Pages in this set

Page 1

Preview of page 1
GCSE Chemistry
`Unit 3a' written by Applequestria

Table of Contents

Table of Contents..................................................................................................................................... 1
The early periodic table ........................................................................................................................... 2
Newlands's Law of Octaves: ................................................................................................................ 2
Mendeleev's Periodic Table of Elements: ........................................................................................... 2
The modern periodic table ....................................................................................................................... 3
Trends within the periodic table .............................................................................................................. 4
The alkali metals (group…

Page 2

Preview of page 2
The early periodic table
In the nineteenth century, scientists attempted to classify the elements by arranging them in order of
their relative atomic masses (mass number, because atomic number wasn't discovered until the
twentieth century when electrons, protons and neutrons were discovered). When the elements were
listed by arranging them…

Page 3

Preview of page 3
The modern periodic table
When electrons, protons and neutrons were discovered in the early twentieth century, the periodic
table was arranged in order of atomic number instead of relative atomic mass (mass number), which
placed the elements in appropriate groups. The modern periodic table can be seen as an arrangement…

Page 4

Preview of page 4
Trends within the periodic table
The alkali metals (group one):
These include lithium, sodium and potassium.
They have low density (the first three elements are less dense than water).
The further down the group an element is, the lower the melting and boiling points.
The further down the group an…

Page 5

Preview of page 5
Trends within the periodic table (continued)
The transition elements (between group two and group three):
Compared with the alkali metals (group one), transition metals have high density.
They have higher melting and boiling points (except for mercury).
They are stronger and harder (except for mercury).
They are much less reactive…

Page 6

Preview of page 6
Hard and soft water
Soft water readily forms lather with soap. Hard water readily forms scum with soap because it reacts
with the soap (meaning more soap is needed to form a later). However, soapless detergents do not
form scum because it does not have soap.
Hard water is caused…

Page 7

Preview of page 7
Hard and soft water (continued)
Boiling hard water:
Temporary hard water becomes soft when boiled. When heated, the hydrogencarbonate ions (HCO3-)
decomposes to form carbonate ions (CO32-) which react with calcium and magnesium ions to form
insoluble precipitates of calcium carbonate and magnesium carbonate. Permanent hard water
remains hard when…

Page 8

Preview of page 8
Purifying water
Water of correct quality is essential for life. For humans, drinking water should have sufficiently low
levels of dissolved salts (such as poisonous phosphate salts and nitrate salts) and microbes (which can
cause diseases such as cholera and dysentery). Water of correct quality is produced by:
Choosing an…

Page 9

Preview of page 9
Making ammonia
A reversible reaction is a reaction where the products of the reaction themselves react to produce the
original reactants. When a reversible reaction occurs in a closed system, equilibrium is reached when
the reactions occur at exactly the same rate in each direction. A closed system is where…

Page 10

Preview of page 10
Making ammonia (continued)
The Haber process is an important industrial process as it produces ammonia (NH3) which is used to
make fertilisers. The raw materials for the Haber process are nitrogen and hydrogen. Nitrogen is
obtained from the air and hydrogen is obtained from natural gasses and other sources. Some…

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all resources »