THINGS TO ADD IN AQUEOUS SOULTIONS (solutions, acids, bases)

Introduction to Chemistry

Element A pure substance that can not be broken down into something simpler. Ex: Copper in pure form (Cu on periodic table)

Biologically Important Elements Carbon* Hydrogen* Oxygen* Nitrogen* Calcium Phosphorus Potassium Sulfur Sodium Chlorine * Make up 96% of the mass of living things

Atom The smallest particle that retains all the properties of the element

Reading a Periodic Table 6 C Carbon 12 Atomic Number Chemical Symbol Atomic Mass

Reading a Periodic Table Atomic Number is the number of protons and the number of electrons in an atom Atomic Mass is the number of protons + neutrons How many protons and neutrons does this have? 79 AU 197

Compound A substance composed of two or more elements H2O: 2-Hydrogen, 1-Oxygen: Water CO2: 1-Carbon, 2-Oxygen: Carbon Dioxide C6H12O6: 6-Carbon, 12-Hydrogen, 6-Oxygen: Sugar

Molecule The smallest unit of a compound that still retains the properties of that compound Composed of 2 or more atoms chemically bonded together (formed when a positive charge interacts with a negative charge)

From Periodic Table we know… Proton is a positive charge Neutron has no electrical charge and weighs the same as a proton. Electron is a negative charge So why do we need this? Understanding these three things allows us to understand how molecules form bonds

Chemical Bond Force holding the atoms together in a molecule

The Chemistry of Water Structure:

Water Electron Oxygen Hydrogen Nucleus

Biological roles of water 1. As a solvent Water is an efficient solvent. It is capable of dissolving many substances.

Biological roles of water 2. As an insulator Water has a maximum density when it is just above its freezing point. Ice layers therefore float and insulate the water below the surface of ponds and lakes.

Biological roles of water 3. Moderator of temperature changes. Water absorbs a lot of heat when changing state. Loss of heat through evaporation cools us when we sweat.

Biological roles of water 4. As a transport medium It’s hydrogen-bonding and solvent properties make water important as a transport medium for living things

Biological roles of water 5. As a reagent Water is an important reactant in some chemical reactions, particularly hydrolysis.

Polarity of water… The polarity of the water molecule causes it to be attracted to other water molecules as well as molecules of other substances.  The attraction between water molecules is called cohesion The attraction of water molecules to other substances, like soil or glass, is called adhesion. 

Cohesive Forces The force that occurs between water molecules is so strong that when comes in contact with another medium, such as air, the water creates a "sticky skin", which is known as surface tension.  These bonds are so strong that they can support insects, you may have seen this before demonstrated by a water strider. To show the surface tension – take a beaker of water and place a needle on top (if need be coat in jelly). This shows the cohesive forces causes the sticky skin. Then push the needle down to the bottom to show how you break it.

Adhesive forces The adhesive powers is a process called capillary action Capillary action is when water molecules move upward through a narrow tube – such as a stem of a plant The attraction of water to the walls is so strong that gravity cannot pull the water down Celery sticks or a glass tube picking up liquid

Here the capillary action is drawing the blood into a glass tube