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Chemistry (C1-Atoms and Elements (SEPARATING MIXTURES (https://www.youtube…
Chemistry
C1-Atoms and Elements
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COMPOUNDS
They are formed during chemical reactions and are made up of a mixture of different atoms. They cannot be separated easily
SEPARATING MIXTURES
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Fractional distillation separates lots of different mixtures by evaporation. Substances have different boiling points so some condense at the top and others condense at the bottom
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CHEMICAL EQUATIONS
A chemical equation has reactants and the products and the mass stays the same throughout. Equations must be balanced.
ATOMIC MODEL
Atoms were thought to be ball of mass that could not be divided. Then, JJ Thompson discovered that atom were balls of positive charge with dotted negative charge. This is called the plum pudding model. Ernest Rutherford fired alpha particles at gold foil and found that the mass is concentrated in the centre. Niels Bohr said that electrons orbit the nucleus at specific energy levels. James Chadwick discovered the neutron
SUBATOMIC PARTICLES
Protons are positive and have a mass of 1. Neutrons have no charge and have a mass of 1. Protons and neutrons are in the nuleus of an atom. Electrons are negative and don't weigh anything and are found in energy levels.
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PERIODIC TABLE
The elements are ordered in the pattern of increasing atomic number. The rows are called periods and show how many shells there are. The columns are called groups and determine how many electrons are in the outer shell.
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NOBLE GASES
They are in group 0 and are inert because the outer shell is full. The boiling points get higher as you go down the group
ALKALI METALS
They are in group 1. They are very reactive and must be stored under oil. They have low melting and boiling points. When they react that loose an electron so they become inert.
THE HALOGENS
These are in group 7. When they react they gain an electron so that the outer shell can become stable. Their boiling points increase down the group and the group is diatomic. It gets harder to attract electrons as you go further down the group.
TRANSITION METALS
They have high melting and boiling points, can conduct heat and electricity and are malleable and strong.
C2-Bonding, Structure and Matter
IONIC BONDING
This is between metals and non metals and involves the transfer of electrons in the outer shells. Ionic bonding causes atoms to become ions and be either positively or negatively charged
COVALENT BONDING
Covalent bonds are formed when atoms share their electrons. A good example is ammonia. Covalent bonds are very strong and form between non metals and non metals
METALLIC BONDING
Metallic bonding is the sharing of delocalised electrons which makes them very strong. Delocalised electrons are electrons that are not attached to a nucleus and are free to move within the structure. It is only the outer electron that is delocalised. This happens in metals and alloys
POLYMERS
Polymers are long chains that are joined by strong covalent bonds. They are also joined by intermolecular forces
STATES OF MATTER
Solids are close together, vibrate in a fixed position and are a regular pattern. Liquids have a random arrangement and can move around freely. Gases are far apart and move quickly in a random arrangement
CHANGES OF STATE
The amount of energy needed to change state depend on the strength of the forces between particles. The stronger the bonds, the higher the boiling point is
IONIC COMPOUNDS
They are giant ionic lattices. There are strong electrostatic forces in all directions. They have high boiling points because the bonds are hard to break. They can conduct electricity
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METALS
Metals are strong and have a high melting and boiling point. They are malleable and good conductors because they have a delocalised electron that can carry charge
ALLOYS
Alloys are harder than pure metals because they are mixtures of metals. They are harder because the atoms are different sizes so the layers are distorted and it is harder for the layers to slide over each other
FULLERENES
They are carbon structures that are hollow. The first one to be discovered was called buckminster fullerene. Nanotubes are useful for electronics
NANO PARTICLES
Nano particles can be used in medicine, health and beauty and electronics. Some people believe they could be toxic
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Errors
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REPEATABILITY
Measurements are very similar when repeated by the same group, equipment and method
REPRODUCABILITY
measurements are very similar when the experiment is conducted by a different group, equipment and method
ACCURACY
A measurement is accurate if it is close to the true value. Anomalies should be removed when calculating the mean.
C4-Chemical Changes
ORES
A metal compound within a rock is called an ore. They are then mined and purified. Most metals in rocks are bonded to other compounds and have been oxidised
REACTIVITY SERIES
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OXIDATION AND REDUCTION
Oxidation is the addition of oxygen, reduction is the loss of oxygen. OILRIG- Oxidation Is Loss of electron Reduction Is Gain of electrons.
SALTS
Salts are formed when an acid and a metal react. This produces a salt and hydrogen. Reactions between metals and acids only happens if the metal is more reactive than hydrogen.
Soluble salt = acid + alkali = salt + water or acid + base = salt + water or acid + metal carbonate = salt + water
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