it
must be above hydrogen in the activity series. In reality, magnesium, which is a
very reactive metal, only reacts very slowly indeed with cold water. Calcium, sodium, and potassium
react increasingly violently with cold water. The reaction of potassium with
water happens instantly, and the potassium catches on fire. Larger pieces will explode. We would not expect copper, silver,
and gold to react with cold water at all. When a metal reacts with water, a
metal hydroxide and hydrogen gas are formed.
In the next section of this video,
we will compare metal oxides with nonmetal oxides. Both metals and nonmetals react
with oxygen gas. We have already seen that
magnesium, which is a metal, can react with oxygen to form magnesium oxide. In a similar way, sulfur, which is
a nonmetal, also reacts with oxygen when it’s hot enough to form a compound called
sulfur dioxide. Both elements will burn in a gas
jar containing oxygen gas when heated to form the respective oxides. In both cases, fumes are seen
exiting the gas jar. The magnesium metal burns with a
brilliant-white light, whilst the sulfur, which is a yellow powder, burns with a
pale-blue flame. The magnesium oxide is a white
powder or smoke, whilst the sulfur dioxide is an unpleasant toxic gas.
If both oxides were collected and
added to water separately, we could test the solutions with litmus paper. The magnesium oxide solution would
turn red litmus paper to a blue color. This would indicate that the
solution is an alkali. The sulfur dioxide solution would
turn blue litmus paper to red. This indicates that the sulfur
dioxide solution is acidic. In general, metal oxides are
classified as basic oxides. Basic oxides dissolve in water to
form alkaline solutions. Nonmetal oxides are described as
acidic oxides. When acidic oxides dissolve in
water, they form an acidic solution.
Coal is a natural product that
contains the nonmetal elements carbon and trace amounts of sulfur. When coal is burnt in power
stations to produce heat, the carbon reacts with oxygen to form carbon dioxide. And the sulfur reacts with oxygen
to form sulfur dioxide. Both of these nonmetal oxides are
therefore acidic oxides, and they exit as gases. When the gases escape into the
atmosphere, they can dissolve in moisture in clouds and form acidic solutions. This can fall from the sky as acid
rain. The acid rain can cause damage to
trees and buildings in certain locations.
Although most metal oxides are
basic in nature and therefore react with acids, some metal oxides can react with
both acids and bases. Oxides that react with both acids
and bases are described as amphoteric oxides. Aluminum oxide is an amphoteric
oxide. If aluminum oxide reacts with
hydrochloric acid, then aluminum chloride and water are formed. In this case, the aluminum oxide is
behaving as a basic oxide. A salt and water are formed. If aluminum oxide reacts with
sodium hydroxide, which is a base, then sodium aluminate and water are formed. In this case, the aluminum oxide is
behaving as an acidic oxide.
Now that we’ve studied the chemical
properties of metals and nonmetals, let us look at some questions.
Which of the following elements
will react with HCl? (A) Sulfur, (B) nitrogen, (C)
phosphorus, (D) calcium, (E) carbon.
HCl is the chemical formula for
hydrochloric acid. In general, nonmetals do not react
with acids. Nonmetals are located towards the
right-hand side of the periodic table, with the exception of hydrogen, which is
found within group one A. From our list of possible answers,
sulfur, symbol S; nitrogen, symbol N; phosphorus, symbol P; and carbon, symbol C,
are all nonmetals. Since all these elements are
nonmetals, they will not react with acids and they cannot be correct responses to
this question.
Calcium is a metallic element, so
it could react with acids. To decide if a metal will react
with dilute acid, we need to use the activity series of metals. The activity series places metals
in order of their chemical reactivity. The most reactive metals are found
at the top of the list and the least reactive metals at the bottom of the list.
For a metal to react with dilute
acids, it must be above hydrogen in the activity series. Hydrogen is located just above
copper but below lead in the series. We can clearly see that calcium is
a very reactive metal, and it is much higher than the hydrogen in the activity
series. Calcium will therefore react with
hydrochloric acid. It will displace hydrogen, and
hydrogen gas bubbles will be seen in the reaction with the metal. The correct answer to the question
“Which of the following elements will react with HCl?” is calcium.
The picture shows three
beakers. One beaker contains sodium with
cold water, another contains calcium with cold water, and the last contains zinc
with cold water. Which of the beakers is cold water
and sodium? (A) Beaker two, (B) beaker one, (C)
beaker three.
This question is asking us about
the chemical behavior of three metals: sodium, calcium, and zinc. Metals can be placed in order of
their chemical reactivity using the activity series of metals. In this series, the most reactive
metals are placed at the top of the list and the least reactive metals at the bottom
of the list. Hydrogen, which is a nonmetal, fits
in between copper and lead in this series. This is an important consideration,
as only metals above hydrogen in the activity series will release hydrogen when they
react with water. In reality, only the metals
magnesium and those above it in the activity series react with cold water to any
great extent.
We can see in the diagram for
beaker one that there is no reaction between the metal and the water. Although zinc is above hydrogen in
the chemical activity series, it does not react with cold water.
From our three metals in the
question, beaker one will contain zinc. The remaining two metals both react
with cold water to produce hydrogen gas, which would be observed as fizzing. Sodium is the most reactive of
these two metals. Sodium is so reactive that it
catches fire when it reacts with cold water, whilst calcium produces a steady stream
of bubbles and fizzes rapidly. From these descriptions, we can see
that beaker three must contain sodium and beaker two must contain calcium metal.
So to answer the question “Which of
the beakers is cold water and sodium?” it must be beaker three. Beaker three is the correct
answer.
Now let’s summarize what we have
learned in this video with the key points. Metals react with oxygen to form
metal oxides. Some metals react with oxygen more
readily than others. We can use the activity series to
predict this. Metals with the highest chemical
activity are placed at the top of the activity series, whilst metals with the lowest
chemical activity are placed at the bottom of the activity series. Metals that are more active than
hydrogen react with dilute acids to make a salt plus hydrogen gas. Nonmetals do not react with
acids. Metals above magnesium in the
activity series react rapidly with cold water to produce hydrogen gas. Nonmetals react with oxygen to form
acidic oxides. When metals react with oxygen, they
usually form basic oxides.
