Upload
kmwall
View
204
Download
1
Tags:
Embed Size (px)
Citation preview
Document Title (Editable via ‘Slide Master’) | Page 11
CHEMICAL BONDS
Companion Text:
Herlihy, B, The Human Body in Health and Illness, 4th Edition, 2011, Saunders Elsevier
Document Title (Editable via ‘Slide Master’) | Page 22
Atoms are attracted to each other because they want to achieve a stable outer electron shell …
In other words, they want either to fill or empty the outer electron shell
Herlihy, B, 2011, p.17
Document Title (Editable via ‘Slide Master’) | Page 33
The force of attraction that occurs between the atoms is like the force of two magnets
When you try to separate the magnets you can still feel the pull
(Herlihy 2011)
Document Title (Editable via ‘Slide Master’) | Page 44
Document Title (Editable via ‘Slide Master’) | Page 55
The electrical attraction between atoms is called a chemical bond
Document Title (Editable via ‘Slide Master’) | Page 66
There are three (3) kinds of chemical bond
• Ionic Bonds• Covalent Bonds• Hydrogen Bonds
Document Title (Editable via ‘Slide Master’) | Page 77
IONIC BONDS
An ionic bond happens when electrons are transferred between atoms
Document Title (Editable via ‘Slide Master’) | Page 88
Rather like moving house!
Document Title (Editable via ‘Slide Master’) | Page 99
Document Title (Editable via ‘Slide Master’) | Page 1010
COVALENT BOND
In a covalent bond, the outer shells of the atoms share electrons
Document Title (Editable via ‘Slide Master’) | Page 1111
Covalent bonding is like holding hands
Document Title (Editable via ‘Slide Master’) | Page 1212
Document Title (Editable via ‘Slide Master’) | Page 1313
Water happens because of covalent bonding …
Document Title (Editable via ‘Slide Master’) | Page 1414
Covalent Bond
Document Title (Editable via ‘Slide Master’) | Page 1515
Covalent bonds are strong and do not break apart in water …
Proteins and Carbohydrates are formed by covalent bonding.
Document Title (Editable via ‘Slide Master’) | Page 1616
The strength of these bonds is important because the protein produced by the body must not fall apart when exposed to water
Herlihy, B, p.17 (2011)
Document Title (Editable via ‘Slide Master’) | Page 1717
Many proteins, such as hormones, are transported around the body in blood, and blood is made up mainly of water’
If the covalent bonds of the protein broke apart in water the hormones would not be able to accomplish their tasks
Herlihy, 2011, p.17
Document Title (Editable via ‘Slide Master’) | Page 1818
Many chemical reactions that happen in the body involve carbon.
Because of this a separate branch of chemistry called organic-chemistry studies only carbon-containing substances
Inorganic chemistry studies non-carbon-containing substances
Document Title (Editable via ‘Slide Master’) | Page 1919
HYDROGEN BONDS
This kind of bond is different to ionic and covalent bonds
A hydrogen bond is not caused by either the transfer or the sharing of electrons in the outer shells of the atom
Document Title (Editable via ‘Slide Master’) | Page 2020
Hydrogen Bonds are best described as the weak attraction between water molecules
Herlihy, B, P.18 (2011)
Document Title (Editable via ‘Slide Master’) | Page 2121
Water is composed of hydrogen and oxygen
The weak positive charge around the hydrogen of one water molecule is attracted to the weak negative charge of the oxygen in a second water molecule
Herlihy, 2011, p.18
Document Title (Editable via ‘Slide Master’) | Page 2222
POLARITY
Water engages in hydrogen bonding because it is a polar molecule
A polar molecule has a ‘lop-sided’ charge (a + end and a – end)
Document Title (Editable via ‘Slide Master’) | Page 2323
02
H+
Pos
Neg
Document Title (Editable via ‘Slide Master’) | Page 2424
Document Title (Editable via ‘Slide Master’) | Page 2525
Hydrogen Bond
Document Title (Editable via ‘Slide Master’) | Page 2626
Several other terms are related to the activity of electrons in the outer shells of the atoms …
Herlihy, 2011, p.19
Document Title (Editable via ‘Slide Master’) | Page 2727
Electrons, for instance carry a (-ve) charge, and if they are lost from or gained by the outer shell of an atom, the electrical charge of the atom changes
Herlihy, 2011, p.19
Document Title (Editable via ‘Slide Master’) | Page 2828
The electrical charge of the atom or element changes from a neutral charge (no charge) to either a positive (+) or a negative (-) charge
Document Title (Editable via ‘Slide Master’) | Page 2929
Atoms that carry an electrical charge are called ions
If an ion is positively charged it is called a cation
If an ion is negatively charged it is called an anion
Document Title (Editable via ‘Slide Master’) | Page 3030
An electrolyte is a substance that forms ions when it is dissolved in water
Electrolytes can conduct an electrical current
Document Title (Editable via ‘Slide Master’) | Page 3131
For Example …
The electrocardiogram (ECG) records the electrical events of the heart.
It is the movement of ions through the tissues that cause the electrical events to be recorded on the ECG
Document Title (Editable via ‘Slide Master’) | Page 3232
Document Title (Editable via ‘Slide Master’) | Page 3333
So how are ions formed?Ions are formed when the outer shell of the atom loses or gains electrons
Document Title (Editable via ‘Slide Master’) | Page 3434
For instance …
The sodium atom has 11 protons (+ve) and 11 electrons (-ve) …
If a single electron is donated the sodium is left with 11 positive (+) charges and only 10 negative (-) charges
The sodium is said to carry a net charge of +1
Document Title (Editable via ‘Slide Master’) | Page 3535
The sodium ion is therefore a cation and is represented as Na+
Document Title (Editable via ‘Slide Master’) | Page 3636
and …
The chlorine atom has 17 protons (+) and 17 electrons (-ve)
If an electron is gained, the chlorine then contains 17 (+) charges and 18 (-) charges
The chlorine has a net charge of -1, so it is an anion
Document Title (Editable via ‘Slide Master’) | Page 3737
Some atoms give up more than one (-ve) electron so they have a more positive charge
Calcium is an example, because it gives up 2 electrons – its chemical symbol is therefore Ca2+
Herlihy, 2011, p.19
Document Title (Editable via ‘Slide Master’) | Page 3838
Ionization
Ionization happens when an electrolyte splits or breaks apart in solution
Document Title (Editable via ‘Slide Master’) | Page 3939
For Example …
NaCl (sodium chloride) is an electrolyte.
In its solid state it looks like tiny white granules
When it is dissolved in water the table salt dissociates
Document Title (Editable via ‘Slide Master’) | Page 4040
The ionic bonds holding the sodium and chloride together weaken and the solid NaCl splits into Na+ (sodium ion) and Cl- (chloride ion).
The NaCl has dissociated and because the products are ions, the process is called ionization
Document Title (Editable via ‘Slide Master’) | Page 4141
Remember!Only electrolytes ionize
Document Title (Editable via ‘Slide Master’) | Page 4242
What is a Molecule?A molecule is formed when two or more atoms bond together …
Two identical atoms can bond, for instance –one atom of oxygen can bond with another atom of oxygen to form a molecule of oxygen which is called 02
Document Title (Editable via ‘Slide Master’) | Page 4343
A molecule can also be formed when atoms of different elements combine.
For example – when 2 atoms of hydrogen combine with 1 atom of oxygen a molecule of water is formed
Herlihy, 2011, p.20
Document Title (Editable via ‘Slide Master’) | Page 4444
COMPOUNDSA substance that contains molecules formed by two or more different atoms is called a compound …
We can use the example of water again – when 2 atoms of hydrogen and 1 atom of oxygen combine
Water is considered to be both a molecule and a compound
Document Title (Editable via ‘Slide Master’) | Page 4545
Some Important Compounds & Molecules
• Water • Oxygen• Carbon Dioxide
Document Title (Editable via ‘Slide Master’) | Page 4646
Water …• Most abundant compound in the body
• Makes up nearly 2/3 of an adult’s body weight
• Essential to life
Document Title (Editable via ‘Slide Master’) | Page 4747
UNIVERSAL SOLVENT
Water is the universal solvent because most substances dissolve in water
When substances are dissolved in water they move more easily and this facilitates their involvement in chemical reactions
Document Title (Editable via ‘Slide Master’) | Page 4848
REGULATES TEMPERATURE
Water can absorb large amounts of heat without dramatically increasing the temperature of the water itself
This means that heat can be removed from heat-producing tissue, like exercising muscle, while the body maintains a normal body temperature
Document Title (Editable via ‘Slide Master’) | Page 4949
WATER AS A LUBRICANT
Water is a major component of mucus and other lubricating fluids
These lubricating fluids decrease friction when two lubricating surfaces slide past each other
Document Title (Editable via ‘Slide Master’) | Page 5050
WATER IN CHEMICAL REACTIONS
Water often has a crucial role to play in chemical reactions
We need water to break down carbohydrates during digestion
Herlihy, 2011, p.20
Document Title (Editable via ‘Slide Master’) | Page 5151
WATER AS A PROTECTIVE DEVICE
Water also protects important structures.
The cerebrospinal fluid that surrounds and cushions the brain and spinal cord is an example
Amniotic fluid surrounds and cushions the developing infant in its mother’s womb
Herlihy, 2011, p.20
Document Title (Editable via ‘Slide Master’) | Page 5252
OXYGEN
Oxygen (02) exists in nature as a gas and is essential to life
There is 21% of Oxygen in the air that we breath
Oxygen is used by the cells to liberate energy from the food we eat. This energy powers the body
If there is no energy, the body like a motor without fuel stops running and we die.
Document Title (Editable via ‘Slide Master’) | Page 5353
CARBON DIOXIDE
Carbon Dioxide (CO2) is a compound that consists of one carbon atom and two oxygen atoms …
CO2 is a waste product and must be eliminated from the body.
It is made when food is chemically broken down for energy
Document Title (Editable via ‘Slide Master’) | Page 5454
CHEMICAL REACTIONS
A chemical reaction is a process whereby the atoms of molecules or compounds interact and form new chemical combinations
For example, glucose interacts with oxygen to form carbon dioxide, water and energy
Herlihy, 2011, p.21
Document Title (Editable via ‘Slide Master’) | Page 5555
CHEMICAL REACTIONS … Cont.
The rate of chemical reactions are importantMost of them take place quite slowly , and chemical substances called catalysts can speed them upEnzymes are proteins that are acting as catalystsMost chemical reactions need a catalyst or an enzyme
Document Title (Editable via ‘Slide Master’) | Page 5656
REFERENCEHerlihy, B, The Human Body in Health and Illness, 4th Edition, 2011, Saunders Elsevier