Background Na2O, MgO, Al2O3 , SiO2 , P4O10, P4O6,

Background Information:The third row of the periodic table represents Period number 3. Period number 3 includes the following elements: Sodium, Magnesium, Aluminium, Silicon, Phosphorus, Sulfur, Chlorine and Argon. Elements in this period fill the 3s and 3p orbitals with electrons. Period 3 elements are known to form oxides. An Oxide is a binary compound formed by elements chemically bonded with one or more atoms of oxygen. Given that oxygen is a reactive element and is abundantly present in the atmosphere, oxides are extremely common. The reaction to form oxides is exothermic in nature and releases a high measure of energy. Oxides are classified as acidic, basic, amphoteric or neutral based upon their acid-base characteristics. The compounds formed by the reaction of oxygen atoms and period 3 elements are known as Period 3 Oxides. Period 3 Oxides include: Na2O, MgO, Al2O3 ,  SiO2 , P4O10, P4O6, SO3, SO2, Cl2O7. The only period 3 element not to form an oxide is Argon. This is due to Argon being unreactive as it is a noble gas. Bonding of the period 3 oxides illustrates the transition from metallic to non-metallic character. Ionic compounds are generally formed between metal and nonmetal elements thus oxides of elements from Sodium to Aluminium have giant ionic structures. Covalent compounds are formed between nonmetals, so the oxides of Phosphorus, Sulfur and Chlorine are covalent compounds. But the oxides of the metalloid element Silicon, in period 3 has a giant covalent structure. The origin of the word acid is derived from the latin word acidus, which means sour. This relates to the modern view of the word acid, as most aqueous solutions of acids are sour in taste. Substances can be classified in 3 differentiated forms as acids, bases or neutral. This classification depends upon the acidic nature of the substance which is derived depending on its pH. It is also seen through its reactions with other compounds. The pH scale refers to the quantifiable measure of hydrogen ion concentration, from 0 to 14, in substances. The representation of this is through the alteration in color observed when a substance is added to a pH indicator. Substances that are acidic in nature dissociate in water to produce H+ Hydrogen ions. It is because of this (H+ ions) that acids have a sour taste. The extent to which an acid dissociates in water indicates its level of strength. Stronger acids will dissociate to a greater extent. Examples of strong acid are Hydrochloric acid, Sulfuric acid and Nitric acid. While Carbonic acid and Ethanoic acid are known to be weaker acids. Because of the presence of the H+ ions, acids turn blue litmus paper red. Acids are known to have a pH of less than 7. Substances that have a pH of 7 are neutral in nature. They turn universal indicator green but do not have any effect on litmus paper. Substance that have a pH of greater than 7 are known to be basic in nature. A base is a substance that can neutralise acid. Soluble bases are known as alkalis. Alkalis dissociate into OH- Hydroxide ions when dissolved in water. They turn red litmus paper blue. Like acids, the strength of an alkali is shown through the extent at which they dissociate into OH- Hydroxide Ions. Examples of strong alkalis are Sodium Hydroxide and Potassium Hydroxide. Ammonia is know as a weak acid. When an acid and base react it is known as neutralisation and a salt and water are formed. Electrical conductivity refers to the ability of a substance to carry an electric current. The SI unit for electrical conductivity is Siemens per metre and the symbol used in the denotation of electrical conductivity is ?. Electrical conductivity is identified as the reciprocal of electrical resistivity. This shown through the formula ? = 1 / ? where resistivity is for a specimen with a uniform shape ? = (R x A) / l where R is the electrical resistance, A is the are of the cross-section, and l is the length of the specimen. Thus the formula ? =  l / (R x A), which can be used to calculate electrical conductivity of a substance with a uniform shape, can be derived through this understanding. To test this theory and accurately show the electrical conductivity of powdered period 3 oxides they must be pressurised. This possible through the use of electrodes to pressurise the specimens. An ohmmeter is an instrument used to measure resistance of an element in a circuit. Although an ohmmeter is very accurate at measuring values above 1 ohm when it comes to measuring smaller values of electrical resistance the presence of a kelvin bridge is important. A kelvin bridge is an instrument used to measure electrical resistance. A kelvin bridge is especially useful to measure electrical resistance values of lower than 1 Ohm. A kelvin bridge can be inbuilt inside an ohmmeter to allow it measure a wider range of values of electrical resistance. A Galvanometer is an instrument that is utilized for calculating small electrical current by the redirection of an active coil. The deflection indicates the amount of current moving.  The deflection is a result of mechanical revolution obtained because of the current. A galvanometer has minimal resistance and is connected in series.Research Question/Aim: To investigate the trend in electrical conductivity and acid-base behaviour of the oxides of elements across period 3.Hypothesis:Electrical conductivity will decrease in the oxides of elements across (to the right) period 3.The pH and acidic nature of the oxides will increase as you move across (to the right) the period 3 elements. Variables:Experiment 1 (trend in electrical conductivity)-Type of VariableVariableIndependentMass of the oxidesElectrical resistance of the oxidesDependentHeight and area of cross section in which the oxide is filled.Controlled The voltage passed through the circuitUncontrolledSurrounding temperature during the experimentExperiment 2 (trend in acid-base behaviour)-Type of VariableVariableIndependentThe volume of universal indicator usedDependentThe purity of the oxides and universal indicatorControlled The mass of oxides and volume of water usedUncontrolledTemperature and pressure of the surroundingsProcedure:Materials*Material requiredQuantityBeakers7Measuring cylinder1Petri Dishes5Dropper1Universal Indicator10mlpH color chart1Na2O20gMgO20gAl2O320gSiO220gP4O620gSO215gCl2O715gDigital top pan balance1Gas syringe1Marker pen1Gloves1Lab coat1Safety Goggles1Distilled Water50cm3Transparent Polymer Cylinder with a hollow in the center of diameter 1 cm1Power Supply1Ohmmeter with inbuilt Kelvin Bridge (with a measurement range of 0.01 ?? to 1000 ?)1Connecting Wires4Switch1Electrodes of diameter 1 cm2* The materials mentioned and quantity used is in accordance to its usage in both of the experiments.Method 1 (trend in electrical conductivity):DiagramConnect the circuit as seen in the above diagram using the connecting wires, power supply, switch, ohmmeter, lower electrode and transparent polymer cylinder. Make sure that the lower electrode is fit firmly in place. Do not fix the upper electrode as yet.Using the marker pen and ruler make a mark 4 cm above the height of the lower electrode.Fill Na2O in the hollow in the space on top of the lower electrode till it reaches the top of the hollow. Then fit the upper electrode which will touch the powder compressing it in the hollow. Make sure the powder is compressed to the 4 cm height marked. Add more powder or remove powder if necessary to meet the mark.When both the electrodes are touching the powder on the top and bottom and the powder is compressed upto the 4 cm mark, switch on the circuit and then check for readings on the ohmmeter.Repeat this 3 times, while noting down the electrical resistance each time. Calculate the average electrical resistance reading on this basis.Repeat the same process for each of the other oxides. Noting down the readings each time. Record the observations on the data table.Method 2 (trend in acid-base behaviour): Take the 7 petri dishes, labelling them from A to G and take the 7 beakers and label them from 1 to 7 using the marker pen.Fill each beaker with exactly 5cm3  of distilled water.Using the Digital top pan balance measure 7g of each oxide and keep the oxides aside in a separate petri dish. To measure 7g of Cl2O7, first measure the weight of the measuring cylinder and then null the value on the balance. Then add the Cl2O7 till the balance shows that 7g of the substance are present. Add 7g of Na2O to the beaker numbered 1, then add 7g of MgO to beaker number 2. Keep on adding 7g of individual period 3 oxides (except SO2 and Cl2O7) to separate beakers in a similar manner. For SO2 in particular, use the gas syringe to bubble the SO2  into the water in the beaker. Add 3 cm3 of universal indicator in each of the beakers with the help of the dropper.Observe the color produced in the beakers numbered 1 to 7 and match it with the colors from the pH color sheet.Note the color of the pH that matches most closely to the observed color.If there is any inaccuracy or mistake during this time repeat steps one to 8 again while observing the colors and making a note of the corresponding pH. Once the experiment is accurately completed, record the observations on the data table.Safety precautions:Make sure the Safety goggles, Gloves and Lab Coat are all the correct size to guarantee maximum protection from hazardous equipment during the experiment.Safety goggles, Gloves and Lab Coat to be worn at all times to protection from hazardous equipment during the experiment.Do not put your face in close proximity to the beakers to make sure you do not inhale any fumes or dodge splashing of the solutions in use.Handle the beakers with extreme care and do not place them near the edge of the platform or in close proximity to each other as this may lead to breakage of apparatus.Let the instructor know immediately if there are any spills or breakage of beakers to prevent any hazardous equipment coming into contact with people working in the lab.Do not attempt to inhale or taste any of the substances used as the substances may be toxic.Despite using lower voltages for the experiment make sure the voltage supplied is never increased to above 24 volts.Do not conduct the experiment when water is present on hands or any body part.Make sure to wear insulated footwear during the experiment.Make sure the connecting wires are correctly insulated.Do not touch the circuit while the power supply is on.Alternative Methods:Measuring the electrical conductivity of the oxides in an aqueous solution.Instead of calculating the electrical resistance created by the addition of a period 3 oxide in a circuit to interpret the electrical conductivity of a period 3 oxide one can use a different technique. This would involve taking specimens of period 3 oxides and adding them to distilled water to form aqueous solutions. These solutions could each be placed in a glass tube square (with a uniform size) which could be attached to a circuit (as shown in the diagram above). The circuit would include a galvanometer which would calculate the value of current flowing through the circuit. This could then be used to calculate the electrical resistance caused by each individual period 3 oxide by manipulating the Ohm’s law to derive the formula Resistance = Voltage / Current. This value of Resistance could then be used in the formula                   ? =  l / (R x A), this would provide a value for electrical conductivity of the oxide. This could be repeated thrice for each oxide. Thus the results would display the trend of electrical conductivity in period 3 oxides.Testing for acidity through reactions with acids and alkaliAnother way in which the trend of changing acid-base behaviour across Period 3’s Oxides can be identified is through testing for acidity. To do so one would need to conduct two different methods one involving the addition of an acid to the tested substance and one involving adding an alkali. To conduct such an experiment one would need seven flasks, Phenolphthalein indicator, an alkali and an acid. In the method, the period 3 oxides should be added to water to create a known quantity of aqueous solutions. These aqueous solutions would one by one be placed in flasks in the setup. Phenolphthalein indicator would then be added to the flask. Then a fixed proportion of the alkali would be added to the flask. Following this one would need to observe changes in color in all the period 3 oxides’ flask. If there is no change note that down. Then repeat the same steps but this time instead of adding an acid add the alkali, making note of the color of the specimen (containing Phenolphthalein). If the specimen only reacted with the acid then it can be concluded to be basic in nature. But considering that the specimen only reacted with the alkali then it can be concluded to be acidic in nature. If the substance was amphoteric then it would have reacted with both the alkali and acid. Through this form of identification one could infer the trend in acid-base behaviour of the period 3 oxides.Data processing:Data Tables-Experiment 1The formula to calculate Electrical conductivity is ? = l / (R x A)But for this experiment the calculation does not involve length and so length is being replaced by the measure of the height. Thus Electrical conductivity is derived on the basis of the formula ? = H / (R x A) ? representing the electrical conductivity.A representing the area of cross section of the hollow from the cylinder in cm3.H representing the height of the substance filled part of the hollow from the cylinder in cm.R representing the electrical resistance in Ohms which will be calculated through the use of the circuit in the experiment.No.OxideElectrical Resistance in OhmsAverage Electrical Resistance in OhmsHeight (H in cm)Area Of Cross Section (A in cm3)? = H / (A x S)Electrical conductivity ? (In siemens per metre)1Na2O40.54 / (R x 0.5)2MgO40.54 / (R x 0.5)3Al2O340.54 / (R x 0.5)4SiO240.54 / (R x 0.5)5P4O640.54 / (R x 0.5)6SO40.54 / (R x 0.5)7 Cl2O740.54 / (R x 0.5)Experiment 2No.OxideColor producedApproximatepHInference1Na2O2MgO3Al2O34SiO25P4O66SO27 Cl2O7