Unit 2: Physical Science - Chemical ReactionsUnit 2: Physical Science - Chemical Reactions

What the heck is “Chemistry” What the heck is “Chemistry” anyway?anyway?

The study of the The study of the composition, structure, composition, structure, and properties of and properties of mattermatter

Includes the study of the Includes the study of the changeschanges matter matter undergoesundergoes

Chemistry is incorporated Chemistry is incorporated into every aspect of life into every aspect of life because everything in the because everything in the world is made of world is made of mattermatter!!

Properties of MatterProperties of Matter

Matter is anything that has a mass and Matter is anything that has a mass and takes up spacetakes up space

Matter has a wide variety of chemical and Matter has a wide variety of chemical and physical Propertiesphysical Properties

Classification of MatterClassification of Matter

Matter can be classified by observing the Matter can be classified by observing the following physical properties:following physical properties:AppearanceAppearance

What it looks likeWhat it looks like

CompositionCompositionWhat it is made ofWhat it is made of How it can be separated or broken downHow it can be separated or broken down

Classification of Matter: Classification of Matter: AppearanceAppearance

Homogeneous:Homogeneous: It looks the It looks the same same

throughoutthroughout Has a Has a uniform uniform

appearanceappearance

Heterogeneous:Heterogeneous: You can see You can see differentdifferent

parts or componentsparts or components Has a Has a variablevariable

appearanceappearance

Classification of Matter: Classification of Matter: CompositionComposition

Physical SeparationPhysical Separation Filtering or strainingFiltering or straining BoilingBoiling

Chemical SeparationChemical Separation Chemical reactions Chemical reactions

are requiredare required DecompositionDecomposition

Classification of Matter: Different TypesClassification of Matter: Different Types All matter can be classified as an element, All matter can be classified as an element,

compound or a mixturecompound or a mixture Element:Element:

Matter that is composed of only one Matter that is composed of only one type oftype of atom atom

Cannot be Cannot be broken down broken down into simpler into simpler substancessubstances

Homogeneous Homogeneous appearance appearance Compound:Compound:

Matter that is composed of more than Matter that is composed of more than oneone element element

Can only be broken down by Can only be broken down by chemical chemical reactionsreactions

Homogeneous Homogeneous appearanceappearance Mixture:Mixture:

Many Many elements or compoundselements or compounds together together Not Not purepure substances substances Can easily be separated by Can easily be separated by physical physical

processesprocesses Can be either homogeneous or Can be either homogeneous or

heterogeneous based on their heterogeneous based on their appearanceappearance

Matter can change in two ways: Matter can change in two ways: physical change & chemical changephysical change & chemical change

1. 1. Physical Change:Physical Change:- In a physical change- In a physical changethere is only a there is only a changechangeof stateof state- For example: ice melting to - For example: ice melting to

water or water boiling water or water boiling - The new substance has - The new substance has

the the samesame properties as properties as the old one.the old one.

- No - No new substancenew substance is is produced. produced.

Physical Change continued…Physical Change continued…

- A physical change may A physical change may also involve changing the also involve changing the shapeshape of the substance. of the substance.

- For example: paper cut For example: paper cut into pieces is still paper, into pieces is still paper, sloughing a field but the sloughing a field but the field still remains as soil, field still remains as soil, cutting wood into pieces cutting wood into pieces is still wood, and molding is still wood, and molding a sculpture is still cement a sculpture is still cement or marble! or marble!

Physical Change continued…Physical Change continued…

The bottom line for a physical change The bottom line for a physical change is to always remember that…is to always remember that…

THERE IS NO NEW SUBSTANCE THERE IS NO NEW SUBSTANCE FORMEDFORMED!!

**In all of these changes, you can **In all of these changes, you can get get the original materials back!**the original materials back!**

Chemical ChangeChemical Change

2. 2. Chemical Change:Chemical Change: In a chemical change In a chemical change one one

or more NEW substancesor more NEW substances are created. are created.

The new substance is The new substance is differentdifferent from the original. from the original.

It has properties that are It has properties that are different than those of the different than those of the starting materials.starting materials.

Plus, you Plus, you cannot get the cannot get the original materials backoriginal materials back easily (or at all)easily (or at all)

Chemical Change continued…Chemical Change continued… For Example: Think about For Example: Think about

an ordinary box of an ordinary box of matches. A single match matches. A single match in a box can remain in a box can remain unchanged forever. But if unchanged forever. But if someone were to take the someone were to take the match and then light it...A match and then light it...A flame lights up and then flame lights up and then burns out. What remains burns out. What remains will have changed will have changed foreverforever. The match can . The match can never be lit again. The never be lit again. The match has undergone a match has undergone a chemical reactionchemical reaction..

Signs that a Chemical Change has Signs that a Chemical Change has Occurred:Occurred:

1.1. Color ChangeColor Change

2.2. Heat or light is given offHeat or light is given off

3.3. Gas is releasedGas is released

4.4. A solid precipitate is formed in a liquidA solid precipitate is formed in a liquid

5.5. The change is difficult or impossible to The change is difficult or impossible to reversereverse

Chemical Change continued…Chemical Change continued…

**Despite the 5 signs that a chemical **Despite the 5 signs that a chemical change has occurred, the most important change has occurred, the most important thing to remember is that thing to remember is that one or more new one or more new substances must be formedsubstances must be formed!**!**

Sometimes one or more of the signs of a Sometimes one or more of the signs of a chemical change are visible but with no chemical change are visible but with no new substance formed, so you have to be new substance formed, so you have to be careful!careful!

The Atom: ComponentsThe Atom: Components The Atom is the fundamental The Atom is the fundamental

building blockbuilding block of all of the of all of the stuff in the world (Remember, stuff in the world (Remember, the scientific word for stuff is the scientific word for stuff is mattermatter))

Atoms are the Atoms are the smallest piecesmallest piece of any type of “stuff” you can of any type of “stuff” you can think of think of

Even though atoms are the Even though atoms are the smallest piece of any type of smallest piece of any type of stuff, they are composed of stuff, they are composed of smaller componentssmaller components

There are 3 types of There are 3 types of components in every atom:components in every atom: 1. Proton1. Proton 2. Neutron2. Neutron 3. Electron3. Electron

The Atom Components - ProtonsThe Atom Components - Protons

Protons:Protons:PositivePositive charge charge (+)(+)DenseDenseGive an atom its Give an atom its identityidentity

The number of protons determines which The number of protons determines which elementelement the atom isthe atom is

Example: The only difference between a carbon Example: The only difference between a carbon atom and a nitrogen atom is one proton. Carbon atom and a nitrogen atom is one proton. Carbon has 6 and nitrogen has 7has 6 and nitrogen has 7

Located in the Located in the nucleusnucleus of an atom of an atom

The Atom: Components - NeutronsThe Atom: Components - Neutrons

Neutrons:Neutrons:Neutral, Neutral, no charge, (0)no charge, (0)Similar to protons:Similar to protons:

Also very Also very densedenseWeigh the same as a protonWeigh the same as a protonLocated in the Located in the nucleusnucleus of an atom of an atom

Differ from protons:Differ from protons:Do not determine the identity of an atom, but they Do not determine the identity of an atom, but they

do contribute significantly to its do contribute significantly to its massmass

The Atom: Components - ElectronsThe Atom: Components - Electrons

ElectronsElectrons NegativeNegative charge, charge, (-)(-) Very Very light, not denselight, not dense

Do not contribute to the Do not contribute to the weight of an atom at allweight of an atom at all

Very Very smallsmall in size in size compared to protons and compared to protons and neutronsneutrons

Located in Located in orbitalsorbitals around around the nucleusthe nucleus

Orbitals:Orbitals: energy levelsenergy levels located located

outside of the nucleusoutside of the nucleus Region where electrons Region where electrons

are foundare found

The Atom: Components – The NucleusThe Atom: Components – The Nucleus

Nucleus:Nucleus: Structure located in the Structure located in the centercenter

of an atomof an atom Consists of 2 componentsConsists of 2 components

ProtonsProtons NeutronsNeutrons

Very Very densedense: protons and : protons and neutrons are packed together neutrons are packed together very very tightly tightly

Positively chargedPositively charged Why is it important?Why is it important?

Gives an atom its Gives an atom its identityidentity The number of The number of protonsprotons in in

an atom’s nucleus an atom’s nucleus determines which element determines which element it isit is

Components of the Atom & the Periodic TableComponents of the Atom & the Periodic Table

The periodic table of elements is a list of all the different types of The periodic table of elements is a list of all the different types of atomsatoms in in the worldthe world Each element is a different type of Each element is a different type of atomatom Each type of atom has its own Each type of atom has its own propertiesproperties and and characteristics characteristics

Gold is different from carbon, which is different from oxygen, etc.Gold is different from carbon, which is different from oxygen, etc. The differences in elements is based on the differences in the The differences in elements is based on the differences in the structurestructure

of the atomsof the atoms The number ofThe number of protons protons being the most important being the most important