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1. Chapter 2: facts about matter
Section one: the three states of
matter

2. • Matter: is anything that occupies space and
has mass. The three states of matter are
solid, liquid, and gas. A physical change
involves the conversion of a substance from
one state of matter to another, without
changing its chemical composition.

3. The three states of matter:
• Under normal conditions, there are three distinct states of matter: solids, liquids,
and gases. Solids are relatively rigid and have fixed shapes and volumes (definite
shapes and definite volume). A rock, for example, is a solid. In contrast, liquids
have fixed volumes but flow to assume the shape of their containers, such as
water in a bottle. Gases, such as air in an automobile tire, have neither fixed
shapes nor fixed volumes and expand to completely fill their containers. Whereas
the volume of gases strongly depends on their temperature and pressure the
volumes of liquids and solids are virtually independent of temperature and
pressure. Matter can often change from one physical state to another in a
process called a physical change. For example, liquid water can be heated to
form a gas called steam, or steam can be cooled to form liquid water. However,
such changes of state do not affect the chemical composition of the substance.
• The term "phase" is sometimes used as a synonym for state of matter, but it is
possible for a single compound to form different phases that are in the same
state of matter. For example, ice is the solid state of water, but there are
multiple phases of ice with different crystal structures, which are formed at
different pressures and temperatures.

5. Solids
• In solids, the forces keeping the particles
together are relatively strong, and the
particles stay very close to each other. The
particles can vibrate but they are not moving
around much. This is why solids are hard and
rigid. Left on their own, solids will keep their
shape.

6. Liquids
• In liquids, the forces between the particles
are weaker than in solids. Particles are still
fairly close together, but can move around
freely. Liquids can flow around inside a
container, and don’t have any particular fixed
shape.

7. Gases
• Gases are difficult to relate to because they are often invisible, but
found all around. You can feel them when, for example, the wind
blows. You can sometimes smell them when, for example, you
smell the odour of food that is cooking, or when a skunk has been
upset. Some gases are important for our health (e.g., oxygen)
while others can be deadly (e.g., hydrogen sulfide and chlorine).
Before surgery, you may receive an anaesthetic gas ‫مخدر‬ ‫غاز‬
) ),
which contains chemicals, to relieve pain and make you
unconscious during the procedure. Gases are also responsible for
the force of explosions. Gases have no definite volume and shape.
The atoms and molecules move freely and spread apart from one
another. They are compressible fluids. Not only will gases conform
to the shape of their containers but they will also expand to fill the
container.

8. Vocabularies
• hypothesis: A suggested explanation for a phenomenon to guide an experimental investigation.
• condensation: To go from a gaseous state to a liquid state.
• evaporation: To change from a liquid state to a gaseous state.
• solidification: The transition from a liquid state to a solid state.
• sublimation: To change from a solid state directly to the gaseous state without going through a liquid
phase.
• melting: The change of state from a solid to a liquid.
• deposition: The change of state directly from a gas to a solid.
• temperature: The degree of hotness of a substance, related to the average kinetic energy of its
molecules or atoms.
• pressure: The pressure of a force upon a surface or an object by another force.
• boiling point: The temperature required for a liquid to become a gas.
• melting point: The temperature required for a solid to become a liquid.
• freezing point: The temperature required for a liquid to change to a solid.
• plasma: A state, similar to a gas, where the electrons are not stuck with their atoms but are free in the
cloud; plasma is naturally occurring in flames, lightning and auroras

11. • Remember that a physical change: is a change in properties such as texture,
shape, or state, while a chemical change represents the formation of a new
substance after atoms are rearranged in a chemical reaction.
• The difference between a physical reaction and a chemical reaction
is composition. In a chemical reaction, there is a change in the composition of the
substances in question; in a physical change there is a difference in the
appearance, smell, or simple display of a sample of matter without a change in
composition. Although we call them physical "reactions," no reaction is actually
occurring. In order for a reaction to take place, there must be a change in the
elemental composition of the substance in question. Thus, we shall simply refer
to physical "reactions" as physical changes from now on.
• Physical changes are limited to changes that result in a difference in display
without changing the composition. Some common changes (but not limited to)
are:

12. • Texture→‫الملمس‬
• Color→‫اللون‬
• Temperature→‫الحرارة‬ ‫درجة‬
• Shape→‫الشكل‬
• Change of State→‫الحالة‬ ‫في‬ ‫التغير‬
• Physical properties include many other aspects of a substance. The
following are (but not limited to) physical properties.
• Density→‫الكثافة‬
• Viscosity→‫اللزوجة‬
• Solubility→‫الذوبان‬
• Mass→‫الكتلة‬
• Volume→‫الحجم‬

13. Section 2: the boiling point of water:
• The boiling point of water: is 100 °C or 212 °F at 1 atmosphere of
pressure.
• Explanation:
• The boiling point of water depends on the atmospheric pressure,
which changes according to elevation. Water boils at a lower
temperature as you gain altitude (e.g., going higher on a mountain),
and boils at a higher temperature if you increase atmospheric
pressure (coming back down to sea level or going below it).
• If the external pressure is higher than one atmosphere, the liquid will
boil at a higher temperature than the normal boiling point.
• If the force of attraction between the molecules is relatively strong,
the boiling point will be relatively high

14. Section three: molecules in motion
• Molecular Motion Definition
• Molecular motion is defined as the movement of constituent particles or
molecules in a certain direction. The molecular motions are affected by
heat and temperature. This is because the temperature is the
measurement of the average kinetic energy of the molecules and
represents the motion of molecules.

15. Types of Molecular Motion:
• The different types of molecular motions are:
• Translational motion: In such kind of motion, molecules
can move from one place to another in the same or
different direction but always remains in the same axis.
• Rotational motion: In this type of motion, the molecule
can rotate in and around the axis.
• Vibrational motion: In this type of motion, molecules can
vibrate at their mean position. These motions are very
common in solid state.
• Electronic motion: In this type of motion, electrons can
move from place to place. Electronic motions cause a
change in the colour of substances.

16. • Unlike the solid and liquid state, molecules in the gaseous state show random
motion. That is the reason; gases take the shape of the container and spread
quickly in space. The random motion of molecules in the gaseous state is due to
high kinetic energy in molecules. They have weak intermolecular interactions
between them. The intermolecular space between gaseous molecules is very
large. They can show all the three types of molecular motion, vibrational,
rotational and translational motion.
• In vibrational motion, molecules move back and forth whereas in rotational
motion the molecule rotates in space. In translational motion, molecules move in
certain directions. Molecules of solid-state are capable of vibrational motion due
to strong intermolecular forces.
The end of chapter