In this article, we shall learn about the properties of metal both chemical and physical. We have also provided a PDf download link for the same.
Introduction to Properties of Metals
A physical property is a measurable characteristic whose value describes the state of a physical system. Changes in the physical properties of a system can be used to describe transformations or evolution between instantaneous states. Physical properties that can be quantified are called physical quantities.
Identifying material properties can prove to be a challenging task, as certain properties may not always be immediately apparent. Take, for example, the perception and measurement of colors. While colors can be seen and quantified, they are ultimately an interpretation of the reflective qualities of a given surface and the light that interacts with it. Such properties are often classified as transcendental, as they are secondary to the underlying reality.
This is akin to the concept of supervenience in atomic structure, where physical attributes such as mass, shape, color, and temperature are transcendental to the fundamental atomic and quantum structure of an object. In summary, while objects may exhibit a range of physical properties, their underlying essence can be characterized by a deeper, more fundamental reality.
Physical Properties of metals
Conductivity
Metals are known for their high thermal and electrical conductivity, with silver being a noteworthy exception as it exhibits both the best and worst conductivity in these domains. Commonly used metals for home kitchen utensils include zinc, copper, and aluminum, owing to their favorable heat conductivity.
The presence of free electrons in metals facilitates the flow of electric current, resulting in their ability to conduct electricity. Of all metals, silver and copper boast the highest electrical conductivity, followed by gold, aluminum, and tungsten. However, certain metals such as mercury and iron present greater resistance to the flow of electric current. It should be noted that the electrical conductivity of metals decreases as temperature increases, as the increased vibration of core electrons impedes the flow of electrons.
Shape & Size
The size and shape of a metal are reflected in its various dimensions. These dimensions may include the length, width, height, depth, or radius of curvature, among others, which together determine the overall size of the material.
Additionally, the shape of the metal is indicated by its cross-section, which may take the form of a rectangle, square, circle, or other geometric shape.
Lustre
Metal exhibits a shiny appearance known as metallic luster. Prominent examples of shiny metals include gold, silver, platinum, aluminum, iron, zinc, and tin, which are commonly used in jewelry and decorative items. However, certain metals can lose their luster upon exposure to air, as they react with moisture to form a thin oxide film on their surface.
These metals, which change color as a result, are referred to as tarnish metals. In contrast, non-metallic materials generally have a matte appearance, except graphite, diamond, and iodine, which exhibit a shiny appearance.
Sonority
The sonority of metal is greater than other materials due to its ability to produce a deep or resonant sound when struck by a hard object.
Porosity
If a material has pores, it is considered porous or permeable.
Density
Metals are typically characterized by their high density, although there are certain exceptions. For instance, metals like sodium and potassium have notably low densities and are often referred to as light metals.
Melting point & Boiling point
When a metal changes from a solid state to a liquid or gaseous state, it changes its state of matter. This phase transition requires the addition of energy to the metal, which must overcome the attractive forces between metal ions and delocalized electrons within the metal. The amount of energy required for this transition correlates directly with the metal’s melting or boiling point.
Due to their large lattice structures, metals have numerous electrostatic forces that must be overcome during melting or boiling. As a result, metals tend to have high melting and boiling points, making them more similar in this regard to ionic compounds than to covalent substances. However, some metals, such as sodium and potassium, have relatively low melting and boiling points, while others like gallium and cesium will melt instantly upon contact with skin.
Hardness
The majority of metals exhibit high hardness, making them resistant to cutting and crushing. Nonetheless, there are some exceptions such as sodium and potassium which possess a lower hardness and can be easily cut with a knife. These types of metals are classified as soft metals.
State
Metals are generally solid at room temperature. Mercury and gallium are the only metals that exist in liquid form at this temperature. At room temperature, nonmetals occur in all three states of aggregation: solid, liquid, and gas. For example, sulfur and phosphorus are solids. Bromine is a liquid, but oxygen, nitrogen, and chlorine are gases at normal temperatures and pressure.
Solubility
Metals are insoluble in water and other solvents. Metal oxides are having good solubility in acids and water.
Corrosiveness
Metals tend to corrode because they oxidize in the air and rust easily. Corrosion destroys them over time.
Alloy
Alloys are defined as mixtures of metals and at least one other element. The added elements are either metallic or non-metallic.
Importance of Alloying
It makes the metal harder and stronger
The sizes of the main metal & alloying elements in an alloy are different. It completely changes the regular arrangement of the atoms in the pure metal. Atoms of different sizes oppose the external force when applied. It makes an alloy much stronger, harder & less malleable.
It makes the metal more corrosion resistant
The coins we use in our daily life are made of cupronickel, an alloy of copper and nickel. Not easy to corrode.
It enhances the appearance of metals
One such example is Pewter. It is an alloy of copper (Cu), tin (Sn), and antimony (Sb). Because it looks more beautiful than Tin, it is often used for ornaments such as key chains and ornaments.
It slows down the melting point of metals
Soldering is the main process used in the industry to join two pieces of metal. Solder materials are usually alloys of tin and lead, which have a lower melting point than most metals.
Chemical Properties of Metals
Reaction With Base (Water)
Only highly reactive metals react with water, not all metals. For example, sodium reacts violently with water and oxygen, releasing a lot of heat. So sodium is stored in kerosene so that it does not come into contact with moisture and oxygen. The strength of the reaction between metals and water depends on their chemical reactivity.
Metal + Water to Metal Hydroxide + Hydrogen
For example, Potassium and sodium react violently with cold water to form potassium hydroxide and sodium hydroxide respectively, producing H2.
Magnesium does not react with cold water. It reacts with hot water to produce magnesium hydroxide and hydrogen gas.
Reaction with Acid
Metals usually displace hydrogen from dilute acids. However, less reactive metals such as copper and silver do not displace hydrogen from dilute acids. All metals that are more reactive than hydrogen, that is, can donate electrons more readily than hydrogen, and displace hydrogen from dilute acids to form hydrogen gas. This is because the more reactive metal readily donates electrons and these electrons reduce the hydrogen ions of the acid to hydrogen gas. Metal salts and hydrogen gas are formed when metals react with dilute acids.
Metal + Dilute Acid to Metal Salt + Hydrogen
For example,
Metallic sodium reacts violently with dilute hydrochloric acid to produce sodium chloride and H2 gas.
Hydrogen gas is not generated when metal reacts with dilute nitric acid because nitric acid is having strong oxidizing properties. Therefore, as soon as hydrogen gas is formed in the reaction between the metal and dilute nitric acid, nitric acid oxidizes it to water.
However, very dilute nitric acid will react with magnesium and manganese metals to produce hydrogen gas. Very dilute nitric acid is a weak oxidizing agent and cannot oxidize hydrogen to water. The reactions of magnesium metals with very dilute nitric acid are shown below. Magnesium reacts with very dilute nitric acid to form magnesium nitrate and hydrogen gas.
Reaction with Salt Solution
When a highly reactive metal is added to a brine of less reactive metals, the more reactive metal displaces the less reactive metal from the brine. More reactive metals replace less reactive metals, forming their salt solution.
For example,
- When Iron reacts with Copper Sulphate solution, the Iron displaces the copper and makes Iron Sulphate and leaves copper.
Reaction with Chlorine
Ionic chlorides are formed when metals react with chlorine. A metal atom loses an electron in the formation of a metal chloride and becomes a positively charged ion, whereas a chlorine atom gains an electron and becomes a negatively charged chloride ion.
For example,
- Sodium metal readily reacts with chlorine to form an ionic chloride called sodium chloride.
Reaction with Oxygen
Metal oxides are formed when metals burn in the presence of oxygen which is oxidic in nature. For example, burning a magnesium ribbon in the presence of oxygen forms magnesium oxide, and magnesium oxide dissolves in water to form magnesium hydroxide. A metal’s chemical reactivity determines its ability to react with oxygen. Some metals react with oxygen even at room temperature, others only when heated, and others only when heated strongly.
For example,
- Sodium metal reacts with oxygen at room temperature to form sodium oxide.
Sodium Oxide which is a basic oxide further reacts with water to form Sodium Hydroxide.
Sodium and potassium metals are very reactive and can react violently with oxygen and can ignite and burn. Potassium and sodium metals are therefore preserved in kerosene to prevent reactions with oxygen and moisture. If we try to react to magnesium with oxygen at room temperature, it will not react. However, when heated, magnesium metal burns in the air, releasing intense heat and light to form a basic oxide called magnesium oxide.
Conclusion
In conclusion, metals have a variety of physical and chemical properties that make them an essential part of our lives. Their malleability, ductility, and conductivity make them useful in a range of applications, from construction and transportation to electronics and medicine. Additionally, their reactivity and ability to form alloys make them versatile materials with unique properties. It is important to understand these properties in order to properly use and manipulate metals for various purposes.
