Chapter 2 Element, Compound And Chemical Reaction Nature of Matter Experiments
To determine whether a particular substance is a good conductor of electricity or not, we need an experimental setup, which can be constructed as follows :
The end of a battery is connected to any one side by a wire. The open end of the wire is connected to one end of a holder where a bulb is fitted.
Another piece of wire is connected to the other end of the holder. Its free end is now connected to a clip (marked “A” Another piece of wire is connected at one side to the other end of the battery and on the other side connected to another clip (marked “B”).
WBBSE Class 8 Science practicals on chemical reactions
The substances whose electrical conductivity is to be tested can be connected between the two clips and thus the electrical circuit is completed.
If one substance is attached between the two clips, then the circuit becomes completed and electricity will flow through the circuit only if the substance is a good conductor of electricity and the bulb glows.
For a poor conductor of electricity, the bulb glows dimly and for a bad conductor, the bulb will not glow at all.
From the above experiment, we will find that iron, copper, and aluminium are good conductors of electricity whereas non-metals like charcoal, sulphur etc., are bad conductors of electricity.
Read And Learn More WBBSE Solutions For Class 8 School Science Experiments
So we must study different physical and chemical properties of an element to classify it as metal or non-metal.
We should also note that various physical and chemical properties of different elements are utilized to prepare different things which are used in our everyday life. This can be illustrated in the following table.
| Element | Name of the materials prepared by the element | Property of the elements utilized to make such materials | Use of such materials |
| Iron (Fe) | 1. Railway lines | Hardness | In the field of agriculture, the engineering industry, the transport sector, in infrastructure preparation |
| 2. Bridge | |||
| 3. Agricultural and engineering instrument | |||
| 4. Rod used in houses, building | |||
| Copper(Cu) | Electrical wire | Good conductor of electricity | Electricity distribution |
| Cooking utensils | Good conductor of heat | In the kitchen | |
| Coins | Chemically less active when exposed to moisture and air | Commerce | |
| Aluminium (Al) | Manufacturing the body of automobiles and aircraft | Lightweight material | Transport sector |
| Electrical w.ire and electrical appliances | Good conductor of electricity | Electricity production and distribution | |
| Cooking utensils | Good conductor of heat | In the kitchen | |
| Lead (Pb) | Battery, electrical wire | Good conductor of electricity | Electricity distribution and storage cells |
| Paints | Ability to form coloured substances | Paint industry, preparation of rust-proof paint | |
| Anti-knock material (tetraethyl lead) | Ability to form | In automobiles, it is used as an anti-knock agent and mixed with petrol or diesel | |
| organometallic compound (i.e., a compound having a metal part and an “organic” part) | |||
| Gold (Au) | Ornaments and coins | Brightness and malleability | For the preparation of gold ornaments and in commerce |
| Zinc (Zn) | Battery | Good conductor of electricity, | Generation of Direct current |
| Chemically inert under ordinary condition | |||
| Electroplating | Chemically less reactive when exposed to moisture and air under ordinary condition | Used in galvanization (coating of the iron surface by zinc to prevent rusting of iron) | |
| Graphite (c) | Used as lubricants with oil and water | Slippery | In automobiles |
| For making pencil | Soft and Slippery | To write or draw something on paper | |
| Making a crucible (a kind of container used in the laboratory) which can sustain high temperature | High melting point | In laboratory | |
| Carbon | For making gas musk | High adsorption capacity | To prevent exposure to poisonous gas |
| For making shoe polish | Soft and slippery | In electrolysis | |
| For making adsorbent | High adsorption capacity | In the laboratory and chemical industry it is used to adsorb the impurities present in the system and to purify the desired product(s) | |
| Sulphur (S) | For the preparation of H2S04 | Ability to combine with oxygen to produce oxides which can be converted to H2S04 | In the chemical industry and laboratory |
| For the preparation of gunpowder | Easily inflammable | To manufacture | |
| explosives and firecrackers | |||
| To prepare match sticks | Easily inflammable | To ignite fire |
WBBSE Class 8 Nature of Matter experiments
Chemical Properties of Metals and Non-metals
1. Reaction with Oxygen
When a metal or a non-metal is burnt or heated in air, it reacts with the oxygen present in the air and forms an oxide of that element.
This oxide compound may be acidic or basic or amphoteric (i.e., having both acidic or basic character) or neutral (i.e., neither acidic nor basic).
Generally, metals form basic oxides and non-metals form acidic oxides. For example, the oxide of magnesium (a metal) is basic, but the oxide of sulphur (a non-metal) is acidic.
Again oxides of aluminium and zinc are amphoteric and one oxide of carbon (a non-metal) – carbon monoxide – is neutral. Nitrous oxide is also a neutral oxide.
The reaction of magnesium and sulphur with oxygen can be illustrated in the following experiment.
Experiment -1
2. Reaction Of Magnesium With Oxygen:
A magnesium filament is burnt in a porcelain dish. After it is completely burnt, some amount of water is added to the residue left in the porcelain dish. In this solution, a strip of red litmus paper is immersed.
Observation: It is observed that the red litmus paper turns blue.
Inference: Magnesium filament burns in oxygen to produce magnesium oxide (MgO). MgO is a metallic oxide, which reacts with water to produce magnesium hydroxide [Mg(OH)2] which is basic in nature. That is why red litmus turned blue.
⇒ \(2 \mathrm{Mg}+\mathrm{O}_2 \rightarrow 2 \mathrm{MgO}\)
⇒ \(\mathrm{MgO}+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Mg}(\mathrm{OH})_2\)
Experiment-2
Let us take some amount of sulphur powder in a porcelain dish. The dish is covered with a glass funnel.
The other end of it is connected to a glass tube which is immersed in water taken in a beaker. Sulphur powder is then carefully burnt.
The gas produced in this reaction is bubbled through water and some gas is dissolved in water.
Observation: Now a strip of blue litmus paper is dipped in the water solution. It turns red.
Inference: Sulphur reacts with oxygen to produce sulphur dioxide gas (SO2) which further reacts with water to produce sulphurous acid (H2SO3). This is an acid, so blue litmus turns red when dipped in its solution.
⇒ \(\begin{gathered}
\mathrm{S}+\mathrm{O}_2 \rightarrow \mathrm{SO}_2 \\
\mathrm{SO}_2+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{H}_2 \mathrm{SO}_3
\end{gathered}\)
3. Amphoteric oxides: There are many oxides which exhibit both the characteristics of basic oxides and acidic oxides. These are called amphoteric oxides.
Examples are ZnO, Al2O3, PbO etc. The reactions of these oxides, which characterise their amphoteric nature, are shown below.
Behaviour As Basic Oxides:
⇒ \(\begin{aligned}
\mathrm{ZnO}+2 \mathrm{HCl} & =\mathrm{ZnCl}_2(\text { Salt })+\mathrm{H}_2 \mathrm{O} \\
\mathrm{Al}_2 \mathrm{O}_3+6 \mathrm{HCl} & =2 \mathrm{AlCl}_3\left(\text { Salt) }+3 \mathrm{H}_2 \mathrm{O}\right.
\end{aligned}\)
Behaviour As Acidic Oxides:
⇒ \(\begin{gathered}
\mathrm{ZnO}+2 \mathrm{NaOH}=\mathrm{Na}_2 \mathrm{ZnO}_2 \text { (Salt) }+\mathrm{H}_2 \mathrm{O} \\
\text { (Sodium Zincate) } \\
\mathrm{Al}_2 \mathrm{O}_3+2 \mathrm{NaOH}=2 \mathrm{NaAlO}_2 \text { (Salt) }+\mathrm{H}_2 \mathrm{O} \\
\text { (Sodium aluminate) }
\end{gathered}\)
Neutral oxides: There are some oxides (mainly non-metals) which show neither acidic nor basic properties. They do not react with acids or with bases to form salts.
If they dissolve in water, the aqueous solution remains neutral to litmus. Important examples of neutral oxides are carbon monoxide (CO2) nitrous oxide (N2O) and nitric oxide (NO).
Experiments on elements and compounds for Class 8
2. Reaction with Water Some metals may react with water under different conditions to produce metal hydroxides. For example, Sodium and potassium react vigorously with cold water and form hydrogen gas. The gas catches fire and burns with blue flame by the heat produced during the reaction.
⇒ \(\begin{aligned}
2 \mathrm{Na}+2 \mathrm{H}_2 \mathrm{O} & \rightarrow 2 \mathrm{NaOH}+\mathrm{H}_2 \uparrow \\
2 \mathrm{~K}+2 \mathrm{H}_2 \mathrm{O} & \rightarrow 2 \mathrm{KOH}+\mathrm{H}_2 \uparrow
\end{aligned}\)
1. Lithium reacts less vigorously compared to potassium and sodium, with water.
2. Calcium reacts less vigorously with cold water. \(\mathrm{Ca}+2 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Ca}(\mathrm{OH})_2+\mathrm{H}_2 \uparrow\)
3. Magnesium reacts with water vapour to produce magnesium hydroxide and hydrogen gas. \(\mathrm{Mg}+2 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Mg}(\mathrm{OH})_2+\mathrm{H}_2 \uparrow\)
4. Aluminium and zinc do not react with either cold or hot water. They react with steam to produce metallic oxide and hydrogen gas.
⇒ \(\begin{aligned}
2 \mathrm{Al}+3 \mathrm{H}_2 \mathrm{O} & \rightarrow \mathrm{Al}_2 \mathrm{O}_3+3 \mathrm{H}_2 \uparrow \\
\mathrm{Zn}+\mathrm{H}_2 \mathrm{O} & \rightarrow \mathrm{ZnO}+\mathrm{H}_2 \uparrow
\end{aligned}\)
5. Copper, gold, lead, etc., do not react with water under any condition. The experimental setup for the reaction between a metal and water is shown below.
Here a hard glass test tube is horizontally placed with the help of a stand, Some glass wool moistened with water is placed at the bottom of the test tube and the metal is placed at the middle part of the test tube.
The open end of the test tube is closed with a rubber cork and one end of a glass tube is pierced through the rubber cork.
The other end of the glass tube is placed below another vertically inverted test tube containing water.
If the moistened glass wool is now heated with a spirit lamp, hot water vapour is produced and it comes in contact with the metal.
If any gaseous product is formed it comes out of the first test tube through the glass tube and is collected in the other test tube by downward displacement of water. Non-metals do not react with water (or steam) to evolve hydrogen gas.
3. Reaction with Dilute Acid
When a metal is allowed to react with dilute acid (say dilute hydrochloric acid), it may or may not evolve hydrogen gas.
Even in cases where hydrogen gas is evolved due to a reaction between the metal and the dilute acid, the “power” of metals to produce hydrogen (i.e., the reactivity of the metals towards the dilute acid) is different.
On The Basis Of Experimental Observation, The Following Series Can Be Prepared:
WBBSE Chapter 2 chemical reactions experiments
The reactivity series of metals with respect to hydrogen is given above. The trend of reactivity of these metals can be summarized as follows:
Any metal situated on the left-hand side of hydrogen is able to react with dilute acid and produce hydrogen gas.
But any metal on the right-hand side of hydrogen cannot liberate hydrogen when it reacts with dilute acid.
When a metal reacts with dilute acid, then a metal salt and hydrogen gas are formed:
⇒ \(\text { Metal + Dilute Acid } \rightarrow \text { Metal Salt + Hydrogen }\)
For example, Zinc granules react with dilute sulphuric acid to produce zinc sulphate and hydrogen gas. Zinc, as we see, is situated at the left-hand side of hydrogen in the above series.
⇒ \(\mathrm{Zn}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{ZnSO}_4+\mathrm{H}_2 \uparrow\)
The reaction between different metals and non-metals with dilute hydrochloric acid is described below.
Let us take small pieces of metals like iron, magnesium, aluminium, zinc, copper etc., and pieces of non-metals like carbon and sulphur.
Each Of Them Is Taken Separately In A Test Tube And Dilute Hydrochloric Acid Is Added. The Observation Is As Follows :
| Experiment | Observation |
| A piece of iron is added to a test tube partially filled with dilute hydrochloric acid | Bubbles of hydrogen gas evolved from the solution Fe + 2HCI FeCI2 + H2↑ |
| A piece of magnesium is added to a test tube partially filled with dilute hydrochloric acid | Bubbles of hydrogen gas evolved from the solution. The rate of evolution of hydrogen gas is maximum in this case.Mg + 2HCI →MgCI2 + H2↑ |
| A piece of aluminium is added to a test tube partially filled with dilute hydrochloric acid | Bubbles of hydrogen gas evolved from the solution. 2AI + 6HCI →2AICI3 + 3H2 ↑ |
| A piece of zinc is added to a test tube partially filled with dilute hydrochloric acid | Bubbles of hydrogen gas evolved from the solution. Zn + 2HCI → ZnCI2 + H2 ↑ |
| A piece of copper is added to a test tube partially filled with dilute hydrochloric acid | No reaction occurs |
| Some amount of carbon is added to a test tube partially filled with dilute hydrochloric acid | No reaction occurs |
| Some amount of sulphur is added to a test tube partially filled with dilute hydrochloric acid | No reaction occurs |
In the above reactions also, we see that the metals situated on the left-hand side of hydrogen (i.e., Fe, Mg, Al and Zn) in the electrochemical series, are able to react with dilute hydrochloric acid and produce hydrogen gas.
Copper is situated on the right-hand side of hydrogen in the above series, and it cannot liberate hydrogen when it reacts with dilute hydrochloric acid.
Non-metal also does not react with dilute acids. For example, non-metals like carbon, sulphur and phosphorus do not react with dilute hydrochloric acid (HCI) or dilute sulphuric acid (H2SO4) to produce hydrogen gas.
Simple experiments for understanding nature of matter Class 8
4. Reaction with salt solution
When a more reactive metal is put in the salt solution of a less reactive metal, then the more reactive metal displaces or pushes out the less reactive metal from its salt solution.
If metal A is more reactive than metal B, then metal A will displace metal B from its salt solution to form a salt solution of metal A according to the following reaction:
Metal A + Salt solution of metal B → Salt solution of metal A + Metal B
If an iron nail is dipped in an aqueous solution of copper sulphate, reddish-brown metallic copper is precipitated on the iron nails.
In the reactivity series iron (Fe) is situated on the left-hand side of hydrogen (H) and is expected to displace copper (Cu) from its salt (CuSO4). Cu is situated at the right-hand side of hydrogen.
⇒ \(\mathrm{Fe}+\mathrm{CuSO}_4 \rightarrow \mathrm{FeSO}_4+\mathrm{Cu}\)
If, however, a strip of copper metal is placed in a ferrous sulphate (FeSO4) solution, then no reaction occurs. This is because copper, being less reactive than iron, can not displace iron from its salt.
A more reactive non-metal displaces a less reactive non-metal from its salt solution. For example, when chlorine (Cl2) is passed through a solution of sodium bromide (NaBr), then sodium chloride (NaCI) and bromine (Br2) are formed.
⇒ \(2 \mathrm{NaBr}+\mathrm{Cl}_2 \rightarrow 2 \mathrm{NaCl}+\mathrm{Br}_2\)
Here, more reactive non-metal chlorine is displacing less reactive non-metal bromine from its salt solution (sodium bromide solution).