2. CChhaapptteerr 22:: CChheemmiissttrryy ooff LLiiffee
• Vocabulary
• 2-1
◦ Atom
◦ Nucleus
◦ Electron
◦ Element
◦ Isotopes
◦ Compound
◦ Ionic Bond
◦ Ions
◦ Covalent Bond
◦ Molecule
◦ Van der Waals forces
• 2-2
◦ Cohesion
◦ Adhesion
◦ Mixture
◦ Solution
◦ Solute
◦ Solvent
◦ Suspension
◦ pH Scale
◦ Acid
◦ Base
◦ Buffer
• 2-3
o Monomer
o Polymer
o Carbohydrate
o Monosaccharide
o Polysaccharide
o Lipid
o Nucleic Acid
o Nucleotide
o Ribonucleic Acid (RNA)
o Deoxyribonucleic Acid (DNA)
o Protein
o Amino acid
• 2-4
o Chemical Reaction
o Reactant
o Product
o Activation Energy
o Catalyst
o Enzyme
o Substrate
4. WWaatteerr BBaassiiccss
Water, H2O, is made of two hydrogen
atoms bonded covalently with one
oxygen atom.
Can exist on Earth as a solid, liquid or gas
depending on the temperature.
Covers 70% f the Earth’s surface.
It is essential for life
Water Cycle
7. WWaatteerr aanndd tthhee HHyyddrrooggeenn BBoonndd
• High surface tension
• Relatively high boiling point
• High heat capacity
• Adhesion
• Cohesion
• Density in solid state is less dense
•Unique
8. PPrrooppeerrttiieess ooff WWaatteerr
Universal solvency
Phases of water
◦ Solid
◦ Liquid
◦ Gas
Surface tension
Capillary Action
Density
Specific Heat
17. [H+] =
[OH-] = 2.74 x 10-2M
pH =
pOH =
acidic, basic, or neutral? ______________
18. YYoouurr ttuurrnn –– WWhhaatt ddoo yyoouu aallrreeaaddyy
kknnooww??
What are mixtures (solutions, colloids and suspensions)?
Define a mixture in your own words & give 2 examples
19. MMiixxttuurree
A mixture is a combination of two or more substances
where there is no chemical combination or reaction.
Mixtures combine physically in no specific proportions.
They just mix.
Mixtures are classified as:
◦ HOMOGENOUS/HETEROGENOUS
◦ SOLUTIONS
◦ COLLOIDS
◦ SUSPENSIONS
21. CCoollllooiiddss
In a colloid the particles are mixed together but not dissolved.
The particles are relatively large and are kept permanently suspended.
A colloid will not separate upon standing.
The particles are constantly colliding, and this allows a colloid to scatter
light – thus colloids often seem cloudy.
Colloids are heterogeneous or homogeneous mixtures of intermediate
sized particles (between 1 nm and 1000 nm) and do not settle out.
23. SSoolluuttiioonnss
A solution is a type of homogeneous mixture formed
when one substance dissolves in another.
It is the best mixed of all mixtures.
A solution always has a substance that is dissolved and
a substance that does the dissolving.
The substance that is dissolved is the solute and the
substance that does the dissolving is the solvent.
26. SSuussppeennssiioonn
Suspension- a heterogeneous mixture in which the particles
are large enough to be seen by a microscope or the unaided
eye (eventually, they settle out of the mixture). Example:
stirring a teaspoon of dirt in a glass of water.
27. SSoolluuttiioonn,, SSuussppeennssiioonn oorr CCoollllooiidd??
Finger paints
Mayonnaise
Sugar in Water
Muddy water
• Muddy water
• Italian Dressing
• Jell-O
• Sulfur vapor in air
Water is one of the few compounds that is a liquid at the temperatures found over much of Earth's surface. Unlike most substances, water expands as it freezes. Thus, ice is less dense than liquid water, which explains why ice floats on the surface of lakes and rivers.
Water is a common chemical substance on planet Earth. In fact, Earth is sometimes called the “water planet” because almost 75% of its surface is covered with water. We will see where Earth’s water is found in a few slides. The term water generally refers to its liquid state, and water is a liquid over a wide range of temperatures on Earth. However, water also occurs on Earth as a solid (ice) and as a gas (water vapor).
Water, like carbon, has a special role in living things. It is needed by all known forms of life. As you have seen, water is a simple molecule, containing just three atoms. Nonetheless, water’s structure gives it unique properties that help explain why it is vital to all living organisms.
Structure and Properties of Water
No doubt, you are already aware of some of the properties of water. For example, you probably know that water is tasteless and odorless. You also probably know that water is transparent, which means that light can pass through it. This is important for organisms that live in the water, because some of them need sunlight to make food.
Chemical Structure of Water
To understand some of water’s properties, you need to know more about its chemical structure. As you have seen, each molecule of water consists of one atom of oxygen and two atoms of hydrogen. The oxygen atom in a water molecule attracts electrons more strongly than the hydrogen atoms do. As a result, the oxygen atom has a slightly negative charge, and the hydrogen atoms have a slightly positive charge. A difference in electrical charge between different parts of the same molecule is called polarity.
Opposites attract when it comes to charged molecules. In the case of water, the positive (hydrogen) end of one water molecule is attracted to the negative (oxygen) end of a nearby water molecule. Because of this attraction, weak bonds form between adjacent water molecules, as shown in Figure below. The type of bond that forms between molecules is called a hydrogen bond. Bonds between molecules are not as strong as bonds within molecules, but in water they are strong enough to hold together nearby molecules.
Water has some pretty unique properties.
Contains 2 hydrogen and one oxygen atom. Because of the partial polarity of the water molecule, hydrogen bonds can form.
Hydrogen bonds form when the partial positive end of the water is attracted to another water’s partial negative end.
A hydrogen bond is the electromagnetic attractive interaction between polar molecules in which hydrogen (H) is bound to a highly electronegative atom, such as nitrogen (N), oxygen (O) or fluorine (F). The name hydrogen bond is something of a misnomer, as it is not a true bond but a particularly strong dipole-dipole attraction, and should not be confused with a covalent bond.
These hydrogen-bond attractions can occur between molecules (intermolecular) or within different parts of a single molecule (intramolecular).[1] The hydrogen bond (5 to 30 kJ/mole) is stronger than a van der Waals interaction, but weaker than covalent or ionic bonds. This type of bond can occur in inorganic molecules such as water and in organic molecules like DNA and proteins.
Intermolecular hydrogen bonding is responsible for the high boiling point of water (100 °C) compared to the other group 16 hydrides that have no hydrogen bonds. Intramolecular hydrogen bonding is partly responsible for the secondary and tertiary structures of proteins and nucleic acids. It also plays an important role in the structure of polymers, both synthetic and natural.
Hydrogen bonds between water molecules explain some of water’s properties. For example, hydrogen bonds explain why water molecules tend to stick together. Did you ever watch water drip from a leaky faucet or from a melting icicle? If you did, then you know that water always falls in drops rather than as separate molecules.
Hydrogen bonds cause water to have a relatively high boiling point of 100°C (212°F). Because of its high boiling point, most water on Earth is in a liquid state rather than in a gaseous state. Water in its liquid state is needed by all living things. Hydrogen bonds also cause water to expand when it freezes. This, in turn, causes ice to have a lower density (mass/volume) than liquid water. The lower density of ice means that it floats on water. For example, in cold climates, ice floats on top of the water in lakes. This allows lake animals such as fish to survive the winter by staying in the water under the ice.
Water and Life
The human body is about 70% water (not counting the water in body fat, which varies from person to person). The body needs all this water to function normally. Just why is so much water required by human beings and other organisms? Water can dissolve many substances that organisms need, and it is necessary for many biochemical reactions. The examples below are among the most important biochemical processes that occur in living things, but they are just two of many ways that water is involved in biochemical reactions.
Photosynthesis—In this process, cells use the energy in sunlight to change carbon dioxide and water to glucose and oxygen. The reactions of photosynthesis can be represented by the chemical equation
6CO2 + 6H2O + Energy → C6H12O6 + 6O2
Cellular respiration—In this process, cells break down glucose in the presence of oxygen and release carbon dioxide, water, and energy. The reactions of cellular respiration can be represented by the chemical equation
C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy
Water is involved in many other biochemical reactions. As a result, just about all life processes depend on water. Clearly, life as we know it could not exist without water.
The strength of an acid or base is determined by the extent of its ionization in aqueous solution. Strong acids, such as hydrochloric acid, are 100 percent ionized in aqueous solution, whereas weak acids, such as acetic acid, are less than 5 percent ionized. Experimentally, the extent of ionization is determined by measuring the electrical conductance of solutions. Strong acids and bases are strong electrolytes, and weak acids and bases are weak electrolytes. The table here lists some common acids and bases and indicates whether they are strong or weak.
Soda – Acid – Carbonic and phosphoric acid
Soap – Base - slippery
Coffee – Base – bitter taste
Wine – Slightly acidic – Sour taste
Water - Neutral
Grapefruit – acidic – Sour taste
[H+]= 3.65 X 10-13M
[OH-]= 2.74 x 10-2M
pH= 12.44
pOH= 1.56
Basic
Trail mix
Air is a solution of oxygen and other gases dissolved in nitrogen
Is it uniform throughout?
If the answer is no, the matter is a heterogeneous mixture.
Considered the “least mixed.”
Does not appear to be the same throughout.
Particles are large enough to be seen and to be separated from the mixture.
If the answer is yes, the matter is homogeneous (looks the same throughout).
That leads us to another question.
HOMOGENEOUS
A mixture that appears to be the same throughout.
It is “well mixed.”
The particles that make up the mixture are very small and not easily recognizable.
Finger paints – Suspension
Mayonnaise – Colloid
Sugar in water – Solution
Muddy water - Suspension
Italian salad dressing – Suspension
Jello – Colloid
Sulfur vapor in air - Solution
