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Introduction to Wikis
1 The Science of Biology
2 Organic Chemistry and Water
7 Cell Structure and Function
10 Cell Growth and Division
11 Introduction to Genetics
12 DNA and RNA
13 Genetic Engineering
13 Genetic Engineering Part 2
14 The Human Genome
2 Organic Chemistry and Water
A chemical element is a pure element that consists entiirely of one type of atom.
A chemical compound is a substance formed by the chemical combination of two or more elements.
Scientists sometimes write compounds in short-hand. For example Table salt is NaCl.
In chemical compounds the atoms are held together by chemical bonds
there are two main types of chemical bonds, Ionic bonds and covalent bonds.
An ionic bond is when one or more electrons are transfered from one atom to another.
A covalent bond is when two atons share one or more electrons.
A water molecule has a covalent bond between the two hydrogen atoms ant the one oxygen atom.
A water molecule is made up of three atoms. two hydrogen atoms and a oxygen atom.
Atoms are made up of protons, electrons and neutrons.
Protons which are positively charged and neutrons which are neutral are found in the nucleus.
The negatively charged electron is found outside the nucleus.
The molecule is the smallest form of compounds.
A mixture is a material compostd of two or more elements or compounds that are physicaly mixed together physicaly, but not chemicaly.
Two types of mixtures that can be made with water are solutions and suspensions.
A solution is made up of solutes and salvents.
A solute is the substance that dissolves.
A salvent is a the substance in which the solute dissolves.
All components of a solution are equally dessolved throughout the solution.
Scientists have invented a measurment system called the pH scale which indicate the concentration of H+ ions.
H+ ions in a low pH solution comes from acids.
A base is a compound that produces hydroxide ions in a solution.
Buffers are weak acids or bases that can react with strong acids or bases to prevent sharp,sudden changes in pH.
A suspension is a mixture that does not fully dessolve but breaks into peices so small that they cann't be seen, but over time will settle at the bottom of the mixture.
Is made up of a chemical compund called H2O. That means there are 2 atoms of
and 1 atom of
Water is a
molecule, which means that the Oxygen end of the molecule has a slight negative charge and the Hydrogen has a slight positive charge.
They have uneven distribution of electrons between the oxygen and hydrogen atoms, thus creating polarity.
The subatomic particles particles that make up atoms are protons, neutrons, and electrons.
surface tension reason is polar and making polar reason is water atomic structure.
If it is hard to understand, just think that way. water made up 2 H and 1 O. and H like make a smail shape and they like gather.
Adhesion is an attraction between molecules of
substances. Cohesion is the attraction between molecules of the
If you have to read the volume of a graduated cylinder at eye level, you will see that its surface dips a little bit in the center, this is because the adhesion between the water molecules and the glass molecules is stronger than the cohesion between water molecules .
The pH scale
Chemists devised a measurment system called the pH scale to indicate the concentration of H+ ions in solution.
In figure 2-10 the pH scale ranges from 0 to 14. At pH 7, th e concentration of H+ and OH- ions is equal. The lower the pH the greater the acidity.
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