Matter and Change

MATTER AND CHANGE
Chemistry
RHS
Mr. Moss
Whatchathinkboutit?
• Write your definition of the term Chemistry.
• Include thoughts about what you think this field includes.
Chemistry
• The study of the composition, structure, and properties of
matter, the processes that matter undergoes, and the
energy changes that accompany those processes.
• Answers questions such as:
• What is the makeup of this material?
• What changes when I heat or cool a substance?
• Why do these materials behave this way when mixed?
• Etc…
Matter, Mass, and Volume
• What is Matter?
• Matter is anything that has mass and takes up space.
• What is Mass?
• Mass is a measure of the amount of matter in an object.
• It’s the reading we get when we measure something on the
balance.
• Mass IS NOT the same thing as weight.
• Mass is a measure of the amount of matter in an object.
• Weight is a measure of the force of gravity acting on the matter.
• An astronaut has the SAME mass on Earth as on the Moon but 1/6th the
weight.
• What is Volume?
• Volume is the amount of 3-dimensional space that an object
occupies.
Matter
• Matter comes in many forms.
• The fundamental building blocks of matter are Atoms and
Molecules.
• Atoms are the smallest unit of an element that maintains
the chemical identity of the element.
• Elements are pure substances that cannot be broken
down into simpler substances and are made of only one
type of atom.
• Compounds are substances that can be broken down
into simpler substances and are made from atoms of two
or more elements that are chemically bonded.
States or Phases of Matter
• Matter exists in one of four states or phases
• Solid
• Liquid
• Gas
• Plasma
• Classification can be made by determining whether the
shape and volume are definite or variable.
• Definite means that it does not change when transferred from one
container to another.
Solid
• Definite Shape
• Definite Volume
• Atoms not free to move
• Vibrate or oscillate in place
• Distance between molecules are is short
• Strong attractive forces.
• Not easily compressible
Molecular Arrangement of Solid
Kinetic Theory in Solids
• Solids have a definite volume and shape because
particles in a solid vibrate around fixed locations.
• Each atom vibrates around its location but it does not exchange
places with its neighbor.
• The particles are held close together by the strong
attractive forces between them.
Liquid
• No definite shape
• Takes shape of container
• Definite Volume
• Molecules are close but are free to move past one
another.
• The attractive forces are moderate.
• Not easily compressible
Molecular Arrangement of Liquid
Kinetic Theory of Liquids
• Attractive forces affect movement of particles.
• Tug-of-War between attraction and constant motion.
• Liquids take the shape of the container and can flow to
new locations.
• The volume is constant due to the forces of attraction
keeping particles close together.
Gas
• No Definite Shape
• Takes shape of container
• No Definite Volume
• Take the volume of the container
• The molecules move independently.
• The attractive forces are weak.
• Large distance between molecules
• Compressible
• Pressure is caused by molecules colliding with the walls
of the container.
Molecular Arrangement of Gas
Kinetic Theory of Gases
• The total kinetic energy of the atoms stays the same.
• During a collision, one speeds up and the other slows down by the
same amount.
• The constant motion of particles in a gas allows a gas to
fill a container of any shape or size.
• 3 main points:
• Particles are in constant, random motion
• The motion of one is unaffected by the motion of another unless
they collide.
• Forces of attraction are weak and can therefore be ignored.
Plasma
• High temperature highly ionized gas like substance.
• Ionized means electrically charged particles.
• No definite shape or volume.
• 99% of known matter is made of plasma.
• Not normally found on Earth
• Most of the matter of the stars and sun.
• Lightning, fire, aurora borealis, fluorescent lights
• Atoms have the most energy of the four phases.
Plasma
A fifth phase???
• Predicted by Einstein after reading a paper written by
Satyendra Bose in the 1920’s.
• Occurs at extremely low temperatures
• Near 0 Kelvin
• Called the Bose-Einstein condensate.
Properties of Matter
• The properties of matter are used by chemist to define or
identify an unknown substance.
• Properties are either Extensive or Intensive.
• Extensive Properties depend on the amount of matter that is
present.
• Volume, Mass, and the amount of Energy present.
• Intensive Properties do not depend on the amount of matter
present.
• Melting/Boiling Point, Density, and Conductivity.
Properties of Matter
• The properties of matter can be grouped into two general
types:
• Physical
• Chemical
Physical Properties
• A Physical Property is a characteristic that can be
observed or measured without changing the identity of the
substance.
• A physical change is a change in a substance that does
not involve a change in the identity of the substance.
Physical Properties
• Viscosity
• Resistance to flow. The higher the number, the slower the flow.
• Density
• mass per unit volume (m / v)
• Solubility
• The ability of a substance to dissolve in another substance.
• Melting / Freezing / Boiling points
• Conductivity
• Malleability
• Hardness
Physical Properties
• Melting / Freezing / Boiling points
• Conductivity
• Malleability
• Hardness
• Color
• Temperature
• Mass
• Volume
• Phase
• Shape
Physical Change
• Any change in a substance in which the composition of
the substance does not change.
• Examples:
• Melting butter
• Slicing a tomato
• Braiding / cutting hair
• Crumpling paper
• Some physical changes are reversible and some are not.
• Reversible: Freezing – melting – refreezing water
• Non reversible: slicing a tomato and cutting hair.
Chemical Properties
• Any ability to produce a change in the composition of
matter.
• Chemical properties can be observed only when the
substances in a sample of matter are changing into
different substances.
• The composition of the substance has been altered.
Chemical Properties
• Flammability
• ability to burn in the presence of oxygen.
• Reactivity
• Describes how readily a substance combines chemically with other
substances.
Chemical Change
• Occurs when a substance reacts and forms one or more
new substances.
• There is a change in the arrangement of atoms.
• Chemical bonds are broken and reformed.
• Example:
• Cake baking in oven
• Leaves changing color
• Digestion of food
• Combustion
Chemical Change
• Three common types of evidence to look for:
• CHANGE IN COLOR
• PRODUCTION OF A GAS
• FORMATION OF A PRECIPITATE
Key Question
• Are different substances
present after the change takes
place?