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ELEMENTS, COMPOUNDS & MIXTURES
What is an Element?
An element is a simple pure substance which cannot be made simpler using chemical means. A pure substance is a form of matter that has the same composition throughout. Elements are the building blocks of matter. Everything around us is made up of an element or elements. All the known elements are listed in a special table called the Periodic Table. There are 115 known elements. 92 of these elements occur naturally. Of the 92 naturally occurring elements there are:
- **11 gases (hydrogen, oxygen, nitrogen, fluorine, chlorine, helium, neon, argon, krypton, xenon & radon);
- 2 liquids (mercury and bromine);
- 79 solids (mostly metals). Note: the elements are in these states at room temperature (25oC).** Each element in the table is denoted by a symbol. The symbol for sodium is shown. You will need to learn some of the symbols given on the Periodic Table. An element is made up atoms joined together. The atoms are all the same for a particular element. For example, copper is made up of copper atoms, iron is made up of iron atoms etc. Some important facts about elements include:
What is a Compound?
A compound is a pure substance that consists of atoms of two or more elements joined together. Compounds are formed when atoms of different elements react together. Compounds can be decomposed into elements using chemical means. Most pure substances are compounds. Compounds have a chemical formula. The chemical formula is made up from the symbols of the elements in the compound. It also indicates the number of atoms of each element in the compound. An example of a very important compound is water. Water is made up of two elements- hydrogen and oxygen. The chemical formula for water is shown. Other important compounds are:
The elements which react together to form a compound have different properties to the compound formed. For example, sodium (a very reactive metal) can combine chemically with chlorine (a poisonous gas) to form sodium chloride, a chemically harmless white powder which we call salt.
Na
Sodium
Atomic number
Symbol
Name
An element is made up of atoms which are all the same: M The most common element on Earth is oxygen (about 50%); M The least common naturally occurring element is Astatine; M The most recently discovered element was Ununoctium - it was produced artificially. M Scientists believe that all matter in the universe is composed of the same elements that are present on Earth.
The symbol for H 2 O
hydrogen. (H)
The symbol for oxygen. (O)
The formula indicates there are two (2) hydrogen atoms for every one (1) oxygen atom.
Compound: Formula:
sodium chloride (common salt used for cooking)
NaCl
carbon dioxide (a gas found in the atmosphere)
CO 2
sucrose (common sugar) C
12 H 22 O 11
Domain: 5. relates properties of elements, compounds and mixtures to scientific models, theories and laws
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Name:…………………………………………………………………… Class:………………
ELEMENTS, COMPOUNDS & MIXTURES
What is a
Mixture?
A mixture is made up of two or more pure substances. These substances are not joined chemically and can be separated without using chemical means. Mixtures are said to be impure. An example of a mixture is air. It is made up of nitrogen, oxygen and oth- er gases. These gases are not chemi- cally combined. Mixtures can be separated into the substances which make up the mix- ture. Methods of separating mixtures include filtration, distillation and chromatography.
What is a Molecule?
Atoms can be bound together as a molecule. Elements can be in the form of molecules. For example, oxygen consists of molecules which are two oxygen atoms bound together (O 2 ). Compounds can also be in the form of molecules. An example of a molecule which is a compound is carbon dioxide (CO 2 ). Water is also a compound which consists of molecules. Compounds can also have a crystalline structure. For example, sodium chloride (table salt) is crystalline when not dissolved in water.
Questions:
- What is an element?
- What is a pure substance?
- Complete the sentence: “elements are the building blocks of ______________”
- Complete the sentence: “ the known elements are listed in the _______________ ____________”
- How many known elements are there?
- What are the elements made up of?
- What is the most common element on Earth?
- What is a compound?
- How are compounds formed?
- Complete the sentence: “ most pure substances are _________”.
- What does a chemical formula show?
- (a) What is the chemical formula for water? (b) What elements are in water? (c) What is the ratio of hydrogen atoms to oxygen atoms in water?
- What is the formula for: (a) sodium chloride; (b) carbon dioxide; (c) sucrose?
- Complete the sentence: “sodium chloride is common ____________”
- In sucrose, what is the ratio of atoms for each element?
- What is a mixture made up of?
- Complete the sentence: “mixtures are not joined _____________ and can be ________________”
- (a) What is a molecule? (b) Name an element which exists as a molecule. (b) Name a compound which exists as
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matter
impure
C
pure
two or more elements combined
cannot be made simpler by chem- ical means
A B
ELEMENTS, COMPOUNDS & MIXTURES
- On your Periodic Table:
- colour in the elements which are gases;
- colour in the elements which are liquids. Include a suitable key e.g.
- Complete the following table by finding the information on your Periodic Table:
Domain: 4. describes observed properties of substances using scientific models and theories
Page 3 of 3
Name:…………………………………………………………………… Class:………………
Element Atomic
Number
Symbol State
(s,l or g)
Hydrogen 1 H g
Helium 2 He g
Lithium 3 Li s
Beryllium 4 Be s
Boron 5 B s
Carbon 6 C s
Nitrogen 7 N g
Oxygen 8 O g
Fluorine 9 F g
Neon 10 Ne g
Sodium 11 Na s
Magnesium 12 Mg s
Aluminium 13 Al s
Silicon 14 Si s
Phosphorus 15 P s
Sulfur 16 S s
Chlorine 17 Cl g
Element Atomic
Number
Symbol State
(s,l or g)
Argon 18 Ar g
Potassium 19 K s
Calcium 20 Ca s
Iron 26 Fe s
Copper 29 Cu s
Zinc 30 Zn s
Bromine 35 Br l
Silver 47 Ag s
Tin 50 Sn s
Iodine 53 I s
Barium 56 Ba s
Platinum 78 Pt s
Gold 79 Au s
Mercury 80 Hg l
Lead 82 Pb s
Uranium 92 U s
Solid Liquid Gas
(^3) Li 6.941 Lithium
1^ H
Hydrogen
(^2) He 4.0003^ Helium
(^3) Li 6.941 Lithium
(^4) Be 9.012 Beryllium
(^5) B 10.81^ Boron
6 C 12.01 Carbon
(^7) N 14.01 Nitrogen
(^8) O 16.00 Oxygen
9 F 19.00 Fluorine
(^10) Ne 20.18^ Neon
(^11) Na 22. Sodium
(^12) Mg 24. Magnesium
13 Al 26.98 Aluminium
14^ Si 28. Silicon
15^ P 30. Phosphorus
16^ S 32.06^ Sulfur
17 Cl 35.45 Chlorine
18 Ar 39.95^ Argon
19^ K 39. Potassium
(^20) Ca 40. Calcium
21 Sc 44. Scandium
22^ Ti 47.90 Titanium
23^ V 50.94 Vanadium
24 Cr 52. Chromium
(^25) Mn 54. Manganese
(^26) Fe 55.85^ Iron
(^27) Co 58.93 Cobalt
28^ Ni 58.71 Nickel
(^29) Cu 63. Copper
(^30) Zn 65.38^ Zinc
(^31) Ga 69.72 Gallium
(^32) Ge 72. Germanium
33 As 74. Arsenic
(^34) Se 78.96 Selenium
35 Br 79.90 Bromine
36 Kr 83.80 Krypton
(^37) Rb 85. Rubidium
38 Sr 87. Strontium
39^ Y 88. Yttrium
40 Zr 91.22 Zirconium
(^41) Nb 92.91 Niobium
(^42) Mo 95. Molybdenum
43 Tc 98. Technetium
(^44) Ru 101.1 Ruthenium
(^45) Rh 102.9 Rhodium
(^46) Pd 106. Palladium
(^47) Ag 107.9 Silver
(^48) Cd 112.4 Cadmium
49^ In 114.8 Indium
50 Sn 118.7 Tin
51 Sb 121. Antimony
(^52) Te 127.6 Tellurium
53^ I 126.9^ Iodine
(^54) Xe 131.3 Xenon
(^55) Cs 132. Caesium
(^56) Ba 137. Barium
57
-^71 Lanthanides
72 Hf 178.5 Hafnium
73 Ta 180.9 Tantalum
74^ W 183. Tungsten
75 Re 186. Rhenium
(^76) Os 190.2 Osmium
77^ Ir 192.2 Iridium
78^ Pt 195. Platinum
(^79) Au 197.0 Gold
(^80) Hg 200.6 Mercury
81^ Tl 204.4 Thallium
82 Pb 207.2 Lead
83^ Bi 209. Bismuth
(^84) Po (210) Polonium
85 At (210) Astatine
(^86) Rn (222) Radon
87^ Fr (223) Francium
(^88) Ra 226. Radium
89
-^103 Actinides
104^ Rf (261.1) Rutherfordium
105^ Db (262.1) Dubnium
106^ Sg (263.1) Seaborgium
107^ Bh (264.1) Bohrium
108^ Hs (265.1) Hassium
109^ Mt (268) Meitnerium
110^ Uu (269) Ununnilium
111^ Uu (272) Unununium
112^ Uu (277) Ununbium
Notfound
114^ Uu (289) Ununquadium
Notfound
116^ Uu (289) Ununhexium
Notfound
(^118) (293) Uuo Ununoctium
57 La 138.9 Lanthanum
58 Ce 140. Cerium
59 Pr 140.9 Praseodymium
(^60) Nd 144. Neodymium
(^61) Pm (145) Promethium
(^62) Sm 150. Samarium
63 Eu 152. Europium
(^64) Gd 157.3 Gadolinium
65 Tb 158. Terbium
(^66) Dy
Dysprosium
(^67) Ho 164. Holmium
68 Er 167.3 Erbium
(^69) Tm 168.9 Thulium
70 Yb 173. Ytterbium
(^71) Lu 175.0 Lutetium
(^89) Ac 227.0 Actinium
90 Th 232. Thorium
(^91) Pa 231.0 Protactinium
92^ U 238. Uranium
(^93) Np
Neptunium
(^94) Pu (239.1) Plutonium
(^95) Am (241.1) Americium
(^96) Cm (244.1) Curium
97 Bk (249.1) Berkelium
98 Cf (252.1) Californium
99 Es (252.1) Einsteinium
100^ Fm (257.1) Fermium
101^ Md (258.1) Mendelevium
102^ No (259.1) Nobelium
103^ Lr (262.1) Lawrencium
- Atomic number (Z) • Symbol • Relative atomic mass • Name of element
Periodic TablePeriodic TablePeriodic Table
200620062006
Metals: Left
side
of
step. Non-metals: Right
side of
step.
∙ There
are 92
naturally
occurring elements
∙ At room temperature and
pressure:
→ 2 are liquids (Hg and Br) → 11
are gases (H,N,O,F,Cl,He,Ne,Ar,Kr,Xe,Rn)
→ the
rest
are solids
Name:……………………………………………………………………
Class:………………
SEPARATING MIXTURES
Types of Solutions-
Three important processes used to separate the components of a solution are:
Evaporation & Crystallisation-
The process of evaporation leads to the separation from a solution of a solute in the form of crystals. Crystallisation is the process of growing crystals of a solid from a solution. Impure crystalline substances can be recrystallised to remove impurities. Common table salt (sodium chloride) is crystallised from sea water by evaporation. It is purified by recrystallisation.
Crystallisation:
Distillation-
Distillation is the process whereby a liquid is purified by being turned into a vapour (gas) and then allowing the vapours to condense in another container. Distillation is used for separating:
- two or more liquids mixed together;
- dissolved solids from liquids. For example, a mixture of water and alcohol could be separated using this method. Also the salt in saltwater could be separated from the water using this method. In distillation, the mixture is heated until the liquid(s) start to boil and turn into a gas. Every liquid boils at a different temperature. The condenser cools the gas down so that it forms a liquid again (condenses). The liquids can be collected as they boil at different temperatures.
Chromatography-
Chromatography is a method which separates substances based on the rate at which a solvent will carry the substances across an adsorbing surface. A substance is adsorbed when it attaches to another material. Paper chromatography can be used to separate a mixture of coloured substances. The colours in black ink can be separated using this method.
Paper chromatography:
Type of Solution Examples
solid dissolved in a liquid * sugar dissolved in water
liquid dissolved in a liquid * ethanol (an alcohol) dissolved in water
gas dissolved in a liquid * carbon dioxide dissolved in water- as in soda water
black ink dot
condenser
distillation flask
water in
water out
Apparatus for distillation:
solution of salt (^) crystals of salt
evaporation
black ink separates into colours
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SEPARATING MIXTURES
Filtration & Sedimentation-
Filtration is used to separate undissolved solids or suspended matter from a liquid. For example, if muddy water is filtered, the mud particles can be separated from the water. Filtration usually involves pouring the mixture through filter paper. The liquid which passes through the filter paper is called the filtrate. The solids collected in the filter paper is called the residue. A suspension can also be allowed to stand so that the solid matter drops to the bottom of the container. This is referred to as sedimentation. The process of sedimentation can be accelerated by using a centrifuge. A centrifuge spins rapidly so that the sediments move towards the base of the container.
Filtration:
Magnetic separation-
In the separation of some ores use is made of the fact that one mineral will be more strongly attracted to a magnet than another. The ore is crushed and then dropped on to a conveyor belt. The rollers which turn the conveyor belt are magnetic. The non-magnetic minerals drop directly from the end of the conveyor belt into a chute. The magnetic minerals travel further being attracted to the roller. When the magnetic force is too weak to support the magnetic mineral, it drops into a second chute.
Magnetic separation:
Froth flotation-
This method is used extensively to separate minerals from useless rock material. The minerals are ‘wetted’ by a special oil. This oil helps the mineral grains adhere to the froth. In the froth flotation tank, air is bubbled through the water containing the minerals and detergent. The froth produced carries the light mineral to the surface. The froth carrying the mineral grains is collected from the top of the tank and undergoes further chemical treatment.
Froth flotation:
filter funnel
filter paper
retort ring
mixed ore
magnetic ore non-magnetic ore
conveyor belt with magnetic rollers
rotating blades draw in air and liquid and beat them into froth
froth carries mineral to the surface
froth bubbles with solid sticking to them
magnified
Suspensions & Rocks Containing Minerals- A suspension is a liquid containing an insoluble material suspended in it. The material is referred to as a sediment when it settles to the bottom of the container. Many minerals are used to manufacture metals. These minerals are called ore minerals. They are mined from the ground and are usually found mixed with other minerals and rock material. The metal mineral must be extracted from the mixture. Three important separations processes are:
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Name:…………………………………………………………………… Class:………………
PHYSICAL & CHEMICAL CHANGES
Physical & Chemical Changes Matter is constantly undergoing change. These changes are either:
Physical changes: Chemical changes:
involved
Examples:
Examples:
- burning wood * iron rusting
- dynamite exploding * petrol burning
Recognising a chemical change:
- Heat may be produced;
- There may be a colour change;
- A gas may be produced (bubbles may be seen);
- The substance involved in the reaction dissolves.
Domain: 4. describes observed properties of substances using scientific models and theories
ELEMENTS, COMPOUNDS & MIXTURES
Questions:
- What is an element?
- What is a pure substance?
- Complete the sentence: “elements are the building blocks of ______________”
- Complete the sentence: “ the known elements are listed in the _______________ ____________”
- How many known elements are there?
- On your Periodic Table:
- colour in the elements which are gases; * colour in the elements which are liquids. Include a suitable key e.g.
- Draw up a table as shown. Use your Periodic Table to complete the table for the following elements: *** first twenty elements (1-20) plus:** iron, copper, zinc, bromine, silver, tin, barium, gold, mercury & lead
- What are the elements made up of?
- What is the most common element on Earth?
- What is a compound?
- How are compounds formed?
- Complete the sentence: “ most pure substances are _________”.
- What does a chemical formula show?
- (a) What is the chemical formula for water? (b) What elements are in water? (c) What is the ratio of hydrogen atoms to oxygen atoms in water?
- What is the formula for: (a) sodium chloride; (b) carbon dioxide; (c) sucrose?
- Complete the sentence: “sodium chloride is common ____________”
- In sucrose, what is the ratio of atoms for each element?
- What is a mixture made up of?
- Complete the sentence: “mixtures are not joined _____________ and can be ________________”
- What are three methods used to separate mixtures?
- Which separation method could be used to separate: (a) the colours in black ink; (b) suspended matter in water; (c) salt from saltwater?
- Classify the following as an element compound or mixture. *the diagram opposite may help;
- draw up a table with the headings element, compound, mixture for your answers. iron, air, sodium chloride, saltwater, concrete, ice cream, aluminium, water, hydrogen, carbon dioxide, lemonade, sodium, lithium iodide, soup, nitrogen, iron sulfide
- What are the two types of changes matter can undergo?
- What are three differences between physical and chemical changes?
- Classify the following as physical or chemical changes: (a) margarine melts; (b) water boils; (c) wax melts; (d) kerosene burns; (e) aluminium corrodes.
Solid Liquid Gas
Element Atomic number
State (solid, liquid or gas)
Symbol
30 lines
Is it listed in the Periodic Table?
No (move to next col- umn)
Does it have two words and elements in its name?
Yes- it is an:
element!
No (move to next column)
It must be a:
mixture!
Yes- it is a:
compound!
water in
water out
Apparatus for distillation:
water in
water out
Apparatus for distillation:
