Chem paper 1

• What are atoms?


  Atoms are the particles that make up everything
• What is an element?


  An element is a substance in which all the atoms are the same
• Where are elements shown?

  Elements are shown in the Periodic table
• How many elements are there?

  There are around 118 elements
• What is a compound?


  A compound is a substance that contain two or more elements chemically combined
• Describe the properties of compounds

  The properties of compounds are usually different to the elements that they are made from
• What is a mixture?

  A mixture is a substance with different elements or compounds not chemically combined
• Give an example of a mixture

  An example of a mixture is sand and water as they are not chemically combined and can be separated by physical means
• What is a molecule?


  A molecule is a substance that has any elements chemically joined
• What does a chemical formula tell you about a molecule?


  A chemical formula tells the elements in a molecule and the number of atoms of each element
• How is a chemical formula presented?

  Each element symbol starts with a capital letter, if there is a second letter it is in lower case
• Give an example of a chemical formula

  
• What are state symbols?

  State symbols show the physical state of the substance solid (s), liquid (l), gas (g), or dissolved in water (aq)
• Name three properties of Metals

  -Strong

  -Good conductors of heat and electricity

  -High melting and boiling points
• Name three properties of Non-Metals

  -Weak

  -Bad conductors of heat and electricity

  -Low melting and boiling points
• State the four different ways of separating mixtures

  Four different ways of separating mixtures are filtration, crystallisation, distillation or chromatography
• Describe the process of filtration

  Pour your mixture onto the filter paper, the liquid simply passes through the filter paper into the flask. The insoluble solid cannot pass through and so it stays on the paper
• Describe the process of crystallisation

  Use the method of filtration to filter off any excess soluble solid. Evaporate the mixture then transfer the hot mixture onto a dish. Crystals are formed when the mixture has cooled
• Describe the process of simple distillation

  First we evaporate the mixture by heating it, the dissolved solid then vaporises. These vapours condense in the condenser, the dissolved solid then flows into the beaker and liquid stays in the flask
• Describe the process of chromatography

  Take a strip of filter paper and draw a line on the bottom of the paper. Put a small drop of ink on the line, take a jar full of water up to the line and put the filter paper in. As the water moves up we see different colours on the paper these are the dyes in the ink
• What were the early ideas of the structure of atoms?

  Early ideas of the structure of atoms stated that they are tiny spheres that cannot be divided
• What is the plum pudding model?


  The plum pudding model is what scientists suggested is the structure of atoms is after the discovery of the electron
• Describe the plum pudding model

  The plum pudding model suggested that an atom is a ball of positive charge with negative electrons in embedded in it
• Describe how Rutherford carried out the gold foil experiment

  Rutherford took a piece of gold foil, he then fired tiny positive alpha particles at the gold foil
• What did Rutherford observe in the experiment?

  Rutherford observed that most of the particles when straight through the gold foil and sometimes the alpha particles bounce back of the gold foil
• What did Rutherford discover from these observations?

  Rutherford discovered that atoms are mainly empty space as most of the alpha particles went straight through the gold atoms and that the nucleus of the atom is very small as only a small number of alpha particles bounce back
• Describe the structure of the nuclear model

  The nuclear model states that most of an atom is empty space, in the centre is the nucleus which contains protons and neutrons around the edge we find electrons
• What is the Relative mass and the relative charge of protons, neutrons and electrons?

  
• Why do atoms have the same number of protons as electrons?

  Because atoms have have no overall charge
• What is an Ion?

  An ion is a charged particle, it is possible to get positive or negative ions
• What is an Isotope?

  Atoms of the same element with different numbers of neutrons are called isotopes
• What is the mass number of an element?

  The mass number is the number on the top of an element it is the number of proton and neutrons combined
• What is the atomic number of an element?

  The atomic number is the number on the bottom it is number of protons in an atom, which is the same as the number of electrons
• How many electrons can you fit in the first, second and third shells?

  Shell 1 : 2 electrons

  Shell 2 : 8 electrons

  Shell 3 : 8 electrons
• What is an Electronic structure?


  A set of number to show the arrangement of electrons in their shells, eg. [2,6]
• What did John Newlands periodic table look like?


  He arranged the elements in order of increasing atomic mass, he saw that every eighth element reacted in a similar way
• What did Dmitri Mendeleev's periodic table look like?

  He arranged the elements in order of increasing atomic mass, he switched the order of some elements to the fitted in the patterns of other elements. He left gaps for undiscovered elements
• What does the modern periodic table look like?

  Elements are arranged in order of atomic number, the elements are organised in groups and periods which have the similar properties
• Why are elements in the periodic table grouped the way they are?

  Elements with similar chemical properties are grouped together in groups
• Why do elements in a group have similar chemical properties?

  Elements in a group have similar chemical properties because they all have the same number of electrons in their outer energy level therefore react similarly