Biology

Physical Science Notes

• Chemistry – study of all forms of matter (solids, liquids, gases, plasma)

• Physics – study of the way energy affects matter

• Property is the ability to do something• Can be observed or measured without

changing the matter’s identity

Matter

• Matter is made of atoms in motion• Matter is anything that has mass and takes up space

(volume)• 4 states of matter – solid, liquid, gas, plasma• Water is the only compound that exists on earth in all

3 states • No 2 objects can occupy the same space at the same

time • Inertia is a property of matter: moving doesn’t want to

stop, stopped doesn’t want to move

States of Matter

• Solid: either crystalline or amorphous, can not change shape, has a fixed volume

• Liquid: particles slide past each other, change shape, not volume

• Surface tension and viscosity are properties of a liquid

• Gas: particles are spread out, change shape and volume, a gas is the only state of matter that can be compressed

Density/solubility

• Density is mass/volume and identifies how tightly packed matter is.

• Water is the only substance with a density of 1g/mL.

• Density is unique to an element or a compound.

• Solubility- the ability to dissolve at a given temperature and pressure

Examples of physical properties and physical changes

• Physical Property• Boiling Point• Freezing Point• Melting Point• Condensation Point• Evaporation Point• Ductile• Malleable• Solubility• electric conductivity• density

• Physical Change• Boiling• Freezing• Melting• Condensing• Evaporating• Stretching into wire• Hammer into sheet• Dissolving• Moving electricity• Mass/volume

NOT physical properties

• Never use weight, mass, volume, shape or size to describe matter

• Weight is a measure of the force of gravity, relative to location

• In other words, physical changes do not change the identity of the matter

Chemical Properties• Chemical property – a property of matter that

describes a substances ability to participate in chemical reactions (you get something new)

• Examples of chemical properties– Flammability – ability to burn– Reactivity with acid – Reactivity with water– Reactivity with oxygen– Reactivity with other elements– Combustion (ignite, or burst into flame)

Evidence of Chemical Change• Heat produced• Cold produced• Gas produced• Light produced• Odor change• Color change• Precipitate produced (solid)• Oxidation (tarnish)• Electrolysis• Bubbling• Foaming• Fizzing

Mixtures, Solutions, Suspension, Elements, Compounds, Acids, Bases and Salts

• Mixture: Two or more substances that are not chemically combined

• All mixtures can be physically separated• Ratio of mixtures are not fixed• Mixtures can be solid, liquid or gas• Solution: Mixture that appears to be a single

substance• Material must be soluble (able to dissolve)

• Solute is what is dissolved• Solvent what the solute is dissolved in• Water is the universal solvent• Solubility is the ability of substances to dissolve

at a given temperature and pressure• Suspensions: are mixtures where the particles

are heavy enough to settle out (sink to bottom) of the solution, scatter light, can be filtered

Elements

• Elements: are pure substance that cannot be separated into simpler substances by physical or chemical means

• Elements can be identified by their characteristic properties (physical and chemical)

• Elements are classified by large categories:• Metals – shiny, good conductors• Nonmetals – dull, poor conductors• Metalloids –has properties of metals and

nonmetals depending on conditions

Compounds• Compounds: pure substance composed of two or

more elements that are chemically combined• Elements do not form compounds randomly• Compounds form in specific mass ratio• When elements form compounds, new

characteristics properties are created• The only way to separate a compound into

elements or other compounds is by a chemical reaction which allows for a chemical change by adding (endothermic) or taking away (exothermic) energy

Acids, Bases and Salts

• Most acids start with the element H, hydrogen – EX: HCl (hydrochloric acid), H2SO4 (sulfuric acid)

• Any compound that increases the number of hydronium ions, (H+), when dissolved in water is an acid

• NEVER TASTE, SMELL OR TOUCH ACIDS• Properties: has sour taste (think vinegar or

lemons), corrosive, react with some metals to produce hydrogen gas, conduct electricity

• Most widely made acid H2SO4

• Most bases end with OH-, a hydroxide ion, when dissolved in water

• NEVER TASTE, SMELL OR TOUCH BASE• Properties: has bitter taste and slippery feel (think soap),

corrosive, conducts electric current• Strong acids will have additional Hydrogen (H+) molecules

in the compound (HCl – vs- H2SO4)• Strong bases will have additional hydroxide (OH-),

molecules in the compound (MgOH –vs- Ba(OH)2)

• 7 on the pH scale is neutral (H2O)• Bases have a pH greater than 7• Acids have a pH less than 7.

Salts

• Large group of compounds with similar properties (usually formed with elements in group 17, halogens)

• When a reaction occurs between an acid and a base, they neutralize each other

• When an acid neutralizes a base, salt and water are produced

Atomic Theory

• Democritus (440 BCE)- realized that if you continued to cut something, eventually you would end up with something that couldn’t be cut anymore, atomos – meaning not able to divide

• Atoms are the smallest particle that an element can be divided and still be the same substance

• All matter is made of atoms

John Dalton (1803)

• realized that atoms combine in very specific proportions (ratios) based on mass

• all substances are made of atoms and they can not be created, divided or destroyed because they were made of a single substance

• All atoms of the same element are exactly alike and different from other elements, they are unique

• Atoms join with other atoms to form new substance

J. J. Thomson (1897)

• discovered that there were small particles inside the atom, meaning that atoms can be divided into smaller substances

• Electrons – negatively charged particles attracted to positively charged particles

• Plum pudding model – electrons are mixed throughout the atom, soft blobs of matter

Ernest Rutherford (1909)

• Discovered that an atom contains a nucleus with positively charged particles and that the electrons must be “floating” around the nucleus

• Most of an atom is empty space

Niels Bohr (1913)

• Proposed that electron moved around the nucleus in energy levels (shells), but no electrons between the energy level (think ladder)

• Electrons can jump from one level to another• Travel in a definite path

Modern Atomic Theory

• Erwin Shrodinger & Werner Heisenberg• Electrons have no predictable pattern and

move in a region where electrons are likely to be found called the electron cloud

Atoms

• All atoms have a nucleus – protons (+), – neutrons (no chg) – electrons (-)

• Same number of protons and electrons an atom has no charge

• More protons (+) than electrons (-) the atom has a positive ion is formed (more positives than negatives)

• More electrons (-) than protons (+) a negative ion is formed (more negatives than positives)

• 117 different element that are unique and all things known to exist come from a combination of these elements in specific mass ratios

• Simplest atom is made of one proton, and 1 electron – hydrogen (has no neutrons)

• All additional element will have protons, neutrons and electrons

• The atomic number of an element is determined by the number of protons,– 1 is hydrogen, 6 is carbon, hydrogen has 1 proton,

carbon has 6 protons (you can not change the number of protons)

• To find neutrons take the mass number (rounded) and subtract the protons.

Isotopes

• Isotopes have the same number of protons but additional neutrons which causes the atomic mass to be different

• Isotopes can be stable (maintain there structure) and unstable (fall apart over time)

• Unstable isotopes are radioactive and will decay over time giving off particles and energy (radioactive)

• Mass number determines the isotope, the number of protons and neutrons added together

• Most elements have isotopes• All isotopes of an element have the exact

properties of the element

Forces in atoms

• Gravitational force – pulls objects toward each other—depends on mass and distances between the objects—very small force in atoms

• Electromagnetic force –– proton (+) and electrons (-) have strong attraction which keeps the electrons in motion around the nucleus of atoms

• Strong force – force which keeps protons from flying apart due to close distance between protons and neutrons

• Weak force – relevant to radioactive atoms- allows neutrons to change into proton and electron

Periodic Table

• Dmitri Mendeleev-recognized that elements had repeating patterns (periodic) and organized elements into a table by increasing atomic mass

• Henry Moseley - determined that the number of protons - atomic number (which is unique to each element) would allow the elements to fit into very specific pattern

• Separated into 3 large categories: metals, metalloids, nonmetals based on their properties, moving from left (very reactive) to right (gradually becoming completely non-reactive) across each period on the table

• Columns are called groups or family, each has a name

• Each element in a family has the same number of valence electrons in the outer shell

• Group 1 – Alkali Metals• Group 2- Alkaline Earth Metals• Group 3-12 – Transition Metals• Group 13 – Boron Group• Group 14 – Carbon Group• Group 15 – Nitrogen Group• Group 16 – Oxygen Group• Group 17 – Halogens• Group 18 – Noble Gases• 1st Row at bottom – Lanthanides• 2nd Row at bottom - Actinides

• Rows (left to right) are called periods (7 rows)- determines the number of energy levels

• 1st energy level – 2 valence electrons (max)• 2nd energy level – 8 valence electrons (max)• 3rd energy level – 18 valence electrons (max)• And so on….• Each energy level can have less valence

electrons but they can not have more than the maximum valence electrons.

Bonds – Octet Rule

• To form bonds, elements must reach a full state of 8 valence electrons in the outermost energy level (octet rule) (Exception: would be first energy level which is full at 2-helium)

• Atomic number = Number of Protons • Electrons equal to the number of protons• Neutrons equal atomic mass (rounded) minus

the protons• Protons do not change in a atom, neutrons

can change (isotopes), electrons can be shared or transferred (when bonds are made)

Chemical Bonding

• Bonds are formed between elements that can rearrange their molecules to create compounds.

• Bonds only form when energy is put in or taken away (endothermic or exothermic)

• For bonds to form, the outer energy level must equal 8 (octet rule) for one of the elements.

• Ionic bond – electrons are transferred (one element gets to 8) between a metal and a nonmetal

• Covalent Bond – electrons are shared (both elements get to 8) both nonmetals

• If any atom losses electrons, the molecule becomes positively charged ion.

• If an atom gains electrons, the molecule becomes negatively charged ion.

Steps to Draw Bonds

• Determine the number of valence electrons• Determine which elements needs what• Draw the electron dot diagram with the electrons to

be transferred or shared in the middle• Draw the bond – Vin diagram• Determine if the bond is ionic (one reaches 8) metal

bonded to non-metal or covalent (both reach 8), non-metal bonded with non-metal

• Determine whether a single, double or triple bond has occurred

Steps to Draw Molecular Structures

• Determine the elements• Determine the atoms• Determine the number of molecules• First elements is always the center of the

structure• Additional elements are drawn around the

center