My 3 Best Posts

1. http://nglixian.blogspot.com/2011/05/chapter-25-transport-of-materials-in_06.html
2. http://nglixian.blogspot.com/2011/01/week-3.html
3. http://nglixian.blogspot.com/2011/03/chapter-14-chemical-changes.html

Chapter 25: Transport of materials in Plants

Transport system of plants main function is to transport water and mineral salts  from the roots to the leaves and to transport manufactured food (sucrose and amino acids) from the leaves to the other parts of the plant.


Parts of the plant transport system:

Part: Xylem
Function: Transport water and mineral salts from the roots to the stem to the leaves and provides mechanical support
Feature: Dead , long, hollow, fine tube-like and one-way vessels with thick lignified cellulose walls

Part: Phloem
Function: Transport manufactured food from the leaves to the other parts of the plant
Feature: Two-way flow of substances

Chapter 25: Transport of materials in Animals

The system responsible for the transport of materials in humans is called the Circulatory system


The Circulatory system:

• Supplies oxygen and digested food to all parts of the body quickly
• Is made up of the heart - the pump that pumps blood to all parts of body, blood vessels - Veins, Arteries, and the Capillaries, Blood

Organ: Heart

Function: acts like a muscular pump that contracts and relaxes to pumps blood to all parts of body, has valves to prevent the backflow of blood.

Organ: Blood vessels

         - Veins

         - Arteries

         - Capillaries

Function/ : Veins - transports mainly deoxygenated blood towards the heart

Feature            - has thin walls as the pressure is low

             Arteries - transports mainly oxygenated blood away the heart

                       - has thick walls as the vessels need to withstand the pressure caused by the pump                             of the heart

            Capillaries - very thin blood vessels located between the cells of our body

                        - has very thin walls to allow substances to pass through to and fro the cells and                                 blood 

Organ: Blood

Function/ : Plasma - yellow liquid made up of mainly water and dissolved substances like digested food

Feature     White blood cells - kills bacteria and fight diseases

                                  - larger than red blood cells, live for only a few days

              Red blood cells - transports oxygen around the body                                                                                   - biconcave shaped so as to increase the surface area of the cell and to increase                                   the rate of exchange of oxygen

                                - has no nucleus                     
                                - Contain a red pigment - hemoglobin ( iron )

              Platelets - tiny pieces of other blood cells

                         - clot blood when there is wounds 

                                 

Chapter 25: Diffusion and Osmosis

Diffusion
 Diffusion  refers to the movement of matter from a region of higher concentration to a region of lower concentration.

Factors that identify diffusion:

• Occurs in all 3 states - solid, liquid and gaseous state.
• Occur in the presence of absence of a partially permeable membrane
• Can occur in all substances

clear water + potassium permanganate ---> potassium permanganate solution

Examples:

1. When copper sulfate crystals are embedded in the a colorless agar-agar, whole agar-agar to turn blue gradually.
2. When someone wear perfume passes by, there will be a nice fragrance coming from the person.
3. When rose syrup is added to plain water, the solution will turn red gradually. 

Osmosis

Similar to diffusion, in osmosis, molecules diffuses from a region of higher concentration to a region of lower concentration.

However, the factors that identify osmosis is very different, these are the factors:

• Occurs in the presence of a partially permeable membrane
• Occurs only at the liquid state
• Involves only water molecules

Example: 

• Filtering rice out of water with a sieve

Active Transport

Active Transport refers to the movement of matter from a region of lower concentration to a region of higher concentration using energy.

Chapter 8: Acids and Alkalis

Acids


Properties of acids:
   >  Tastes sour
   > Reacts with metals to produce hydrogen gas
      - Test for hydrogen gas: Hydrogen gas extinguishes a lighted wooden splint with a "pop" sound.

      - Examples of Writing word equations for the chemical reactions of acids and metals:

         ~ Sulfuric acid + Zinc ---> Zinc Sulfate + Hydrogen gas

         ~ Hydrochloric acid + Zinc ---> Zinc chloride + Hydrogen gas

         ~ Nitric acid + Zinc ---> Zinc nitrate + Hydrogen gas

   > Reacts with carbonates to produce carbon dioxide gas and water

      - Test for carbon dioxide: forms white precipitate in lime water
      - Examples of Writing word equations for the chemical reactions of acids and metal carbonates:

         ~ Sulfuric acid + Zinc carbonate ---> Zinc Sulfate + Carbon dioxide gas + water

         ~ Hydrochloric acid + Zinc carbonate ---> Zinc chloride + Carbon dioxide gas + water

         ~ Nitric acid + Zinc carbonate ---> Zinc nitrate + Carbon dioxide gas + water

   > Test for acids: Turns red litmus paper red/ turns blue litmus paper red
   > Has a pH level lower than 7


Alkalis


Properties of alkalis:
   > Tastes bitter
   > Has a soapy feel
   > Test for alkalis: Turns red litmus paper blue/ Turns blue litmus paper blue
   > Has a pH level higher the 7


Neutralization of acids and alkalis


Neutralization is a reaction that occurs when acids and alkalis are mixed together. Salt and water will be produce in this reaction. Some examples of Neutralization in our daily lives: Usage of shampoo(alkaline) and conditioners(slightly acidic) and usage of toothpaste(alkaline) on our teeth(acidic).


Indicators


Indicators indicates if the substance is acidic or alkaline or the pH level of the substance. For instance, the blue & red litmus paper, methyl orange, phenolphthalein and the universal indicator. The acidic or alkaline level of a solution is known through its pH level through a scale of colors or a scale of numbers which ranges from 0 to 14.Indicators indicates if the substance is acidic or alkaline or the pH level of the substance. For instance, the blue & red litmus paper, methyl orange, phenolphthalein and the universal indicator. The acidic or alkaline level of a solution is known through its pH level through a scale of colors or a scale of numbers which ranges from 0 to 14.

the universal indicator

a pH scale of colors

Source: google images

Chapter 26: Digestion in Human being

How digestion works
Digestion ensures that larger sized nutrients are broken down into smaller sizes so as to pass through the walls of cell membranes. Digestive enzymes are responsible for digesting these nutrients, different enzymes digests different nutrients. Amylase acts on starch, a form of carbohydrate, to produce Maltose, a complex sugar. After which,  Maltase acts on maltose to produce glucose, simplest form of carbohydrate. Protease acts on proteins to  produce the simplest form of proteins, amino acids. Lastly, Lipase acts on fats to produces fatty acids and glycerol. These enzymes, which can be reused, speed up chemical reactions and remain unchanged through out the whole process as they act like scissors that breaks down large molecules into smaller ones. 


The different organs that makes up the Human digestive system

1.  The Mouth                                                                                                    Food enters from the mouth. In the mouth, food is broken down into smaller pieces as the food is chewed by the teeth and the surface area of the food increases which quickens the rate of digestion. While the salivary glands present in the mouth produces saliva that contains amylase digests starch into sugar and wets the food for easier swallowing. The tongue then rolls the food into balls which pushes its way down the oesophagus.
2. The Oesophagus                                                                                             The Oesophagus is a long muscular tube, connected to the stomach. No digestion occurs in this tube, however, the amylase in the food balls continues to digest the food as the muscles contract and relax to squeeze the food down the tube to the stomach. 
3. The Stomach                                                                                                      The stomach is like a muscular bag that contains gastric juice. The gastric juice consists of proteases that digests proteins and hydrochloric acid that assists proteases to work and kills all bacteria in the food. After which, digested food is passed to the small intestine bit by bit.
4. The Small intestine                                                                            The small intestine is also a muscular tube which the liver and the pancreas are connected to. In the small intestine, there are intestinal juices that produces Maltase, proteases and lipase, Pancreatic juice from the pancreas that contains amylase, proteases and lipase and  bile from the liver. As mentioned earlier, Amylase acts on starch, a form of carbohydrate, to produce Maltose, a complex sugar. Maltase acts on maltose to produce glucose, simplest form of carbohydrate. Protease acts on proteins to  produce the simplest form of proteins, amino acids. While Lipase acts on fats to produces fatty acids and glycerol. While the bile carries out emulsification, that is breaks fats down into smaller oil droplets and increase the surface area of the oil which speeds up the rate of digestion. Digestion ends here. Together with undigested food, fiber, water and mineral salts will be passed to the large intestines.
5. The Large intestine                                                                            In the large intestine, water and mineral salts are absorbed. The rest of the undigested, unwanted matter, known as faeces, are then stored in the rectum before being passed out.

a image of human digestive system

sources: google image

Chapter 14: Chemical changes

Different changes


1. Chemical change

• A chemical change that is permanent
• A new substance will be formed
• A chemical change is irreversible
• Chemical reaction* is involved
• Heat/ Light will be given out or taken in 
• Properties of products differ from starting reactants
• E.g. Raw egg becomes a cooked egg

2. Physical change

• A physical change is temporary
• No new substances is formed
• A physical change is reversible
• No chemical reaction* is involved
• No/ little heat or light will be given out of taken in
• Propeties of substances do not differ
• E.g. Liquid ---> Gas (Boiling)

*A Chemical reaction is a process whereby reactants are changed into products and no matter is destroyed or created, only rearrangement of matter as occurred. It is represented in a chemical equation.


Balancing chemical equations
Balancing chemical enables scientist to know the number of atom involved in the chemical reaction. 


How to balance an equation?
Steps:


  1.  Write down the formula of reactants and
     
      N2 + H3 = NH3     


  2. Check the number of atoms on each element on both sides of the Chemical equation


  3.  Balance the equation by placing number in front of the formulae of the substances in the equation.


      N2 + 3H2 = 2NH3


Interaction between matter and heat


1. Changes in state of matter [physical change]
Heat can cause matter to change in state.
For example, heat causes solid to melt and become liquid.


2. Expansion and contraction [physical change]
This change of expansion is more obvious in liquids and gases as compared to solids. As the matter loses heat, it contracts. Thus, these 2 processes are reversible.


3. Combination [chemical change]
Combination only occurs in the presence of some factors(different processes requires different factors) where 2< substances combine to form 1< new substances.

• E.g. Iron fillings + sulfur ---> Iron sulfates (in the presence of heat)
• Iron/steel ---> Rust (in the presence of water and oxygen)

4. Combustion [chemical change]
Combustion is a process at which oxygen and another substance are combined together to form 1< new substances in the presence of heat.

• E.g. Fireworks are created when: Magnesium + oxygen(in the presence of heat) ---> magnesium oxide (a bright flash will be in the process)

5. Thermal decomposition [chemical change]

Thermal decomposition refers to a process whereby a substance is broken down into 2< simpler substances by heat.

• E.g. Calcium carbonate ---> Calcium oxide + carbon dioxide(in presence of heat)
• Copper carbonate ---> copper oxide + carbon dioxide(in presence of heat)

Interactions between Matter and light

1. Photosynthesis [chemical change]

Photosynthesis is a process at which carbon dioxide and water are converted to glucose and oxygen in the presence of sunlight and chlorophyll. This process only occurs in plants.

2. Photography [chemical change]

Thin, plastic films used in photography are coated with chemicals, in particular silver bromide crystals that changes to silver by light. An image will be created as the film is exposed to light.

3. Solar cells 

Solar cells, also known as photo voltaic cells, are made up of silicon or selenium which are capable of converting light energy to electricity.

Interactions between matter and electricity

1. Electricity causes these effects as it passes through matter:

• Heating effect
• production of light
• magnetic effect
• chemical effect

Interactions between matter-mixing substances

1. Physical change

• E.g. Adding of syrup into plain drinking water (no new substances are formed)

2. Chemical change

• E.g. adding acid to carbonate/metal               
• Copper carbonate + Hydrochloric acid ---> Copper chloride + oxygen + Carbon dioxide gas               Copper + Hydrochloric acid ---> Copper chloride + hydrogen gas

Chapter 23: Atoms and Molecules

Definition of Atom:
Atom is the smallest particle of an element.


An image of an atom



Recap:



Atoms consists of 3 main parts

1. The neutrons

• Has a neutral charge
• Is found in the nucleus

2. The protons

• Has a positive charge
• Is also found in the nucleus

3. The electrons

• Has a negative charge
• Is found in electrons shells that orbits around the nucleus in a fixed path

An atom has a equal number of protons and electrons so that the atom is electrically neutral (no net charge).


Proton/ Atomic number and Mass/ Neucleon number


The Proton/ Atomic number refers to the number of protons or electrons in an atom since there is a equal number of protons and electrons in an atom. While the Mass/ Neucleon number refers to the sum of protons/ electrons and neutrons.The Proton/ Atomic number and Mass/ Nucleon number of an element is found beside the chemical symbol of the element in the periodic table.


Arrangement of Electrons in Atoms
The arrangement of electrons in atoms, known as electronic structure or electronic configuration, are very important because the arrangement affects the chemical properties of an atom.Electrons are found in electron shells, each electron shell can only hold a certain number of electrons.


Rules of the arrangment of electrons in an atom:

• 1st shell: Strictly only a maximum2 electrons
• 2nd and 3rd shell: Strictly only a maximum 8 electrons in each shell
• Each shell must be completely fill with the maximum number of electrons before the next shell can be filled up.   

Ions

Definition of an ion:

A charged particle at created from an atom of a group of atoms by the loss or gain of electrons. 

• 1st scenario: When an atom gains electrons (but the number of neutrons and protons remain the same), the atom becomes a negative ion with a negative charge.
• 2nd scenario: When an atom loses electrons (but the number of neutrons and protons remain the same), the atom becomes a positive ion with a positive charge. 

Why do atoms become ions?

The loss or gain of electrons is due to its chemical unstability. In order to acheive chemical stability, the atom must have a noble gas structure, which means each electron shell of the atom have to be fully filled with electrons.  

However, there are still atoms that are originally chemically stable, in other words, the are already in the noble gas structure. Thus, they are very unlikely to become ions (to stay in the monatomic state) unless being forced.

• These atoms of elements are found at group "0" of the periodic table. E.g. Helium, Argon, etc. 
• These atoms have a unreactive or chemically configuration, which we also call the noble gas configuration or  noble gas structure.

How do the electrons of an atom know what to do (i.e.where to go) so as to acheive the noble gas structure?

• 1st scenario: Metals - Atoms of metal tend to lose electrons and form positiely-charged ions, also known as Cations (read as cat-ions).
• 2nd scenario: Non-metals - Atoms of non-metals tend to gain electrons and form negatively-charged ions, also known as anions (read as an-ions).

Molecules

Definition of molecules:

Molecules are atoms that share electrons with another atom(s). Molecules are made up of at least 2 or more atoms chemically combined together.  

Molecules of elements

• Molecules of elements usually consist of a fixed/ constant number of one type of atom combined chemically.
• Many non-metals tend to exist as molecules.
• Molecules that consists of only 2 atoms are called diatomic molecules. (These elements of atoms can be found under group VII of the periodic table).

Molecules of compounds

• Molecules of compounds are formed when fixed number of different types of atoms are chemically combined.
• The number of different types of atoms are always constant.

Chemical formula

Each chemical formula represents a particular substance. A compound is represented by a chemical formula which from the formula we can infer the types of atoms present in the compound and the ratio of the different atoms present in the atom. On the other hand, scientists communicate with each another by their comman known language - chemical symbols and formulae.

Chapter 22: Particulate model of matter

Particulate model of matter

In this chapter, I gained a deeper understanding of the three states of matter.

All matter of every state is made up of particles that are in constant and random movement.

Solid state

1. Solids have fixed volume and shape.
2. Solids cannot be compressed.
3. Solids are made up of particles that are arranged in a regular pattern where they are very closely packed together and are very strongly attracted to each another.
4. Solid particles can only vibrate lightly at their fixed positions.

Liquid state

1. Liquids have fixed volumes but do not have a fixed shape.
2. Liquids cannot be compressed.
3. Liquids are made up of particles that are packed closely together in a random manner which are also attracted to each another.
4. Liquid particles can move over a short distance.

Gaseous state

1. Gases do not have fixed volumes and shape.
2. Gases can be compressed.
3. Gases are made up of particles that are far apart from one another as they are weakly attracted to one another.
4. Gas particles can move about freely in any way.

Processes

Melting

1. When a solid is heated,the particles will then gain energy.
2. They start to vibrate more vigorously.
3. When the temperature reaches the melting point, the particles will then break free from one another and start moving freely as enough energy is gained.
4. The change in movement and arrangement of the particles from the solid to liquid state is called melting.

Boiling

1. When liquid is heated,the particles will then gain energy.
2. They start to vibrate more vigorously.
3. When the temperature reaches the boiling point, the particles will then break free from one another and become very far apart, moving randomly at high speeds as enough energy is gained.
4. The change in movement and arrangement of the particles from the liquid to gaseous state is called boiling.

Freezing

1. When liquid is cooled,the particles will then lose energy.
2. They start to vibrate less vigorously and slowly.
3. When the temperature decreases to the freezing point, the particles will then be attracted to one another again, back to their fixed positions and as energy is lost.
4. The change in movement and arrangement of the particles from the liquid to solid state is called freezing.
    

Condensation

1. When liquid is cooled,the particles will then lose energy.
2. They start to vibrate less vigorously and slowly.
3. When the temperature decreases to a certain point, the particles will then be attracted to one another again and as certain amount of energy is lost.
4. The change in movement and arrangement of the particles from the gaseous to liquid state is called condensation.

Sublimation - change of state from solid to gas, bypassing the liquid state

1. When a solid is heated,the particles will then gain energy.
2. They start to vibrate very vigorously.
3. When the temperature reaches a certain temperature, the particles will then break free from one another and start moving freely, randomly very far apart at great speeds as enough energy is gained.
4. The change in movement and arrangement of the particles from the solid to gaseous state is called sublimation.   

Heating curve

There is a period whereby the temperature stays constant at the boiling and melting points. This is because the heat energy gained at that period is converted to kinetic energy to overcome the forces of attraction holding the particles together. Thus, when enough heat energy is converted to kinetic energy, all the particles would have already broke free from one another, causing temperature wll start rising again 

Cooling curves

 

There is a period whereby the temperature stays constant at the freezing point and condensation. The particles slows down as kinetic energy is lost over this short period and the particles starts to attract one another again. Then, the particles will change from the liquid state to solid state of from the gaseous to liquid state. The temperature starts to fall when all particles are in their original positions.

done by: Ng Li Xian
source:
http://www.docbrown.info/page03/3_52states.htm

4.10.2010

As for today, We spent the whole lesson filling up the notes. I have nothing to say.

Byes,
Ng Li Xian

30.9.2010

Last day of September. DNA was the topic of the day. We learnt some facts on DNA aka deoxyribonucleic acid that day. DNA is the genetic material of an organism. And we also learnt how to decode a DNA code. In DNA codes, we only have 4 letters-A(adenine) ,T(Thymine) ,C(Cytosine) ,G(Guanine). Three of them makes up codons, which in turn makes up a code. We even made a model of a DNA double helix.

<------My Model

By,

Ng Li Xian

29.9.2010

Extraction of fruit DNA (deoxynucleic acid). We were asked to bring along our own fruits-but I shared with the others in the end since they had extra.
We had to squash the fruit first, add detergent and salt to the smashed fruit and then add alcohol to the mixture and stir. The floating white subtance was the DNA.

By,
Ng Li Xian

27.9.2010

Another make-up for the prevous lesson. That day, we were given a microscope and were taught of the names of different parts of it and how to operate the machine. After which, I learnt how to extract my cheek cells with simple tools. The extracted cells are then put under the microscope for observation. Fortunately, my pair got to see my cheek cells under the microscope when some didn't get to see theirs. I've broaden my knowledge on the microscope and little on cells that lesson.

By,
Ng Li Xian

20.9.2010

Just to make-up for the lesson I had last week on cells. On that day, we were asked to make a 'cell' out of the available materials, such as a plastic container, agar-agar, beads, etc, also with the help of the labelled diagram of a plant cell in the notes. From this fun and interesting activity, I learnt some new parts of the plant cell, for instance, ribosomes and vacuoles. I also on improved our teamwork.

By,
Ng L! Xi@N

17.8.2010

Lesson was at the chemistry lab yesterday. We did a experiment on chromatography. We were asked to choose a paper of our choice to conduct the experiment on; I choose the circle one. Then drip a drop of dye in the middle of the paper followed by drips of alcohol until the dye reacts. For me, the dye 'spreaded' and changed into different colours - dark green> lighter green> blue. In my opinion, the mixture(dye) reacted with the alcohol, and break down into its constituent substances. And we also were given a chance to go up the front to see the distillation set-up Mdm Riza has made. From there, I learnt that the little objects in the round-bottomed flask are called porcelain chips/ boiling stones. They are used to slow down the boiling process and prevents overheating as the heat is distributed to the porcelain chips/ boiling stones. That's all I want to say.



bye,
Ng L! XiAn