Chemistry: Chapter 7 - Writing Equations

7.1 Chemical Equations
Word Equation: Everything in full English.

Chemical Equations: Symbols of elements.

7.2 Ionic Equations
Ionic Equations: Symbols of elements, charge of element and state of elements.

Spectator ions are not to be included in the ionic equations.
Spectator ions are ions still in solution at the end of the reaction.

Chemistry: Chapter 9 - Chemical Calculations

9.1 Calculations from Chemical Reactions
A balanced chemical equation shows the important facts about a reaction:

• The reactants
• The products
• The ration of the amounts (in moles) of the reactants and the products
• The state of the reactants and products indicated.

The relationship between the amounts of reactants and products involved in a chemical equation is know as the stoichiometry of the reaction.

9.2 The Volumes of Reacting Gases
Volume of a gas is proportional to the number of moles of the gas, and vice versa.

9.3 Limiting Reactants
The reactant that is completely used up in a reaction is known as the limiting reactant.
The reactants that are not used up are called the excess reactants.

9.4 The Concentration of a Solution
The concentration of a solution is given by the amount of a solute dissolved in a unit volume of a solution.
Concentration (g/dm³) = Mass of Solute in Grams / Volume of Solution in dm³

Molar Concentration
Concentration (mol/dm³) = number of moles of solute / volume of solution in dm³

Concentration (mol/dm³) = concentration (g/dm³) / Molecular mass of solute

9.5 Volumetric Analysis
Volumetric analysis is a technique used to determine the volumes of solutions that react together. In volumetric analysis, titration is performed to get the results.

Chemistry: Chapter 6 - Chemical Bonding

6.1 The Stable Noble Gas Structure
Atoms of noble gases are usually unreactive or stable.
An atom is stable if it has a duplet or octet configuration.

6.2 Forming Ions
An ion is a charged particle formed from an atom or a group of atoms by the loss or gain of electrons.

Metals form positively charged ions (cations) whereas non-metals form negatively charged ions (anions).

Metals give electrons and non-metals take electrons.

6.3 Ionic Bond : Transferring Electrons
When metals react with non-metals, an ionic compound is formed.

Positive ions and negative ions are attracted to one another by electrostatic attraction.

An ionic bond may also be known as an electrovalent bond.
Compounds that has ionic bonds are called ionic compounds.

Structure of Ionic Compounds
Ionic compounds are arranged in a giant lattice structure or crystal lattice.


Physical Properties of Ionic Compounds

1. Ionic compounds have high melting and high boiling points. (Non-volatile substances)
2. Ionic compounds are soluble in water but not in oil.
3. Ionic compounds do not conduct electricity in the solid state but in the molten state as there are free-moving ions that conduct electricity.

6.4 Covalent Bond: Sharing Electrons
When non-metals react with non-metals, an covalent bond is formed.

Structure of Covalent Bond Compounds



Physical Properties of Covalent Substances

1. Covalent compounds have low melting and low boiling points.
   
2. Covalent compounds are soluble in oil but now in water.
3. Covalent compounds do not conduct electricity in any state.

*Ionic compounds have electrostatic attraction. Covalent compounds have intermolecular forces.

Physics: Chapter 13 - Sound

13.2 Transmission of Sound
Sound waves need a medium in order to travel from one point to another.

13.3 Reflection of Sound
An echo is formed when a sound is reflected off hard, flat surfaces such as a large wall or a distant cliff.

Uses of echos
Use to detect the position of mines and submarines.

13.4 Pitch and Loudness
Pitch
Pitch is related to the frequency of a sound wave.
Sound with lower frequency has a lower pitch.
Sound with higher frequency has a higher pitch.

Loudness
Loudness is related to the amplitude of a sound.
The larger the amplitude, the louder the sound.
The shorter the amplitude, the softer the sound.

Physics: Chapter 12 - Electromagnetic Waves

12.1 Electromagnetic Waves
Ronald Mcdonald is very ugly X-cept Gary

Radio Waves - Longer wavelength Lower Frequency
Microwaves
Infrared
Visible light
Ultraviolet
X-rays

Gamma rays - Shorter wavelength High Frequency

Properties of electromagnetic waves

1. Electromagnetic waves are transverse waves.
2. They transfer energy from one place to another.
3. They can travel through vacuum. Do not require any medium to travel around.
4. They travel at a speed of 3.0 X 10⁸ ms^-1 in vacuum.
5. They obey the laws of reflection and refraction.
6. They carry no electric charge.
7. Their frequencies do not change when they travel from one medium to another. Only their speeds and wavelengths change from one medium to another.
   

12.3 Uses of Electromagnetic Waves
Application of elctromagnetic waves
Gamma Rays: Radiation therapy (Cancer treatment)
X-Rays: Medical and everyday application
Ultraviolet: Sunbeds and sterilisation of medical equipment
Visible light: Optical fibres
Infrared: Remote controllers and ear thermometers
Microwaves: Ovens and satellites
Radio waves: Radio and telecommunications

Effects of Electromagnetic Waves
Infrared heating - Skin absorbs infrared waves, making us feel warm.

Physics: Chapter 11 - Waves

11.1 Describing Waves
The source of a wave is vibration or oscillation.
Waves transfer energy from one point to another.
In waves, energy is transferred without the medium moving/ being transferred.

Transverse waves are waves that travel in a direction perpendicular to the direction of vibration of the particles.
Examples of transverse waves: Light waves

Longitudinal waves are waves that travel in a direction parallel to the direction of vibration of particles.

Examples of longitudinal waves: Sound waves.

11.2 Properties of Wave Motion


Crest and troughs: Highest and lowest points of a transverse waves.
Compression and rarefaction : Highest and lowest points of a longitudinal waves.

Phase: Points of a wave which move in the same direction, have the same speed and the same displacement from the original position.

Wavelength λ: Shortest distance between any two points in a wave that are in phase.
SI Unit: metre (m)

Amplitude A: Maximum distance from the rest position. It is the height of a crest or depth of a trough.
SI Unit: metre (m)


Period (T): Time taken for one point on the wave to complete one oscillation.
SI Unit: second (s)

Frequency (f): Number of complete waves produced per second.
SI Unit: Hertz (Hz)
f = 1/T

Wave speed (v): v = fλ
Wave speed = wavelength(period)
SI Unit: metre per second (m s^-1)

Wavefront: Imaginary line on a wave that joins all points that are in the same phase.

Physics: Chapter 9 - Thermal Properties of Matter

9.1 Temperature and Internal Energy
Internal energy is made up of kinetic energy and potential energy.

9.2 Melting and Solidification
Melting is the change of state from solid to liquid, without a change in temperature
During melting, the temperature remains constant at the melting point.
Thermal energy is absorbed by the substance.

Solidification is the change of state from liquid to solid, without a change in temperature.
During solidification, the temperature remains constant at the freezing point.
Thermal energy is released by the substance.

9.3 Boiling and Condensation
Boiling is the change of state from a liquid into vapour, occurring at a constant temperature called the boiling point.
During boiling, the temperature remains constant at its boiling point.
Thermal energy is being absorbed by the substance.

Condensation is the process whereby vapour changes into liquid at the same constant temperature. Heat is given out during condensation.
During condensation, the temperature remains constant at the condensation point. Thermal energy is released by the substance.

9.4 Evaporation
Factors affecting the rate of evaporation

1. Temperature
2. Humidity of the surrounding air
3. Surface area of the liquid
4. Movement of air
5. Pressure
6. Boiling point of the liquid

1. Temperature
Heating a liquid will increase the rate of evaporation because it means a greater number of molecules at the surface layer are energetic enough to escape.

2. Humidity of the surrounding air
Rate of evaporation decreases with increasing humidity (Water vapour present in the air).

3. Surface area of the liquid
Larger surface area = Increase in evaporation

4. Movement of air
Rate of evaporation increases when the surrounding air is moving.
Moving air removes the molecules of the liquid as soon as they escape from the surface of something.

5. Pressure
Reducing the atmospheric pressure increases the rate of evaporation.
Example: Things can dry faster on mountaintops than at sea level.

6. Boiling point of the liquid
Liquids with lower boiling point evaporates faster.