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Although polio has been completely eradicated from India, it is important to ensure that all children
up to five years of age are given the OPV drops. This is the only way to ensure your child and your
community are protected from polio.
Some parents worry about the side effects of the polio vaccine. The vaccine has proven to be safe and
is the most effective tool we currently have in preventing polio. A combination of OPV and IPV will
put your fears to rest. If you are still worried, discuss your concerns with your doctor.
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Why must my baby be given several doses of OPV?
The OPV is given in several doses to ensure that the disease is controlled and eventually eradicated.
Such repeated immunisations have made several countries around the world, including India poliofree.
If you are worried that multiple doses may result in side effects or an overdose, don't be. They are
perfectly safe. It is advisable to take part in the Pulse Polio programme, even if your doctor has given
your baby all the required doses.
If your scheduled immunisation date falls very close to the Pulse Polio programme date, check with
your doctor if your baby needs to be given the polio drops again.
What are the symptoms of polio?
·
·
·
·
·
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Symptoms of polio can range from mild to severe. They include:
headache
fever
sore throat
nausea
severe muscle pain
stiffness in the neck and back
As most of these symptoms are common to a viral flu, consult your doctor if your baby has any of
them. In most cases, there are no symptoms. In just one per cent of the cases, the virus enters the
nervous system and can cause paralysis.
Can I give IPV to my baby when she has fever or diarrhoea?
If your child is ill at the time the IPV shot is scheduled, it is usually postponed until she recovers. The
OPV, on the other hand, can be given even with fever or diarrhoea. If your baby is unwell, ask your
doctor to be sure about what is best for your child.
Check out our immunisation scheduler to find out when to give your baby the polio vaccine.
Gas, liquid and solid
Gas, liquid, and solid are known as the three states of matter or material, but each of solid and liquid
states may exist in one or more forms. Thus, another term is required to describe the various forms,
and the term phase is used. Each distinct form is called a phase, but the concept of phase defined as a
homogeneous portion of a system, extends beyond a single material, because a phase may also
involve several materials. For example, a homogeneous solution of any number of substances is a
one-phase system. Phase is a concept used to explain many physical and chemical changes
(reactions).
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A solid has a definite shape and volume. A liquid has a definite volume but it takes the shape of a
container whereas a gas fills the entire volume of a container. You already know that diamond and
graphite are solids made up of the element carbon. They are two phases of carbon, but both are solids.
Solids are divided into subclasses of amorphous (or glassy) solids and crystalline solids.
Arrangements of atoms or molecules in crystalline solids are repeated regularly over a very long range
of millions of atoms, but their arrangements in amorphous solids are somewhat random or short range
of say some tens or hundreds of atoms.
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In general, there is only one liquid phase of a material. However, there are two forms of liquid helium,
each have some unique properties. Thus, the two forms are different (liquid) phases of helium. At a
definite temperature and pressure, the two phases co-exist.
So far, all gases behave alike as do mixtures of gases. Thus, a gas is usually considered as a phase.
GASES e.g. the air mixture around us (including the oxygen needed for combustion) and the high
pressure steam in the boiler and cylinders of the steam locomotive. All of these gases are 'invisible',
being colourless and transparent, so note that the 'steam' you see outside of the locomotive is actually
fine liquid droplets of water, formed from the expelled steam gas condensing when it meets the cold
air - the 'state change' of gas to liquid (same effect in mist and fog formation).
LIQUIDS e.g. water is the most common example, but so are, milk, hot butter, petrol, oil, mercury or
alcohol in a thermometer.
SOLIDS e.g. stone, all metals at room temperature (except mercury), rubber of walking boots and the
majority of physical objects around you. In fact most objects are useless unless they have a solid
structure!
On this page the basic physical properties of gases, liquids and solids are described in terms of
structure, particle movement (kinetic particle theory), effects of temperature and pressure changes,
and particle models used to explain these properties and characteristics. Hopefully, theory and fact
will match up to give students a clear understanding of the material world around them in terms
of gases, liquids and solids - referred to as the three physical states of matter. The changes of
state known as melting, fusing, boiling, evaporating, condensing, liquefying, freezing, solidifying,
crystallising are described and explained with particle model pictures to help understanding. There is
also a mention of miscible and immiscible liquids and explaining the terms volatile and volatility
when applied to a liquid. These revision notes on the states of matter should prove useful for the new
AQA, Edexcel and OCR GCSE (9–1) chemistry science courses.
Chemical Reactions
A chemical reaction is a process that is usually characterized by a chemical change in which the
starting materials (reactants) are different from the products. Chemical reactions tend to involve the
motion of electrons, leading to the formation and breaking of chemical bonds. There are several
different types of chemical reactions and more than one way of classifying them. Here are some
common reaction types.
However, if you are asked to name the main 4, 5 or 6 types of chemical reactions, here is how they
are categorized.
·
Direct Combination or Synthesis Reaction
In a synthesis reaction two or more chemical species combine to form a more complex product.
A + B → AB
The combination of iron and sulfur to form iron (II) sulfide is an example of a synthesis reaction:
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8 Fe + S8 → 8 FeS
Learn More About Synthesis Reactions
·
Chemical Decomposition or Analysis Reaction
In a decomposition reaction a compound is broken into smaller chemical species.
AB → A + B
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The electrolysis of water into oxygen and hydrogen gas is an example of a decomposition reaction:
2 H2O → 2 H2 + O2
·
Single Displacement or Substitution Reaction
A substitution or single displacement reaction is characterized by one element being displaced from a
compound by another element.
A + BC → AC + B
An example of a substitution reaction occurs when zinc combines with hydrochloric acid. The zinc
replaces the hydrogen:
Zn + 2 HCl → ZnCl2 + H2
·
Metathesis or Double Displacement Reaction
In a double displacement or metathesis reaction two compounds exchange bonds or ions in order to
formdifferent compounds.
AB + CD → AD + CB
An example of a double displacement reaction occurs between sodium chloride and silver nitrate to
form sodium nitrate and silver chloride.
NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s)
·
Acid-Base Reaction
An acid-base reaction is type of double displacement reaction that occurs between an acid and a base.
The H+ ion in the acid reacts with the OH- ion in the base to form water and an ionic salt:
HA + BOH → H2O + BA
The reaction between hydrobromic acid (HBr) and sodium hydroxide is an example of an acid-base
reaction:
HBr + NaOH → NaBr + H2O
·
Oxidation-Reduction or Redox Reaction
In a redox reaction the oxidation numbers of atoms are changed. Redox reactions may involve the
transfer of electrons between chemical species.
The reaction that occurs when In which I2 is reduced to I- and S2O32- (thiosulfate anion) is oxidized
to S4O62- provides an example of a redox reaction:
2 S2O32−(aq) + I2(aq) → S4O62−(aq) + 2 I−(aq)
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Types of Chemical Reactions
The vast number of chemical reactions can be classified in any number of ways. Under one scheme they can be categorized
either as oxidation-reduction (electron transfer) reactions or non-oxidation-reduction reactions. Another completely
different but common classification scheme recognizes four major reaction types:
(1)
(2)
(3)
(4)
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combination or synthesis reactions
decomposition reactions
substitution or single replacement reactions
metathesis or double displacement reactions
The Four Major Types of Reactions
Name
Combination or synthesis
General Reaction Pattern
A + B ----> AB
Decomposition
AB ----> A + B
Substitution or Single Replacement A + BC ----> B + AC
Metathesis or Double Displacement AB + CD ----> AD + CB
Combination or Synthesis Reactions Two or more reactants unite to form a single product.
S + O2 ---------> SO2
sulphur oxygen
sulphur dioxide
2S +
sulphur
3 O2 ---------> 2 SO3
oxygen
sulphur trioxide
2 Fe + O2 ---------> 2 FeO
iron
oxygen
iron (II) oxide
Decomposition
products.
Reactions
A
single
reactant
CaCO3 ----------> CaO +
calcium carbonate calcium oxide
is
decomposed
or
broken
down
into
two
or
more
CO2
carbon dioxide
2 H2O -----------> 2 H2 +
water
hydrogen
O2
oxygen
2 KClO3 -----------> 2 KCl + 3 O2
potassium chlorate
potassium chloride oxygen
Substitution or Single Replacement Reactions A single free element replaces or is substituted for one of the elements in a
compound. The free element is more reactive than the one its replaces.
Zn + 2 HCl ----------> H2 + ZnCl2
zinc hydrochloric acid hydrogen zinc chloride
Cu + 2 AgNO3 -----------> 2 Ag +
copper
silver nitrate
silver
Cu(NO3)2
copper (II) nitrate
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H2 + 2 AgNO3 -----------> 2 Ag + 2 HNO3
hydrogen silver nitrate
silver
nitric acid
2 Na + 2 H2O -----------> 2 NaOH + H2
sodium
water
sodium hydroxide
hydrogen
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Metathesis or Double Displacement Reactions This reaction type can be viewed as an "exchange of partners." For ionic
compounds, the positive ion in the first compound combines with the negative ion in the second compound, and the
positive ion in the second compound combines with the negative ion in the first compound.
HCl + NaOH -----------> NaCl + HOH
hydrochloric sodium
sodium water
acid hydroxide
chloride
BaCl2 + 2 AgNO3 ----------> 2 AgCl + Ba(NO3)2
barium
silver
silver
barium
chloride
nitrate
chloride
nitrate
(precipitate)
CaCO3 + 2 HCl -----------> CaCl2 + H2CO3
calcium
hydrochloric
calcium carbonic
carbonate acid
chloride acid
Types of Inorganic Chemical Reactions
Elements and compounds react with each other in numerous ways. Memorizing every type of reaction
would be challenging and also unncecessary, since nearly every inorganic chemical reaction falls into
one or more of four broad categories.
1. Combination Reactions
Two or more reactants form one product in a combination reaction. An example of a combination
reaction is the formation of sulfur dioxide when sulfur is burned in air:
S (s) + O2 (g) → SO2 (g)
1. Decomposition Reactions
In a decomposition reaction, a compound breaks down into two or more substances. Decomposition
usually results from electrolysis or heating. An example of a decomposition reaction is the breakdown
of mercury (II) oxide into its component elements.
2HgO (s) + heat → 2Hg (l) + O2 (g)
2. Single Displacement Reactions
A single displacement reaction is characterized by an atom or ion of a single compound replacing an
atom of another element. An example of a single displacement reaction is the displacement of copper
ions in a copper sulfate solution by zinc metal, forming zinc sulfate:
Zn (s) + CuSO4 (aq) → Cu (s) + ZnSO4 (aq)
Single displacement reactions are often subdivided into more specific categories (e.g., redox
reactions).
1. Double Displacement Reactions
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Double displacement reactions also may be called metathesis reactions. In this type of reaction,
elements from two compounds displace each other to form new compounds. Double displacement
reactions may occur when one product is removed from the solution as a gas or precipitate or when
two species combine to form a weak electrolyte that remains undissociated in solution. An example of
a double displacement reaction occurs when solutions of calcium chloride and silver nitrate are
reacted to form insoluble silver chloride in a solution of calcium nitrate.
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CaCl2 (aq) + 2 AgNO3 (aq) → Ca(NO3)2 (aq) + 2 AgCl (s)
A neutralization reaction is a specific type of double displacement reaction that occurs when an acid
reacts with a base, producing a solution of salt and water. An example of a neutralization reaction is
the reaction of hydrochloric acid and sodium hydroxide to form sodium chloride and water:
HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
Remember that reactions can be belong to more than one category. Also, it would be possible to
present more specific categories, such as combustion reactions or precipitation reactions. Learning the
main categories will help you balance equations and predict the types of compounds formed from a
chemical reaction.
Second Order of Reaction
A second order reaction is a type of chemical reaction that depends on the concentrations of one
second order reactant or on two first order reactants. This reaction proceeds at a rate proportional to
the square of the concentration of one reactant or the product of the concentrations of two
reactants. How fast the reactants are consumed is called the reaction rate. This reaction rate for a
general chemical reaction.
aA + bB → cC + dD
can be expressed in terms of the concentrations of the reactants by the equation:
rate = k[A]x[B]y
where
k is a constant
[A] and [B] are the concentrations of the reactants
x and y are the orders of the reactions determined by experimentation and not to be confused with the
stoichiometric coefficients a and b.
The order of a chemical reaction is the sum of the values x and y. A second order reaction is a
reaction where x + y = 2. This can happen if one reactant is consumed at a rate proportional to the
square of the reactant's concentration (rate = k[A]2) or both reactants are consumed linearly over time
(rate = k[A][B]).
The units of the rate constant, k, of a second order reaction are M-1·s-1. In general, second order
reactions take the form:
2 A → products
or
A + B → products.
10 Examples of Second Order Chemical Reactions
This is a list of ten second order chemical reactions.
Note that some reactions are not balanced. This is because some reactions are intermediate reactions
of other reactions. The listed reactions are all second order.
H+ + OH- → H2O
Hydrogen ions and hydroxy ions form water.
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2 NO2 → 2 NO + O2
Nitrogen dioxide decomposing into nitrogen monoxide and oxygen molecule.
2 HI → I2 + H2
Hydrogen Iodide decomposing into iodine gas and hydrogen gas.
O + O3 → O2 + O2
During combustion, oxygen atoms and ozone can form oxygen molecules.
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O2 + C → O + CO
Another combustion reaction, oxygen molecules react with carbon to form oxygen atoms and carbon
monoxide.
O2 + CO → O + CO2
This reaction often follows the previous reaction. Oxygen molecules react with carbon monoxide to
form carbon dioxide and oxygen atoms.
O + H2O → 2 OH
One common product of combustion is water.
his in turn can react with all the loose oxygen atoms produced in the previous reactions toform
hydroxides.
2 NOBr → 2 NO + Br2
In the gas phase, nitrosyl bromide decomposes into nitrogen oxide and bromine gas.
NH4CNO → H2NCONH2
Ammonium cyanate in water isomerizes into urea.
CH3COOC2H5 + NaOH → CH3COONa + C2H5OH
An example of the hydrolysis of an ester in the presence of a base. In this case, ethyl acetate in the
presence of sodium hydroxide.
Ion
Solubility Rule
NO3-
All nitrates are soluble.
C2H3O2-
All acetates are soluble except silver acetate (AgC2H3O2), which is moderately soluble.
Cl-, Br-, I-
All chlorides, bromides, and iodides are soluble except Ag+, Pb+, and Hg22+. PbCl2 is
moderately soluble in hot water and slightly soluble in cold water.
SO42-
All sulfates are soluble except sulfates of Pb2+, Ba2+, Ca2+ and Sr2+.
OH-
All hydroxides are insoluble except those of the Group 1 elements, Ba2+, and Sr2+. Ca(OH)2 is
slightly soluble.
S2-
All sulfides are insoluble except those of the Group 1 elements, Group 2 elements, and NH4+.
Sulfides of Al3+ and Cr3+ hydrolyze and precipitate as hydroxides.
Na+, K+,
NH4+
Most salts of sodium potassium, and ammonium ions are soluble in water. There are some
exceptions.
CO32-, PO43- Carbonates and phosphates are insoluble, except those formed with Na+, K+, and NH4+. Most
acid phosphates are soluble.
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