Matter

2A: Composition of Matter

• Matter: anything that occupies space and has mass

  • light, sound, and volume are NOT matter

What is matter made of?

• Ancient Thoughts

  • “Atomists” thought that matter was made of indivisible atoms and nothing existed between them

  • Aristotle, believed that matter consisted of a continuum that could be infinitely cut without changing the characteristics of that matter

  • Over time, the law of definite proportions, Brownian motion, and the concept of diffusion all gave evidence for a particle model of matter

• Law of Definite Proportions: the law that states that the masses of chemical substances combine in definite, characteristic integer ratios when forming compounds

• Particle Model of Matter: a model that states that all physical matter exists in the form of particles (atoms or molecules) in constant motion

  • also called the kinetic model

• Atom: the building block of all matter, consisting of protons, electrons, and (usually) neutrons

• Molecule: a distinct group of two or more covalently bonded together

2B: Classifying Matter

Why bother with classifying matter?

• classification systems provide a structure within which we can conduct a scientific study

• classification enables us to do science

How do we classify matter?

• we classify matter based on its properties

• Pure substance: a material made of only one kind of element or compound; not a mixture

  • a pure substance may be either an element or a compound

  • Element: a pure substance that consists of atoms with the same atomic number

    • elements are the simplest of the pure substances

• Compound: a pure substance consisting of atoms of two or more different elements that are chemically combined

  • atoms of a particular compound always combine in the same proportion

• Mixture: a physical combination of two or more substances (elements, compounds, or other mixtures) in a changeable ratio

  • a mixture may be either heterogeneous or homogeneous

  • Heterogeneous mixture: a mixture that does not have uniform appearances since the combined are unevenly distributed

  • Homogeneous mixture: a mixture that has a uniform appearance throughout

    • a homogeneous mixture is also known as a solution

2C States of Matter

What are the states of matter?

• Solid: the state of matter in which particles vibrate in fixed positions, giving a substance a fixed shaped and volume

  • Particle spacing: close

  • Particle motion: vibrating in space

  • Volume: fixed

  • Shape: fixed

  • Compressibility: low

  • Density: high

  • Fluid? no

• Liquid: the state of matter in which particles are close together but able to move around

  • Particle spacing: close

  • Particle motion: able to slide past each other

  • Volume: fixed

  • Shape: changes to fill a container from the bottom

  • Compressibility: low

  • Density: between that of a solid and that of a gas

  Fluid? yes

• Viscosity: the attractive forces between the liquid particles determine the viscosity of a liquid (resistance to flowing)

• Gas: the state of matter in which particles are far apart, move rapidly, and have little interaction with each other

  • Particle spacing: widely spread

  • Particle motion: high speed

  • Volume: changes to fill the container

  • Shape: changes to fill the container

  • Compressibility: high

  • Density: low

  • Fluid? yes

  • Pressure: due to collisions with container surface

• Plasma: a gas-like state of matter, formed at very high temperatures, that consists of high-energy ions and free electrons

2D: Changes in State

What are physical properties?

• Physical Properties: anything a substance that can be observed or measures without altering the substance’s chemical composition

  • Ductility: the ability of a solid material to be pulled into a wire

  • Malleability: the ability of some solid materials to be hammered or pressed into sheets

  • Conductivity: the ease with which a material allows the transfer of either electrical or thermal energy

  • Luster: the quality of how a material reflects lights

• Physical Changes: any change in matter that does not alter the composition of the substance

What are chemical properties?

• Chemical Properties: a property of a substance that describes how its chemical identity changes in the presence of another substance or under certain conditions

  • Reactivity: the degree to which a material will react with other substances

  • Flammability: the ability of a material to burn in the presence of oxygen

• Chemical Changes: changes that alter the chemical composition of a substance

Is it possible to get rid of matter? Or make more?

NO!!

• Law of Conservation: a fundamental natural law that states that matter can neither be created nor destroyed but can only change forms

What does it mean for matter to “change states”?

• Melting: the change of state from solid to a liquid

• Melting point: the temperature at which a solid turns to a liquid

• Freezing: the change of state from a liquid to a solid

  • the freezing point is the same temperature as the melting point

• Vaporization: the change of state from a liquid to a vapor (gas)

  • vaporization can occur in two ways: evaporation and boiling

• Evaporation: the relatively slow form of vaporization in which liquid particles obtain sufficient energy to change to the gaseous state through the random collisions of particles

• Boiling: the relatively fast form of vaporization in which the energy within a liquid creates higher pressure within the liquid than the air pressure outside the liquid

  • boiling point: the temperature at which a liquid starts to boil

    • the boiling point changes as air pressure changes

• Condensation: the change of state from a vapor to a liquid

• Sublimation: the change in state directly from a solid to a gas (vapor) without melting first

• Deposition: the change in state directly from a gas (vapor) to a solid without condensing first