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)