SNC1D1 NOTES: PARTICLE THEORY OF MATER
Particle Theory of Matter States:
 All matter is made up of extremely tiny particles
 Each pure substance has its own kind of particle, different from the particle of other
pure substances.
 Particles attract each other
 Particles are always moving
 Particles at a higher temperature move faster on average than particles at a lower
temperature.
We can use the particle theory to distinguish between a pure substance,
solution and mechanical mixture.
Mechanical Mixtures: Unlike solutions, mechanical mixtures are heterogeneous.
This means you can see different particles in them. Mechanical mixtures can be
further classified based on the size of the particles.
i)
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One type of mechanical mixture is a suspension. The particles in a
suspension can be seen with the unaided eye or through a low powered
microscope. If left undisturbed, the particles in a suspension will
separate out due to gravity. Eg Milk of Magnesia. The size of the
particles determines the rate of separation.
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ii)
Another type of mechanical mixtures is a colloid. Colloids although they
are heterogeneous, have a homogenous appearance. The particles in a
colloid are too small to be seen using an optical microscope, but they are
larger than particles in a solution. To tell the difference between a colloid
and solution a beam of light can be used. A colloid will scatter the light
while a solution will not. The scattering of light by colloid particles is called
the tyndall effect. Eg Whipped cream, mayonnaise, paint, butter, milk,
etc.
Pure Substances: According to the particle theory, a pure substance is made up
of identical particles. For example, gold is made up of the same particles, and
although silver is made up from different particles in comparison to gold, silver
itself is made up of identical particles.
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Solutions: Solutions contain at least two different types of particle unevenly
mixed together. For example, in a salt solution, the solvent (water) particles are
more numerous than the solute (salt) particles. The particles are invisible to the
naked eye in a solution. A mechanical mixture also contains two or more
particles unevenly mixed together.
Particles Theory and The Change of State
By using the particle theory, we can understand the changes that occur during
changes in states of matter. Let’s consider the uniqueness of water. Water is
the only substance that is capable of existing in all three states (solid, liquid &
gas) at once. In it’s solid state the particles of water are vibrating very slowly and
the forces of attraction between the molecules are the strongest. In it’s liquid
state, the particles are moving or vibrating more rapidly and the forces of
attraction are not as strong as they were in the solid state. In it’s gas state, the
particles speed are at there greatest and the bond strength are at there weakest.
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Particle Theory and Density Among Metals
Density can be loosely interpreted as the amount of mass crowded into a given
space. Since the mass of any object is determined by the collected mass of all
its particles, therefore the greater the amount of particles crowded into a given
space, the greater the density of that substance.
Electrolysis
Electrolysis use electricity to decomposes (separate) water into its basic
components of two parts hydrogen and one part oxygen. The properties of the
hydrogen and oxygen elements differ from the properties of water, a compound
that is made up of oxygen and hydrogen elements.
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Atomic Theory: Laws vs Theories
Laws
Laws do not explain anything. They just describe and summarize
what happens.
For example:
1. The law of conservation of mass states that the total mass of the
reactants before a chemical change is equal to the total mass of the
products after the change.
2. The law of definite proportions states that compounds that contains two or more
elements combine together in fixed (or definite) proportions.
For example, pure water (H20) always contains the elements hydrogen and
oxygen combined together in a fixed proportion, 2 parts hydrogen and one part
oxygen. These proportion whole true no matter where the water is obtained.
Hydrogen peroxide (H2O2) contains the same two atoms, but combined in
different proportion. As a result of this, pure substances always have a constant
composition, therefore they also tend to have constant, unvarying properties.
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Theories
Theories are imaginative ways to explain why something happens. Dalton
atomic theory can be used to further
understand the two previously mentioned
law.
Dalton Atomic Theory States:
1) All matter is made up of small particles called atoms.
2) Atoms cannot be created, destroyed, or divided into smaller particles.
3) All atoms of the same element are identical in mass and size, but they are
different in mass and size from the atoms of different elements.
4) Compounds are created when atoms of different elements link together in
defined proportions.
Evolutions of Models Of The Atom
1. In 1803, Dalton pictured the atom as a tiny indivisible sphere, like a tiny
billiard ball.
Dalton’s Model
2. In Thomson’s time, it was clear that atoms could be torn apart by high-energy
electricity, thus proving that atoms were divisible after all. At this point in
time, protons and electrons where known as subatomic particles. Thomson
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pictured the atom as a composite of these subatomic particles. His muffinlike model was a major step forward in our understanding of atomic structure.
Thomson’s Model
3. Rutherford later concluded that the atom had a nucleus: a tiny core that is
very small in volume, dense compared to the rest of the atom, and highly
positive with an electron cloud. The electron cloud is an “envelope” that is
very light compared to the nucleus, and negatively charged.
Rutherford’s Nuclear Model
4. The Bohr-Rutherford model compared the atom to the solar system. The
nucleus was compared to the Sun and the electrons to the planets. The Sun
exerts enormous gravitational pull on the planets in like manner, the nucleus
of the atom exerts enormous gravitational pull on the electrons. Both the
planets and electrons do not spiral inward and crash into the Sun or nucleus
because they revolve at just the right speed to remain in their orbits.
Electrons orbit around the nucleus in regions known as electron shells.
Bohr-Rutherford Model
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