Ohne Titel

Seite 1

Week 1: Chemistry

Properties of metals and non-metals

Elements are pure substances

if it it ends with ium its a metal

good conductors for electricity

low melting point

low density

Chemical bond

Most of the time they share their electrons and create covalent bonds

transfer of electron = positive ion and negative ion - common in salt and crystal

Matter:

What the earth and the things around us are made from. Includes liquid, gasses and solids.

Material is a type of matter

Physical and Chemical Changes

Physical Changes: Such as melting, dissolving, condensing and freezing - reversible

DO NOT create NEW materials/substances

Chemical changes: Such as cooking, burning, decaying, corroding - irreversible

DO create NEW substances

Dissolving

Requires 2 substances to be mixed together

DOES NOT require heat energy

Regarded as a type of MIXING (not change of state)

Dissolved or not?

A solution is formed when a solute (substance) dissolves in a solvent

Water is known as a universal solvent

Dissolving occurs at the surface of a solid

Suspension occurs when the solute is insoluble

Often the mixture will have a cloudy appearance.

Turbidity = Pollution measurement for waterways

Higher temperatures of a solvent (e.g. water) allow more solids (e.g.salt, sugar) - but less gasses e.g. air/oxygen) to dissolve

Elements

They cannot be broken down in to other substances by chemical or physical means

Pure substances

most elements are combined with other elements

Each elements made up of a particular type of atoms

Compounds

Always contain atoms of different elements

always has the same composition e.g. water always contains hydrogen (H) and oxygen (O) with twice as many H and O; formula is always H2O

Mixture

A mixture has two or more pure substances combined together which are discrete and NOT chemically combined.

They can be classified as either homogeneous (the same throughout) or heterogeneous (different properties in different areas of the mixture) E.g. Sugar and coffee disolves in water = solution

Separating Mixtures

Filtration

Distillation

Crystallisation

pH

pH that is more than 7 is a base

pH that is less than 7 is acid

Seite 2

Week 4:

Waves and Vibrations

340m/s

A lot of water in atmosphere = Rainbow

Frequency - how many times the vibration occurs

Period - how long it takes one complete vibrations

Hertz - Frequency how many times - one cycle per second is called a Hertz

Simple Vibrations

Vibration = Back and Forth motion of an object

Equilibrium position = central position of the motion

Cycle = one complete vibration that must begin and end at the same place of the motion

Period (T) = time required for one cycle

Amplitude = Maximum distance of the object from the central (equilibrium) position

Frequency (f) = the number of cycles that occur during a given length of time

Vibration of a wave length is visible

Speed of a Wave

Speed = distance x time

Light and Sounds

Travels in straight line

Travels 3x10(8) m/s (around the world in 3 seconds)

Thunder and lightning occur at the same time but we see lightening first

Shadows are places where light is blocked

Shadows is the axis of light