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STATES & PROPERTIES OF MATTER

Matter - any object with mass; substance that has inertia, consists of particles, and occupies physical space
This includes gases (air, oxygen, helium, etc.), liquids, and solids. Any matter is comprised of basic particles - atoms - bonded together. 

Molecules - groups of two or more atoms; the smallest unit in which a pure substance can be identified and still retain all of its chemical composition and properties

STATES OF MATTER

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Solids:

  • Molecules are packed closely together

  • Molecules are not free to move within their substance, and instead vibrate

  • This lack of movement means that solids have a fixed shape, and will not change their shape to match the shape of the container/space in which they are placed

    • If a strawberry is placed in a bowl, it does not change its shape the way water might when being moved from a glass to a bowl

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Liquids:

  • Molecules are not packed as closely together as they are in solids

  • Molecules are free to move around within the confines of their container and gravity

  • Liquids do not have fixed shapes, and will thus take the shape of their containers

    • When in a bottle, coke takes the shape of the bottle. When transferred to a glass, the coke takes the shape of the glass

 

Gases:

  • Molecules are not packed closely together

  • Molecules are free to move around within the confines of their containers, and are not typically confined by gravity

    • This means that molecules in a gas can escape a bowl, for example, and move around in the room where the bowl was placed

  • Gases do not have fixed shapes, and will thus take the shape of their surroundings

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Fig. 1 - Diagrams showing the molecular arrangements of gases, liquids, and solids (left to right).

FLUIDS

 

Fluid - a substance that flows and takes the shape of its container; liquids and gases are both fluids

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A liquid like water is easily identifiable as a fluid - once poured into a cup or bowl, it adapts to the shape of the cup of bowl and moves freely within its confines. Similarly, if air is trapped within a sealed flask, it will move freely within the flask's confines, and only move out when the seal is broken.

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Hydraulics - the mechanics, science and technology of liquids and their pressure; an example of a hydraulic system is a syringe

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Fluid statics - the study of fluids at rest​

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Pneumatics - the mechanics, science and technology of gases and their pressure; an example of a pneumatic system is a chair with an adjustable height

DENSITY

 

Density - the ratio of mass to volume in a substance; the mass of a unit volume of a material substance; how compact a substance is

  • scalar quantity

  • SI unit is kilogram per cubic meter (kg/m^3)

  • can be quantified with ρ = m/v

    • ρ - density (kg/m^3)​

    • m - mass (kg)

    • v - volume (m^3)

 

If an object is not dense, it is lighter than other objects with the same volume, and the spaces between its particles allow for that substance to be compressed; 25mL of gas is less dense (and thus lighter) than 25mL of water because it has fewer particles per unit volume.

PRESSURE

 

When assessing fluids (gasses and liquids) and their behaviors, it becomes more convenient to refer to pressure rather than force. When dealing with gas pressure, we assess the pressure of gas molecules on the walls of their container - this is the same concept applied in blood pressure. 

 

Pressure - force applied per unit area

  • scalar quantity

  • SI Unit is a pascal (Pa)

  • can be quantified with P = F/A

    • P - pressure (Pa)​

    • F - force (N)

    • A - area (m^2)

 

Barometric/atmospheric pressure - the force exerted on a surface by the air above it; the total weight of the air above a unit area​. 

 

At higher altitudes, the atmospheric pressure is lower, because less air is weighing down on a space.

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MOLECULAR ARRANGEMENTS

 

Diamonds are the hardest known naturally occurring material known to man. They are extremely dense, rated the highest on the Mohs scale of mineral hardness, unreactive, insoluble, and transparent in X-rays. The hardness and density of diamonds is because of their molecular structure, a giant lattice formation.

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Giant lattice formation -a molecular structure in which pure carbon atoms are linked together in covalent tetrahedral units and one carbon atom shares its electrons with four other carbon atoms.

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Uses of diamonds

  • fashion industry

  • glass cutting

  • polishing of precious stones → diamond dust enhances lustre

  • drilling

  • heat sinks in electrical systems

  • engravings

  • tungsten wires

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Graphite is the only non-metal that can conduct electricity. It is not dense, but rather soft, has a metallic lustre, and is opaque. The properties of graphite arise from its molecular structure, the honeycomb lattice. Carbon atoms in graphite form metallic bonds (rather than covalent bonds), which means there are free electrons between the carbon layers. The vertical bonds that connect separate layers are very weak, which is why it is softer and less dense.

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Graphenes - single-atom layers of carbon arranged in a honeycomb lattice structure


Honeycomb lattice structure - each carbon atom is joined to three other carbon atoms.

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Uses of graphite

  • pencil lead for writing or art → more graphite means darker pigment

  • lubricant in manufacturing processes → graphite reacts with atmospheric water vapor to form a thin film on nearby surfaces

  • lithium-ion batteries → graphite anodes with lithium cathode last long as batteries

  • lightweight sports equipment → graphene technology 

  • moderator rods in nuclear fission reactors → carbon nuclides absorb kinetic energy

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