Warm Up – 9/18
Conversion Practice
2.5 Km = ________________ cm
4.67 mm = ___________________ m
5.89 L = _________________ ml
15m = ____________________mm
26ml = ____________________ L
Warm-Up 9/25
1. Compare covalent and ionic bonding
2. What are isotopes?
3. Define: Compound
4. Provide one example of a chemical formula.
Warm Up 10/1
What is Cohesion and Adhesion?
Provide one example of each.
Chapter 2
The Nature of Matter &
Biomolecules
Living things consist of atoms of different
elements.
• Matter - anything that occupies space and
has mass
• An element is one type of atom, cannot be
broken down into other substances.
Essential VS Trace Elements???
H
Hydrogen atom (H)
Essential Elements:
C, H, O, N = 96%
P, Ca, K, S = ~4%
Trace Elements: > 0.01 %
ex: iodine, iron, copper, etc.
Oxygen atom (O)
O
Atoms
• Three subatomic particles make up atoms.
• Protons
• Neutrons
• Electrons
• 100 million atoms side by side would make a
row—about the width of your little finger!
Protons and Neutrons
• Protons and neutrons have about the same mass.
• Protons = positively charged particles (+)
• Neutrons = neutral particles (No net charge)
• Nucleus is the center of the atom
• Made of both protons and neutrons
• Protons and neutrons are held in the
nucleus by the strong force.
Electrons
• Negatively charged particle (–)
• Extremely small
• 1/1840 the mass of a proton.
• Attracted to the positively
charged nucleus and are
inconstant motion around the
nucleus.
Electrons
• Electrons are in energy levels outside nucleus.
• The first energy level can hold two electrons
• The second energy level can hold up to eight.
2n2 = # of electrons an energy level can hold
Oxygen atom (O)
Nucleus:
8 protons (+)
8 neutrons
outermost energy
level:
6 electrons (-)
inner energy level:
2 electrons (-)
Atoms
• In general atoms have equal
numbers of electrons and protons.
• The positive and negative charges
balance out.
• Atoms are electrically neutral.
Atomic Basics Video
The carbon atom shown has
6 protons and 6 electrons.
Elements
• Element - a pure substance that
consists entirely of one type of
atom.
• Elements represented are one- or
two-letter symbols.
• Example:
• C for carbon
• H for hydrogen
• Na for sodium
• Hg for mercury
Atomic Basics
• Atomic number - The number of protons in the atoms
nucleus
• Atomic Mass – Total number of
protons and neutrons in and atoms
nucleus.
• Carbon’s atomic number is 6
• What does this mean?
• Each atom of carbon has _____ # of:
• Protons = 6
• Electrons = 6
12 Atomic Mass
• Protons ___ + Neutrons ___ = _____
Isotope
Isotope - Atoms of the same element that differ in the
number of neutrons
•
Atoms of carbon have 6 neutrons. Some can have 7 or
8. These are isotopes of carbon
• Isotopes are identified by their mass number.
• carbon-12, carbon-13, and carbon-14.
Radioactive Isotopes
• Radioactive means - that their nuclei are unstable and
break down at a constant rate over time.
• Practical Uses for Radioactive Isotopes
• Geologists can determine the ages of rocks and
fossils by analyzing the isotopes found in them.
• Radiation from certain isotopes can be used to
detect and treat cancer
• To kill bacteria that cause food to spoil.
• Labels or “tracers” to follow the movements of
substances within organisms.
Chemical Compounds
Food for Thought!
The physical and chemical properties of a compound
are usually very different from those of the elements
from which it is formed.
What elements are pictured below?
Chemical Compounds
• Example:
• Sodium is a silver-colored metal that is soft enough to
cut with a knife. It reacts explosively with cold water.
• Chlorine is a very reactive, poisonous, greenish gas that
was used in battles during World War I.
• However, the compound sodium chloride--table salt--is a
white solid that dissolves easily in water, is not poisonous,
and is essential for the survival of most living things.
Compounds
• Compound - a substance formed by the chemical
combination of two or more elements in fixed proportions.
Chemical Bonds
Two main types of chemical bonds
• Ionic bond
• Covalent bond
Ionic Bond
• Ionic bond - formed when one or more
electrons are transferred from one atom to
another.
• Atom that loses electrons = positively
charged.
• The atom that gains electrons = negatively
charged.
• Ions = positively and negatively charged atoms
Ionic Bond Example
Ionic Bond Example
Ionic Bond Example
Ionic Bond Example
These oppositely charged ions have a strong
attraction for each other, forming an ionic
bond.
Dogs Teach Chemistry - Ionic Bond Video
Covalent Bonds
• Covalent Bond – Formed when pairs electrons are shared by
atoms
• The shared electrons travel around both nuclei!
• Single Bond = share two electrons
• Double Bond = share four electrons.
• Triple Bond = share six electrons,
2 Oxygen Atoms = O2
Molecules
o Molecules - when 2 or more atoms are held together
by covalent bonds.
• Chemical formula - Shorthand writing of the elements
and number of atoms in a compound.
• Water contains two atoms of hydrogen for each atom of
oxygen
• Chemical formula - H2O.
• The formula for table salt - NaCl
• Sodium (Na) –
• Chlorine (Cl) –
• Combine in a 1:1 ratio
Molecules
o Structural formula: shows types of atoms in a
molecule and how they are bonded together.
PRACTICE!!!
1. Determine if each is the chemical or structural formula
of the molecule.
KMnO4
MgSO4
Chemical Reactions
Chemical reaction: The breaking of old bonds and forming
of new chemical bonds.
Reactants: starting materials for a reaction
Products: ending materials from a reaction
1
+
1
=
2
2.2 Properties of Water
Objectives 2.2
•
•
•
•
Describe the structure of a water molecule
List and describe water’s unique properties
Distinguish between an acid and a base
Explain how Earth’s conditions are fit for life
The Water Molecule
Key Topic!
How does the structure of water contribute
to its unique properties?
Polarity
• The oxygen atom has a greater attraction on the shared
electrons.
• As a result:
• The oxygen end of the molecule has a slight negative
charge
• The hydrogen end of the molecule has a slight positive
charge.
• This is called a polar molecule
Hydrogen Bonding
Hydrogen bond – attraction between a
hydrogen atom on one water molecule
and the oxygen atom on another.
Hydrogen Bonding
• Water can form multiple hydrogen bonds
• Not as strong as covalent or ionic bonds
• Can form in other compounds besides
water.
• DNA
Properties of Water
Hydrogen bonds are responsible for three important
properties of water.
– high specific heat (1 calorie/gram °C = 4.186
joule/gram °C)
– Cohesion: tendency of like molecules to stick together
– Adhesion: type of attraction that occurs between
unlike molecules
Cohesion
• Cohesion - an attraction between
molecules of the same substance.
• a single water molecule can form up to four
hydrogen bonds simultaneously
• Water is extremely cohesive.
Cohesion
• Cohesion causes water molecules to be drawn together,
which is why drops of water form beads on a smooth surface.
• Cohesion also produces surface tension, explaining why
some insects and spiders can walk on a pond’s surface.
Adhesion
• Adhesion - an attraction between
molecules of different substances.
• The surface of water is attracted to the
glass of the graduated cylinder
• Causing the meniscus
Cohesion & Adhesion
Cohesion: tendency of
like molecules to stick
together
Adhesion: attraction
that occurs between
unlike molecules
Heat Capacity
• Heat capacity - The amount of heat energy required
to increase its temperature.
• Relatively high compared to other compounds
• Examples
• Large bodies of water, such as oceans and lakes, can
absorb .
• This protects organisms living within from
dramatic changes in temperature.
• At the cellular level, water absorbs the heat produced by
cell processes, regulating the temperature of the cell.
Water Properties Video
Dissolving compounds in water.
Solution - when one substance dissolves in
another.
Solvents - dissolve other substances.
(H2O)
Solutes - dissolve in a solvent. (NaCl)
Aqueous Solution – any solution where
water is the solvent.
solution
Solutions
“Like dissolves like.”
– Polar solvents dissolve polar solutes.
– Nonpolar solvents dissolve nonpolar solutes.
– Polar substances and nonpolar substances
generally remain separate.
– They don’t mix!!
Explain why some salad dressings needs to be shaken
before you use them.
Acids, Bases, and pH
• Water molecules sometimes split apart to
form hydrogen ions and hydroxide ions.
The pH Scale
pH scale - indicates the concentration of H+ ions in
solution.
The pH scale ranges from 0 to 14.
< 7 = Acidic
7 = Neutral
> 7 = Basic
Acids
o Acid - any compound that forms H+ ions in
solution.
• pH values below 7
• High levels of H+ ions
Bases
o Base – any compound that produces
hydroxide (OH–) ions in solution.
• pH values above 7
• Basic, or alkaline, solutions contain
low concentrations of H+ ions.
The pH Scale