Biology I

Scientific Method, Life, and Membranes

• Observation-Something we know to be true based on one or more of our five senses.

• Inference- A conclusion which is based on observations

• Hypothesis- a testable inference usually stated in the “if” “then” format.

• Independent Variable is the variable that an experimenter changes on purpose.

• Dependent variable is the variable that an experimenter measures and records as data.

• Control variables or experimental control -these are all of the factors that are held constant to make sure that any changes measured in the dependent variable are the result of the independent variable

Observation

• Control experiment – is run in conditions identical to the experiment except the independent variable is not manipulated. This establishes the difference between the two.

• Fact- Something that can be verified with the use of a tool like weight, length, or temperature

• Scientific Law- relationship that is limited in scope and can often be described by a mathematical formula

• Scientific theory- an idea that scientists are sure of. A theory must withstand challenges (hundreds of thousands or more) to be widely accepted.

Hang in there, only one more slide

• Good science is ALWAYS:• 1. Testable 2. Repeatable• 3. Falsifiable 4. Published to invite

Challenge• Science is better today than it has ever been

because technology has greater capability than ever and communication is better resulting in greater scrutiny

• Religion- based on faith and depends on a source of truth. Religion is rarely if ever testable or falsifiable.

• Data- Measurements collected during an experiment

• Quantitative data- Data that is numerical (based on Quantity)

• Qualitative Data- Data that is merely observational, sometimes comparative in nature but not numerical.

• Inductive Reasoning- when you use specific cases to develop a generalization. This tends to lead new understanding in science

• Deductive Reasoning- uses generalizations to identify specifics

• Theory development occurs through inductive reasoning and then deductive reasoning helps develop hypothesis to test theories.

• Atoms are the smallest particles of elements and consist of protons, neutrons, and electrons.

Atoms are made of sub atomic particles that are even smaller• Protons-in the nucleus have a mass of 1.007 daltons

and a positive charge• Neutrons-in the nucleus have a mass of 1.009

daltons• Electrons- orbit the nucleus,have a mass of .002

daltons, and have a negative charge. • Protons determine the identity of an atom but

electrons determine their behavior

• The number of protons in an atom give that atom its atomic number on the periodic table

• The number of protons and neutrons in an atom equal that atoms atomic mass.

• Any atom that is neutral has a number of electrons equal to its number of protons

• Ions are atoms that have different numbers of electrons than protonsPositive Ions have lost electrons (- -1= +1)Negative Ions have gained electrons (+ -1= -1)

Formal writing of chemical information

23 11

The 23 at the top is the number of neutrons plus protons. The 11 says there are 11 protons so there must be 12 neutrons.

Na+1

The +1 above notes that there is one more proton than electrons in this atom meaning that 11-1=10 electrons justifying the +1 charge.

• Electrons are found in orbitals, and orbitals can be put together to form electron shells.

• S orbitals can hold 2 electrons and the first is noted as the 1s orbital.

• P orbitals can hold 6 electrons and the 2p orbital is the first one.

• Electron shells are made up of one or more orbitals, the first electron shell is made of the 1s orbital so it only holds 2 electrons.

• The second Electron shell includes the 2s and 2p orbitals meaning it holds 8 electrons. The third shell is made of the 3s and 3p orbitals.

Use this graphic

• Shell 1= 1s• Shell 2= 2s

2pShell 3= 3s

3p

Each blank represents an orbital which can hold two electrons. You can see from the chart that the first shell only holds one orbital and therefore, one electron pair. The second and third shells hold four orbitals or 8 electrons each.

The lewis dot structure

• Please note that oxygen has eight electrons all total but only

six are shown here. The other two are in the full 1s orbital and are not available for bonding so they are not shown here. The other six have filled the orbitals as shown on the next slide.

Notice that O has eight total electrons but only the six valence electrons are

shown on the lewis dot structure because they are the ones that determine chemical behavior

• Shell 1= 1s ll• Shell 2= 2s ll

2p ll l lShell 3= 3s

3p

• Elements that are in Group 1a have 1 valence electron and are likely to kick off that electron to fall back to the next shell.

• Elements in 7a have 7 electrons in the valence shell and tend to steal one more to gain a full valence shell

• Elements in the 4a group have 4 valence electrons and tend to share their four in covalent bonds.

Covalent bonding is when two atoms are attached to one another as the result of sharing electrons.

Polar Covalent Bond- occurs when electrons shared by two different atoms are not shared equally. This makes one of the atoms slightly positive and one slightly negative.

Polar molecules that contain polar bonds and exhibit negative and positive asymmetry causing them to act like a magnet.

Hydrogen Bonds are actually magnetic attraction between the oppositely charged portions to two polar molecules.

• Water’s polarity allows it to dissolve other polarcompounds, show

• Cohesion- water sticking to other waters• Adhesion- water sticking to other molecules• capillary action- adhesion and cohesion that

allows water to move upward in a tube• Temperature buffer- resist temperature change.• Structural component of cells- provides pressure

that keeps the cells “full”

Like dissolves Like

Water also breaks down into H+ and OH- H+ is acid OH- is base• Neutral solutions have equal amounts of H+ and OH-

• Acids have more H+ than OH-.• Bases have less H+ than OH-.• If a pH goes from 7 to 6, it is ten times as acidic.• A pH of 5 is 100 times as acidic as a pH of 7

• Graphing• Title- Explains the graphed relationship in a short

statement• The right type of graph is chosen• Axis are labeled for what they represent and the

units they measure• Points are plotted correctly • Lines that are drawn show trends correctly• There is a key when appropriate