MLT 1101 CHEMISTRY
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Transcript of MLT 1101 CHEMISTRY
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TOPIC 1MATTER AND THE THEORY OF STATE
MATTER
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INTRODUCTION TO THE MATTER
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Matter is anything that occupies space and has mass.
Matter can classified into physical and chemical state.
There are 4 physical states of matter :
1) Gas or VaporNo fixed volume or shape - it conforms to the
container.Can be compressed or expandedMove randomly at great speedsCan vibrate, rotate, translate & have highest energy
content
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2) Liquid Has a fixed volume - shape depends on its
container.Cannot compressed. Particle can vibrate, rotate & translate.
3) Solid • Has a fixed shape and volume; it is rigid• Cannot compressed.• Particles can vibrate & rotate at fixed positions
4) Plasma is a substance similar to gas in which
electrically neutral medium of positive and negative particles
they generate electrical currents by charges.
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THEORY OF STATE MATTERMatter is made up of tiny and discrete particles.
There are spaces between these particles.
The particles may be atoms, molecules or ions.
An atom is the smallest particle of an element that can participate in a chemical reaction.
A molecules is a group of two or more atoms which are chemically bonded together.
An ion is a positively-charged or negatively-charged particle.
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Particles of Matter are constantly moving & contain kinetic energy.
Particles of Matter are held together by very strong electric forces
Matter can be classified by its chemical constituent whch are elements and compounds.
a) An elements is a substance that consists of only one type of atom.
b) A compound is a substance that contains two or more elements that are chemically bonded together.
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5. Each substance has unique particles that are different from the particles of other substances
6. Temperature affects the speed of the particles. The higher the temperature, the faster the speed of the particles.
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Solid Liquid GasAttractive force among particles
Strong Fairly strong Very weak
Compressibility Incompressible Incompressible Easy to compress
Volume Fixed Fixed and similar to solid
No fixed volume(occupies the
whole container)Particle
movementCan only vibrate Free to move
slowlyFree to move
quicklyShape Definite No definite
shape(Fill bottom of the container)
No definite shape
(Fill the whole container)
Kinetic energy Low Medium HighParticles
arrangement
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SOLIDSOLID LIQUIDLIQUID GASGAS
MeltingMelting Boiling/Boiling/evaporationevaporation
FreezingFreezingCondensationCondensation
Heat energy absorbedHeat energy absorbedHeat energy releasedHeat energy released
SublimationSublimation
SublimationSublimation
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Melting pointMelting point – – Temperature at which it Temperature at which it changes from solid to changes from solid to
liquid state liquid state
Boiling point Boiling point – – Temperature at which it Temperature at which it changes from liquid to changes from liquid to
gas state.gas state.
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During Heating…When a solid is heated, the particles absorb heat
energy.
The particles vibrate faster and kinetic energy increase.
The movement of particles is increase
The force of attraction become weak
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Freezing point Freezing point – – Temperature at which it Temperature at which it changes from liquid to changes from liquid to
solid state solid state
Condensation point Condensation point – – Temperature at which it Temperature at which it
changes from gas to changes from gas to liquid stateliquid state
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During Cooling…When a gas is cooled, the particles release the
energy.
The kinetic energy will decrease
The movement of particles is decrease
The force of attraction become strong
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PHYSICAL AND CHEMICAL CHANGES
PHYSICAL CHANGES CHEMICAL CHANGES
A change that alters the APPEARANCE of a material but does not make the material into another substance
Physical changes are REVERSIBLE
Examples: tearing paper, chopping wood, molding clay, melting ice
a change in matter that PRODUCES A NEW SUBSTANCE
Signs that a chemical change has taken place: bubbles appear precipitate forms color change light is emitted temperature change change in smell or taste
Energy is ALWAYS involved during BOTH physical and chemical changesEnergy is ALWAYS involved during BOTH physical and chemical changes
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Subatomic particles of an atomAtoms are made up of three types of smaller
particles, namely protons, neutrons and electrons. These particles are known as subatomic particles.
The relative masses and charges of these three subatomic particles in table below.
SUBATOMIC PARTICLE
SYMBOL RELATIVE MASS
RELATIVE ELECTRIC CHARGE
PROTON P 1 +1
NEUTRON n 1 0
ELECTRON e 0 (almost) -1
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Subatomic particles of an atomProtons and neutrons are found in the nucleus
of an atom while electrons surround the nucleus.
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SYMBOLS OF ELEMENTSEach element is given a name and a symbol.
Some examples of elements and their symbols are shown below.
ELEMENT SYMBOL ELEMENT SYMBOLHydrogen H Sodium Na
Helium He Magnesium Mg
Lithium Li Aluminium Al
Beryllium Be Silicon Si
Boron B Phosphorus P
Carbon C Sulphur S
Nitrogen N Chlorine Cl
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Notice that:(a)Each symbols consists of one or two letters. (b)For most elements, the letters used in their
symbols take either the first letter or first and another letter of their names. Eg. Hydrogen, H; neon, Ne and Magnesium, Mg.
(c)For some elements, the symbols come from Latin names such as natrium (Na) for sodium and kalium (K) for potassium.
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xxAA
ZZ
Nucleon number
Proton number
Symbol of element
BB11
5
Proton number = 5Nucleon number = 11Neutron number = 11 – 5
= 6
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PROTON NUMBER & NUCLEON NUMBERProton number : an elements is the number of
protons in its atom.Since atoms are neutral, the proton number is
also the number of electrons in the atom.Each elements has its own proton number.E.g:
sodium has a proton number of 11. Hence all atoms of sodium have 11 protons.
Oxygen has a proton number of 8, so all oxygen atoms have 8 protons.
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The nucleon number is also known as the mass number.
The relative mass of an atom is almost the same as its nucleon number. The nucleon number is sometimes used as the approximate relative mass in calculations.
Protons and neutrons are collectively called nucleons because protons and neutrons occupy the nucleus.
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Nucleon number: total number of protons and total number of neutrons in its atom.
From definition,
or
Nucleon number = number of proton + number of neutrons
Number of neutrons = nucleon number – number of proton
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Remember the charge on each subatomic particle like this: Protons are positive,Neutrons are neutral,so electrons must be negative.
In a neutral atom, number of electrons = number of protons
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ISOTOPESIsotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
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Isotopes of an element have the same:
(a) number of protons in an atom.(b) number of electrons in an atom.(c) electron arrangement.(d) chemical properties because they have the same electron arrangement.
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Isotopes of an element have different: (a) nucleon number.
(b) number of neutrons in an atom.(c) physical properties (such as density, melting point and boiling point), though these different are very small.
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USES OF ISOTOPESThere are 2 types of isotopes, namely the
radioactive and the non-radioactive isotopes.Radioactive isotopes or radioisotopes
produce harmful radiation.However, radioisotopes can have important
uses if they are handled properly. They are used in medicine, industry, agriculture and general research.
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1) Medical useGamma-rays emitted from cobalt-60 are used
in radiotherapy for the treatment of cancer.Superficial cancers such as skin cancer can be
treated by less penetrating radiation from phosphorus-32 or strontium-90.
A heart pacemaker which contains plutonium-238 is used to regulate the heartbeats of patients with heart problems.
Iodine-131 is used in the treatment of thyroid diseases.
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2) Agricultural usesThe uptake of phosphate and the metabolism
of phosphorus by plants can be studied using a phosphate fertiliser containing phosphorus-32.
Radioactive tracer studies using carbon-14 have helped in the understanding of photosynthesis and protein synthesis.
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3) Industry usesSodium-24 can be used to trace leaks in gas or
oil pipes and ventilating systems.The gamma rays of cobalt-60 are passed
through food to destroy bacteria which cause the food to spoil without changing the quality, flavour, or texture of the food.
The radiation from krypton-85 can be used to control the thickness of plastic sheets in the industry.
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4) Power sourcesUranium-235 is the most common fuel used in
nuclear power stations.
5) Archaeological uses• Carbon-14 can be used to estimate the
age bone, wood or fossils by measuring the fraction of carbon-14 it contains.
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ELECTRONIC STRUCTURE OF AN ATOMElectrons are arranged around the nucleus in
the shells of an atom.The shell of an atom are numbered 1, 2, 3 and
so on, starting from the one closest to the nucleus.
Each shell can occupy a certain number of electron.
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ELECTRONIC STRUCTURE OF AN ATOM
++ 11 22 33
First shell : 2 electrons
Second shell: 8 electrons
Third shell: 8 electrons
nucleus
Fourth shell: 18 electrons
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FINDING THE ELECTRON ARRANGEMENT
To write the electron arrangement of an atom, follow these steps:
STEPS 1 – Find out the proton number of the atom. (can refer to the Periodic Table)
STEPS 2 – Find out the number of electrons of the atom. For a neutral atom, the number of electrons is the same as the number of protons.
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FINDING THE ELECTRON ARRANGEMENT
STEPS 3 – Arrange the electrons in shells. Electrons occupy the shell closest to the nucleus first. The electrons only start occupying a new shell when the previous one has been occupied.
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VALENCE ELECTRONSValence electrons are found in the outermost
occupied shell of an atom.They determine the chemical properties of
the element
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VALENCE ELECTRONSFor e.g:
the electron arrangement of a chlorine atom is 2.8.7. There are 7 electrons in the outermost occupied shell of the chlorine atom. Therefore, the number of valence electrons in a chlorine atom is 7.
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1) How many states of matter are there?A) 1 B)2 C) 3 D)4
ANS: There are 4 states of matter. You will find solids, liquids, gases and plasmas.
2) Atoms in a liquid are farther apart than the atoms in a gas.
A) trueB) false
ANS: Atoms in a gas are actually farther apart than the atoms in a liquid. Solids are the densest state of matter (of solids liquids, and gases). Gases are the least dense and have atoms that are the most spread out.
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3) Which has the least energetic molecules?a) Solids b) Liquids c) Gases d) Plasmas
Ans : Solids have the least energetic molecules. Plasmas and gases have the most energetic atoms.
4) What force pulls liquids towards the ground?a) Pressure b) Temperature c) Gravity d) centrifugal
Ans: Gravity is the one force that pulls every object towards the surface of the Earth.
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5) When a substance goes from being a solid to a liquid, it is a...a) chemical change b) Physical change
Ans: When a substance moves from one state to another, it is a physical change. Physical changes usually happen because you add or take away energy. If one substance combines with another to make a new compound... That is a chemical change.
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