MATTER AND CHANGEChemistry

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?