Synthesis reactions Decomposition reactions Single replacement reactions Double replacement reactions Precipitate reaction Chemical Reactions can be written as Word equation Chemical equation ID: 645867
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Slide1
Chemical Reactions
Aim to look at a ‘varity of reactions…’
Synthesis reactions
Decomposition reactions
Single replacement reactions
Double replacement reactions
(Precipitate reaction)Slide2
Chemical Reactions can be written as:Word equation
Chemical equation
Equations must be balanced
ie
have the same # and type of atoms on either side of →
Reactant (s) Product (s)
2H
2
+
O
2
2 H2O
Hydrogen + Oxygen water Slide3
Equations must be balanced ie have the same # and type of atoms on either side of →Slide4
Aim: Investigate the decomposition of hydrogen peroxide catalyzed by Iodine (Elephants toothpaste)
Method: To 2 ml of concentrated 30% Hydrogen peroxide add 1 ml of KI (acts as a catalyst – initiates / starts the decomposition reaction)Check for O2 gas with a flame test
Word Equation:Formulae Equation:
Observations:
2H2O2 → 2H
2
O + 0
2
Hydrogen peroxide → Water + Oxygen gas
1) Decomposition reactions
Is when a compound ‘breaks down’ into elements or simpler compounds
AB A + BSlide5
2) Synthesis reactions Is when an element or compounds build or make new simpler compounds A + B AB
2Mg + O
2
2MgO
Mg
2+
O
2-
2Fe
+
3O
2
2Fe
2
O
3
Fe
3+
O
2-
Heat
HeatSlide6
Aim: Does
steel wool weigh more
or less after burning?
Word Equation:
Chemical Equation:Observations:
Assumptions & conclusions
Theory: Iron in steel wool reacts with oxygen from the air to form iron oxides. The oxygen from the air has mass and adds to the mass of the iron. The result is material that is heavier than the iron alone.
Synthesis reactions Slide7
Procedure:Pull apart steel wool. Fluff as big as you can without it hanging off of the scale. This is so oxygen can get into all parts of the woolMake observations on the wool.
Accurately measure the mass of the fluffed steel wool.
While the wool is still on the scale light it with a
candle, holding the wool
with tongs.
Write observations during and after the wool is burning.
Make observations on the
burnt wool
.
Record
the mass of the wool after it has burned.Slide8
Observations of Steel wool before during and after burningBefore the BurnGray materialStrong metallic smellSmall wires of metal interwovenFlexible, strong material
Mass = 0.243gDuring the Burndark smoke
Some sparksThe Reaction seems to follow each strand of the wool.
After the BurnThere is a new color
~ it is more ‘bluer’ in color Some small parts are
the same as before being burnt.
It looks
a similar same
shape and size as before.
Mass= 0.262gSlide9
3) Single replacement reactionsOne elements or group is replaced by another element or group of elements. A + BC AB + C An example is an acid + metal reaction
Aim: Investigate adding Mg to
HCl acidMethod: Add 1 strip
Mg to 2ml HCl and collect H2 gas in a small balloon then pop (explode) with a candle flame.
Word Equation:Chemical Equation:Observations:
2HCl + Mg → MgCl
2
+ H
2
Acid + Metal = Metal salt + Hydrogen gasSlide10
Chemical state notation
(aq)
(aq)
(s)
(g)
(
aq
) means exists in an aqueous state
(g) means exists in a gaseous state
(s) means exists in a solid state
(l) means exists in a liquid stateSlide11
(aq) means exists in an aqueous state
NaCl
(s)
NaCl
(
aq
)Slide12
4) Double replacement reactions (Precipitate reaction)A precipitate is formed whenever two solutions that chemically react can provide a combination of ions, which are
insoluble.
If the substance lacks the ability to dissolve in water (form
aqueous ions) the molecules form a precipitate
.Slide13
Precipitate reactions is when a solid forms in a solution
Metal
Non-
Metal
Metal
Non-
Metal
Metal
Non-
Metal
Metal
Non-
Metal
Na
2
CO3 (sodium carbonate)
CaCl
2
(calcium chloride)
CaCO
3
(calcium carbonate)
NaCl
(sodium chloride)
4) Double replacement (precipitate) reactions
A double replacement happens when two lots of ions are swapped over.
AB
+
CD
AD
+
CB Slide14
Aim: to Observe and analyse Five Precipitate reactions Observations:Describe what you started with
Describe what you are left with
Equations- for the reaction that has occurred write out;1. a word equation2. a balanced chemical equation
1)
Method: Add 1ml of Na2CO3 (sodium carbonate) to 1 ml of CaCl
2
(calcium chloride)
2)
Method
: Add 1ml of FeSO
4 (iron (ii) sulfate
) to 1ml of NaOH
(sodium hydroxide)3) Method: Add 1ml of FeCl3(iron (iii) chloride) to 1ml of NaOH (sodium hydroxide)
4) Method: Add 1ml of of KI (potassium iodine) to 1ml of
Pb(NO3
)2 (lead nitrate)
5)
Method
: Add 1ml of CuSO
4
to 1ml of
NaOH
(sodium hydroxide )Slide15
Aim: to Observe and analyse Five Precipitate reactions 1) Method: Add 1ml of Na2CO
3 (sodium carbonate) to 1 ml of CaCl2 (calcium chloride)
2) Method: Add 1ml of FeSO
4 (iron (ii) sulfate) to 1ml of NaOH
(sodium hydroxide)
3)
Method
: Add 1ml of FeCl
3
(iron (iii) chloride) to 1ml of
NaOH (sodium hydroxide)
4) Method: Add 1ml of
of KI (potassium iodine) to 1ml of Pb(NO3)2 (lead nitrate)5) Method: Add 1ml of CuSO4 to 1ml of
NaOH (sodium hydroxide)
Na2CO
3 + CaCl2 =
FeSO
4
+
NaOH
=
FeCl
3
+
NaOH
=
KI
+
Pb
(NO
3)2 =
CuSO4
+
NaOH
=
Observations:
Word equation:
Chemical equation:
Observations:
Word equation:
Chemical equation:
Observations:
Word equation:
Chemical equation:
Observations:
Word equation:
Chemical equation:
Observations:
Word equation:
Chemical equation:Slide16