Warm Up – 9/18Conversion 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.
H
O
Hydrogen atom (H)
Oxygen atom (O)
Trace Elements: > 0.01 % ex: iodine, iron, copper, etc.
Essential Elements:C, H, O, N = 96%P, Ca, K, S = ~4%
Essential VS Trace Elements???
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 are in energy levels outside nucleus.• The first energy level can hold two electrons• The second energy level can hold up to eight.
Oxygen atom (O)
Nucleus:8 protons (+)8 neutrons
outermost energy level: 6 electrons (-)
inner energy level: 2 electrons (-)
Electrons
2n2 = # of electrons an energy level can hold
Atoms• In general atoms have equal
numbers of electrons and protons.
• The positive and negative charges balance out. • Atoms are electrically neutral.
The carbon atom shown has 6 protons and 6 electrons.Atomic Basics Video
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
• Carbon’s atomic number is 6• What does this mean?
• Each atom of carbon has _____ # of: • Protons = • Electrons =
• Protons ___ + Neutrons ___ = _____ Atomic Mass
• Atomic Mass – Total number of protons and neutrons in and atoms nucleus.
12
6
6
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
Dogs Teach Chemistry - Ionic Bond Video
These oppositely charged ions have a strong attraction for each other, forming an ionic bond.
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
Moleculeso 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
o Structural formula: shows types of atoms in a molecule and how they are bonded together.
Molecules
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
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
2.2 Properties of Water
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
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
Properties of Water
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
“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!!
Solutions
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
oBase – 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