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