National Chemistry

National 4

Rate of Reactions

 

Chemical reactions can be identified by

       (i) a change in appearance of substance  

      (ii) a detectable energy change

     (iii) the formation of at least one new substance

 

Examples of reactions:  iodine clock       decomposition      x

 

  There are about 100 elements (each has a name, a symbol and an Atomic Number).

     An element has only one type of atom while a compound has at least two different types of atoms.

When different elements react together a compound is produced.

 

Compounds ending in "ide" usually have two different elements present, while

compounds ending in "ite" or "ate" have oxygen as a third element present.

 

  

 

Following chemical reactions - information

  Chemical reactions can be speeded up by

      (i) increasing temperature

      (ii) decreasing particle size (increasing surface area)

      (iii) increasing concentration

      (iv) using a catalyst

Further explanation

 

 Catalysts are substances which speed up reactions and are not used up during the

reaction - they can be recovered chemically unchanged e.g., transition metals in car

exhausts to reduce pollutant gases changing to harmless gases.

Catalysts can enable reactions to occur at lower temperatures

 

 

The 100 plus elements can be classified as

(i)   solids (s), liquids (1), or gases (g)

(ii)  metals or non metals

(iii) man-made (synthetic) or occurring naturally

(iv) by chemical properties

 

 Chemists have classified elements by their chemical properties and arranged them

in the Periodic Table in groups (columns) of elements with similar chemical properties due to them having the same number of outer electrons

 

Group 7         = halogens; very reactive gases with 7 outer electrons

     Group 8 (or 0) = Noble (or Inert) Gases - UNREACTIVE - full outer orbital.

     Group 1           = Alkali metals - reactive metals - one outer electron.

 

     Transition Metals - middle box of Periodic Table.

 

 Every element is made up of very small particles called atoms each with a different number of protons called the Atomic Number.

 Atoms of different elements vary in size and in mass.

Atomic structure lecture

             

                     

             particle                         mass               charge                  position in nucleus  

             proton                              1                    +1                        nucleus at centre

             neutron                            1                neutral                     nucleus at centre

            electron-                           0                     -1                        spinning around the nucleus

 

Equal numbers of positive protons and negative electrons make the atom neutral

 

      mass number = number of +ve protons = number of neutral neutrons

                   

                                        mass number = 27

                                                                        Al   = symbol

                                       atomic number=13

 

thus   number of protons = 13

          number of neutrons= mass number - protons = 27-13 = 14

          number of electrons = 13 same as protos in neutral atom (or look it up in data book where electron arrangement is 2,8,3  which add together to be 13

 

or for Sulphur

                                       mass number = 32

                                                                       S   = symbol for sulphur

                                       atomic number=16

 

thus   number of protons = 16

          number of neutrons= mass number - protons = 32-16 = 16

          number of electrons = 16 same as protons in neutral atom (or look it up in data book where electron arrangement is 2,8,6  which add together to be 16)

 

Atomic and mass number demo

 

Formation of ions

The only atoms that do not react are those of the nobel gases.

Most atoms are unstable and react to become stable. This invloves the atom obtaining a structure which has a full outer orbital; whuich is usually 8

 

(i) For aluminium with an electron arrangement of 2,8,3 this would become 2.8.

 

thus for Aluminium                      number of protons = 13

                                                      number of neutrons= mass number - protons = 27-13 = 14

          number of electrons = where electron arrangement is 2,8  which add together to be 10

                                   

          This means that there are 13 positive protons and 10 negative electrons giving an                

          overall charge of +ve 3

                                       mass number = 27      +3 = charge

                                                                        Al  

                                       atomic number=13

 

(i) For sulphur with an electron arrangement of 2,8,6 this would become 2.8,8

 

thus for sulpur                              number of protons = 16

                                                      number of neutrons= mass number - protons = 32-16 = 16          number of electrons = where electron arrangement is 2,8,8  which add together to be 18

                                   

          This means that there are 16 positive protons and 18 negative electrons giving an                

          overall charge of -ve 2

                                       mass number = 32      -2 = charge

                                                                        S  

                                       atomic number=16

 

 Isotopes are atoms of the same "element/ atomic number/ number of protons" but

different "mass number/ number of neutrons"

 

isotopes of chlorine

 

 

                                         mass number = 35                     37

                                                                        Cl        and        Cl

                                        atomic number=17                      17

 

atomic number ie number of protons the same (or they would be different elements).

 

mass number different - subtraction shows 18 neutron and 20 neutrons so neutrons different.

 

 

 

Isotopes of an atom have different abundances which results in the calculation of  an average mass for each element called the relative atomic mass - rarely a whole  number as it is an average.

 

 

Timeline of atomic theory

History of atomic theory

National 3

 

When two substances come together without reacting, then a mixture is formed.

Mixtures can be easily separated by physical methods such as filtration and evaporation depending on their solubility.

 

Chemicals can exist as solids (s), liquids (1), or gases (g)

 

At the melting point a chemical changes from solid to liquid

At the boiling point  a chemical changes from liquid to gas

 

 

There are 114 different elements

Each element is made of the same type of atom.  Oxygen is made from oxygen atoms, only.

 

A compound is made from different types of atoms. hydrogen oxide is made from oxygen atoms and hydrogen atoms bonded together.

 

Rate of Reactions

 

Examples of reactions:  iodine clock       decomposition      x

 

Chemical reactions can be identified by

       (i) a change in appearance of substance  

      (ii) a detectable energy change

     (iii) the formation of at least one new substance

 

A solution is formed when a solute dissolves in a solvent.

 

eg salt solution is formed when salt (solute) dissolves in water (solvent).

 

If a solution has a lot of solute dossolved is it said to be concentrated while one with only a little solute dissolved is called dilute. Think about 'concentrated' orange juice that you add water to (to dilute it) before drinking it.

 

If no more solute can dissolve then the solution is said to be saturated.

 

Chemists have classified elements by their chemical properties and arranged them in the Periodic Table in groups (columns) of elements with similar chemical properties.

 

Elements that conduct electricity when  are called metals while elements that do not conduct electricity are called non-metals.

However, carbon in the form of graphite is a non-metal that can conduct electricity

 

Compounds ending in "ide" usually have two different elements present, while

compounds ending in "ite" or "ate" have oxygen as a third element present.

 

eg magnesium sulphide is made of magnesium atoms and sulphide atoms bonded together

copper carbonate is made from copper atoms and carbon atoms and oxygen atoms bonded together

 

Chemical reactions can be illustated as word equations.

eg carbon dioxide and water react in photosynthesis to produce glucose and oxygen can be written as

 

carbon dioxide  +  Water ---> glucose   +   oxygen

 

These notes are for the Scottish National Chemistry course taught in fourth year in most Scottish schools.

 

The notes available here are concise notes. They are NOT to be considered as material to learn from - they are for revision.

 

 The notes are arranged under the following topics

 

National 3          Unit 1

                          Unit 2

                          Unit 3

 

National 4 and 5  Unit 1            Rates of Reaction

                                                  Atomic Structure

                                                  Bonding and Properties

                                                  Acids and bases

 

National 4 and 5  Unit 2       Fuels and Homologous Series

                                                Consumer Products

                                                Carbohydrates

 

National 4 and 5  Unit 3         Metals

                                                   Plastics

                                                   Fertilisers

                                                   Nuclear Chemistry

                                                  Chemical analysis

 

 

 

 

 

 

 

 

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