WBBSE Notes For Class 8 School Science Chapter 2 Element Compound And Chemical Reaction Nature Of Matter

Chapter 2 Element Compound and Chemical Reaction Nature Of Matter


Physical State of the Substances

We are surrounded by different substances. All the substances can be sensed by our sense organs. They have mass and occupy some volume. They have inertia.

These substances can be divided into three categories according to their physical states solid, liquid and gas. Below a table is given where the natural physical states of different substances are given.

Physical State Substances
Solid Iron, gold, aluminium, ice, common salt, naphthalene, and chalk.
Liquid Milk, water, oil, chloroform, acetone, glycerine, sulphuric acid, rectified spirit, kerosene, petrol etc.
Gas Oxygen, hydrogen, water vapour, ozone, nitrogen, etc.


Read And Learn More WBBSE Notes For Class 8 School Science

The basic building block of matter or substance is known as a molecule. The molecule is the smallest constituent particle of matter which retains all the properties of the matter and has independent existence.

The arrangement of the molecules gives rise to the variation in the physical appearance and behaviour of matter in the form of solid, liquid and gas.

Arrangement of molecules in the different states of matter Molecules is packed in different ways in three different states of matter which leads to variation in parameters like intermolecular space, an intermolecular force of attraction and the movement of the molecules. Let us study them one by one:

1. Intermolecular Space: The space between the constituent molecules of the matter is called intermolecular space.

The molecules of a solid are very closely packed with negligible intermolecular space. This sort of arrangement gives them definite volume, definite shape and high density.

The rigidity (i.e. they can not flow) of solids is also due to the closed packing of the solid molecules. The molecules in a liquid are loosely packed resulting in more intermolecular space than that among the solid molecules.

Hence liquids do not have a definite shape and have lesser density than solids though they possess definite volume. Due to a greater magnitude of intermolecular spaces, liquids are slightly compressible.

They are less rigid and can flow (that is why they are also called fluids). Gas molecules are very loosely packed with the maximum amount of intermolecular spaces among them.

This results in gases having no definite volume and shape, the least density and very high fluidity (viz. diffusion occurs due to high fluidity). Gases are highly compressible also.

2. Intermolecular forces of attraction: The attractive forces that exist between the adjacent molecules of matter are called intermolecular forces of attraction.

This can either be cohesive force or adhesive force depending upon the nature of the participant molecules involved.

The intermolecular forces of attraction are maximum among molecules of solids followed by those in the liquids and it is negligible among molecules of gases.

Hence solid is rigid and they do not diffuse. Some liquids can diffuse spontaneously into others (for example water and alcohol) but others do not diffuse (for example oil and water).

Gas molecules can diffuse spontaneously and rapidly due to the least and very minimal magnitude of intermolecular forces of attraction that exist between them.

A Substance can occur in all states at suitable temperatures and pressure. This means varying the temperature and pressure,

the physical state of a particular substance can be changed Matter can be transformed from one state to another by altering the temperature and pressure and this phenomenon is called interconversion of states of matter.

So, let us now discuss the inter-conversion between the various physical states of a particular substance by changing the temperature.

Melting And Boiling: Let us take some amount of ice in a beaker and a thermometer is dipped in the beaker. Suppose, the thermometer shows the temperature of the ice as 0°C. Now the beaker is slowly warmed.

Name of the solid Melting point Name of the liquid Boiling point
Ice 0°C Ether 35°C
Zinc 420°C Acetone 56°C
Aluminium 659°C Chloroform 61°C
Common salt 801°C Ethyl alcohol 78°C
Silver 962°C Benzene 80.1°C
Gold 1063°C Water 100°C
Copper 1083°C Sulphuric acid 338°C
Iron 1530°C Mercury 357°C


So the heat is being supplied to the beaker and ice starts melting, but still, the temperature of the system remains at 0°C until all the ice melts.

Once all the ice in the beaker melts, the temperature of the system starts rising. After some time, the water starts boiling and its temperature becomes 100°C.

Until all the water in the beaker is vaporized, the temperature remains the same, that is, remains at 100°C We should note here that during this experiment, the pressure over the system is constant (which is equal to 1 atmospheric pressure).

So, from the above experiment, we find that the melting point of ice is 0°C (at 1 atmospheric pressure) and the boiling point of water is 100°C (at 1 atmospheric pressure).

The melting point and boiling point of a substance can be changed by changing the pressure over it.

Also, from the above experiment we find that by changing temperature, the physical state of a substance can be changed.

The melting point and boiling point of some pure substances are listed below (at 1 atmospheric pressure).

Condensation and freezing: We have just found that when heat is supplied to a solid, it melts. So, if we extract heat from a liquid, it will be transformed into a solid.

Similarly, the exchange of heat can transform a liquid into vapour and vapour into liquid. Condensation is the process which involves the change of matter from gas to liquid on cooling, viz. conversion of steam to water.

The process involving the change of matter from liquid to solid on cooling is called freezing or solidification.

Water changes to the ice at 0°C under normal atmospheric pressure. The temperature of 0°C is called the freezing point of water.

Sublimation: Generally, when heat is supplied directly into the vapour state is called sublimation. The solid obtained on cooling the vapour is called sublimate and the vapour formed is called sublime.

Substances which sublime are iodine, naphthalene, ammonium chloride, etc. The sublimation of iodine can be easily demonstrated with an experiment.

Let us take some amount of solid iodine in an evaporating dish (or a round-bottomed dish) and cover it with a glass funnel, The other end of the funnel is plugged with cotton.

WBBSE Solutions For Class 8 Chapter-2 Element, compound and chemical reaction sec-1 Nature of matter Condensation and freezing

The evaporating dish is then heated slowly. It is found that as the temperature is increased, the solid iodine sublimes (i.e., transformed directly into vapour, without going through the liquid state) and it again collects as solid at the inner surface of the upper and colder part of the funnel.

Actually, the vapour formed due to the sublimation of iodine condenses as a solid when comes in contact with the upper part of the funnel which is comparatively colder.

The experiment can be repeated with camphor, naphthalene and ammonium chloride. We will observe the same result.
Solid substances have a definite shape, but liquids and gas do not have definite shapes.

Liquids and gases can “flow”; this means they have fluidity. So, liquids and gases are commonly called fluids. When a solid is transformed into a liquid, generally its volume increases.

One important exception is ice. When ice melts, its volume decreases. All liquids, when transformed into vapour, their volume increases significantly.

Different substances have different properties. Generally, each substance has special properties by which it can1 be distinguished from the others. We sometimes term these properties as “characteristic properties” of the substance.

WBBSE Solutions For Class 8 Chapter-2 Element, compound and chemical reaction sec-1 Nature of matter Heat

Such Properties Can Be Classified Into Two Categories:

  1. Physical properties
  2. Chemical properties

Physical properties: The property of a substance, which gives us an idea about the nature and external condition of the substance is called its physical property.

It cannot provide us with an idea about its internal structure (or “molecular-level information”). Examples of physical properties are – physical state, colour, odour, melting point, boiling point, magnetic property, solubility in a particular solvent, etc.

Chemical properties: The property of a substance which decides the tendency and capacity of that substance to react with other substances is called its chemical properties.

For example, the sulphur burns in the air to produce sulphur dioxide (S02); zinc reacts with dilute sulphuric acid to produce hydrogen gas.WBBSE Solutions For Class 8 Chapter-2 Element, compound and chemical reaction sec-1 Nature of matter round bottomed dish

Identification of Substances by their Physical Properties As we have already stated, the physical properties of substances from others and so preliminary of substances are those characteristics which are identification of a substance becomes easy, exhibited externally.

They distinguish one The physical properties, which help the differentiation of substances, are given below :


Physical property Examples
1 State of the substance The physical state of a system sometimes helps to identify a system:

For example, let one be provided with three containers, one containing iron powder, another containing benzene and the rest nitrogen.

At normal temperature and pressure, iron powder is solid, benzene is liquid and nitrogen is in a gaseous state.

So an idea about the physical state of a system can distinguish a particular substance from others.

2 Touch Many substances can be identified by touch. Graphite is soft and slippery.

Chalk feels rough when touched. Glycerine is denser than water and slippery and sticky to the touch. Water is neither slippery nor sticky.

3 Odour Many substances may be distinguished by their typical smell.

Ammonia (NH3) gas has a pungent smell. Hydrogen sulphide (H2S) has a distinctive smell of rotten eggs.

4 Solubility Ozone has a fish-like smell. Rectified spirit has a sweet smell.

Glycerine does not have any characteristic smell. Naphthalene, Camphor, petrol, and kerosene all have distinct characteristic smells by which they can be identified.

Substances may be identified by their solubility in different solvents.

Sugar is soluble in water but not in petrol (or kerosene).

Common salt is soluble in water, but not in petrol (or kerosene). Sulphur is not soluble in water but soluble in carbon disulphide (CS2).

Copper sulphate is soluble in water but not in petrol (or kerosene).

Camphor is slightly soluble in water but completely soluble in petrol.

5 Magnetic property Some substances can be identified by their magnetic properties.

For example, iron, nickel, cobalt etc., are attracted by magnets, but aluminium, magnesium etc., do not have such magnetic properties.

6 Melting point and Boiling point The melting point and boiling point of a pure substance at a particular pressure (say at 1 atmospheric pressure) are constant.

So, knowing the value of the melting point and boiling point of substances, one can identify a particular substance.

For example, we find that the melting point of copper is 1083°C and that of aluminium is 659°C (at 1 atmospheric pressure).

Similarly, the boiling point of water is 100°C and that of benzene is 80.1°C (at 1 atmospheric pressure).


Identification of Substances by their Chemical Properties

The properties that a substance exhibits when it undergoes a complete change of its initial atomic composition and arrangement due to some action with other substances or influenced by heat or electricity are known as chemical properties.

Different substances show different chemical properties when they are treated similarly. A substance can be uniquely identified or distinguished from others with its chemical properties.

To determine its chemical property, the substance is allowed to react with air, water, acid, alkali and some other chemical reagents under various conditions

(such as at different temperatures and pressures) and the change in the composition of the substance and the properties of the products formed under such reaction conditions are analyzed. Some examples are given below.

1. Nitric oxide (NO) gas is colourless. Suppose it is stored in a closed container. When the lid is opened, NO reacts with oxygen present in the air and produces brown fumes of nitrogen dioxide

⇒ \(2 \mathrm{NO}+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}_2\)

2. If sugar and quicklime are added separately to two glasses of water, then the glass in which quicklime is added becomes hot.

Here, quicklime (Calcium oxide, CaO) reacts with water to form calcium hydroxide [Ca(OH)2] and during this reaction, heat is produced. (It is an example of an exothermic reaction.

⇒ \(\mathrm{CaO}+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_2+\text { heat }\)

For sugar added to water, no chemical reaction takes place, only the sugar dissolves in water as it is highly soluble in water.

3. Two stainless steel spoons with insulated handles are taken. In one, powdered sugar and in the other common salt are taken.

Both the spoons are then heated over a flame. The sugar first turns brown and then becomes black, but no such visible change is observed for common salt.

In the case of sugar, water is first liberated from it and ultimately only black carbon (charcoal) is left on the spoon. This is called charring.

⇒ \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11} \rightarrow 12 \mathrm{C}+11 \mathrm{H}_2 \mathrm{O}\)

4. Heating a substance may cause chemical changes in it and it may be transformed into new substances.

For example, some amount of hydrated cupric nitrate, solid iodine and a magnesium ribbon is separately heated at elevated temperatures. Cupric nitrate forms deep blue hydrated crystals of the composition \(\mathrm{Cu}\left(\mathrm{NO}_3\right)_2, 3 \mathrm{H}_2 \mathrm{O}\)
When hydrated cupric nitrate \(\left[\mathrm{Cu}\left(\mathrm{NO}_3\right)_2 \cdot 3 \mathrm{H}_2 \mathrm{O}\right]\) Is strongly heated, then brown-coloured nitrogen dioxide is produced and a black residue of copper oxide (CuO) is left.

⇒ \(2 \mathrm{Cu}\left(\mathrm{NO}_3\right)_2 \cdot 3 \mathrm{H}_2 \mathrm{O} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{CuO}+4 \mathrm{NO}_2+\mathrm{O}_2\)

Iodine is a deep brown (almost black) crystalline solid with a shining lustre. When solid iodine is heated, it sublimes and is converted into violet-coloured iodine vapour. No chemical change takes place in this case.

⇒ \(\mathrm{I}_2 \text { (solid) } \stackrel{\Delta}{\longrightarrow} \mathrm{I}_2 \text { (vapour) }\)

5. The addition of dilute acids to some substances may cause chemical changes in them, forming new substances which may (or may not) have characteristic colour or odour.

So some substances may be identified by reacting them with dilute acids such as sulphuric acid or hydrochloric acid.

For example, zinc powder, iron powder and solid ferrous sulphide are taken separately in three dry test tubes. Dilute sulphuric acid (H2S04) is added to each of them.

When dilute sulphuric acid is added to zinc powder, a colourless and odourless gas bubbles out from the mixture.

This gas burns with a blue flame when ignited with a burning stick. This gas is hydrogen (H2).

⇒ \(2 \mathrm{Mg}+\mathrm{O}_2 \stackrel{\Delta}{\longrightarrow} 2 \mathrm{MgO}\)

When dilute sulphuric acid is added to the iron powder, here also a colourless and odourless gas bubbles out from the solution.

This gas is hydrogen. The solution turns light green due to the formation of water-soluble ferrous sulphate (FeSaO4).

⇒ \(\mathrm{Fe}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{FeSO}_4+\mathrm{H}_2 \uparrow\)

When the same acid is added to ferrous sulphide, a gas bubbles out with the smell of a rotten egg. This gas is hydrogen sulphide (H2S). The solution turns faint green due to the formation of ferrous sulphate.

⇒ \(\mathrm{FeS}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{FeSO}_4 \text { (faint green) }+\mathrm{H}_2 \mathrm{~S} \uparrow\)

As we have just shown some substances can be identified by their reaction with dilute acids, similarly, some substances can be identified by their reaction with alkaline substances.

For example, common salt and ammonium chloride (NH4CI) are separately mixed with sodium bicarbonate (NaHCO3) or quicklime or sodium hydroxide (NaOH) using a mortar and a pestle.

In the case of common salt, no observable change occurs. But in the case of ammonium chloride, a gas evolves (vapour).

When magnesium ribbon is strongly heated, it burns brightly producing light and white-coloured magnesium oxide is formed and has a strong, pungent odour. The gas is ammonia (NH3).

When NH4CI reacts with NaHCO3:

⇒ \(\mathrm{NH}_4 \mathrm{Cl}+\mathrm{NaHCO}_3\rightarrow\mathrm{NaCl}+\mathrm{NH}_3 \uparrow+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2\) reacts with NaOH:

⇒ \(\mathrm{NH}_4 \mathrm{Cl}+\mathrm{NaOH} \rightarrow \mathrm{NaCl}+\mathrm{NH}_3 \uparrow+\mathrm{H}_2 \mathrm{O}\)

When NH4CI reacts with Ca(OH)2:

∴ \(2 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{Ca}(\mathrm{OH})_2 \rightarrow\mathrm{CaCl}_2+2 \mathrm{NH}_3 \uparrow+\mathrm{H}_2 \mathrm{O}\)

So, it is clear now that physical and chemical properties can be utilized to identify a substance.
In fact, both the physical and chemical properties of a particular substance are studied to conclusively identify the substance.

Metals and Non-metals: Characteristics and Uses

There are about 92 naturally occurring elements, out of which about 70 are metals. The rest are categorized as non-metals and metalloids.

Physical properties of metals: The Important Physical Properties Of Metals Are Briefly Given Below

1. Malleability: The property which allows the metals to be hammered into thin sheets is called malleability. Most of the metals are malleable.

Gold and silver are some of the best malleable metals. Aluminium and copper are also highly malleable metals. All these metals can be beaten with a hammer to form very thin sheets called foils.

2. Ductility: The property which allows the metals to be drawn into thin wires is called ductility. Gold is the most ductile metal.

Silver is also among the best ductile metals. Copper and aluminium are also very ductile and can be drawn into thin copper wires and aluminium wires. Thin wires of tungsten metal are used to make filaments of electric bulbs.

3. Good thermal conductivity: Metals are generally good conductors of heat as they allow heat to pass through them easily.

Silver metal is the best conductor of heat. Copper and aluminium are also very good conductors of heat.

4. Good electrical conductivity: Metals are good conductors of electricity as they allow an electric current to pass through them easily.

Silver is the best conductor of electricity followed by copper. Gold, aluminium and tungsten are also good conductors of electricity. Metals are good conductors of, electricity because they contain free electrons.

5. Metallic lustre: The property of metal having a shining surface is called metallic lustre. The shining surface of metals makes them good reflectors of light and useful in making jewellery and decoration pieces. Gold and silver are used in ornaments. Silver is used in mirrors.

6. Hardness: Most metals like iron, copper, aluminium etc are very hard. They can not be cut with a knife.

7. High strength: Metals are strong and they can hold large weights without snapping. For example, iron (in the form of steel) is very strong and due to this, it is used in the construction of bridges, buildings, railway lines, chains etc.

8. Solid at room temperature: Most metals like iron, copper, aluminium, silver and gold etc are solids at room temperature.

9. High melting and boiling points: Metals have high melting and boiling points. Iron has a melting point of 1535°C, copper has a melting point of 1083°C etc.

10. High density: Metals are heavy due to their high density.

11. Sonorousness: Metals are sonorous by virtue of which they are capable of producing a deep or ringing sound.

It is due to this property of sonorousness that metals are used for making bells and strings of musical instruments.

12. Physical properties of non-metals: The physical properties of non-metals are just the opposite of those of the metals:

1. Brittleness: Non-metals are neither malleable nor ductile; non-metals are brittle. Solid non-metals can neither be hammered into thin sheets nor drawn into thin wires.

Non-metals break into pieces when hammered or stretched. Carbon, sulphur and phosphorous are solid non-metals that are. brittle.

However brittleness is only applicable for solid non-metals, it is not applicable for liquid or gaseous non-metals.

2. Non-conductor of heat and electricity: Non-metals do not conduct heat and electricity because they have no free electrons.

3. Dull appearance: Solid non-metals have a dull appearance. For example, sulphur and phosphorus have no lustre and they appear to be dull.

4. Soft: Most of the solid non-metals are quite soft.

5. Low strength: Non-metals are not strong, they are easily broken and they do not have appreciable tensile strength.

Solid, liquid or gas at room temperature: Non-metals can exist in all three physical states: solid, liquid and gaseous.

For example, carbon and sulphur are solid non-metals, bromine is a liquid non-metal whereas hydrogen, oxygen etc are gaseous non-metals at room temperature.

Low melting and boiling points: The melting point of sulphur is only 115°C, which is quite low.

6. Light in weight: Due to their low density, non-metals are light substances.

7. Non-sonorous: Non-metals do not produce sound when hit with an object.

Different Physical Properties Of Metals And Non-Metals Can Be Summarized As Follows:

Properties of Metals Properties of Non-Metals
Lustrous (shining/appearance) Non-lustrous
Ductile (can be made into a thin wire) Non-ductile
Malleable (can be hammered or pressed into different shapes easily without breaking or cracking) Non-malleable
High melting point and boiling point (generally exists as solid at or near room temperature) Low melting point and boiling point (generally exists as liquid or gas at or near room temperature)
High density Low density
Good conductors of heat and electricity Bad conductors of heat and electricity

Metalloids are those elements which have both metallic and non-metallic properties. Examples of metalloids are arsenic, antimony, etc.

Metalloids have a metallic appearance (i.e., shiny) but they are brittle. Chemically they have similarities with non-metals. They generally form alloys with metals.

One should always remember that there are exceptions that exist in the physical properties of both metals and non-metals.
For example:

Generally, metals are solid at or near room temperature. But mercury is a metal which is liquid at normal temperature.

1. Metals are generally hard and they cannot be cut into pieces easily by a knife. But lithium, sodium and potassium – all metals are soft and can be cut with a knife.

2. Carbon (in the form of a diamond) is a non-metal that is very hard. In fact, diamond is the hardest natural substance known.

3. Metal surfaces appear shining and it is called metallic lustre. It reflects light from the polished or freshly cut surface. Non-metals have a dull appearance. But iodine, which is a non-metal, has a metallic lustre.

4. Metals usually have high densities. But there are several exceptions. For example, lithium is a light metal (density = 0.53 g/ cm3); sodium, potassium, calcium, magnesium and aluminium also have low densities. Non-metals have low densities. Diamond, though non-metal, has high density.

5. Metals generally have a very high melting point and boiling point. But gallium (Ga) and caesium (Cs) have low melting points (29.75°C and 26.45°C, respectively).

6. Non-metals are usually gases or volatile solids or liquids. For example, fluorine and chlorine are gases, bromine is a liquid while iodine is a volatile solid (which sublimes when heated).

On the other hand carbon, silicon and boron have high melting and boiling points.

7. Metals are good conductors of electricity and heat, but non-metals are not. Carbon is non-metal. One of its “allotropes” – graphite – is a very good conductor of heat and electricity.

8. Metals possess tenacity and toughness which means they possess resistance to, rupture by a stretching force and twisting respectively.

They are also malleable and ductile. But some metals, such as bismuth and antimony are brittle and can be easily crushed to powder.

It can be proved with an experiment that metals such as iron, copper, aluminium, etc., are good conductors of electricity but non-metals such as charcoal, sulphur etc., are bad conductors of electricity.

Use Of Metals And Non-Metals In Human Life And Environment

The earth was created nearly 4500 million years ago. Initially, it was in a very hot condition. Gradually with the progress of time, it started to cool down.

The molten substances also began to cool down and the earth’s crust was formed. Life originated on earth much later (nearly 3500 million years ago). The first life form was very much simple.

Gradually it became more and more complex. Various species appeared and disappeared on earth with the passage of time. At different ages different species were dominant.

In the modern world, the most important and dominating species is the human being. Among all the species which exist in today’s world, human beings were probably the last species to come.

Yet, human beings tried to adapt themselves to changing situations and have been struggling to improve the condition of their living.

In this process, we, human beings have utilized various natural resources for our own benefit and development.

One of the most important natural resources human beings have been using is the metals such as iron, copper etc.

Various non-metals are also used by us. Every metal and non-metal has its specific uses depending on their physical and chemical properties.

Below are some important materials used in our everyday life and the metals and non-metals present in them have been listed.

Name of the materials Metal and non-metals present in the material
1 Cement, brick Silicon, aluminium, oxygen
2 Stainless steel Iron, chromium, carbon
3 Ornament Silver, copper, gold, platinum
4 Chemical Fertiliser Phosphorous, nitrogen, potassium, oxygen
5 Plastic Carbon, hydrogen, nitrogen, oxygen, chlorine
6 Toothpaste Carbon, hydrogen, oxygen, calcium, aluminium, etc.
7 Soap Carbon, hydrogen, oxygen, etc.
8 Photographic film Silver, carbon, hydrogen, oxygen
9 Medicine, drug Carbon, hydrogen, oxygen, nitrogen, aluminium, sodium, calcium, sulphur, etc.
10 Gunpowder of match stick Red phosphorous, chlorine, potassium, oxygen


Our body is made up of several elements (metals and non-metals). This includes metals like sodium, potassium, calcium, iron etc., and non-metals like nitrogen, carbon, hydrogen, oxygen, phosphorous etc.

All these metals or non-metals remain within our body mostly as ions, bounded to other ions, forming complex substances.

They are always undergoing some complex but specific processes which are responsible for the functioning of all the physiological processes due to which we remain “alive”.

Various metals and non-metals are present in our bodies in definite proportion. A large deviation from this may result in severe problems in the human body and may sometimes prove fatal.

Let Us Now Briefly Discuss The Role Of Various Elements In Different Important Physiological Processes.

1. Maintenance Of Water Balance In the Human Body:

Na+ and K+ are two of the most important ions present in intracellular and extra-cellular body fluids.

Sodium is present in soft tissues, like muscle and nerves, in blood and extracellular fluids and in bones.

Potassium is present mainly in skeletal muscles and approximately 75% of potassium present in our body is found in the skeletal muscles.

The presence of sodium ions in extra-cellular body fluid helps in maintaining the level of water in the intracellular and extracellular regions by a process known as “osmosis”.

When urine is formed, the volume of water in it is regulated by Na+ ions, so that the level of water in the blood is maintained.

If we start taking more raw salts through our dietary intake, the concentration of Na+ in the extra-cellular fluid increases. This increases the osmotic pressure of the extra-cellular fluid.

To normalize this, water from the intracellular fluid comes out through the cell membrane to the outside, resulting in the absorption of more water by blood.

So, the level of water within the intracellular fluid decreases. As a result blood pressure increases, which in turn can adversely affect the proper functioning of the heart and kidneys.

Similarly, when excess Na is lost from our body (for example, due to diarrhoea or due to profuse sweating), water from extracellular regions moves towards the intracellular region.

Hence, blood pressure decreases to an alarming level and may even cause cardiac arrest.

2. Functioning Of Heart:

Cardiac muscles require calcium to contract and squeeze blood out of the heart and into the arteries.

Calcium flows into the muscle cells and works as a switch that allows cardiac muscles to contract.

At the end of the contraction, calcium flows out of the muscle cells to allow the muscle to relax and expand again.

So the rate of heart contraction increases with increasing concentration of Ca2+ and decreases with decreasing concentration of this Ca ion.

K is also crucial to the functioning of the heart. A low level of K+ leads to irregular contraction of the heart and abnormal electrocardiogram results.

Actually, the electrocardiogram is a measure of heart function and is related to the force and rate of contraction of cardiac muscles. Too much K+ in the body may cause palpitation and disruption of heart rhythm.

3. Acid-Base Equilibrium:

K+ions play a significant role to maintain acid-base equilibrium in our body. Acidity (due to the high concentration of H+ ions inside the cellular fluid) causes a shift, in the concentration of K+ extracellularly.

H+ ions are then exchanged with K+ and Na+. Unless sufficient K+ and Na+ are not taken withstood, this causes alkalinity in extracellular fluid.

In the ‘same way, if the concentration of K+ and Na+ increases in extracellular fluid, then they go inside the cellular fluid and H+ ions come outside into the extracellular fluids, causing increased acidity.

Due to loss of acid-base balance, erosion of bone joints is initiated and bone density may be lowered.

4. Formation of teeth and bone:

Several ions like Ca2+, Mg2+ and phosphorous play a major role in the formation of the skeletal structure of our body.

Besides they are important for the formation of teeth. They give mechanical stability to the teeth and bones. These ions are also present in the enamel, dentine and cementum of teeth.

5. Functioning Of Enzymes:

Enzymes can be regarded as bio-catalyst since they function as catalysts inside the body and they are highly selective (in the sense that each enzyme participates-)h only in a specific reaction involving a specific substance).

All the important physiological processes occur due to the involvement of enzymes. Several metallic and non-metallic species like Ca2+, Mg2+, Na+, Fe2+, Fe[ Naphthalene and camphor can be identified and are required for the proper functioning of different enzymes.

6. Coagulation Of Blood:

Whenever our skin tissues are broken, blood comes out. As soon as blood from the wound is exposed to air, the platelets (present in the blood) disintegrate and react with fibrinogen to create fibrin – a mass of tiny threads.

This triggers a whole series of reactions that relies on an adequate concentration of Ca2+ and vitamin K. Fibrin eventually hardens quickly to form a coating over the wound and the blood clots.

Without adequate levels of Ca2+, blood will take a longer time to clot.

7. Contraction Of Muscle And Conduction Of Nerve Impulse:

Contraction and relaxation of muscles occur due to rapidly changing concentrations of Ca2+ inside the muscle cells.

This process is commonly referred to as the calcium cycle. Two proteins play a vital role in muscle contraction.

The contraction of smooth muscles is dependent on myosins and the contraction of the striated muscle depends on actin. Muscles contain myofilaments.

Contraction represents the shortening of myofilaments. Too much or too little Ca2+ causes muscular symptoms due to disruption of the calcium cycle.

Mg2+, Na+ and K+ also control the excitability of muscles. Ca2+ ion also plays a major role in the conduction of nerve impulses from one nerve cell to the other.

8. Oxidation—Reduction Of Tissues And Cells:

During breathing, we inhale oxygen. This is utilized by various proteins to generate energy in mitochondria present within the cell.

9. Transport, storage and utilization of oxygen: Iron is one of the most important metals n being has 4.2 to 6.1 grams of iron in his body.

Iron is present within our body as an iron-containing protein. These proteins are usually called heme proteins. They are responsible for oxygen transport and the electron transfer process in our body.

It is done by changing the oxidation state of iron (inter-conversion between Besides, they play a major role in iron storage and its transport across the body. Haemoglobin in blood transports oxygen.

Myoglobin – an iron-containing binding protein found in muscle tissues of vertebrates and mammals, are regarded as the primary oxygen-carrying pigment within muscle tissues.

Its higher concentration allows an organism to hold its breath for a longer time. Diving mammals such as whales have muscles with a high abundance of myoglobin.

10. Prevention Of Excess Oxidation And The Process Of Ageing:

The presence of different free radicals is held responsible for the ageing process. Compounds of metals like copper, selenium, magnesium and zinc generally neutralize the activities of free radicals such as superoxide anion. Thus the ageing process is delayed.

11. Formation of hormones:

Type – I diabetes is caused by a lack of insulin production in our body. Zinc plays an important role in the production of insulin in the beta-cells of the pancreas for the vast majority of animal species.

Iodine plays a vital role in the synthesis of thyroxine hormone. Secreted from the thyroid gland, thyroxine hormone controls the oxygen intake by different cells of our body and the production of heat energy.

12. Formation Of Blood :

Cobalt plays a significant role in the process of maturation of red blood corpuscle (RBC) in the bone marrow and the formation of haemoglobin.

13. Formation Of Some Important Compounds In the Human Body:

Phospholipids, glycolipids, nucleic acid, DNA, RNA etc., play the most important role in all biological systems. Several metals.

(such as Fe, Cu, Mn, Se) and several non-metals (such as C, H, N, O, and P, So we can conclude that the role of metals and non-metals are not only important for our everyday life but is also crucial for our physiological and biochemical activities.

As we have learnt that presence of some elements in the proper amounts is mandatory for the proper functioning of our body, similarly, there are some elements too, which may cause damage to several of our body parts like the brain, kidney, liver, heart, lungs, etc.

In today’s world, sometimes we are exposed to such elements unknowingly. Examples of such elements are lead, mercury, arsenic, fluorine, cadmium, aluminium etc.

The source of these elements is various. Below, we have outlined some of the common sources of such elements which are harmful to our bodies.

Element Common source
Lead Insecticide, leaded petrol (nowadays leaded petrol is not at all sold from any petrol pumps throughout India), pipes made of lead, and storage cells (containing lead electrodes).
Mercury Factories producing batteries, factories producing mercury vapour lamps, paper factories, plastic factories, thermometers, and fly ash produced in thermal power generation units.
Cadmium Fungicides, super phosphate, tobacco leaf, cheap toys, smoke produced from cigarettes etc.
Aluminium Cosmetics, medicines like antacids, cooking utensils, aluminium wrappers etc.
Fluorine Underground water, plastic, medicine.
Arsenic Underground water, insecticides, fly ash produced in thermal power generation units, etc.

(ln South Bengal, particularly in Gangetic West Bengal, the presence of arsenic much above the permissible level has emerged as one of the biggest environmental problems.

Efforts have been initiated to provide safe drinking water to persons living in these affected areas.)



Leave a Comment