Teaching+and+Learning+Issues

Teaching and Learning Issues

Year 2011


 * __Term 1 Reflections:__**

As usual, Term 1 was a very short term. However, I learnt a lot in this term and this is the overview of what I have learnt in Term 1: They are:
 * 1) Atomic Structure
 * 2) Periodic Table
 * 3) Ionic Bonding
 * 4) Convalent Bonding


 * __Atomic Structure__**

I learnt about Protons, Neutrons and Electrons and their symbol, relative mass and charge. This table below shows their symbols, relative masses and charges:
 * Particle || Symbol || Relative Mass || Charge ||
 * Proton || p || 1 || 1+ ||
 * Neutron || n || 1 || 0 ||
 * Electron || e - || 1/1836 || 1- ||

I also learnt about Proton Number, Nucleon Number and Isotopes:


 * Proton Number**
 * Also known as Atomic Number
 * Number of Protons in an atom is the proton number
 * Number Electrons in neutral atom is the proton number
 * Atoms of same elements have the same number of protons
 * Atoms of different elements have different number of protons


 * Nucleon Number**
 * Also known as Mass Number
 * Number of protons and neutrons in the nucles of an atom
 * Can be derived by adding number of protons with number of neutrons

This diagram shows where the Symbol of element, Nucleon Number and Atomic Number are in a period table.


 * Isotopes**
 * Atoms of the same element with different number of neutrons


 * __Period Table__**

I learnt that elements are arranged in order of increasing atomic number and are classified according to Groups and Periods.


 * Period:**
 * A horizontal row of elements


 * Groups:**
 * A vertical set of element
 * Numbered from I to VII and then to Group 0. Names of these groups include:
 * = Group Number ||= Group ||
 * = I ||= Alkali Metals ||
 * = II ||= Alkaline Earth Metals ||
 * = VII ||= Halogens ||
 * = 0 ||= Noble Gases ||
 * Elements in same groups have similar chemical properities and thus will undergo same type of chemical reactions
 * This similarity in chemical properities is due to the same number of valence electrons.


 * Pattern in the Periodic Table**

1. Electronic Structure
 * The number of valence electrons = group number
 * For example, Group I Elements, Lithium (Li), Sodium (Na) and Potassium (K) have the same number of valence electrons. (Their electronic configuration proves it: 2.1, 2.8.1 and 2.8.8.1 respectively).
 * As stated above, elements in the same group undergoes same type of chemical reaction. Hence, Group I elements would undergo similar type of chemical reaction.

2. Metals and Non-metals This periodic table clearly shows the dividing 'staircase' line between metals and non-metals.

3. Charge on Ions
 * Charges on ions are closely related to the group number and number of valence electrons
 * Element || Na || Mg || Ai || Si || P || S || Cl || Ar ||
 * Group Number || I || II || III || IV || V || VI || VII || 0 ||
 * Formula of Ion || Na + || Mg 2+ || Al 3+ || - || P 3- || S 2- || Cl - || - ||


 * __Ionic Bonding__**
 * Usually formed between metals and non-metals
 * Defined as: Electrostatic force of attraction between oppositely charged ions in an ionic compound.
 * Name of Ionic Compound is written as: [Cation] [Anion]

Let the elements be Element A and Element B. Element A would electron(s) to form a Cation in order to obtain a stable octet structure. On the other hand, Electron B would gain the electron(s) lost by Element A in order to obtain a stable octet structure. Due to the fact that these ions have opposite charges, they would attract each other and hence form an ionic compound known as [Name of Cation] [Name of Anion], for example, Sodium Chloride. Using Sodium Chloride as an example, The Sodium Ion would be writtern as Na + as it carries an overall positive charge of 1+ due to the loss of 1 electron (From 11 Protons and 11 Electrons to 11 Protons and 10 Electrons) The Chloride ion would be written as Cl - as it carries an overall positive charge of 1- due to the increase of 1 electron (From 17 Protons and 17 Electrons to 17 Protons and 18 Electrons).
 * Formation of Ionic Bonds**

The steps are as follow: For example,
 * 'Dot-and-Cross' Diagrams of Ionic Compounds**
 * 1) Draw the valence electrons of the elements using 'Dot-and-Cross' only.
 * 2) Electrons is/are transferred from the valence shell of the metal to the valence shell of the non-metal.
 * 3) The anion that has gained electrons from the cation will now have two types of electrons - one originally from its valence shell, another one from the cation - differetiated by 'dots' and 'crosses'.
 * 4) Remember to indicate the charges of the ions.

This diagram shows the 'Dot-and-Cross' Diagram for Sodim Chloride.


 * __Covalent Bonding__**
 * Defined as a bond formed by the sharing of a pair of electrons
 * Generally between atoms of non-metals
 * Single Convalent Bond (One pair of shared electrons between two atoms)
 * Double Convalent Bond (Two pair of shared electrons between two atoms)
 * TripleConvalent Bond (Three pair of shared electrons between two atoms)
 * The electron of one atom is represented by a 'cross' while the other electron of another atom is represented by a 'dot'.

For example, This diagram shows the convalent bonding of Methane.


 * __Term 2 Reflections__**

This term's science lesson consisted of Chemistry and Biology. These are the topics I have convered:
 * 1) Acids, Bases & Salts
 * 2) Sexual Reproduction


 * __Acids, Bases & Salts__**


 * Acids:**
 * Defined as a substance which produces hydrogen ions as the only positive ions when it is dissolved in water.


 * Examples of Strong Acid**
 * = Common / Mineral Name ||= Chemical Name ||= Chemical Formula ||
 * = Hydrochloric Acid ||= Hydrogen nitrate ||= HCl ||
 * = Nitric Acid ||= Hydrogen nitrate ||= HNO 3 ||
 * = Sulfuric Acid ||= Hydrogen sulfate ||= H 2 SO 4 ||


 * Examples of Weak Acid**
 * = Name of Acid ||= Source ||
 * = Acetic Acid (Ethanoic Acid) ||= Vinegar ||
 * = Citric Acid ||= Lemmon ||
 * = Tartaric Acid ||= Grape ||


 * Strength of an acid depends on its degree of dissociation / ionisation in water to form hydrogen ions.


 * Strong Acid**
 * Ionises / dissociates completely in water to produce hydrogen ion
 * No molecules left
 * Solution contains a high concentration of ions
 * Good electrical conductor


 * Weak Acid**
 * Ionises / dissociates incompletely / partially in water to produce few hydrogen ions
 * Most of the acid molecules remain as molecules
 * Solution contains a low concentation of ions
 * Poor electrical conductor


 * Importance of Water for acidity**
 * Pure acids exist as molecules instead of ions
 * Pure acids do not behavve as acids because properties of acids are due to the prescence of hydrogen ions
 * Acid can only behave as acids when they are dissolved in water

When dissolved in water it forms a colourless solution. This solutions have the following properities:
 * Properties of Acids**
 * Sour taste
 * Change the colour of indicators (e.g. turn blue litmus paper red)
 * Contain hydrogen ions
 * Conduct electrcity
 * React with metals, carbonates and bases

Observations: Examples: Zinc sulfate, Potassium nitrate and Sodium chloride.
 * Reactions with Metals**
 * Acids react with metals to procude a salt and hydrogen
 * Acid + Metal --> Salt + Hydrogen
 * Effervescence observed
 * Colourless, odourless gas evolved which extingused a lighted wooden splint with a 'pop sound'
 * Solid reduced in size when in excess.
 * Solid dissolves to form a colourless solution
 * Heat is liberated

Observations:
 * Reactions with Carbonate**
 * Acids react with carbonates to produce a salf, carbon dioxide and water
 * Acid + Carbonate --> Salt + Carbon Dioxide + Water
 * Effervescence observed
 * Colourless, odourless gas evolved with reacts with calcium hydroxide to form a white precipitate
 * Solid dissolved to form a colourless solution

Observations:
 * Reactions With Bases**
 * Acids react with bases (metal oxides and metal hydroxides) to produce a salt and water.
 * Acid + Base --> Salt + Water
 * Solid dissolves to form a colourless solution
 * Heat is evolved
 * No visible change


 * Use of Acids**
 * Sulfuric acids is used to make detergents, fertilisers and car batteries
 * Ethanoic acid is used to preserve food


 * Colour Change of Indicators**
 * = Indicators ||= Observations ||
 * = Litmius Paper ||= * An acid turns blue litmus paper red ||
 * = Methyl Orange ||= * Used to identify strong acids
 * Colour change at pH 4
 * Strong acid turns methyl orange red
 * Alkali turn methyl orange yellow ||
 * = Phenolphtalein ||= * Used to identify strong alkalis
 * Colour Change at pH 9
 * Strong alkali turn phenolphthalein pink
 * Phenolphthalein remains colourless in acid ||
 * = Universal Indicator ||= * Remains green in neutral solutions
 * Turns red in strong acids
 * Turns violet in strong alkali ||

The higher the concentration of the hydrogen ion, the lower the pH value
 * pH Value**
 * Depends on the concentration of acid/base and degree of dissociation
 * Used to measure strength of an acid


 * Bases and Alkalis**


 * Bases**
 * Defined as the oxides or hydroxides of metal that reacts with an acid to form a salt and water only.


 * Alkalis**
 * Defned as a metal hydroxide which is soluable in water and produces hydroxide ions in water.
 * All alkalis are bases but not all bases are alkalis


 * Examples**
 * Insoluable bases include copper (II) oxide, aluminium oxide and zinc oxide.
 * Soluable base / alkali include sodium oxide, potassium oxide and ammonium hydroxide.


 * Strength of an Alkali**
 * The strength of an alkali deends on its degree of dissociation / ionisation in water to form hydroxide ions.
 * The properities of alkalis are due to the hydroxide ions


 * Strong Alkali**
 * A strong alkali is an alkali which ionises / dissociates completely in water to produce hydroxide ions
 * There are no molecules left
 * The common strong alkalis are sodium hydroxide and potassium hydroxide.


 * Weak Alkali**
 * A weak alkali is an alkali which ionises / dissociates incompletely in water to produce few hydroxide ions
 * Most of the alkali molecules remain as molecules


 * Properities of Bases**
 * Alkalis have a soapy feel and a bitter taste
 * Alkalis can change the colour of indicators (turn red litmus paper blue)
 * Bases can react with acids to form salt and water only (Neutralisation)


 * Reactions of Bases**
 * Base + Acid --> Salt + Water
 * Bases can react with ammonium salts to form salt, ammonia and water (Base + Ammonium Salt --> Salt + Ammonia + Water)


 * Uses of Bases and Alkalis**
 * Magnesium Hydroxide: Used in toothpaste to neutralised the acids on our teeth produces by bacteria
 * Ammonia Solution: Used for cleaning glass windows


 * __Sexual Reproduction__**


 * Sexual Reproduction in Man**

Sexual Reproduction
 * Sexual reproduction is the biological process of forming a new individual through the fusion of two very specalised cells known as gametes
 * The fusion process is also known as feterlisation
 * Gametes are the egg/ovum or the sperm

Asexual Reproduction
 * Asexual reproduction is the biological processo f forming a new individual from a single parent without the fusion of gametes.

Secondary Sexual Characteristics:
 * Puberty**
 * Developmental process where a child's body maturres into an adult body where he or she is now capable of reproduction
 * Process triggered by the release of hormones from the brain to the gonads (Testes for males, Ovaries for females)
 * Gonands would then begin secreting sex hormones, such as testosterone and oestrogen
 * Sperm would then be produced while egges would begin maturing
 * Secondary sexual characteristics would also begin to develop
 * = Males ||= Females ||
 * = Onset at 11 to 15 Years Old ||= Onset at age 9 to 13 Years Old ||
 * = Predominant growth of facial, underarm, chest, abdominal and pubic hair ||= Predominant growth of facial, underarm, chest, abdominal and pubic hair ||
 * = Broadening of chest and shoulder ||= Broadening of hips ||
 * = Enlargement of penis and testes ||= Enlargement of breasts ||
 * = Sebaceous and sweat glands become more active, leading to acne in severe cases ||= Sebaceous and sweat glands become more active, leading to acne in severe cases ||
 * = Deepening of voice as larynx enlarges ||=  ||
 * = Increased muscle mass and strength; increase in height ||=  ||


 * Anatomy and Function of the Human Reproductive System**

Male Reproductive System bulbourethral or Cowper's glands || * Production of seminal fluid (Alkaline to neutralise acidity in female reproductive tract, activates sperms by causing them to swim freely, nourish sperms with nutrients) ||
 * Structure || Function ||
 * 1. Testes || * Production of male gametes (sperm)
 * Production of male sex hormones ||
 * 2. Epididymis || * Temporary storage of sperm
 * Muscles in epididymis contract to ejaculate sperms ||
 * 3. Sperm duct || * Transport sperm from the epididymis to the urethra ||
 * 4. Glands (Seminal vesicles, prostate gland,
 * 5. Penis || * Insertion into vagina when erected ||

Physiology of Erection and Ejaculation
 * 1) Arterioles bringing blood to the penis and its erectile tissue dilate
 * 2) Blood begin entering the erectile tissues and fill up the blood spaces in the erectile tissue
 * 3) Penis becomes turgid
 * 4) Epididymis contracts
 * 5) Semen is released


 * The Female Reproductive System**

3a. Endometrium (Uterine Lining) ||= * Muscular and elastic, to push foetus out during birth
 * = Structure ||= Function OR Adaptation ||
 * = 1. Ovary ||= * Production of female gametes (ova) and release of mature ovum
 * Production of female sex hormones ||
 * = 2. Oviduct ||= * Deliver mature ovum from ovary to uterus
 * Beating of cilia to move ovum along oviduct
 * Muscular, strong contractions ||
 * = 3. Uterus (or womb)
 * Soft and smooth endometrium prepares for implantation of fertilised egg ||


 * Structural Adaptation of the Male and Female Gametes**

Sperm: To dilver the male's genes to the egg by fertilising it Ovum: To contain the female's genes and to be fertilised by one sperm

Structural adaptation of the sperm cell:
 * = Structure ||= Adaptation ||
 * = 1. Acrosome ||= * Contains acrosin, a protease enzyme, released by the sperm upon contact with the membrane surrounding the ovum
 * Acrosin aids in digesting away this membrane, known as zona pellucida, which surrounds the cell membrane of the ovum. This allows the sperm's cell membrane to eventually fuse with that of the ovum ||
 * = 2 Nucleus ||= * Contains the male genes that will eventually be combined with the female genes in the ovum during fertilisation ||
 * = 3. Minimal cytoplasm ||= * The thinner cytoplasm reduces resistance to the motion of the sperm towards the ovum ||
 * = 4. Middle piece ||= * The middle piece consists of a spiral mitochondrion
 * The mitochondrion supplies energy for the beating of the tail ||
 * = 5. Tail (or flagellum) ||= * The tail beats to propel the sperm towards the ovum ||

Differences between the Sperm and the Ovum
 * = Feature ||= Sperm ||= Ovum ||
 * = 1. Shape ||= * 3 distinct regions: Head, middle piece and tail ||= * Spherical ||
 * = 2. Size ||= * Small, head about 2.5 micrometer, full length about 40 micrometer ||= * Large, about 120 micrometer ||
 * = 3. Numbers ||= * 200 to 500 million sperm cells per seminal discharge ||= * One released on an average of about 28 days ||
 * = 4. Motility ||= * Motile
 * Move by beating of flagella ||= * Non motile
 * Swept along oviduct by cilia lining the walls of the oviduct or by contraction of the muscles in the oviduct wall ||
 * = 5. Lifespan ||= * Die rapidy in open air
 * Die within a few hours in the vagina
 * Lifespan of 2 to 5 days in the oviduct ||= * Only 24 hours if fertilised ||


 * The Menstrual Cycle**
 * Refers to a cycle of physiological change that occur in a female woman's reproductive system
 * Each cycle last for about 28 days
 * Might also range between 14 to 25 days depending on stress levels and lifestyles
 * Under direct control of hormoes (progesterone and oestrogen)

Day 1 to Day 14 - Menstruation-Follicular Phase
 * Day 1 is marked by menstrual bleeding/menstruation
 * Discharge of blood and breakdown product of the thick uterine lining (menses) from the vagina
 * Discharge might persist up to Day 7
 * Oestrogen is secereted in increasing concentration
 * Breakdown of uterine lining stops and menstrual bleeding ceases due to the relatively higher concentration of oestrogen concentration
 * Uterine lining reaches a minimum thickness by Day 7
 * Under the influence of a complex interplay of hormones, a new ovum begins to mature
 * The uterine lining begins to thickens after Day 7.

Day 14 - Ovulation
 * Oestrogen level reaches a maximum by Day 14
 * A sudden increase in luteinizing hormone leel triggers the release of mature ovum from one of the ovaries
 * Ovum then begins to pass through the oviduct to the uterus
 * Upon release from the ovary, the mature ovum may only survive for 24 hours or less if it is not fertilised

Day 14 to 28 - Luteal Phase
 * After ovulation, the ovaries begin to produce high concentrations of progesterone
 * This would encourage the growth of the uterine lining, which causes more bloog capillaries in the endometrial tissues
 * The uterine lining would then become thicker, reaching its maximum thickness.
 * This thickness is maintained by the relatively high concentrations of progesterone
 * This growth of the uterine lining is to prepare the implantation of the fertilised egg
 * If implantation does not occur, the production of progesterone and oestrogen will fall sharply, resulting in the breakdown of the uterine wall
 * The unfertilised egg, together with the fragments of endometrial tissues, blood capillaries and blood would be removed through menstrual bleeding, thus starting a new cycle


 * Copulation & Fertilisation**
 * Copulation refers to the process of placing the male genitals into the female reproductive tract
 * Fertilisation refers to the fusion of the male and female gametes, restoring the diploid number of chromosomes in the zygote

Chromosomes
 * Structures found in the nucleus of most body cells prior to cell division
 * Contain hereditary information in the form of genes


 * Post-fertilisation**
 * The formation of the zygote would be followed by several cycles of cell division of the zygote
 * The zygote would eventually form a ball of undifferentiated cells
 * This ball of cells would thenbein to form simple tissue layers (embryo)
 * The embryo would then to continue to develop and form distinguishable organs (foetus)

The foetus would be protected by several structures:

Amniotic Sac and Amniotic Fluid
 * The amniotic sac encloses the foetus in the amniotic cavity, which contains the amniotic fluid

Functions of Amniotic Fluid
 * Supports and cushions the foetus while in the uterus
 * Absorbs shock
 * Protects the foetus against physical injuries as it cannot be compressed
 * Acts as a lubricant and reduces friction in the birth canal during birth
 * Allow foetus to move more easily during gestation

The Placenta
 * Fetal blood system must be separated from the maternal's system as the two systems are functioning at different blood pressure
 * The foetus' blood type might also differ from the mother's blood type. Mixing of bloods of different blood type may cause agglutination.

Functions of the Plancenta
 * Allows oxygen and nutrient (glucose, amino acids and mineral salts) to diffuse from the mother's blood into the foetus' blood
 * Allows excretory products (urea and carbon dioxide) to diffuse from the foetus' blood into the mother's blood
 * Allow antibodies to diffuse from the mother's blood into the foetus' blood
 * Produces progesterone which maintains the uterine lining during pregnancy

The Umbilical Cord
 * Attaches foetus to the Placenta
 * Contains 2 umbilical arteries and 1 umbilical vein

Functions of the Umbilical Cord
 * Transports deoxygenated blood and metabolic wastes products from foetus to the Placenta through its umbilical arteries
 * Transports oxygenated blood, nutrients (gulcose, amino acids) and other useful substanes (antibodies, hormones) from the Placenta to the foetus through its umbilical vein.


 * Sexually Transmitted Diseases (STDs)**
 * Diseases transmitted through sexual intercourse
 * Caused by bacterial or viruses
 * Affect the reprodutive system and/or other parts of the body
 * May not show visible signs or symptoms and thus pass on the disease unknowingly to their partners
 * Fatal infections


 * = Name ||= Cause ||= Trasmission ||= Symptoms ||= Effects ||= Treatment ||
 * = Gonorrhea ||= Spherical bacteria ||= * Sexual intercourse
 * From infected mother to baby during birth
 * Sharing of injection needles with infected person
 * Tranfusion of infected blood ||= * Painful sensation during urination
 * Discharge of pus from vagina or penis ||= * Infection of the urethra
 * Infection of the oviducts which may lead to infertility
 * Ectopic Pregnancy
 * Infection of newborn's eye which may lead to blindness ||= * Antibiotics, but some strains of the bacteria have developed drug resistance ||
 * = Syphilis ||= Spiral bacteria ||~  ||= * Painless sores on penis, vagina, cervix or mouth
 * Non-itchy skin rashes ||= * Deformed joints
 * Paralysis
 * Insanity
 * Death
 * Newborn may be deaf or with abnormal teeth and bone ||= * Antibodies only effective at early stage ||
 * = Acquired Immune Deficiency Syndrome (AIDS) ||= Human Immunodeficiency Virus (HIV) ||=  ||= * Weaken immune system
 * Loss of appetite and weight
 * Diarrohea
 * Night sweat
 * Flu-like symptoms ||= * Immune System fails
 * Pneumonia
 * Tubercolosis
 * Brain infection
 * Kaposi sarcoma ||= * Currently no cure. Cocktail of antiretroviral drugs is used to prolong lifespan and improve quality of lives of patients. ||

Prevention of STDs
 * Pratice monogamy or abstinence
 * Wear a condom during sexual intercourse
 * Do not abuse drugs
 * Do not share instruments that may break the skin
 * Go to reliable practitioners who used sterilized instruments


 * Issues on Sex**

Family Planning
 * Process of planning how when and how many children to have
 * Uses birth control methods for the implementation of the plans
 * Poor faily planning many lead to unwanted or unplanned pregnancies. Consequences includes financial cost of raising the child and struggling with career and family commitments.

Premartial Sex
 * Refers to sexual intercourse between a couple who are not married

Birth Control
 * Prevent unwanted pregnancy
 * Family may have already enough children
 * Reduce risk of being infected with STDs

Options for Birth Control
 * Some options are temporarily while some options are permanent

Temporarily Methods
 * Rhythm method
 * Withdrawal method
 * Spermicide
 * Condom
 * Diaphragm
 * Hormonal pill
 * Hormonal injection

Permanent Methods
 * Ligation
 * Vasectomy

Facilitated Reproduction

Couples who opt for facilitated reproduction due to various physical reasons
 * Ovaries may be defective
 * Oviduts may be blocked
 * Sperms may be too weak
 * Uterus/Cervix too weak to sustain a pregnancy

Types of Facilitated Reproduction
 * In-virto Fertilisation
 * In-situ Fertilisation
 * Surrogate Mother


 * __Term 3 Reflections:__**

In this term, I learnt about:
 * 1) Ecosystem (Biology)
 * 2) Optics - Reflection (Physics)


 * __Ecosystem__**


 * Introduction**
 * Habitat is where an organism lives
 * Population is a group of ogranisms of the same species living in a particular habitat
 * Community refers to all populations of organism living and interacting with one another in a particular habitat

Ecosystem
 * A community and its abiotic environment
 * Organisms are interdependent
 * Energy is transferred from one organism to another mainly through feedin
 * The Sun is the main source of energy for Planet Earth
 * Solar energy from the Sun is aborbed by the plants and are passed on to other organisms as chemical energy
 * Most of this energy is eventually lost as heat
 * Energy flow is non-cyclical


 * Abiotic Environment**
 * = Factor ||= Examples of how factor influences life ||
 * = Temperature ||= Affects the proper functioning of enzymes. Extreme temperatures and pH disrupts the hydrophobic, hydrophilic and ionic interactions in enzymes, causing them to lose their shape and functionality. ||
 * = pH ||=  ||
 * = Oxygen content ||= Oxygen is required for aerobic respiration. Lack of oxygen slows down metabolism. ||
 * = Humidity ||= High humidity slows down the rate of transpiration in plants but is also critical to the survival of epiphytes and organisms living in arid places. ||
 * = Amount of water ||= Affects number and locations of flora and fauna. Dependent on rain pattern ||
 * = Wave action ||= Prevents marine organisms from settling down and feeding. ||
 * = Wind speed ||= High wind speed may break the stems of certain plant species and may dissipate humidity. ||
 * = Light intensity ||= Low light intensity retards plant growth, but high light intensity may bleach chlorophyll and impairs the ability of plants to photosynthesize. ||
 * = Salinity ||= Affects osmotic balance in many aquatic animals and coastal plant species. ||
 * = Type of substratum ||= Clayey, sandy or rocky substratum influences ability of plants and sessile organisms to anchor themselves. ||


 * Biotic Environment**
 * Arises from interaction between organisms
 * Outcome of these interactions may increase (+), decrease (-) or makes no difference (0) to the fitness, or the ability to grow, survive and reproduce successfully of either or both organisms.


 * = Interation ||= Organism A ||= Organism B ||= Example ||
 * = Mutualism ||= + ||= + ||= Lichen ||
 * = Commensalism ||= + ||= 0 ||= Remora fish and Shark ||
 * = Explotative Relationships (Predation, Parasitism, Herbivory) ||= + ||= - ||= Snake and Rabbit ||
 * = Competition ||= - ||= - ||= Snake and Eagle have similar feeding habits ||
 * = Ammensalism ||= - ||= 0 ||=  ||

Biotic influences may limit the distribution and abundance of organisms and are hence crucial elements that shape an ecosystem.


 * Feeding Relationship**

A food chain is a sequence of organisms, starting with a photosynthesising organism through which energy is passed as one organism is eaten by the next in the sequence.
 * Pondweeds --> Mayfly Larvar --> Stickleback --> Kingfisher --> Sparrow Hawk --> Decomposers

Many foodchains can be interconnected to form a more complex food web
 * A food web comprises of interlinked food chains involving organisms from the same ecosystem



In foodwebs
 * The bottom consists of autotrophic organims. They are also the primary producers in the ecosystem
 * Each level may be occupied by more than one organism
 * Each organism may occupy more than one level in a food web
 * Organisms are decomposed by decomposers or saprotrophic organisms when they die.

Terms used in the description of food web: Note: Since autotrophs are the only organisms that are capable of harnessing energy directly from their environment, they are also primary producers because all other organisms in the respective ecosystems depend on them for energy. Essentially all primary producers are autotrophic but not all autotrophs are primary producers (albeit this is extremely unlikely because almost all the time, consumers have evolved to exploit autotrophic organisms). ||=  || Note: All consumers must be heterotrophic, and all heterotrophs must be consumers. While this is true, the terms “heterotroph” and “consumer” have very different meanings and should be used in the appropriate context ||=  ||
 * = Terms ||= Definition ||= Example ||
 * = Autotrophs ||= Autotrophs are organisms that are capable of synthesizing organic molecules (such as glucose) using inorganic molecules (such as carbon dioxide) and energy derived from either sunlight (photoautotrophs) or other inorganic molecules (such as hydrogen sulphide) (chemoautotrophs). ||= Green algae, Pond weeds ||
 * = Primary Producers ||= Primary producers are autotrophic organisms that supply energy to all other organisms in the food chain/ food web.
 * = Heterotrophs ||= Heterotrophs are organisms which use organic molecules both as a source of carbon and as a source of energy, and acquire these molecules by feeding on other organisms. ||= Common pond snail, stickleback, sparrow hawk ||
 * = Consumers ||= Consumers are heterotrophic organisms that depend ultimately on the producers as energy sources.
 * = Herbivores ||= Organisms with a strict diet consisting of plant matter only. ||= Mosquito larvae ||
 * = Primary Consumers ||= Organisms that feed directly on producers. ||=  ||
 * = Secondary Consumers ||= Consumers which feed on the herbivore/primary consumer ||= Water flea, mayfly larvae ||
 * = Tertiary consumers ||= Consumers which feed on the secondary consumer ||= Stickleback ||
 * = Carnivores ||= Organisms with a strict diet consisting only of other animals. The dominant consumer in an ecosystem is usually a carnivore. ||= Sparrow hawk, kingfisher ||
 * = Omnivores ||= Organisms that feed on both plant matter and on other animals. ||=  ||
 * = Decomposers ||= Organisms which release enzymes to break down large molecules in dead organic matter into smaller ones which can then be recycled. ||= Bacteria, fungi ||

> - As species go extinct, food webs become destabilized and an entire ecosystem may collapse.- This in turn affects mankind
 * Conservation**
 * Man exploits the natural environment for fossil fuel, wood and other forms of natural resources. Through this process, man has greatly altered natural habitats.
 * As highlighted earlier, ecosystems are in a delicate state of balance. Disturbances to this natural balance may result in increased rates of species extinction as organisms are unable to adapt fast enough to rapid changes.

Therefore, conservation is important for the following reasons:
 * 1) Prevent extinction of plant and animal species
 * 2) Maintain a stable and balanced ecosystem, prevents disruption of natural cycles such as water and carbon cycles; also prevents global warming
 * 3) Maintain large gene pool, preserve favourable genes; helps to improve agricultural produce or crops with better resistance to diseases
 * 4) Conserve marine life as a food source
 * 5) Scientific value – study of evolution
 * 6) Nature appreciation – recreational purposes such as hiking, fishing, skiing
 * 7) Maintain biodiversity – economical (rice, pineapple and banana are food plants developed from rainforest plants), medical (Quinine, an anti-malarial drug is found from the bark of Cinchona), industrial (latex is tapped from rubber trees and used to make tyres) purposes


 * Effects of selective addition/removal of species**
 * The dynamic flow of energy, nutrients and intricate interactions between organisms and their environment establishes a state of delicate balance in the ecosystem, which changes only gradually over time.
 * This state of balance gives stability and self-sustainability to an ecosystem.
 * Such stability and self-sustainability requires:

> 3) A continuous circulation of matter between the biotic and abiotic components of an
 * 1) A constant input of energy.2) Presence of producers which are able to harness this source of energy, converting it into chemical energy required to power the rest of the food chain.
 * The stability of an ecosystem may be distrupted with the alteration of any of the above requirements.
 * An example of addition or removal of species from a habitat would be a biological pest control.


 * __Carbon Cycle__**


 * __ ﻿ __**
 * Carbon is found in all ecosystems as all living things are made up of carbon compounds
 * The atmosphere is the main source of carbon for all ecosystems

Carbon exchanges between the atmosphere and the biosphere occur via the following processes


 * Photosynthesis**
 * Carbon is absorbed in the form of CO2 and converted to glucose which may then be used for respiration and for the building of protoplasm in plants.
 * Plants are then consumed by primary consumers and the carbon is then transferred into the body tissues of animals.
 * Through successive feeding, carbon compounds move up the trophic levels in the ecosystem.


 * Respiration**
 * Plants and animals respire, converting glucose into CO2 which is released back into the atmosphere.


 * Excretion and Egestion**
 * Microorganism ferment carbon-rich food in the stomachs of cattle and releases carbon back into the atmosphere in the form of natural gas or methane, CH4.
 * Undigested food removed as faeces contains much of the carbon that was initially ingested.


 * Decomposition**
 * As dead organisms decay and become decomposed they release carbon dioxide into the atmosphere.


 * Destruction of vegetation**
 * Bush fires or slash-and-burn agriculture may burn away large areas of forests which release large quantity of carbon dioxide from plant material.


 * Sedimentation and Mineralization**
 * When organisms die and are very quickly buried, they do not undergo decomposition, but may be compacted by layers of mud and rock. Overtime these dead organisms may become fossil fuels. Much of the carbon in the tissues of these organisms thus becomes stored in the form of fossil fuel.
 * Carbon dioxide from the atmosphere dissolves in the sea in the form of bicarbonate ions or carbonate ions. Marine organisms use carbonate ions to produce hard shells and support structures. When these organisms die, their hard shells will settle down to the bottom of the ocean (sedimentation) and become compacted. This becomes limestone (calcium carbonate) over a long period of time, storing the carbon in limestone.


 * Dissolution (Chemical weathering)**
 * Precipitation may dissolve limestone structures, thus releasing the carbonate ions back into rivers and streams.
 * Carbon exchanges between atmosphere and biosphere.


 * Burning of fossil fuel (Combustion)**
 * When fossil fuel is removed from deep underground, and burnt for energy, the carbon in the fossil fuel is released as large quantities of carbon dioxide.


 * __Optics - Reflection__**


 * Light is the form of energy that enters our eyes and enables us to see things
 * It moves at 3 x 10 8 m/s
 * Light can be obtained from a luminous source or reflected off a non-luminous source into our eyes
 * The wave-particle duality of light shows that light is both a wave and a particle but we approximate that light travels in a straight line.


 * Terms**
 * Incident ray: The ray of light that strikes the surface
 * Reflected ray: The ray of light that is reflected off a surface
 * Normal: An imaginary line that is perpendicular to the surface at the point of incidence
 * Point of indicence: The point where the incident ray strikes the surface
 * Angle of incidence: The angle between the incident ray and the normal
 * Angle of reflection: The angle between the reflected ray and the normal.

**Law of Reflection**


 * 1) The incident ray, the reflected ray and the normal at the point of incidence all lies in the same plane.
 * 2) The angle of incidence is equal to the angle of reflection

**Image Characteristics of a Mirror**

The image formed in a plane mirror
 * Has the same size as the obeject
 * Is as far as behind the mirror as the object is in front of the mirror
 * Has the same orientation as the object
 * Is laterally inverted
 * Is virtual

Virtual images cannot be captured on a screen because no actual light rays meet at the image position.

|| **mirror type ** (inside //F//) || on the opposite side of the mirror as the object || **virtual ** || **same as object ** || larger than object (magnified) || (outside //F//) || on the same side of the mirror as the object || real || opposite of object || **larger than object ** **(magnified) ** ||  image distance <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">(outside //F//) || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">on the same side of the mirror as the object ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">real ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">opposite of object ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">same as object ** || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">(outside //F//) || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">on the same side of the mirror as the object ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">real ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">opposite of object ** || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">smaller than object <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">(diminished) || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">(diminished) ** ||
 * **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">object position ** |||||||| **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">image ** ||
 * ^  || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">position ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">type ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">orientation ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">size ** ||
 * <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">plane || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">anywhere* || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">as far behind the mirror as the object is in front of it || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">virtual || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">same as object || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">same as object ||
 * <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">concave || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">near mirror*
 * ^  || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">exactly at //F// || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">at infinity || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">- || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">- || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">- ||
 * ^  || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">object distance less than image distance
 * ^  || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">object distance is equal to
 * ^  || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">object distance* greater than image distance
 * <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">convex || <span style="display: block; font-family: 'Arial','sans-serif'; font-size: 14.6667px; text-align: center;">anywhere* || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">on the opposite side of the mirror as the object ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">virtual ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">same as object ** || **<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">smaller than object **

Bold represented tested in Exams*


 * Ray Diagram Drawing for Reflection**

<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px; line-height: 0px; overflow: hidden;"> __<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">Step 1 __<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">: Draw image I in the mirror. __<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">Step 2 __<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">: Draw 2 rays from the image to the eye. __<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">Step 3 __<span style="font-family: 'Arial','sans-serif'; font-size: 14.6667px;">: Draw 2 rays from the object to the points of reflected rays on mirror.(Use solid lines)

<span style="display: block; font-family: 'Comic Sans MS',cursive; font-size: 150%; text-align: center;">Year 2010


 * __Term 1 Reflections:__**

Term 1 passed very quickly and I learnt alot of things in this term. Now I would write the overview of what I learnt in Term 1.

They are: 1. The types of Symbols used in Science 2. The anatomy of the Bunsen burner 3. How to operate a Bunsen burner (steps on how to use a Bunsen burner) 4. Safety precautions taken in the lab & Dos and Don'ts in the lab 5. Name and functions of apparatus


 * __The types of Symbols used in Science__**

For us, we learnt a couple of symbols which are usually used in Science. They are the Corrosive Substances, Flammable Substances, Radioactive Substances, Explosive Substances and the Harmful Substances. An example of the symbols are below:

Explosive Symbol Corrosive Symbol Flammable Symbol Poisonous Symbol Radioactive Symbol




 * __The anatomy of the Bunsen burner__**

The anatomy of the Bunsen burner is rather simple. There are the: 1. Barrel (adjust the level of the flame) 2. Base (to support the burner) 3. Air Hole (to allow air to enter the burner) 4. Collar (to adjust the amount of air entering the burner) 5. Gas Tap (to allow the gas to enter the burner) 6. Gas Jet (to allow the gas to be burnt)


 * __How to operate a Bunsen burner__**

1st: Ensure that the air holes of the Bunsen burner are closed. 2nd: Hold the lighter directly above the mouth of the Bunsen burner with one hand and turn open the Gas Tap with the other hand. 3rd: Light the Bunsen burner. 4th: Turn the air holes slowly till you have a non-luminous flame.


 * __Saftey Precautions taken in the lab & Dos and Don'ts in the lab__**

Whenever we are heating or boiling substances, we should always wear a safety goggle unless we are already wearing spectacles. Do not look at the mouth of the test tube whenever we are heating substances in a test tube. Never point the mouth of the test tube to our friends when we are heating a liquid in a test tube as the liquid in the test tube might squirt out. Instead, we should point the mouth of the test tube to an empty area. Do not run or behave roughly in the lab. Do not place our notes beside the Bunsen burner whenever we are heating substances. Do not hold a test tube with our bare hands when we are heating substances. Move the test tube continuously in the flame when we are heating substances in a test tube. Do not eat in the science lab. Inform the teacher in charge immediately whenever we hurt ourselves, spill substances or break any equipments. Do not place apparatus at the edge of the bench. Do not pour substances into the sink without our teacher's permission. Do not throw matches into the sink, instead, we should throw them into the rubbish bin located at the corner of the benches.


 * __Name and Functions of the apparatus__**

Thistle Funnel - For transferring liquid into flasks. Retort Stand - For supporting apparatus during experiments. Tripod Stand - For supporting apparatus during heating. Filter Funnel - For separating an insoluble solid from a liquid with the help of a filter paper. Bell Jar - For separating an experimental set-up with the outside environment. Beaker- For collecting liquids or containing chemicals. Flat-bottomed Flask - For containing chemicals when preparing gases if the process does not requires heating. Test Tube - For containing or heating small amount of substances. Measuring Cylinder - For measuring a volume of liquid to an accuracy of 0.5 cm3. Glass Jar - For collecting gases. Round-bottomed Flask - For containing chemicals when preparing gases if the process requires heating. Crucible- For heating a solid over a flame directly. It is usually used with a clay triangle. Evaporating Dish - For evaporating liquid from a solid over direct heating. Water Trough - For containing water when collecting gases. Conical Flask - For containing chemicals or collecting liquids.

The name and functions of the apparatus really caught my interest as I did not know the names of the apparatus despite knowing how they look like. I learnt a lot in this topic, not only learning about both the name and functions of the apparatus, but also learn how to use them when conducting experiments.

I also found the topic, 'The Name and Functions of the Apparatus' the most difficult to learn. I had to memorize 15 names and functions for the test, not forgetting how to draw 15 types of apparatus. I knew that it would be virtually impossible to memorize everything just a night before the test so I took some time and learnt how to draw the apparatus and memorize the names and functions of the apparatus.


 * __Term 2 Reflections:__**

In this term, I learnt:
 * 1) Mass, Weight and Density
 * 2) Use of Measuring Instruments
 * 3) Physical Quantities and SI Units
 * 4) Kinetic Model of Matter

__**Mass, Weight and Density**__


 * Name || Mass || Weight || Density ||
 * Definition || Mass is the amount of matter in a body || Weight is the vertical force exerted by a mass as a result of gravity || Density is the mass per unit volume ||
 * SI Unit used || Kilograms (kg) || Newton (N) || Kilograms per cubic metre (kg/m³) ||
 * Instrument used to measure it (if any) || An Electronic Balance or a beam balance. || A Spring Balance || Can be calculated by using the formula [[image:Density_Formula.png width="46" height="31"]] where //p// is the Density, //m// is the mass while //v// is the volume of an object. ||

Then, after learning about the definition, SI Unit used and the instruments used to measure Mass, Weight and Density, we moved on learning how to find the density of objects. These questions really required us to use the formula in order to find the density of the object after finding both the mass and the volume of the object. While covering this topic, we also learnt about the Archimedes' The Golden Crown.


 * __Use of Measuring Instruments__**

In this topic, we learnt 2 instruments, which are the
 * Vernier Caliper [[image:Vernier_Caliper.jpg width="100" height="75"]]


 * Micrometer Screw Gauge [[image:Micrometer_Screw_Gauge.jpg width="291" height="142"]]

In each division of the Vernier Caliper, each division on the Main Scale represents 0.1 cm while each division on the Vernier Scale represents 0.01 cm.

While checking for Zero Error, if the Vernier scale is on the right of the Main Scale, it is a Positive Zero Error. From the zero mark of the Vernier Scale, find which marking matches the marking on the Main Scale. For example, if it is the 3rd marking of the Vernier Scale which matches the marking of the Main Scale, 0.03 cm is subtracted from the overall reading.

On the other hand, if the Vernier Scale is on the left of the Main Scale, it is a Negative Zero Error. From the 10 mark of the Vernier Scale, find which marking matches the marking on the Main Scale. For example, if it the 3rd marking of the Vernier Scale from the right which matches the marking on the Main Scale, 0.03 cm is added to the overall reading.


 * __Physical Quantities and SI Units__**

A Physical Quantity is one which can be measured and used in the mathematical equations of science.
 * Temperature
 * Time
 * Length
 * Mass
 * Speed
 * Area
 * Volume
 * Density

A Base Quantity is a Physical Quantity which cannot be defined in terms of other quantities


 * Temperature
 * Time
 * Length
 * Mass

A Derived Quantity is a Physical Quantity that is derived from Base Quantities


 * Speed
 * Area
 * Volume
 * Density

The table below shows the Physical Quantity and the SI Unit I have learnt


 * Physical Quantities || SI Unit (Symbol) ||
 * Temperature || Kelvin (K) ||
 * Time || Second (s) ||
 * Length || Metre (m) ||
 * Mass || Kilogram (kg) ||
 * Speed || Metre per Second (m/s) ||
 * Area || Square Metre (m**2**) ||
 * Volume || Cubic Metre (m**3**) ||
 * Density || Kilogram per Cubic Metre (kg/(m**3**) ||

By combining a magnitude and a prefix unit, you will have a physical quantity.
 * Prefix || Factor ||
 * Milli- || 1/1000 ||
 * Centi- || 1/100 ||
 * Kilo- || 1000 ||


 * __Kinetic Model of Matter__**

In this chapter, I learnt that matter is made up of tiny particles called atoms or molecules and the particles area always in continuous motion. And the motion of the particles will determine of the properties of a matter. The assumption that the tiny particles move in continuous motion is known as the name of the topic that I an learning, the 'Kinetic Model of Matter'

We learnt the 3 different States of Matter in Primary School. In this topic, we recap the properties of the 3 States of Matter and learn both the Arrangement and the Movement of Particles.

I learnt that by using the Kinetic Model of Matter, I was able to determine the properties for each state of matter.


 * Solid**
 * Closely packed together, usually in a regular pattern, occupying minimum space
 * This results in solids having high density
 * The particles about fixed position only and they are held in position by very strong intermolecular bonds.
 * This explains why solids have fixed volumes and shapes.


 * Liquid**
 * Randomly arranged with the particles slightly further apart as compared to that of solids.
 * This results in liquid relatively high density.
 * Free to move about but confined within the vessel containing it. The particles have attractive forces between particles.
 * This explains why liquids have fixed volume but will take the shape of the vessel containing them.


 * Gas**
 * The particles are very far apart and they are randomly arranged and will occupy any available space.
 * This results in gases having very low density.
 * The particles have very little attraction between them and move about randomly at very high speed.
 * This explains why gases have no fixed volume and shape and why they are highly compressed.

I found the topic 'Kinetic Particles of Matter' the most interesting before I learnt this topic, I had totally no idea how the particles moved. It was really interesting as I learnt how the particles are arranged and move and how it matches with the properties of the 3 states of matter I have learnt in primary school.

I found the topic Mass, Weight and Density a little difficult to learn because of the calculations of Density. I was unsure how many Significant Figures I should round my calculations to and how to present my answers. However, with the notes given by my teacher, I memorized and learnt that: When (+) or (-), we must round the answer to the least decimal place When (x) or (÷), we must round the answer to the least significant figures with the numbers given in the question.
 * Formula should be included in the statement
 * We must show substitution with the correct units
 * An equal sign for every line
 * Final answers should be corrected to significant figures


 * __Term 3 Reflections:__**

In this term, I learnt:
 * 1) Elements, Compounds and Mixtures
 * 2) Solutions and Suspensions
 * 3) Separation Techniques


 * __Elements, Compounds and Mixtures__ [[image:perodic_table.gif width="370" height="231"]]**

What are elements?

Elements...
 * Are substances which cannot be broken down into two or more simpler substances by chemical methods
 * Are listed in the periodic table and each element have a unique atomic number and chemical symbol.


 * Name of Element || Chemical Symbol ||
 * Aluminum || Al ||
 * Zinc || Zn ||
 * Copper || Cu ||
 * Magnesium || Mg ||
 * Mercury || Hg ||
 * Iron || Fe ||
 * Carbon || C ||
 * Sulfur || S ||
 * Chlorine || Cl ||
 * Nitrogen || N ||
 * Iodine || I ||
 * Hydrogen || H ||
 * Oxygen || O ||

I also learnt about the differences of metals and non-metals.

Metals...


 * Are shiny in appearance
 * Are good conductors of electricity and heat
 * Are malleable and ductile
 * Are sonorous
 * Generally have high density

While non-metals...
 * Are dull in appearance
 * Are poor conductors of electricity and heat
 * Are brittle
 * Are non-sonorous
 * Generally have low density

Compounds...
 * Are substances which contain 2 or more elements chemically joined together
 * Are formed by chemical reactions. The chemical reactions usually involves an exchange of energy in the form of heat, light or both with the surroundings
 * Are not able to be broken down by physical methods. The only way to break a compound down is to use chemical methods and this involves heating, lighting or electric current.
 * Are formed only if the fixed proportion by mass and the number of atoms is correct.

Mixtures...
 * Consist of 2 of more substances that are mixed but not chemically combined.
 * Can be in all 3 stages

I also learnt about the differences between compounds and mixtures.


 * Chemical reaction is needed for the formation of compounds but no chemical reaction is needed for the formation of mixtures.
 * Compounds are formed with the exchange of heat of light with the surrounding while mixtures are formed with no exchange of energy with the surrounding.
 * Compounds have properties of its constituent elements while mixtures do not have properties of its constituent elements.
 * Compounds are formed with fixed amount of atoms and mass while mixtures are formed with any proportion of atoms and mass.
 * Compounds are separated into its components by using chemical methods while mixtures are separated into its components by using physical methods.
 * Compounds have fixed and sharp melting point while mixtures have melting points over a range of temperatures.

__**Solutions and Suspension**__

A solution is a mixture formed when one or more **solutes** (substance that dissolves) dissolve in a **solvent** (substance which the solute dissolves in; usually the main portion of the solution).

A suspension is a mixture in which solid or liquid particles are suspended in a liquid or a gas.

I also learnt about the differences between solutions and suspension.
 * There will be no visible changes when a solutions are passed through filter a paper while there will be visible changes when suspensions are passed through a filter paper.
 * There will be non visible changes when a solution is left to settle while the solid particles will settle on the bottom of the beaker if a suspension is left to settle.
 * Solutions are homogeneous while suspensions are not homogeneous.
 * Light can pass through solutions while light cannot pass through suspensions.

Solubility is defined as the maximum quantity of the substance which can dissolve in a given quantity of the solvent at a given temperature.

Solubility is dependent on...
 * Nature of solute
 * Nature of solvent
 * Temperature of solvent
 * Pressure of surroundings

Rate of dissolving is dependent on...
 * Rate of stirring
 * Temperature
 * Surface of the solute

Different types of solutions:
 * Dilute solution - Small amount of solute dissolved in a solvent
 * Concentrated solution - Large amount of solute dissolved in a solvent
 * Saturated solution - Maximum amount of solute dissolved in a solvent dissolved at a given temperature

__**Separation Techniques**__

I learnt about
 * Filtration [[image:Filtration.jpg width="208" height="224"]]

Filtration is a physical method in which it is used to separate solids from liquids or gases by placing a medium where only the liquid or gases can pass.
 * Evaporation to dryness [[image:evaporation_to_dryness.jpeg]]

Evaporation to dryness occurs when a solution is heated and the solvent evaporates completely leaving only the dissolved solids as the resiude. This method is used to separate dissolved solids from solution.


 * Crystallization [[image:crystallization.jpg]]

Crystallization separates dissolved solids from solutions as well-formed crystals.


 * Simple distillation [[image:simple_distillation.PNG]]

Simple distillation is used to obtain a pure liquid from a solution.
 * Fractional distillation [[image:fractional_distillation.png]]

Fractional distillation is used to separate two or more liquids that are completely soluble in each other.


 * Reverse osmosis [[image:reverse_osomosis.jpg width="252" height="264"]]

Reverse osmosis is used for desalination.
 * Magnetic separation [[image:magnetic_separation.jpeg width="269" height="235"]]

Magnetic separation is a process in which magnetic material is extracted from a mixture using a magnetic force


 * Separation funnel [[image:separation_funnel.png width="173" height="256"]]

Separation funnel is used to separate two immiscible liquids of different densities.


 * Chromatography [[image:chromatography.jpg width="307" height="226"]]

Chromatography is used to separate mixture based on the solubility of the different solutes in the mixture in a solvent. This is only possible as different solutes have different solubilities in a solvent.