Term 2 2012

In this term, we started on new physics topics like reflection, refraction, lenses and light.

Reflection

-occurs when rays of light strike a surface and changes its direction

-incident ray, reflected ray, point of incidence appears when reflection occurs

Types of reflection

Specular reflection- occurs on smooth surface

Diffused reflection-occurs on rough surface

Refraction

-When light is transmitted through a medium and bends

-Degree of bend of light depends on the optical density of medium

-IMPT FORMULAS: sin i/ sin r = refractive index, refractive index = 1/sin c

Lenses

This topic is slightly similar to the previous, where virtual and real image is involved once again. There are two types of lenses: converging and diverging lenses.

1)Optical centre- centre point of lens
2)Principal axis- line passing straight through optical centre
3)Principal focus (F) - point where all rays converge towards after refraction
4)Focal length- distance between principal focus and optical centre.

Term 1 2012

This term, we were working on chemistry. The main topics were atomic structure, periodic table, chemical bonding and acids and bases.

Atoms
-Made up of Protons, Neutrons and Electrons
-Relative mass number of Protons,Neutrons =1
-Electrons Relative mass= 0.00054347826

-Electrons orbit around nucleus, which contains the protons and Neutrons

-Atomic no.=Number of protons or Number of electrons

-Mass no. =Nucleon no.= Number of Protons AND Neutrons

-Note that no. of electrons and no. of protons will always be the same in order to keep the atom stable. This is because protons contain positive charge and electrons contain a negative charge. This gives a balanced charge and the atom becomes electrically neutral.

Electrons
-Arranged in shells (Also known as energy levels)
-1st shell= 2 electrons
-2nd shell= 8 electrons

-3rd shell= 8 electrons

-4th and 5th shell= 18 electrons each

Isotopes
-Atoms with different no. of Neutrons

  -Eg. Chlorine

Periodic table

The periodic table was a a grouping systems for all the possible atoms in the world. In the periodic table, these atoms are arranged according to their physical and chemical properties, which includes their size, mass, reactivity, melting point etc. Below is a picture of the periodic table

The Periodic tables have 8 groups; each group with its own unique chemical property. In addition, the atoms are arranged in ascending order according to their proton number. This allows us to identify an atom right away since it is grouped according to its physical/chemical property.

Acid and Bases

Another chemistry-related topic. In this topic, we learnt about certain reactions that occur with acids and bases. Below is a mindmap that I made myself to summarise what is the topic about

Acid

-Ph lower than 7

-Ionises in water to produce hydrogen ions

-Tastes sour(not telling you to try and taste them though, some will burn a hole in your tongue)

Base

-Ph higher than 7

-Ionises in water to produce hydroxide ions

-tastes bitter, feels soapy(might as well taste acid, both of them don't taste nice)

Cells

Animal Cells:


The parts of the Animal Cell we learnt about are the Nucleus, Cytoplasm, Cell Membrane and Vacuoles.


Nucleus --> The Nucleus is also known as the brain of the cell. It controls all chemical reactions and activities taking place in the cell, such as reproduction. The Nucleus contains chromosomes, which stores vital generic information about the organism. This information is passed down to the future generation. This is evident by children having similar traits as their parents.


Cytoplasm --> It is a jelly-like substance that fills the entire cell. This is where the chemical reactions take place and contains many substances.


Cell membrane --> The cell membrane is a thin partially-permeable layer around the cell. It allows the shape of the cell to change and controls the movement of substances in and out of the cell. Only some particles, such as water, oxygen and carbon dioxide can pass through the cell membrane.


Vacuole--> They are small and numerous in the animal cell. The vacuoles are located in the cytoplasm and contain many substances such as water and waste materials.


Plant Cells:


The parts of the plant cell include the Nucleus, Cytoplasm, Cellulose Cell Wall, Chloroplasts, Cell membrane and the Vacuole.


Nucleus --> Same as the Animal Cell


Cytoplasm --> In the plant cell, the cytoplasm does not fill up the entire cell. Instead, it is reduced to a thin lining behind the cellulose cell wall. However, it still contains substances such as water, and is similarly still the location where chemical reactions occur.


Cellulose Cell Wall --> The cell wall surrounds the plant cell and gives the plant cell it's shape. This cell is absent in the structure of the animal cells.


Chloroplasts --> These cells are only present in particular parts of the plant, such as the leaves. They are tiny-disc like structures that contain a green pigment known as chlorophyll. Chlorophyll is the substance that is responsible for photosynthesis. It traps light energy so the plant would be able to make food. This cell is also absent in the structure of the animal cells.


Cell Membrane --> Same as the Animal Cell.


Vacuole --> In the plant cell, there is only one large vacuole, unlike the animal cell. The vacuole is the largest part of the cell and contains cell sap. The cell sap takes in water to keep the cell turgid.

tissues!

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning.



Cells group together in the body to form tissues - a collection of similar cells that group together to perform a specialized function. There are 4 primary tissue types in the human body: epithelial tissue, connective tissue, muscle tissue and nerve tissue.

1. Epithelial Tissue - The cells of epithelial tissue pack tightly together and form continuous sheets that serve as linings in different parts of the body. Epithelial tissue serve as membranes lining organs and helping to keep the body's organs separate, in place and protected. Some examples of epithelial tissue are the outer layer of the skin, the inside of the mouth and stomach, and the tissue surrounding the body's organs.
2. Connective Tissue - There are many types of connective tissue in the body. Generally speaking, connective tissue adds support and structure to the body. Most types of connective tissue contain fibrous strands of the protein collagen that add strength to connective tissue. Some examples of connective tissue include the inner layers of skin, tendons, ligaments, cartilage, bone and fat tissue. In addition to these more recognizable forms of connective tissue, blood is also considered a form of connective tissue.
3. Muscle Tissue - Muscle tissue is a specialized tissue that can contract. Muscle tissue contains the specialized proteins actin and myosin that slide past one another and allow movement. Examples of muscle tissue are contained in the muscles throughout your body.
4. Nerve Tissue - Nerve tissue contains two types of cells: neurons and glial cells. Nerve tissue has the ability to generate and conduct electrical signals in the body. These electrical messages are managed by nerve tissue in the brain and transmitted down the spinal cord to the body.

Sources: http://web.jjay.cuny.edu/~acarpi/NSC/14-anatomy.htm

After reading this I learnt about the different types of tissues and there is more to tissues than just tissue paper. Who knew that many cells grouped together could form something totally different, such as a tissue? I also learnt that the primary tissues in the body are absolutely vital for us to carry out what we do on a daily basis.

Yay!

respiration

Respiration is the release of energy from glucose or another organic chemical. The chemical energy in glucose can be used to provide the energy required for growth, repair and movement. In fact most things you do require energy

Aerobic Respiration is the normal form of respiration. It requires oxygen and releases the most energy from glucose. 1Mole of Glucose produces 2830 Kilojoules of energy. When we respire like this we have to breathe oxygen in and breathe carbon dioxide out. We also have to excrete (get rid of) the extra water in our urine.
Anaerobic Respiration also releases energy from glucose but not so much I mole of glucose will produce 118 Kilojoules of energy. When yeast respires anaerobically it produces carbon dioxide and alcohol. When we respire we produce lactic acid. Too much lactic acid poisons our muscles (you get cramp).
Summary:

	Respiration: is the release of energy from food, takes place in animal and plant cells.
	Aerobic Respiration requires: Glucose, Oxygen.
	Anaerobic Respiration requires: Glucose.
	Aerobic Respiration produces: Energy, Carbon Dioxide, Water.
	Anaerobic Respiration produces: Energy (not as much), Carbon Dioxide, Lactic Acid or Alcohol. Reflection: When Ms Leong explained this in class, I didn't really understand it. After additional research, I think I finally can make sense of what's happening. There will be more posts for more information on aerobic and anaerobic respiration

Aerobic and anaerobic respiration

There are two types of respiration (i) aerobic respiration and (ii) anaerobic respiration. While aerobic respiration is a process that requires oxygen, but in anaerobic respiration, oxygen is not required. Therefore aerobic and anaerobic respiration differs in terms of the amount of energy that is produced. n aerobic respiration, oxygen is always required.
During the process of aerobic respiration, the molecules of food are broken down to obtain energy. Oxygen is present at the end point of the electron acceptor. The molecules of fuel that are generally used by the cells of the body during the process of the respiration are composed of glucose, fatty acids and amino acids. In other words, when there is respiration through the aerobic process, Glucose together with Oxygen produces Energy, Carbon Dioxide and Water. Aerobic Respiration also produces more energy than Anaerobic Respiration.
Generally anaerobic respiration is always used by the primitive living organisms, which live in places where oxygen is missing, like muddy bottom of a river. In such places, the organism survives without depending to a large extent on oxygen. These habitats are known as anoxic.

Anaerobic respiration produces less energy in comparison to aerobic respiration. When the anaerobic respiration (alcoholic fermentation) as at one above functions, only two molecules of ATP are given out for one glucose molecule, while for lactate fermentation as at two above, 2 ATP molecules are given out for each glucose molecule used during the process. Thus, during anaerobic respiration, only one molecule of glucose is broken down to obtain only 2 ATP molecule.

Reflection: Now I have a more in-depth knowledge of these to forms of respiration. I never knew that you could respire without oxygen!

Forensic science assignment one

1) Evidence that may have been left at the scene of the crime

- Oil trail (Lewis' car leaked oil)

- Tire tracks (Lewis' car tires were a little bald)

- Muddy shoe prints (imprinted on the freshly dug flower bed and on the floor and steps of the mansion)

- Blood prints left on glass pane, curtain, drawers and banister (from the small wound)

- Fingerprints left on glass pane, curtain, drawers and banister (forgot to put on his gloves)

- Fabric from his shirt stuck on the creeper (while climbing)

- His own torch (dropped out while he was climbing)

- Paint left behind on the broken fence (by the car)


2) Evidence that may have been taken away by Lefty

- Mud from the mansion stuck on the tires (wheels spinning in the muddy shoulder)

- Seeds/pollen grains from jacaranda tree stuck under his shoes (Lewis parked his car under a jacaranda tree, therefore he might have stepped on them)

- Small glass shards stuck in his wound (from glass pane)

- Mud on shoe (walked across the flowerbed)

- Parts of Jacaranda tree stuck on the car (wet weather, might be pollen or some flower)

- Parts of creeper stuck to his shirt (while climbing)


- Fabric from the curtain stuck in his wound ("Lefty" used left hand to grab the curtain)

- Pieces/splinters stuck to the mudguard of the car (car clipped the gate)

- Pollen stuck to his pants (passed through the flowerbed)


3) Suggestions for the forensic scientist


- Check for fingerprints at the crime scene eg. The Torch that the guy dropped
- Compare the blood sample obtained at the crime scene with the guy's blood
- Check the tyre tracks left behind by the guy's car
- Trace the oil leaks/tyre tracks
- Search the guy's house for the stolen items