Properties of Metals: Physical & Chemical (PDF)

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.

Metals
Metals

It can be difficult to tell if a particular property is a material property. For example, you can see and measure colors. However, what humans perceive as color is actually an interpretation of the reflective properties of a surface and the light that strikes it. In this sense, many seemingly physical properties are said to be transcendental. Transcendental traits are traits that are actually present but secondary to the underlying reality. This is analogous to atomic structure objects being supervenient. A cup can have physical properties such as mass, shape, color, temperature, etc., but these properties are transcendent to the underlying atomic structure and the underlying quantum structure.

Below is the list of some of the Physical Properties of the Metals.

Conductivity

Metals are having good conductivity for heat and electricity. Silver is the best and worst conductor of heat and electricity. Our home kitchen utensils are made of zinc, copper, and aluminum. Because these are having good conductivity of heat.

 All metals contain free electrons and are therefore good conductors of electricity. These free electrons conduct current. Silver & copper are having best electrical conductivity, followed by gold. All metals contain free electrons and are therefore good conductors of electricity. These free electrons conduct current. Silver and copper are the best conductors of electricity, followed by gold, aluminum, and tungsten. Metals such as mercury and iron offer greater resistance to the flow of electric current. However, the electrical conductivity of metals decreases with increasing temperature. As the temperature rises, the core electrons vibrate more, impeding the flow of electrons.

Shape & Size

Each metal dimension reflects the size and shape of the material. Length, width, height, depth, radius of curvature, etc. determine size. Shape indicates a rectangular, square, circular, or other cross-section.

Lustre

Lustre
Lustre

Metal has a shiny appearance. Luster peculiar to metals is called metallic luster. Gold, silver, platinum, aluminum, iron, zinc, and tin are shiny metals. In fact, because of this property, gold, silver, and platinum are used in jewelry and ornaments. Some metals lose their luster when exposed to air. This is because the metal reacts with air and moisture in the atmosphere and forms a thin oxide film on the surface. Metals that change color are called tarnish metals. Non-metallic has a matte appearance. The only shiny non-metals are graphite, diamond, and iodine.

Sonority

Metal makes a louder sound because it emits a deep or ringing sound when struck by another hard object.

Porosity

A material is said to be porous or permeable if it has pores.

Density

Metals are generally very dense. The exception is that certain metals such as sodium and potassium have very low densities. These low-density metals are commonly called light metals.

Melting point & Boiling point

When a metal melts or boils, it is a change in the state of matter.

 Energy is given to the matter in order to melt or boil it. This energy is required to overcome the attractive force between the metal ion and the delocalized electrons within the metal. The more energy required, the higher the melting or boiling point.

 Metals are huge lattice structures, so the number of electrostatic forces that can be broken down is very high, so the melting and boiling points of metals are high. This means that the melting and boiling points of metals are more similar to those of ionic compounds than of covalent substances.

However, some metals do not have a high melting point. For example, sodium and potassium have a very low melting point & boiling point. If you put a metal such as gallium or cesium on your palm, it will instantly melt.

Hardness

Most metals are very hard. Not easy to cut or crush. However, metals such as sodium and potassium are soft and can be cut with a knife.

 They are therefore called 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
Corrosiveness

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.

Why Alloying is done?

It makes the metal harder and stronger

The most common question that students will be asked in their Chemistry tests and examinations is how alloying increases strength and hardness.

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

When reacting with 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.

When reacting 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 property. 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.

When reacting 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 own salt solution.

For example,

  1. When Iron reacts with Copper Sulphate solution, the Iron displaces the copper and makes Iron Sulphate and leaves copper.

When reacting 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,

  1. Sodium metal readily reacts with chlorine to form an ionic chloride called sodium chloride.

When reacting 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,

  1. 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.

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Atul Singla

Hi ! I 'm Atul. I am PMP certified Mechanical (Piping) Engineer with more than 17 Years of experience. Worked in the field of Plant design for various industries such as refinery, petrochemical & chemical, Fertilizer, gas Processing industries. Developed passion about Piping while working with national & international engineering consultants on diverse projects involving international clients. Developed courses on Piping Engineering to share the knowledge gained after working with many industry experts, through out these years.

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