Chem 1

• Mixtures


  Made of 2 or more substances that haven't been chemically combined
• The chemical properties of substances in a mixture don't change when they have been mixed with another substance
• Separating mixtures


  Use physical processes to separate the substances in a mixture, does not create new chemical substances
• Filtration


  Mixture goes through filter paper, the solid is trapped and liquid flows through
• Crystallization


  Separates a mixture into solutes and solvents. Heat it up until the solvent evaporates, the solute crystals will form. To get the solvent we can condense it.
• Chromatography


  Separates a solution with a few different solutes in the solvent. Step 1 is to place a drop of the solution to be separated near the bottom of a piece of chromatography paper, then dip the bottom into a suitable solvent. Then the solvent should move up the paper and carry the solutes in the solution.
• Simple distillation


  Heat the mixture until the liquid with the lower BP boils, the vapor released goes through a condenser, this will cool it back down into a liquid.
• Fractional distillation


  Separates lots of liquids, same as before but keeps on raising the temp.
• Atoms


  Building blocks of all matter, each atom is an element with its own symbol
• Compounds


  Contain different elements
• Mass number


  Total number of protons and neutrons an atom has in the nucleus
• Atomic number


  Number of protons
• Plum pudding model


  • JJ Thompson, discovered electrons, he said that the atom was a ball of positive charge with negatively charged electrons mixed in.
• Rutherford


  • Discovered alpha particles could bounce back of atoms, concluded that atoms mass was concentrated in the atoms centre, this was the positively charged nucleus.
• Chadwick


  • The modern model
• Isotopes


  All the same elements have the same number of protons, same atomic number. Isotopes form when they have a different number of neutrons.
• Relative atomic mass


  Calculated by the average mass of all isotopes of an element.
• Periods


  Rows in the periodic table, left to right. Elements with similar properties are on the same period.
• Groups


  Columns in the periodic table, up to down. Atoms have the same amount of electrons in their outer shell if they are in the same group.
• All elements in a column have the same electrons on the outer shell, they will have similar properties.
• Metals


  • Found on the left of the periodic table, they have few electrons in the outer shell. They lose electrons and form positively charged ions- high BP and MP, good conductors, all solid at room temp.
• Nonmetals


  • Found on the right on the periodic table, they either share electrons or gain to form negatively charged ions. These have low BP and MP, mainly do not conduct electricity or heat.
• Halogens


  Group 7 elements, have 7 electrons in their outer shell. They gain 1 electron when they react, form a negative ion.
• When a metal bonds with a group 7, a salt is formed
• As halogens become less reactive going down the group


  The nucleus can't attract another atom as it is further away
• Transition metals


  • Found in the middle of the table, in-between group 2 and 3. Higher melting points than alkali metals, they are also stronger and harder. They are also denser. They are less reactive than alkali metals, they take a long time to rust. They are used for certain purposes such as cooking due to their high melting point. They are important as they are used as catalysts. They can form ions with different positive charges, this can cause the color of the metal to change.
• Alkali metals


  • Group one of the periodic table and have one electron in the outer shell, they lose this electron and gain a positive charge. The metal usually floats on the surface and melts on reaction with water. More reactive with water as you go down. Reaction with chlorine- forms a metal chloride, can dissolve in water to give a colourless solution. Reaction with oxygen- turn from silverly shiny to dull quickly, a metal oxide is produced.
• Ionic bonding


  Attraction between oppositely charged ions, ionic lattice is the structure formed and it holds them together. The charges on the ions must be balanced.
• Covalent bonding


  Formed when 2 nonmetals share pairs of electrons. Bonds are strong as both nucleus of the atom attract each other.
• Metallic bonding


  Attraction between positive metals and a sea of delocalized negative electrons. Not bound to an atom but they can move around the lattice.
• The amount of energy required to change state depends on the strength of the force between particles. Stronger forces mean a higher boiling and melting point.
• Ionic compounds


  Form giant ionic lattice structures, held together by strong electrostatic forces between oppositely charged ions. These are called ionic bonds. These have high melting/boiling points as lots of energy is needed to break the electrostatic forces between the ions. They can only conduct electricity when they are liquid or in a solution, the ions in the lattice are free to move and carry an electric charge.
• Covalent molecules


  Can be held together by intermolecular forces, these can be weak and easy to break, meaning they have low melting and boiling points.
• Polymers


  Large, chain like molecules that can extend for thousands of atoms. They are held together by strong covalent bonds between atoms in molecules, and weak intermolecular forces between molecules. Each intermolecular force is weak on its own, but since there are so many they add up to be quite strong. Polymers are often solid at room temp due to strong intermolecular forces, they can melt easily though as the intermolecular forces are still weak. Polymers are made up of repeating units, we can show their chemical structure as a unit that is repeated lots of times.
• Pure metals


  • Have giant structures with strong electrostatic forces with positive ions and delocalized electrons. All of the ions are the same size, and these ions are arranged in layers. They have high melting/boiling points, the electrostatic forces mean they have high melting and boiling points. They are soft and malleable, because they are in layers, they slide over each other very easily, making pure metals soft and malleable.
• Alloys


  • A mixture of multiple elements where one is a metal, they have different sized ions. Alloys are stronger than pure metal as it is harder to slide the layers over each other, making them stronger and better for construction.
• Metals


  • They are good for electricity and heat; this is because the delocalized electrons can pick up a charge.
• Diamond


  • An allotrope of carbon, where each carbon atom is covalently bonded to four other atoms to give a giant covalent structure. Lots of covalent bonds making it strong, lots of energy is needed to break these bonds, giving it a high melting point. Can't conduct electricity.
• Graphite


  • An allotrope of carbon, it has a giant covalent structure but they only bond to three others. Soft as carbon form layers of hexagonal rings, these slide over each other due to the weak intermolecular forces. Conducts electricity as one electron is delocalized.
• Graphene


  • Another allotrope of carbon and is a single layer of graphite. It is very light but still strong because of the covalent bonds between carbon atoms. It can also conduct electricity, making it useful in electronics.