Tuesday, September 29, 2009

Chemistry: Chapter 15 - Energy Changes

15.1 Exothermic and Endothermic Changes
Energy cannot be created or destroyed.
However, it can be changed from one form to another.

a) Exothermic Reactions
Reactions that give out heat energy to the surroundings are called exothermic reactions.

Characteristics of exothermic reactions
  1. Heat is liberated and is transferred from the chemicals to the surroundings, and
  2. the temperature of the reaction mixture rises. 
Examples of exothermic reactions include:
  • combustion of fuels
  • rusting of iron
  • corrosion of metals
  • reaction between acid and alkali (neutralisation)
  • respiration
b) Endothermic Reactions
Reaction that absorb heat from the surroundings are called endothermic reactions.

Characteristics of endothermic reaction:
  1. Heat energy is absorbed and is transferred from the surroundings to the reactants, and
  2. the temperature of the reaction mixture falls.
Examples of endothermic reactions include
  • Photosynthesis
  • Action of light on silver bromide in photographic film
  • thermal decomposition
Heat Changes in a Reaction
The amount of energy involved in a reaction is known as the heat change or enthaly change of the reaction.

For exothermic reaction, energy change is negative because it lose energy to the surroundings.
For endothermic reaction, energy change is positice because it gain energy to the surroundings.

15.2 Combustion of Fuels
Fuels give out energy when burnt.

Imcomplete combustion occurs when there is a limited supply of air is used.
The combustion of fuels is an exothermic reaction.

***
Hot, Exothermic
Cold, Endothermic

Chemistry: Chapter 5 - Atomic Structure

5.1 Inside Atons
Atoms are made up of protons, neutrons and electrons.

 Electrons:
  • Carries one negative electric charge -1
  • Has a relative mass of 1/1840
Protons:
  • Carries one positive electric charge +1
  • Has a relative mass of 1
Neutrons:
  • Carries no electric charge
  • Has a relative mass of 1

5.2 The Proton Number and Nucleon Number
Proton number + Nucleon number = Nucleon number

5.3 Isotopes
Isotops are atoms of the same element with the same number of protons but different number of neutrons.

5.4 Arranging Electrons in Atoms
First shell
  • Hold a maximum number of 2 electrons.
  • Is always filled first.
Second, third and sebsequent shells
  • Can hold up to 8 electrons each.
  • Are filled in order. Second shell must be filled before going to third, fourth shell.
The way the electrons are arranged in an atom is called electronic structure or electronic configuration.
The shell that is furthest from the nucleus is called the outer shell or the valence shell.
The electrons in this shell are called valence electrons.

Chemistry: Chapter 2 - Measurement and Experimental Techniques

2.1 Measuring Time
S.I. unit: second (s)
Other units: minute (min), hour (h)
Apparatus used: stopwatch 


2.2 Measuring Temperature
S.I. unit: Kelvin (K)
Other units: degree Celsius (°C)
Apparatus used: Mercury thermomenter, data logger


2.3 Measuring Mass
S.I. unit: kilogram (kg)
Other units: gram (g)
Apparatus used: Electronic balance, beam balance


2.4 Measuring Volume
S.I. unit: cubic metre (m3)
Other units: cubic centimetre (cm3), litre (ℓ), millilitre (ml)
Apparatus used: beaker, measuring cylinder, burette, pipette
Accuracy:
  1. beaker -  used to estimate the volume of a liquid e.g. approximately 100cm3
  2. measuring cylinder - more accurate than a beaker; measures up to the nearest cm3
  3. burette - accurately measures out the volume of a liquid to the nearest ± 0.1cm3
  4. pipette - accurately measures out fixed bolumes of liquids e.g. 20.0cm3




2.5 Collecting Gases and Measuring Volumes of Gases
To collect a gas, we have to take note of the
  • Solubility - how soluble the gas is in water
  • Density - how dense the gas is compared to air
Methods to collect gas:
  • Displacement of water - suitable for gas which are insoluble or slightly soluble in water
  • Downward delivery - suitable for gas that are soluble in water and denser than air
  • Upward delivery - suitable for gas that are soluble in water but less dense that air


Measuring of gas
Using a gas syringe can measure the volume of a gas.


2.6 Determining if a Substance is Pure
A pure substance is made up of only one substances.

a) Solids
A pure solid will melt completely at one temperature.
Impurities affect the melting point of a substance in two ways.
  • The > the amount of inpurities, the lower the melting point.
  • They cause melting to take place over a range of temperatures.
b) Liquids
A pure liquid has an exact and constant boiling point.
Impurities affect the boiling point.
  • Boiling point will increase and will boil over a range of temperatures.
Pressure will affect the boiling point.
  • If pressure ↑, boiling point is raised. 
  • If pressure ↓, boiling point is lowered. 
***
Common gases arranged in terms of Solubility:
Ammonia (Extremely soluble) -> Hydrogen Chloride, Sulphur Dioxide (Very soluble) -> Oxygen (Very slightly soluble) -> Chlorine (Soluble) -> Carbon Dioxide (Slightly soluble) -> Hydrogen (Not soluble)

Common gases arranged in terms of Density
Sulphur Dioxide, Hydrogen Chloride, Chlorine, Carbon Dioxide (Denser) -> Oxygen (Slightly denser) -> Ammonia, Hydrogen (Less dense)

Social Studies: Book 3 Chapter 5 - Bonding Singapore

1 & 2 Introduction + Singapore; Who are we?
Singapore is a multi-ethnic country with people from many different racial, cultural and religious background.
It is important to maintain peace and harmony in Singapore.

3 What are the challenges of a multi-ethnic society?
  1. Managing perceptions of different racial groups
  2. Managing perceptions of different religious groups
  3. Threats from external forces
3.1 + 3.2 Managing perceptios of different racial or religious groups.
Lack of understanding among the racial or religious groups can create suspicion and unhappiness among the people.
Riots and fight may occur between racial or religious groups and this make Singapore unsafe.
Investments from other countries will decrease and economy will be in a bad state.
In whole, Singapore may not be prosperous if people in Singapore behave insensitively.

Examples for racial riot:
1964 riot
PAP wants Malaysia to be a country where everybody would be given equal rights and privilleges -> United Malays National Organisation (UMNO) felt threatened -> Anti-PAP campaign organised by some UMNO leaders spread incorrect information about PAP treating the Malays in Singapore unfairly -> Caused dissatisfaction among Singapore Malays towards PAP

July 1964, Prophet Muhammad's birthday celebration -> Clash between a Chinese policeman and a group of Malay participants during the celebration -> Full-blown race race riots occured over the next few days -> Properties destroyed, people injured -> Broke peace and harmony in Singapore because of irresponsible media reports

Examples for religious riot:
Maria Hertogh riot
In 1940s, a Dutch couple was imprisoned by the Japanese -> They placed their daughter Maria Hertogh under the care of a Malay lady, Aminah -> Maria was raised as a Muslim and got married to a Malay teacher at the age of 13 -> The Dutch couple demanded that Maria be returned to them

A court trial followed and it had much media coverage which provoked much unhappiness among the Muslim community -> Court decided to give custody to the Hertoghs -> The Muslims felt that British legal system was unfair -> Outbreak of riots happened between the Muslims and Christians

3.3 Threats from external forces
Threats from other countries are unpredictable, unexpected and cannot be control.
People in Singapore can be influenced by incorrect ideology through exposure from
  1. teachings, 
  2. internet, 
  3. media, 
  4. travelling to other countries or 
  5. communicating with people from other countries.
They (people) might bring back those ideology and influence other people.
They may attempt to commit acts of terrorism / attempt to brain-wash people into believing their extreme beliefs.
Example would be Jemaah Islamiyah (JI).
They planned to bomb Yishun MRT and when their plots were exposed, other races / religious groups began to get suspicious of the Muslims.
Singapore became unstable. Religious leaders had to come out to clarify their stand.
If not handled properly, Singapore would be unstable and investments would decrease.

4 Can ethnic diversity be managed?
  1. Building a national identity
  2. Safeguarding the interest of the minority groups
  3. Deceloping common space
4.1 Building a national identity
  • a) Multi- racialism
  • b) Common practices
  • c) Bilingualism
a) Multi- racialism
This policy promotes equality among the races, with no special rights granted to any particular racial or religious group. Favouring a certain group of people because of their race or religion is prohibited.

b) Common practices
Actions that Singaporeans carry out together like singing the national anthem, taking the pledge and attending the flag raising ceremony help foster national identity by inculcating loyalty and national pride to Singapore. This gets Singaporeans to see themselves as one people.

National Pledge
We, the citizens of Singapore
pledge ourselves as one united people,
regardless of race, language or religion,
to build a democratic society,
based on justice and equality,
so as to achieve happiness, prosperity and
progress for our nation.

c) Bilingualism
Students were expected to learn English and their own Mother Tongue. With bilingualism, English is used as the language linking the different ethnic groups. Mother Tongue language is used to impart moral values and cultural traditions of each race.

4.2 Safeguarding the interests of the minority groups
  • a) Minority representation
  • b) Self-help groups
a) Minority representation
The policy of minority representation gives minority groups a say in governance.
The Presidential Council of Minority Rights (PCMR) and the Group Representation Constituency (GRC) are two examples of how representation of the minority groups is achieved.

PCMR consists of members from the minority racial and religious groups. It ensures that no racial or religious group is disadvantaged as a result of a law that is passed in Parliment.

GRC ensures that at least one of the candidates in the team contesting in the General Election is from the minority racial communities such as Malay, Indian or Eurasian. GRC system ensures that the minority racial groups are represented in the Parliment. Needs of the minority groups are made known to the government.

b) Self- help groups
Self- help groups play an important role in helping members of their community who are less fortunate. They also give moral support to their members of their own community.
Self help groups in Singapore
  • Chinese Development Assistance Council (CDAC)
  • Singapore Indian Development Association (SINDA)
  • Mendaki
  • Eurasian Association
4.3 Developing common space
Common space refers to the time and place that people come together. This provide opportunities for Singaporeans to interact.
Ways to make Singaporeans interact:
  • a) Events and programmes organised by grassroots organisation
  • b) Opportunities offered by educational institutions
  • c) Common living space provided by public housing
  • d) Activities conducted by Inter-Racial Confidence Circles (IRCCs) and Harmony Circles (HCs)
  • e) Shared experience through National Service
a) Events and programmes organised by grassroots organisation
Organisations such as People's Association (PA) create common space through their wide range of programmes and activities developed to cater to the needs and interests of every Singaporean.

b) Opportunities offered by educational institutions
Daily interaction that take place among students during lessons and school activities provides an opportunity for friendships to be cultivated and strengthened.

Co- Curricular Activities (CCAs) in schools helps to promote closer bonds among youths from all races.

c) Common living space provided by public housing
Ethnic integration policy was introduced to ensure that there is an even distribution of the different races in all the housing estates.

d) Activities conducted by Inter-Racial Confidence Circles (IRCCs) and Harmony Circles (HCs)
IRCCs and HCs were introduced to provide common space to foster greater inter-racial understanding.

e) Shared experience through National Service
NS was introduced in 1967 requires all able-bodied men to serve in the defense of the country. The shared experiences help to strengthen the bond among the men.

5 Why is it important to manage ethnic diversity?
For:
  • Security and peace
  • Economic progress
6 Conclusion
People in Singapore need to be sensitive to one another's needs.
Failure to understand and respect one another's way of life will affect the country.
Managing racial and religious sensitivities will promote tolerance and harmony.
Building a national identity will instill a sense of belonging.
Staying vigilant and active in identifying threats and strengthening social bonds are responsibilities of the Singapore government and its people.

Monday, September 28, 2009

Chemistry: Chapter 1 - Kinetic Particle Theory

1.1 States of Matter
a) Matter is a substance that has mass and occupies space.
b) 3 forms of matter:
  1. Solid
  2. Liquid
  3. Gas
1.2 Kinetic Particle Theory
a) Solid state:
  1. Orderly, closely packed arrangement.
  2. Very strong attractive force between particles.
  3. Very low kinetic energy of particles.
  4. Particles vibrate and rotate about a fixed position.
b) Liquid state:
  1. Disorderly, less closely packed than in a solid arrangement.
  2. Strong attractive force between particles.
  3. Low kinetic energy of particles.
  4. Particles slide over each other.
c) Gaseous state:
  1. Disorderly, very far apart arrangement.
  2. Very weak attractive force between particles.
  3. High kinetic energy of particles.
  4. Particles move about at a great speed.
1.3 Changes of State and the Kinetic Particle Theory
  1. Melting
  2. Freezing
  3. Boiling
  4. Evaporation
  5. Condensation
  6. Sublimation
1. Melting (Solid to Liquid)
a)Solid --------------------------------b)--------------------------------c)Liquid
a) Heat energy that is absorbed is converted to kinetic energy which cause the praticles to vibrate faster about their fixed positions.
b) Particles begin to break away from their fixed positions as they gain enough vibration to overcome the attractive forces between them. (Temperature remains constant throughout that period)
c) Particles are no longer in their fixed positions. They slide over one another. Substance is now a liquid.

2. Freezing (Liquid to Solid)
a)Liquid --------------------------------b)--------------------------------c)Solid
a) Particles give out energy which decreases their kinetic energy and they began to move slowly.
b) Particles no longer have energy to move about which cause them to settle into fixed positions. (Temperature remains the same throughout the period)
c) Particles settle into fixed position and can only vibrate about in their fixed positions. Substance is now a solid.

3. Boiling (Liquid to Gas)
a)Liquid ------------------------------------------------------------------b)Gas
a) Through heating, energy is absorbed and kinetic energy increases causes the particles in a liquid to move faster.
b) Eventually, the particles have enough energy to overcome the forces that is holding them together. Particles can now spread far apart in all directions. Substance is now a gas.
*Temperature remains constant during the boiling process.*

4. Evaporation (Liquid to Gas at a lower boiling point)
a) Evaporation occurs because some particles have enough energy to escape as a gas from the surface of the liquid.

5. Condensation (Gas to Liquid)
a) Condensation occurs because gas particles that evaporate loses energy and move more slowly. Movement of parrticles becomes slow enough for the gas to change into a liquid.

6. Sublimation (Solid to Gas)
a)Sublimation occurs because particles at the surface of the solid have enough energy to break away from the solid and escape as a gas. Example: Dry ice

*Heat absorbed causes particles to move faster. OR Heat given out causes particles to move slower.