Lecture 5 - Effect of Temperature on Volume of a Gas, at constant Pressure

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 8a	https://prezi.com/myiigflss0gg/charless-law/
Figure 8b	https://prezi.com/myiigflss0gg/charless-law/
Figure 8c	www.physics-reference.com

Gases & the effect of temperature and pressure on their volumes:

The particles of the gas are far apart, moving in random directions with their K.E. Therefore, there are large empty spaces between the particles which gives the gases their compressibility. For a fixed volume of gas in a gas jar, the volume of a gas is affected by temperature and pressure.

Case 1: Effect of temperature on Volume of a gas, at Constant Pressure:

Figure 8a:

Figure 8b:

Figure 8a shows a gas jar containing a certain volume of gas V1 at a temperature of T1. The piston exerts a constant pressure P on the Volume V1. The gas is heated to a temperature T2. As the gas is heated, the particles of the gas gain K.E and they start moving with greater velocities and K.E. The start striking/colliding against the piston and to maintain the pressure P, the piston rises; INCREASING the volume of the gas to V2.

Therefore, it can be concluded that gases expand on heating.

Charles’ Law stated this effect as:

“The Volume of a gas is directly proportional to its absolute Temperature, at Constant Pressure.”

Mathematically:

Graphically: Figure 8c

©Tanzeela Zafar Siddiqui

Chapter 15 - Lecture 7 – Homologous series of Alkenes

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 8a	http://www.easychem.com.au/
Figure 8b	http://www.easychem.com.au/
Figure Table 4a	http://www.easychem.com.au/
Figure Table 4b	http://alevelchem.com/
Figure Table 4c	http://www.sciencequiz.net/
Figure Table 4d	http://spmchemistry.onlinetuition.com/

Alkenes:

Alkenes are unsaturated hydrocarbons. They form a homologous series of covalent bonded molecules with the general formula C_nH_2n. That is, each successive member of the series differ by CH₂.’

By unsaturated; it means that 2 adjacent carbon atoms in the chain share a double bond between them.

Example:

Figure 8: Ethene

a) 

Or a more 3D reperesentation b)  

The second bond of the double bond has been formed due to the insufficient amount of hydrogen. In presence of hydrogen, and proper conditions; this bond can easily break to yield a saturated hydrocarbon.

Example:

  

Table 4 shows the physical structures of ethene, propene and butane and iso-butene.

Table 4:

Alkene	Formula	Physical Structure	Isomer(s)
Ethene	C2H4
Propene	C3H6
Butene	C4H8

It is important to note that the double bond may be present anywhere in the carbon chain. 

Referring to Table 4, it is easy to deduce the following conclusions:

1. Melting and boiling point, increases with increase in molecular size.
2. Density increases with increase in molecular size.
3. Viscosity increases with increase in molecular size.

                                                                                       ©Tanzeela Zafar Siddiqui

Chapter 15 - Lecture 9 – Polymerization in Alkenes

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 9	http://pixgood.com

Polymer:

Polymers are synthetic macromolecules, made up of numerous small repeating units called the monomers.  

Addition Polymerization:

Addition polymerization can be defined as the reaction in which, a large number of alkene molecules join together, under a temperature of 200°C and pressure of 2000 atmosphere and oxygen as the reaction initiator, to form a single product called the polymer.

Let us consider the polymerization of ethane to Polyethene. Here, the monomer is a single molecule of ethane. Figure 9 shows the reaction.

Figure 9:

The resulting polymer is NO longer a hydrocarbon like its parent reactants, instead is plastic in nature and has wide range on industrial uses.

Uses of Polyethene:

Polyethene is plastic in nature and has a wide variety of industrial uses. It is used to make:

1. Plastic bags
2. Stretch wraps
3. PVC pipes
4. Containers
5. Toys 

                                                                                       ©Tanzeela Zafar Siddiqui

Chapter 16 - Lecture 1 – Functional Group & Alcohols

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 17a	http://www.studyblue.com
Figure 17b	http://www.ck12.org
Figure Table 6a	http://www.decodedscience.com
Figure Table 6b	http://commons.wikimedia.org/
Figure Table 6c	http://commons.wikimedia.org/
Figure Table 6d	http://www.wikiwand.com/

Functional Groups:

Functional groups are some specific groups of atoms that show a certain characteristic behavior, in their reactions.

In this course, will teach 2 such functional groups:

• Hydroxyl group: -OH

Figure 17a:

• Carboxyl group: -COOH

Figure 17b:

Alcohols:

Alcohols form a homologous series of organic compounds with the hydroxyl functional group or –OH. Each successive member of the series differ by CH₂, and the general formula of the series is C_nH_2n+1OH.

Table 6 shows their physical structures.

Table 6:

Alcohol	Formula	Physical Structure
Methanol	CH3OH
Ethanol	C2H5OH
Propanol	C3H7OH
Butanol	C4H9OH

Chemical properties of Alcohols:

Alcohols undergo 2 types of reactions:

1. Combustion
2. Oxidation

Combustion:

Alcohols are highly flammable and react with oxygen in the presence of heat to form carbon dioxide and water. 

 Oxidation:

Alcohols react with oxygen to oxidize to carboxylic acids.

                                                                                       ©Tanzeela Zafar Siddiqui

Chapter 15 - Lecture 8 – Chemical Properties of Alkenes

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 13a	http://2012books.lardbucket.org/
Figure 13b	https://www.flickr.com/
Figure 14	https://sites.google.com/site/internationalgcsechemistry/
Figure 15	en.wikibooks.org

Chemical Properties of Alkanes:

Alkenes undergo 3 types of chemical reactions. They are:

1. Combustion
2. Addition
3. Polymerization

Combustion:

Alkenes react with oxygen in the presence of heat, to form carbon dioxide and water.

  

Addition Reaction:

Alkenes have a temporary double bond, which breaks to form different types of compounds, depending on the other reactant present.

Example:

• Addition reaction of ethene with Bromine:

Ethene reacts with bromine, to form Dibromoethane.

  

This reaction decolourises bromine water and is used as a test for unsaturation.

Figure 13: 

Test for Unsaturation: (L) Before ; (R) After

If an alkane if added to bromine water, no reaction will take place and bromine water would not be decolourised.

• Addition reaction of ethene with steam:

Ethene reacts with steam, at 300°C temperature and 60 atmosphere pressure, with Phosphoric acid as a catalyst, to form ethanol.

 

Figure 14:

• Addition reaction of ethene with Hydrogen:

Ethene reacts with hydrogen, in the presence of Palladium or Nickel as a catalyst to yield ethane.

  Figure 15:

This process is knows as hydrogenation of alkenes.

                                                                                       ©Tanzeela Zafar Siddiqui