chemistry paper 1 foundation

• chemical symbol


  a chemical symbol represents one atom of an element, chemical symbols have one or two letters
• one letter chemical symbols:

  hydrogen: H

  oxygen: O

  carbon : C

  potassium: K
• two letter chemical symbols

  magnesium: MG

  aluminium: AL

  helium: HE
• what is an atom?

  the smallest part of an element that can exist
• what is an element?

  a substance made up of one type of atom only
• the chemical formulae of elements


  the formula for most elements is just their chemical symbol. some non metals exist as molecules that are made up of two atoms joined together, a substrict 2 shows a two atom molecule
• what is a molecule?


  a collection of two or more atoms held together by chemical bonds
• compounds


  a compound contains two or more elements that are chemically combined, the elements in a compound are present in fixed proportions the formula of a compound shows the symbol for the elements in the compound and the number of atoms of each element in a unit of the compound
• what is a compound?

  a substance formed by the chemical union of two or more elements
• balanced chemical equations


  a balanced equation shows the formula of reactants and products and the relative amounts for each, a balanced equation has the same number of atoms of each element on both sides of the arrow
• what is a formula?

  a combination of symbols that indicates the chemical composition of a substance
• pure substances and mixtures

  a pure substance consists of one element or compound only. A mixture consists of two or more substances not chemically joined together. The substances in a mixture can be elements or compounds or both. Mixtures can be separated by physical processes. In a physical process no new substance is made
• what is a mixture?

  two or more substances that are not joined together the substances can be elements, compounds or both
• filteration 


  filteration separates an insoluble solid from a liquid, it only works because filter paper has tiny holes in it: dissolved solids and solvent molecules go through holes, pieces of undissolved solid do not go through the holes
• crystallisation


  makes solid crystals from a solution on warming a solution for crystallisation: the solvent evaporates and crystals form in the evaporating basin
• simple distillation


  separates a solvent from a solution, it is useful for obtaining pure water from seawater, simple distillation works because the dissolved solute has a much higher boiling point than the solvent, on heating the solution the solvent: evaporates, moves away, cools, condenses
• what is simple distillation?

  seperation method used to separate a solvent from a solution
• fractional distillation


  separates diffrent liquids from a mixture of liquids, it is useful for obtaining ethanol from a mixture of ethanol and water, fractions from crude oil, fractional distillation works because the liquids in the mixture have different boiling points. On heating the mixture vapours: rise up a column and condense when they reach a part of the column that is cooler than the temperature of their boiling point
• fractional distillation


  a mixture of several substances such as crude oil is distilled and the evaporated components are collected as they condense at different temperatures
• what is chromatography?


  is used to seperate different substances dissolved in a liquid
• chromatography


  separates mixtures of soluble substances, has two phases: the mobile phase that moves through the paper, the stationary phase on the paper, works because different substances in the mixture are attached to the two phases in different proportions. Paper chromatography is useful for: distinguishing pure and impure substances and identifying substances
• developing models of atoms

  scientists developed new atomic models as they gathered new evidence, the discovery of the electron led to the plum pudding model with negative electrons embedded in a ball of a positive charge, the alpha particle scattering experiment led to the nuclear model, later experiments led to the idea that the nucleus contains protons
• what is a proton?

  subatomic particle with a positive charge and a relative mass of 1. the relative charge of a proton is +1
• what is a neutron?

  uncharged subatomic particle with a mass of 1 relative to a proton the relative charge of a neutron is 0
• what is an electron?

  subatomic particle with a negative charge and a negligible mass relative to protons and neutrons
• structure of an atom

  atoms are tiny, almost all the mass of an atom is in its nucleus, the nucleus contains protons, of relative mass and charge +1, neutrons of relative mass and charge 0, electrons orbit the nucleus their relative mass is very small and their charge is -1
• atomic number and mass number

  the atomic number of an atom is the number of protons in the atom atoms of the same element have the same atomic number atoms have equal numbers of protons and electrons so there overall charge is zero the mass number of an atom is the total number of protons and neutrons in an atom: number of protons/ number of electrons = the atomic number and the number of neutrons= mass number and atomic number
• what is a mass number?

  Number of protons and neutrons found in the nucleus of an atom
• isotopes


  Atoms of the same element with different numbers of neutrons are called isotopes isotopes of an element have: the same atomic number and different mass numbers the relative atomic waste of an element is the weighted average of the masses of the atom of the isotopes relative atomic masses take account of the abundance of each isotope of the element
• what is relative atomic mass?

  the mean relative mass of the atoms of the different isotopes in a element it is the number of times heavier an atom is than one twelfth of a carbon 12 atom
• mendeleevs periodic table


  arranged elements by arranging them in order of increasing atomic weight he took the amount of element properties and atomic weight, it also had gaps and showed elements with similar properties lined up in groups, he also predicted properties of elements to fill gaps and reversed the orders of some pairs of elements
• the modern periodic table

  elements are arranged in order of increasing atomic number, periods are in horizontal rows and groups are vertical columns and elements in a group have similar properties and the existence of isotopes justifies mendeleevs pair reversals
• what is a period?

  a horizontal row in the periodic table
• what is a group?

  a vertical column in the periodic table containing elements with similar chemical properties
• metals and non metals in the periodic table

  there are more metals then non metals, metals are on the left and non metals are on the right, atoms of metal elements give away electrons in their reactions to form positive ions the ions have full outer electron shell they are very stable, atoms of non metals elements gain electrons in some of their reactions to form negative ions the ions gage full outer electron shells so they are very stable
• properties of metals and non metals

  in chemical reactions metals lose electrons to form postive ions some non metal atoms gain electrons to form negative ions and some non metal atoms do not form ions at all
• properties of metals and non metals

  metals have high boiling points and melting points while non metals have low melting and boiling points, metals conduct heat and electricity but non metals don’t, in the solid state most metals have high densities and most non metals have low densities
• what is an electronic structure?

  a notation that shows the number of electrons in each shell
• electronic structure 


  the number of electrons in the outer shell give the group number of an element in the periodic table, electrons occupy energy shells also called shells outside the nucleus, different shells can hold different maximum numbers of electron: the lowest energy level or first shell holds up to 2 electrons, the second shell holds up to 8 electrons, the third shell holds up to 8 electrons
• group 0


  column on the right, called the noble gases, have stable arrangements of electrons, unreactive, do not form molecules, have 8 electrons in their outer shell except for helium which has 2 electrons, the boiling point of the group 0 elements increase down the group