Csec Chemistry Chapter 1: States of Matter
Objectives:
1.1
Explain how evidence supports the particulate theory of matter;
Evidence obtained from practical work involving processes, such as diffusion and
osmosis. Use of salt or sugar to control garden pests and as a preservative.
Experiments of diffusion of ammonia and hydrogen chloride gases in cylindrical
tube.
Osmosis of Pawpaw (green) strips in a container of distilled water.
Potassium manganate (VII) in water
1.2
Distinguish among the three states of matter;
Arrangement of particles, energy of particles, strength of forces of interaction.
Consideration of physical characteristics of states.
Example: Volume, density, compressibility.
1.3
Explain the changes between the three states of matter in terms of energy and
arrangement of particles.
Consideration of freezing, melting, boiling, evaporation, sublimation, condensation;
heating and cooling curves.
Solids, Liquid, Gas
The three states of matter are solids, liquids and gases. Most substances can exist in all
three states depending on the temperature
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Solid (ice) below 0c
Liquid (water) between 0c and 100c
Gas (steam) above 100 c
The particulate theory of matter states:
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All matter is made up of particles
The particles are in constant, random motion either vibrate (as in solids) or move from
place to place (as in liquids and gases) and temperature affects the speed of motion
There are forces of attraction and repulsion between the particles
The particles that make up matter can be atoms, molecules or ions.
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An atom is the smallest unis of a chemical element which have all the characteristics of
the element
A molecule is a particle containing two or more atoms bonded together and which can
exist on their own. Molecules can be made up of atoms of the same kind or different
kinds
An ion is an atom or group of atoms with either a positive or negative charge. Ions may
be formed from a single atom. The may also be formed from groups of two or more
atoms bonded together
Evidence to support the particulate theory of matter
The processes of diffusion and osmosis provide evidence to support the fact that all matter
is made of particles
Diffusion
Diffusion is the net movement of particles from a region of higher concentration to a region
of lower concentration, until the particles are evenly distributed due to random movement
of the particles
Example 1:
When pieces of cotton wool soaked in concentrated ammonia solution and concentrated
hydrochloric acid are placed simultaneously at opposite ends of a glass tube, a white ring of
ammonium chloride forms inside the tube. Ammonia solution gives of ammonia gas and
hydrochloric acid gives of hydrogen chloride gas. The particles of the gases diffuse through
the air inside the tube, collide and react to form ammonium chloride.
Example 2:
When a purple potassium manganate (VII) crystal is placed in water, it dissolves to produce
a uniformly purple solution. The particles making up the crystal separate from each other
and diffuse through the spaces between the water particles until they were evenly
distributed
Osmosis:
Osmosis is the movement of water molecules through a differentially permeable membrane
from a solution containing a lot of water molecules to a solution containing fewer water
molecules
Example 1:
When a dilute sucrose solution is separated from a concentrated sucrose solution by a
differentially permeable membrane, water molecules move through the membrane from the
dilute solution into the concentrated solution but the sucrose molecules cannot move in the
other direction. The volume of the concentrated solution increases and the volume of the
dilute solution decreases
Example 2:
The membranes of living cells are differentially permeable and the cytoplasm inside the cell
contains 80% water
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When a strip of living tissue is place in water, water molecules move into the cells by
osmosis. Each cell swells slightly, and the strop increases in length and becomes rigid
When the strip is placed in a concentrated sodium-chloride solution water molecules
move out of the cells by osmosis. Each cell shrinks slightly and the strip decreases in
length and becomes softer
Uses of Osmosis:
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To control garden pests:
Slugs and snails are garden pests, whose skin is differentially permeable and always
moist. When salt is sprinkled on slugs and snails, it dissolved in the moisture around
their bodies forming a concentrated solution. Water inside their bodies move out by
osmosis and into the solution. The slugs and snails die from dehydration if their bodies
lose more water than they can tolerate
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To preserve food: Salt and sugar are used to preserve food such as meat, fish and fruit.
They draw water out of the cells of the food by osmosis. This prevents the food from
decaying because there is no water available in the cells for the chemical reactions
which cause the decay
They draw water out of microorganisms by osmosis. This prevents the food from
decaying because it inhibits the growth of the micro-organisms that cause this decay
Comparison of the three states of matter
Changing States:
Matter can exist in any of the three states depending on its temperature. It can change from
one state to another by heating or cooling as this causes a change in the kinetic energy and
arrangement of the particles:
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When a solid is heated, it usually changes states to a liquid and then a gas. This occurs
because the particles gain kinetic energy, move increasingly faster and further apart
and the forces of attraction between them become increasingly weaker
When a gas is cooled it usually changes states to a liquid and then to a solid. This
occurs because the particles lose kinetic energy, move more and more slowly and closer
together and the forces of attraction between them become increasingly stronger
In melting and boiling/ evaporation energy is absorbed
In condensing and freezing energy is released
Evaporation and Boiling are different in the following ways:
Evaporation can take place at any temperature, whereas boiling occurs at a specific
temperature.
Evaporation takes place at the surface of the liquid only, where-as boiling takes place
throughout the liquid
Sublimation:
Sublimation is the direct change from a solid to a gas on heating without any liquid state
being formed. It also refers to the direct change of a gas to a solid on cooling without the
liquid state being formed
. The reverse process in which a gas changes directly to a solid is called deposition.
Examples of substances that sublime include carbon dioxide (solid carbon dioxide changes
directly to carbon dioxide gas when heated), iodine and naphthalene
Heating and Cooling Curves:
A heating curve is drawn when the temperature of a solid is measured at intervals as it is
heated and changes states to a liquid and then to a gas and the temperature is then plotted
against time
Heat gives the particles more energy to move and overcome the forces between them
A solid melt when the particles have enough energy to break free from their normal
positions and move around
A cooling curve is drawn when the temperature of a gas is measured at intervals as it is
cooled and changes state to a liquid and then to a solid and the temperature is then plotted
against time
Cooling removes energy from the particles so that they slow down
Graph Explanation:
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AB: Increasing heat energy increases the vibrations of the particles in the solid. So the
temperature of the solid increases
BC: The forces of attraction between the particles are weakened enough so that the
particles slide over each other. The temperature is constant because the energy is going
in to overcome the forces between the particles instead of raising the temperature. The
substances melt
CD: Increasing the energy increases the movement of the particles in the liquid. So the
temperature of the liquid increases
DE: The forces of attraction between the particles are weakened enough so that the
particles move well away from each other. The temperature is constant because the
energy is going in to overcome the forces between the particles instead of raising the
temperature. The substance boils
EF: Increasing the energy increases the speed of the gas particles. So the temperature
increases
The melting point is the constant temperature at which a solid changes states into a
liquid
The boiling point is the constant temperature at which a liquid changes states into a
gas
The freezing point is the constant temperature at which a liquid changes states into a
solid
Graph showing how the temperature of a gas changes when it is cooled to form a
liquid and then a solid
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When the gas is cooled, the particles lose kinetic energy. The temperature falls (AB)
The particles become attracted to each other
Energy is released and the gas turns to a liquid (BC)
When the liquid is cooled, the particles lose more energy. The temperature falls (CD)
Energy is released and the liquid turns to a solid (DE)