AGRICULTURAL SCIENCE
, AGRICULTURAL CHEMISTRY
MATTER: MOLECULES:
→ Anything that occupies space and has mass [=small → atoms = stick to themselves or other elements by chemical
particles] bonding = molecules
PURE SUBSTANCE / COMPONENT → substance that cannot be → binding process = formation of new pure substances
broken down into simpler components by physical methods / A → Molecules = chemically broken down → elements from which
single substance that is not mixed with anything else, and all the they are composed
particles are exactly the same [CONSISTS OF ONE TYPE OF
SUBSTANCE: ELEMENT / COMPOUND]
MIXTURES
ELEMENTS
MIXTURE:
→ Pure substance that cannot be broken down into simpler → combination of two or more pure substances, where these
substances by chemical methods [ONE KIND OF ATOM] substances are not bound (or connected) together [each
substance in the mixture still retains its own special properties
= simplest form of a substance [=atoms]
BUT the composition can vary]
COMPOUNDS
HOMOGENEOUS MIXTURES
→ substance consisting of two or more different atoms and
which are chemically bonded together into a single substance
MIXTURE [HOMOGENEOUS]:
[chemical methods = separate into simpler substances]
→ composition is uniform (is the same throughout) and the
ELEMENTS COMPOUND MIXTURE different components of the mixture cannot be seen
ONE kind of atom Composition is CONSTANT Composition = difference → looks uniform to the naked eye
& consisting of 2 / more
elements & compounds
Properties are UNIQUE Properties DIFFERENT Properties = same as of
from the properties of constituent substances
the constituent elements
Components cannot be Components separated Components separated
separated [physically / with CHEMICAL methods with PHYSICAL methods
chemically]
2© Noted Summaries [Grade 11 Agricultural Sciences] www.notedsummaries.co.za
, HETEROGENEOUS MIXTURES
MIXTURE [HETEROGENEOUS]:
THE PERIODIC TABLE
→ the composition is not uniform (not the same throughout) Z H (hydrogen) – is a metal and non-metal and is found on both sides of
and the different components of the mixture can be seen the periodic table
→ combination
. of substances that cannot dissolve in each other Z the elements are arranged in order of increasing atomic numbers, with
the lightest element (H, HYDROGEN) in the upper left corner
COLLOIDAL MIXTURE Z position of element tells whether it is a metal or non-metal
(A) metals are found on the left side
MIXTURE [COLLOIDALS]:
→ molecule sizes increase / clumps of molecules (micelles) occur (B) non-metals are found on the far right
→ only with an electron microscope (C) tables have rows and columns
→ does not dissolve in water & forms heterogeneous mixture
Z there are 92 natural elements
[suspension] Z rows from left to right are called PERIODS (there are 7 periods)
Z columns from top to bottom are called GROUPS (there are 18 groups)
ISOTYPE
ISOTYPE:
→ Atoms of the same element with the same atomic number
(number of protons) but with different mass numbers (protons
and neutrons)
→ different versions of an element
→ radioactive [Carbon-14 > isotope of Carbon-12]
3© Noted Summaries [Grade 11 Agricultural Sciences] www.notedsummaries.co.za
, GROUP 1 : ALKALI METALS GROUP 17 : HALOGENS
ALKALI METALS: HALOGEN:
→ Stored in oil or paraffin to prevent contact with oxygen and → Diatomic elements. Consists of molecules with two atoms
water. Chemical reactivity increases from top to bottom in a each. Chemical reactivity decreases from top to bottom in group
group [ionization energy > decrease the valence electron] fluorine, chlorine, bromine, iodine, acetate [radioactive]
lithium, sodium, potassium, rubidium, cerium, francium
F₂ Cl₂ Br₂ I₂
CHARACTERISTICS:
F₂ & Cl₂= yellow-green (room temperature) [TOXIC]
Z Low density (floats on water)
Z Soft > potassium = softest & lithium = hardest Br₂ = reddish brown liquid [TOXIC]
Z Silver coloured & shiny surface I₂ = purple crystals
Z GOOD CONDUCTORS [heat + electricity]
Z Fire in air = solid oxides [alkaline solutions] CHARACTERISTICS:
Z Reacts violently with water > hydrogen gas + alkaline solution of the metal Z Non-metals
hydroxide Z Diatomic molecules
Z Form CATIONS > +1 charge Z ANIONS > -1 charge
Z Low melting points & boiling points > increase as you move down the group
Z Coloured > colour becomes stronger > moves down the group
GROUP 2 : ALKALI - EARTH METALS Z Reactivity> move down the group
ALKALI EARTH METALS: GROUP 18 : NOBLE GASES
→ Chemical reactivity increases from top to bottom in a group
NOBLE GASES:
beryllium, magnesium, calcium, strontium, barium + radium
→ Chemically unreactive. Monatomic gases with completed
CHARACTERISTICS: outer energy levels.
Z Silver coloured helium, neon, argon, krypton, xenon, radon
Z GOOD CONDUCTORS [heat + electricity]
CHARACTERISTICS:
Z Fire in air = solid oxides [alkaline solutions]
Z Reactivity with water DIFFERS Z UNREACTIVE
Z Form CATIONS > +2 charge Z Reactivity > move down the group
Z Boiling points
Z > move down the group
4© Noted Summaries [Grade 11 Agricultural Sciences] www.notedsummaries.co.za
, AGRICULTURAL CHEMISTRY
MATTER: MOLECULES:
→ Anything that occupies space and has mass [=small → atoms = stick to themselves or other elements by chemical
particles] bonding = molecules
PURE SUBSTANCE / COMPONENT → substance that cannot be → binding process = formation of new pure substances
broken down into simpler components by physical methods / A → Molecules = chemically broken down → elements from which
single substance that is not mixed with anything else, and all the they are composed
particles are exactly the same [CONSISTS OF ONE TYPE OF
SUBSTANCE: ELEMENT / COMPOUND]
MIXTURES
ELEMENTS
MIXTURE:
→ Pure substance that cannot be broken down into simpler → combination of two or more pure substances, where these
substances by chemical methods [ONE KIND OF ATOM] substances are not bound (or connected) together [each
substance in the mixture still retains its own special properties
= simplest form of a substance [=atoms]
BUT the composition can vary]
COMPOUNDS
HOMOGENEOUS MIXTURES
→ substance consisting of two or more different atoms and
which are chemically bonded together into a single substance
MIXTURE [HOMOGENEOUS]:
[chemical methods = separate into simpler substances]
→ composition is uniform (is the same throughout) and the
ELEMENTS COMPOUND MIXTURE different components of the mixture cannot be seen
ONE kind of atom Composition is CONSTANT Composition = difference → looks uniform to the naked eye
& consisting of 2 / more
elements & compounds
Properties are UNIQUE Properties DIFFERENT Properties = same as of
from the properties of constituent substances
the constituent elements
Components cannot be Components separated Components separated
separated [physically / with CHEMICAL methods with PHYSICAL methods
chemically]
2© Noted Summaries [Grade 11 Agricultural Sciences] www.notedsummaries.co.za
, HETEROGENEOUS MIXTURES
MIXTURE [HETEROGENEOUS]:
THE PERIODIC TABLE
→ the composition is not uniform (not the same throughout) Z H (hydrogen) – is a metal and non-metal and is found on both sides of
and the different components of the mixture can be seen the periodic table
→ combination
. of substances that cannot dissolve in each other Z the elements are arranged in order of increasing atomic numbers, with
the lightest element (H, HYDROGEN) in the upper left corner
COLLOIDAL MIXTURE Z position of element tells whether it is a metal or non-metal
(A) metals are found on the left side
MIXTURE [COLLOIDALS]:
→ molecule sizes increase / clumps of molecules (micelles) occur (B) non-metals are found on the far right
→ only with an electron microscope (C) tables have rows and columns
→ does not dissolve in water & forms heterogeneous mixture
Z there are 92 natural elements
[suspension] Z rows from left to right are called PERIODS (there are 7 periods)
Z columns from top to bottom are called GROUPS (there are 18 groups)
ISOTYPE
ISOTYPE:
→ Atoms of the same element with the same atomic number
(number of protons) but with different mass numbers (protons
and neutrons)
→ different versions of an element
→ radioactive [Carbon-14 > isotope of Carbon-12]
3© Noted Summaries [Grade 11 Agricultural Sciences] www.notedsummaries.co.za
, GROUP 1 : ALKALI METALS GROUP 17 : HALOGENS
ALKALI METALS: HALOGEN:
→ Stored in oil or paraffin to prevent contact with oxygen and → Diatomic elements. Consists of molecules with two atoms
water. Chemical reactivity increases from top to bottom in a each. Chemical reactivity decreases from top to bottom in group
group [ionization energy > decrease the valence electron] fluorine, chlorine, bromine, iodine, acetate [radioactive]
lithium, sodium, potassium, rubidium, cerium, francium
F₂ Cl₂ Br₂ I₂
CHARACTERISTICS:
F₂ & Cl₂= yellow-green (room temperature) [TOXIC]
Z Low density (floats on water)
Z Soft > potassium = softest & lithium = hardest Br₂ = reddish brown liquid [TOXIC]
Z Silver coloured & shiny surface I₂ = purple crystals
Z GOOD CONDUCTORS [heat + electricity]
Z Fire in air = solid oxides [alkaline solutions] CHARACTERISTICS:
Z Reacts violently with water > hydrogen gas + alkaline solution of the metal Z Non-metals
hydroxide Z Diatomic molecules
Z Form CATIONS > +1 charge Z ANIONS > -1 charge
Z Low melting points & boiling points > increase as you move down the group
Z Coloured > colour becomes stronger > moves down the group
GROUP 2 : ALKALI - EARTH METALS Z Reactivity> move down the group
ALKALI EARTH METALS: GROUP 18 : NOBLE GASES
→ Chemical reactivity increases from top to bottom in a group
NOBLE GASES:
beryllium, magnesium, calcium, strontium, barium + radium
→ Chemically unreactive. Monatomic gases with completed
CHARACTERISTICS: outer energy levels.
Z Silver coloured helium, neon, argon, krypton, xenon, radon
Z GOOD CONDUCTORS [heat + electricity]
CHARACTERISTICS:
Z Fire in air = solid oxides [alkaline solutions]
Z Reactivity with water DIFFERS Z UNREACTIVE
Z Form CATIONS > +2 charge Z Reactivity > move down the group
Z Boiling points
Z > move down the group
4© Noted Summaries [Grade 11 Agricultural Sciences] www.notedsummaries.co.za
