GENERAL CHEMISTRYSources for the lecture:1. Author: Petrucci & Harwood

General Chemistry: Principles and Modern Applications

2. Author: Mortimer;

Modern University ChemistryContents:Topic 1: Matter: Properties & MeasurementTopic 2: Atoms and The atomic TheoryTopic 3: Electron Structure of AtomsTopic 4: Chemical CompoundsTopic 5: Chemical ReactionsTopic 6: GasesTopic 7. Thermochemistry

TOPIC 1: Matter—Its Properties and Measurement

What is the matter?

• Matter: Everything that has a certain mass and volume can be defined as matter.

• The matter can be defined as any object which can be perceived through our 5 senses (water, soil, plants, air, etc.). On the other hand, we can observe some substances(the particles which come out as a result of radioactive disintegration or cosmic radiation) only by means of some instruments .

• The matter which has a certain shape and is described within this concept is called body.

The intensive(distinguishable) and extensive(common) characteristics of matter

• EXTENSIVE PROPERTIES:The common characteristics of matter depend upon the amount of the substance (mass, volume, ).

• INTENSIVE PROPERTIES:The distinguishable properties do not depend upon the amount of matter(density, boiling point,melting point, solubility, expansion, conductivity, elasticity, odor, color, hardness)

Physical and Chemical Properties of Matter

• Physical Properties: These are the ones that a sample of matter shows without changing its composition Examples:

• Chemical Properties: These are described as the abilities of a sample of matter to undergo a change in composition under stated conditions

• Example• :

•Melting point•Freezing point

•Density•Color

Whether the matter is active or not, can be combusted with the oxygen or not, can react with acids and bases or not, etc.

STATES OF MATTERSOLID↔ (melting/freezing) ↔ LIQUID↔ (evaporation/ condensation) GAS

(sublimation)

Transactions during the change from the solid state to gas state:

• The distance between the molecules increases• The kinetic energy of the molecules rises• The tensile forces between molecules decline• The mass remains unchanged• The chemical property remains unchanged• The physical property changes• The density generally falls down• The entropy rises

(Deposition)

State of Matter

SOLID LIQUID GAS

The 3 Phase Transitions of water in Temperature verse Time plotted Graph

At 1 atm. pressure ( Ek = Kinetic Energy  Ep = Potential Energy )

Matter

Substances Mixtures

Compounds Elements Homogeneous Heterogenous

Seperation by physical changes

Decomposition by chemcial changes

Elements - Compounds• An element is a substance comprised of a

single type of atom (mercury, gold, etc.). There are overall 111 well known elements existing in the world. These are listed in the periodic table. The elements which are listed in the table after 92. element Uranium, have come across as a result of nuclear reactions,whereas the others are naturally present.

• A compound is a substance in which atoms of different elements are combined with one another(e.g water,salt).

Mixtures

• Homogenous Mixtures are uniform in composition and properties throughout a given sample, but the composition may vary from one sample to another. Examples:

• air : gas-gas mixture• Salty water :solid-liquid mixture• Beverage gas: liquid mixture• Alcohol-water: liquid-liquid mixture • 14 carats gold : solid-solid mixture

Mixtures• Heterogenous mixtures are mixtures in

which the components seperate into distinct regions.Thus, the composition and physical properties vary from one part of the mixture to another.

• Examples: Salad dressing

• A slab of concrete

• The leaf of a plant

• Olive oil-water

Example for heterogenous mixtures: Iron powder and sand mixture

PROPERTIES OF MIXTURES

1.They can be mixed up at any ratio2. The substances constituing the mixture do not lose their own characteristics3. The properties of a mixture relies on the ratio of the substances making up the mixture.4. They can be seperated into their components by physical methods5. They do not have any formula6. They can be either homogenous or heterogenous

PROPERTIES OF COMPOUNDS

1. There is a certain ratio between the substances constituing the mixture.2. The substances which are being a part of the compund lose their own properties3. Compounds can be seperated into their components by some chemical methods.4. The melting and boiling points of the compounds are constant.5. They have a specific formula6. They are homogenous.

SEPERATION OF MIXTURES

The process of recovering the substances induvidually building up a mixture has been defined as seperation or purification. The seperation methods are modified on the basis of the different properties of components . The seperation techniques can be divided into two headlines:

A- SEPERATION OF HETEROGENOUS MIXTURES BY PHYSICAL METHODS

B-SEPERATION OF HOMOGENOUS MIXTURES BY PHYSICAL METHODS

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A) SEPERATION OF MIXTURES BY PHYSICAL METHODS

1.Seperation by means of electricity If an ebonite or plastic bar is rubbed against a piece

of material made of wool, it is charged electrically. . When this electrically charged bar has been brought near to a mixture made up of sulphur and sand , it is observed that it draws the sulphur powder,whereas it does not draw the sand . What it remains after the seperation is just sand.

This method is applied only for small amounts. It is non-convenient for the industrial use. We can seperate some mixtures from each other by making use of the different induction capability of each matter.

2. Seperation by a magnet

The substances such as iron,cobalt, nickel can be drawn by a magnet,whereas the others such as sulfur, salt, copper, gold are not affected by a magnet.When a magnet is closed up to the mixture of sulphur and iron powder, the iron particles are seperated by the magnet. (Figure1.1).

Figure 1.1 When a magnet is closed up to the mixture of sulfur and iron powder, the iron particles are seperated from the sulfur powder.

By means of this method the pins or clips made of iron can be seperated from the pile of papers. Therefore , it is used in the paper industry. Those substances which can be induced magnetically can be seperated from the other substances which do not show this manner. As a result, this method is generally suitable for solid-solid mixtures.

2. Seperation by a magnet

3. Floating and Precipitation(Seperation by the difference of density)•How can we seperate in a mixture the iron powder and the pellicle components?•In order to seperate these components, water that is not reactive with the components is added into the mixture.

Figure 1.2. Precipitation process(k,k: pellicle, water : in the middle of the mixture and iron powder: at the bottom of the container

3. Floating and Precipitation(Seperation by the difference of density)

• While the iron powder which has a greater specific density than water is sinking at the bottom of the container, the pellicle which has a smaller specific gravity than water is collected over the surface of water (Figure 1.2). With the help of a spoon, the pellicle can be removed from the mixture. As the water is filtered slowly, the iron powder remains at the bottom of the container. In this way, the components are seperated successfully.

4. Seperation by Filtering•If a heterogenous mixture comprises solid and liquid

components with different densities, than a further precipitation process is applied in order to seperate these components. This process is also called sedimentation.

•After the solid component is precipitated completely, the liquid component is transferred into another container. This process is called as decantation.

•Unless there is a great difference between the densities of solid and liquid components and the solid components has large-diameter particles, the decantation process becomes difficult. In this case, filtering process is applied.

Figure 1.3. Seperation of the muddy water by filtering

For example; When the soil and water are mixed up thoroughly, the water is filtered through the filter paper and the insoluble soil particles remain over the filter paper. So the muddy water has been seperated into its components (Figure 1.3).

In filtration method, several filters with different pore sizes can be used. In order to perform the filtration process thoroughly, a filter paper with a smaller pore size than the diameter of the solid particles must be selected.

5. Centrifuging:

If the solid particles in the liquid are very small and there is no great difference between the densities of the solid and liquid components, filtration can not be sufficient to seperate these components.

The instruments called centrifuges are used to precipitate the solid particles. This process is also applied in the other regular seperations and is time saving.

Figure 1.4. Seperation of two liquids with different densities by a funnel

6. Seperation Funnel:

To seperate two liquid components with different densities and showing nonsoluble characteristics within eachother a funnel can be used. To illustrate; Olive oil-water mixture has been poured into the funnel.

The olive oil is collected at the top of the funnel, while the water that has a greater density than olive oil is collected at the bottom of the funnel. (Figure 1.4). After waiting for a while, the tap is turned on and the water is poured into another container. With this way the liquids have been seperated.

7. Seperation by the difference in solubilitySince the solubility is a distinguishable property for

the matter, mixtures can be seperated easily by using this principle

Figure 1.5. Seperation of salt and sand components by the difference in solubility

• E.g; sand and salt are mixed up in the water. Salt is soluble in water, whereas the sand particles precipitate because they are not dissolved in water. The solution is seperated by dissolving from sand. When salty water is evaporated, the rest remaining from the evaporation is just salt. As a result, salt and sand are seperated.

• This method is only applicable when one of the components is able to be dissolved in the solvent and the other component is not.

B) Seperation Techniques of Homogenous Mixtures

1. Distillation

Every substance has a different boiling point.The process of changing the state of a component into gas phase and condensating it to recover each component seperately by making use of this property is identified as distillation

The liquid in the distillation flask is evaporated . Further, the vapor is passed through the cooler and the vapor condensate is accumulated in the collector. The liquid obtained by this way is defined as distillate. So, a solid component and and a volatile liquid component are seperated. (Figure 1.6).

Distillation has been classified according to the nature of the matter in two ways:a) There are two methods for the seperation of the substances which have very high boiling points and are not exposed to degradation :Simple distillation: It is applicable if there are two components with very different boiling points. The two liquid components are heated up. Both of them are vaporized. The liquid with a lower boiling point exists in the vapor with considerably greater amounts. This vapor mixture is then condensed in the reflux cooler. As a result, the liquid in the collector contains a little of the liquid with a higher boiling point as impurities. Hence, simple distillation is not a convenient method for obtaining two components in a mixture purely. By making a second simple distillation, the purer form of the liquid with lower boiling point can be achieved

Figure 1.6 Seperation by Distillation

Fractional distillation: To seperate two liquids which have very close boiling points to each other, an engaged fractional colomn is used in additon to the simple distillation mechanism. This colomn is filled up with the glass particles which do not interact with the liquids. The rising vapor is gradually condensed over these glass particles. While the liquid flowing downward, it is heated up again with the rising vapor and some part of the liquid is vaporized and goes upward. This vapor contains greater amount of the vapor from the liquid with lower boiling point, compared to the amount of vapor at the beginning of the distillation.

When the vapor reaches to the end of the column as described above, it does not contain any vapor of the liquid with high boiling point and is collected in the reflux cooler as pure liquid by getting condensed. This process is defined as Fractional Distillation(Figure 1.7).

Figure 1.7 Fractional Distillation

b) Two different distillation methods are used to seperate two liquids which have very high boiling points and degradate before reaching the boiling point :-Vacuum distillation: The ordinary distillation mechanism is closed and a vacuum pump has been engaged into the mechanism. Thus, the components building up the mixture start to boil at lower boiling points.

- Water vapor distillation: This system performs the distillation at 100oC. It is used for the separation of some volatile vegetable oils which do not get mixed with water(e.g production of lemon essence)

2) Condensation. In order to seperate the components of gas-gas mixtures, the property of different condensation points of gases is used. For example; Nitrogen and oxygene are obtained, from liquid air since they have different condensation points.

3) ExtractionIf one of the solutes in a solution is dissolved in another solvent more efficiently and this solvent does not mix with the solvent of the solution , the second solvent is added into the solution. After the addition of the second solvent a second phase has been observed. This mixture is poured into a funnel and shaken strongly. During the process the matter in the solution has been carried into the second solvent which has a better solving ability. This process is called Extraction. After the phase seperation has been completed, the second solvent is seperated through the funnel and after the evaporation of the solvent the matter is obtained purely. E.g ; Some organic compounds and metal complexes dissolved in water can be recovered by means of chloroform which is a better solvent for these substances than water.

4) CrystallizationThe solubility in water of the solid

components building up a mixture vary according to the temperature. By making use of this property the solids can be seperated.

Mixtures can be seperated into their components through the differences in solubility.

Figure1.7. Seperation by the difference in solubility

A saturated solution at high temperature of a solid whose solubility varies with the temperature is prepared and allowed to cool down. After a while, the solid precipitates (Figure 1.7.). The substances whose solubility falls with the decrease in temperature, are accumulated as ordinarily geometric shaped solids.This event is named as crystallisation, the solid particles which have a certain geometrical form are called crystals

4) Crystallization

DECOMPOSITION OF THE COMPOUNDS

In the previous chapters we learnt how mixtures can be seperated into their components by using physical methods. Now, we are going to analyse how the compounds are decomposed into the substances

The substances used in casual life and in the industry, are obtained by the chemical decomposition of the compounds. To achieve this, some chemical methods described below are used.

a.Decomposition by Heat Energy

Some substances are decomposed by the exposition to heat. For example; When Mercuryoxide is heated , two different substances namely Mercury and Oxygene are produced.

Mercuryoxide (HgO) → Mercury (Hg) + 1/2 O2(g)

By means of heat energy two different elements or two different compounds can be produced from a single compound. This method is applied very often in the industry

Mercury (Hg) + O2 → Mercuryoxide (HgO)

HEAT

Mercuryoxide is a compound. When heated,It is decomposed into the substances Mercuryand Oxygene

b. Decomposition by electrical energy (Electrolysis)Some substances which can not be decomposed by heat energy can

be decomposed into pure substances through electrical energy.What is electrolysis?Decomposition of a substance through the passage of electric current

is called electrolysis. The solution which is conducting electricity during electrolyse is defined as electrolyte. The metal rod or plate which is dipped into the electrolyte is defined as electrode

For example; Water can be converted into Oxygene and Hydrogene gases through electrolyse. A large beaker is filled up with water. Then, 2 experiment tubes held by the supporting rods are immerged upside down into the water.(Air pass into the tubes must be avoided).

Later, the steel electrodes are connected into the power supply and installed in the tubes. After the power supply is adjusted to 9 V and when the electric current starts to pass through the tubes, there will be no observable changes in the tubes.

During the electrolysis the gas flows and the events are described as follows:H+ ions go to cathode and are reduced in the cathode.4H+ (aq) + 4 e- 2H2(g)Oxygen atom in water is oxidated in the anode2 H2O 4H+ (aq) + O2(g) +4 e-

Net reaction : 2 H2O 2H2(g) + O2(g)

After the electric current has been cut off and sulfuric acid is poured into the water and the current is allowed to pass through the tubes again, gas flow is observed in both tubes. H2 gas comes out of the tube connected to the cathode(- ) ,O2 gas comes out of the tube connected to the anode(+).

Addition of Sulfuricacid(H2SO4) helps the water to conduct the electric current.

• Do the oxygene and hydrogen gases have the same amount of volume after the electrolysis?

• No, they have different volumes. Since , in the electrolysis proces the volume ratio of the hydrogen to oxygen is 2/1.

EXAMPLE After the electrolysis, it is determined that 30 cm3 gas is collected in the cathode. What will be the amount of volume of which gas collected in the anode?SolutionHydrogen is collected in the cathode, oxygen is produced in the anode 2 cm3 hydrogen and 1 cm3 oxygen is produced 30 cm3 hydrogen and X ____________________________________________________ X = (30x1)/2 = 30/2= 15 cm3 oxygen gas is produced

The electrolysis method is often feasible in the industry to obtain a lot of substances purely.

E.g: NaCl(aq) NaOH + Cl2(g). When the product NaOH is exposed to electrolysis, Na metal is produced. Besides metals such as copper, nickel, gold are obtained in a pure form by the electrolysis.

Electrolysis

c. Other Seperation TechniquesConvertion of some pure substances to other pure substances can be performed by other methods except heat and electrical energy.

In nature, metals are abundant in form of oxides. In order to obtain metals in their purest form, the metaloxides are put into reaction with the carbon.

E.g; Iron (III) oxide reacts in the high temperature ovens with the carbon(coke) and iron is produced.

2 Fe2O3 (s) + 3 C(s) 4 Fe (s) + 3 CO2 (g)

Another way of producing purer metals from metaloxides is reacting metal solutions with another metal which is more active.

E.g;When Zink is immerged into the Copper(II) sulfate solution , it is observed that the Zink rod is coated with copper and the color of the solution is changed. Meanwhile the copper is produced in its pure form.CuSO4 (aq) + Zn (s) Cu (s) + ZnSO4 (aq)

c. Other Seperation Techniques