Foundations of ChemistryChapter 7

Physical Science

Bell Work Ch7 L.1Matter: anything that has mass and takes up space.Atom: a small particle that is a building block of matter.Substance: matter with a composition that is always the same.Element: a substance that consists of just one type of atom.Compound: a type of a substance containing atoms of two or more different elements chemically bonded together.Mixture: matter that can vary in composition.Heterogenous mixture: a type of mixture in which the individual substances are not evenly mixed.Homogeneous mixture:a type of mixture in which individual substances are evenly mixed.Dissolve: to form a solution by mixing evenly.

Matter● Look around- what makes up objects around

you? o Things can be made up of different kinds of matter.

● What about things you can’t see? o Air?

● Does it have mass? Does it take up space?o IF YES TO BOTH= matter.o Air= yeso Sound= noo Light= no

Atom● Small particle that is the building

block of mattero Diameter of hair is 1,000,000x bigger

than diameter of an atom● Structure of an atom

o Nucleus (in center of atom) Protons***

● Have a positive charge● Atomic number= number of protons

that determines properties of atom Neutrons

● Have a neutral chargeo Electrons (floating around nucleus in

electron cloud)● Have a negative charge

The size of an atom is roughly 10,000x wider than its nucleus.

Substances● Matter with a composition

that is always the sameo Substance is always made of

the same combination(s) of atoms

o Examples: oxygen, aluminum, sugar, water

● Two kinds of substanceso Elementso Compounds

Elements● A substance that is made up of

only one kind of atomo Periodic table of elements

About 115 kinds of elements (115 kinds of atoms)

o Each kind of atom has a different number of PROTONS Aluminum has 13, Oxygen has 8

● An Atom with 13 protons is always aluminum. An atom with 8 protons is always oxygen.

● Substances can exist individually (Al) or in groups (O2)

Compounds

● A type of substance containing atoms of two or more different elements chemically bonded together. o Example: CO2

One atom of carbon and two atoms of oxygen Carbon dioxide is a compound because it is

always formed the same way● Compounds often have different properties

from the individual elements that compose it

Chemical formula● The combination of

symbols and numbers that represents a compoundo Show the different atoms in

that make up a compound using the element symbols

o Example: H2O Two hydrogen atoms are

bound to one oxygen atom

Mixtures● Matter that can vary in composition● Combinations of two or more substances

that are physically blended together● DO NOT combine chemically

o They can be separated- filtering● Two kinds of mixtures

o heterogeneouso homogeneous

Heterogeneous mixtures● A mixture in which individual

substances are not mixed evenly

● Two samples of the same mixture can have different concentrations of the substanceso Examples: two buckets of

sand/water taken from the beach

Homogeneous mixture● A mixture in which the individual substances

are evenly mixedo Two samples from a solution will have the same

amounts of each substance● Also known as a solution

o Solvent: what is present in the largest amount, what is doing the dissolving

o Solute: what is present in a smaller amount, what is being dissolved

● Examples: Apple juice, air or salt water

Compounds vs Solutions● Water is a compound so it does not vary

o Composition is ALWAYS the sameo H2O is always H2O no matter how much you haveo H is chemically bound to O

● Salt water is a solutiono NaCl (salt) and H2O (water) are mixed together but

NOT chemically boundo Can add more salt to change relative amounts of

salt relative to water= COMPOSITION CAN VARYo Can’t use chemical formula to describe

Homework Ch7 L.1

● p.237 #1-11● Study for Quiz

Bell work Ch7 L.2

Physical properties: characteristic of matter that you can observe or measure without changing the identify of the matterMass: the amount of matter in an objectDensity: mass per unit volume of a substanceSolubility: ability of one substance to dissolve in another

Physical properties

● The arrangement of atoms determines its properties

● Each element and compound has a unique set of propertieso How they look, how they react etc.

States of matter● ALL atoms that make up matter are constantly

moving● Solid

o particles packed close together, not a lot of motion● Liquid

o More motion than a solid. Particles still can touch but they move around relative to one another

● Gaso Most motion of all three states. Particles move very

quickly and spread out to fill their container

Size dependent properties● Mass: The amount of matter in an object

o The larger the object the more mass it iso Value depends on the size of the objecto NOT THE SAME AS WEIGHT (weight changes with

location but mass does not) Weight depends on gravity

● Volume: Amount of space something takes upo Often measured in mL (milliliters)

Size independent properties

● Melting point: the point at which a substance changes from solid to liquid

● Boiling point: the point at which a substance changes from liquid to gas

Size independent properties cont’

● Density: mass per unit volume of a substance

● Conductivity: o Electrical- ability to

conduct or carry an electrical current

o Thermal- ability to conduct thermal energy

● Solubility: ability of one substance to dissolve in another

Separating mixtures● Use physical

propertieso things with a lower

boiling point will boil off faster

● CANNOT use physical properties to separate a compound into its elements

Homework Ch7 L.2

● p. 246 #1-9● Study for quiz

Bel work Ch7 L.3

Physical change: a change in size, shape, form, or state of matter in which the matter’s identity stays the same

Physical changes

● Does NOT become something different even though physical properties change

● Identity stays the same

Change in shape and size

● Can break things into smaller pieces or fold things into different shapes but doesn’t change the identity of the material

Change in state of matter● To change the state, the

movement of particles has to change (slower or faster)

● Adding thermal energy o Think of this as adding heato Particles move faster until overcome

bonds holding them togethero The more energy added, the faster

the particles move Can change from solid to liquid

(melting) to gas (vaporization) Sublimation= change directly

from solid to gas

Change in state of matter cont’d● Removing thermal energy

o Think of this as removing heato Particles move slowero The more energy removed,

the slower the particles move Can change from gas to

liquid (condensation) to solid (freezing)

Deposition= change directly from gas to solid

● Freezing/Melting are reverse properties and occur at the same temperatureo same for boiling/condensation

Dissolving

● Mixing evenly of substances whose identities do NOT change

Conservation of mass

● During a physical change even though physical properties can change, the mass does not change

Homework Ch7 L.3

● p.253 #1-7● Study for quiz

Bellwork Ch7 L.4● Chemical property: is a characteristic of

matter that can be observed as it changes to a different type of matter

● Chemical change: is a change in matter in which the substances that make up the matter change into other substances with new physical and chemical properties

● Concentration: is the amount of a substance in a certain volume

Chemical properties

● Observe only when matter is changing identity (different than physical property)

Signs of chemical changes● How do you know if a chemical change has

happened? Some hints:o bubbleso energy changeo odor changeo color change

● These do not automatically mean a chemical change happened, ONLY if a new substance was formed.

Chemical reactions● Particles can move and

collide with one anothero If they hit each other with

enough force they can break apart and then can form new bonds and new combinations New substances can

form

Chemical formulas● Chemical equation: shows the

chemical formulas of each substance in a reaction

● Formulas to the left of the arrow represent the reactants o present before the reaction takes

place

● Formulas to the right of the arrow represent the productso new substances present after the

reaction takes place

Balancing chemical equations● Remember that mass

is conserved● The same number of

atoms from each element should be on the left side and right side of the arrow

C3H8 + O2 → H2O + 3CO2

Is this balanced?If not, how can we balance it?

Rate of chemical reactions● Particles move and

collide with each other- the faster this happens the more the rate of a chemical reaction increases.

Rate of chemical reactions cont’d● Things that affect rate of chemical reactions

o Higher temperature= particles move fastero Concentration= more particles available to bump into

each othero Surface area= affects reaction if one reactant is solid.

More space for reactants to collide.

Homework Ch7 L.4

● p.261 #1-10● Study for quiz● Extra credit:

o Outline all of chapter 7● Test prep:

o p. 265-269