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