Manufacturing Ethanol

How can you manufacture ethanol?

Methods

§1.  Catalytic addition of steam on Ethene

§2.  Fermentation of Glucose

FERMENTATION OF GLUCOSE SOLUTION

§Glucose solution  on fermentation gives ethanol & carbon dioxide

§Exothermic reaction

§Word equation

   glucose  solution  à ethanol  +  carbon dioxide

§Chemical equation:

§

C6H12O6 [aq] à2CH3CH2OH[aq] + 2CO2 [g]

§Catalyst: Enzyme present in yeast

§Temp range : 25 – 40 degree Celsius

§Optimum temp 35 degree Celsius

§Define Respiration?

§Process by which living things break down food to produce energy.

§What are enzymes?

§Enzymes are proteins or biological catalyst.

OBSERVATIONS DURING FERMENTATION

§BUBBLES OF GAS

§SLIGHT INCREASE IN TEMPERATURE

METHOD 1: FERMENTATION

Disadvantage: Carbon dioxide is a greenhouse gas.

Disadvantage: Growing the crop uses land that could be used for food.

Disadvantage: Batch process.

Advantage: It uses plants and so is a renewable source of ethanol.

METHOD 2: CATALYTIC ADDITION OF STEAM

Disadvantage: Needs high temperatures/pressures.

Disadvantage: Uses a lot of energy.

Disadvantage: Ethene is made from crude oil which will run out.

Advantage: Continuous process.

FREQUENTLY ASKED QUESTIONS

§Why is a two way tap used?

  ..Not to let oxygen/bacteria enter

  ..To remove carbon dioxide

§Why should carbon dioxide produced be removed?

  .. More carbon dioxideà more acidic àenzyme denatures

   .. More carbon dioxide à more pressure

§Conditions where enzymes denatures?

  .. More carbon dioxideà more acidic àenzyme denatures

  .. If concentration of ethanol> 15% àenzyme denatures

  .. If temperature above 40 degree Celsius àenzyme denatures

§Why oxygen should not be allowed to enter?

  .. To prevent aerobic respiration

  .. To prevent oxidation of ethanol to ethanoic acid

§Why is it necessary to add yeast?

  .. Yeast is a catalyst, provides enzymes

§Suggest why the amount of yeast in the mixture increases.

  .. Yeast cells grow or reproduce

§Why is a higher temperature not used in this reaction?

  .. Higher temp kills yeast or denatures enzyme

  .. Hence reduces rate of reactions

§Why does fermentation stops?

  .. Glucose is used up

  .. Enzyme denatured/yeast cells killed

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Posted in: Chemistry

Electric Motor

Parts of the Motor

Armature or rotor

Commutator

Brushes

Axle

Field magnet

DC power supply of some sort

Electric Motor

An electromagnet is the basis of an electric motor
A motor uses magnets to create motion.
Opposites attract and likes repel. Inside an electric motor, these attracting and repelling forces create rotational motion.
A motor consist of two magnets.

Armature

The armature is an electromagnet made by coiling thin wire around two or more poles of a metal core.
The armature has an axle, and the commutator is attached to the axle.
When you run electricity into this electromagnet, it creates a magnetic field in the armature that attracts and repels the magnets in the stater. So the armature spins through 180 degrees.

To keep it spinning, you have to change the poles of the electromagnet.

Commutator and Brushes

Commutator is simply a pair of plates attached to the axle. These plates provide the two connections for the coil of the electromagnet.
Commutator and brushes work together to let current flow to the electromagnet, and also to flip the direction that the electrons are flowing at just the right moment.
The contacts of the commutator are attached to the axle of the electromagnet, so they spin with the magnet. The brushes are just two pieces of springy metal or carbon that make contact with the contacts of the commutator.


Force on a current carrying conductor
The basic requirements are

Magnetic field

Current flowing across the magnetic field
A force is exerted on any current carrying conductor that crosses a magnetic field. The direction of the force depends on the direction of field and the current. This force which every motor make use of is known as motor effect

Fleming's left hand rule

According to Fleming's left hand rule, if the thumb, fore-finger and middle finger of the left hand are stretched perpendicular to each other and if the fore finger represents the direction of magnetic field, the middle finger represents the direction of current, then the thumb represents the direction of force. Fleming's left hand rule is applicable for motors.

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Posted in: Physics

World Population Growth

Natural population increase: When birth rates are higher than death rates, like in stage 2 and 3 of the DTM.

Natural population decrease: When death rates are higher than birth rates, like in stage 5 of the DTM.

A country's population can also be changed by immigration and emigration, but when there is reference to natural change, it only refers to changes caused by birth rates and death rates.

Population explosion or population bomb: The rapid growth in population, this might refer to the rapid growth of the world's population in the lat 100 years, or the rapid population growth of just one country.•Reasons for high birth rates include:
Lack of education about family planning
•Poor availability of contraception and cost of contraception
•Polygamy amongst some ethnic groups
•Primary based economy
•High rate of sexual violence often leading to unwanted pregnancies
•
Reasons for declining death rates include:
Better testing for and treatment of HIV/AIDS
•Improved water supply
•Improved housing (although large numbers still live in informal settlements)
•Better education about diet


South Africa also receives large numbers of migrants from countries like Zimbabwe, Mozambique and Swaziland. This is either because of lack of economic opportunities in these countries and/or political problems.
















What is population structure and population pyramids?
•Population structure is usually shown using a population pyramid. A population pyramid can be drawn up for any area, from a whole continent or country to an individual town, city or village.
•Population structure means the 'make up' or composition of a population. Looking at the population structure of a place shows how the population is divided up between males and females of different age groups.


Young Dependents: The number or the percentage of the population under the age of 16.

Old Dependents: The number or the percentage of the population over the age of 65.

Economically Active: People between the ages of 16 and 65. This is basically the working group.

Obviously some people stay at school past the age of 16, some people retire before 65 and some people work after 65. Also some people between 16 and 65 might unemployed. However, when we are look at entire populations we have to look at averages (the norm).

Dependency Ratio: The ratio between the amount of dependents (old and young) and the economically active.







Key things to know about population pyramids
•The shape of a population pyramid can tell us a lot about an area's population.
•It gives us information about birth and death rates as well as life expectancy.
•A population pyramid tells us how many dependants there are. There are two groups of dependants; young dependants (aged below 15) and elderly dependants (aged over 65).
•Dependants rely upon the economically active for economic support.


•Many LEDCs have a high number of young dependants, whilst many MEDCs have a growing number of elderly dependants.




How do pyramids change over time?
•A population pyramid that is very triangular (eg Mozambique in 2000) shows a population with a high number of young dependants and a low life expectancy.
•
•A population pyramid that has fairly straight sides (more like a barrel) shows a population with a falling birth rate and a rising life expectancy.
•
•Over time, as a country develops, the shape changes from triangular to barrel-like.
• Places with an ageing population and a very low birth rate would have a structure that looks like an upside-down pyramid




Migration: The movement from one location to another location.

There are many different types of migration. The most commonly referred to are:


Rural-urban migration: This is a type of internal migration. It is the movement of people from rural areas

(the countryside) to urban areas (towns and cities). In the settlements topic we look at the causes, problems

and solutions of and to rural-urban migration in Rio de Janeiro.
International Migration: Migration between countries e.g. El Salvador to US.

Temporary Migration: Migration for a limited period, this might only be for a few weeks or even several years.

Permanent Migration: Migration with the intention of staying forever.

Forced Migration: When people are forced to migrate, often because their life is in danger.

Voluntary Migration: When people freely choose to migrate e.g. for better weather or better universities.

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Posted in: Biology,EVM