1. Chapter 2
The Chemistry of Life

2. Section 2.1: The Nature of Matter
We are all walking, talking chemistry experiments!!
We are made from chemical compounds
We use chemical reactions to keep
us alive
Since chemistry is so critical to life, we need to start here with the “behind-the-scenes” stuff to understand the “chemistry” of life.

3. Matter
Matter – the building blocks or the “stuff” that everything is made of (yes, even non-living things too!)
About 2500 years ago, a Greek philosopher named Democritus made some observations with chalk
He wondered, if you keep breaking a piece of chalk, is it still considered chalk?
He believed that eventually you would get to the point where you could not break the chalk anymore
He called this smallest piece an atom which means unable to be cut

4. Atoms An atom is the basic unit of matter Atoms are very small
100 million atoms would fit across the width of your pinky finger!!
Even though atoms are very small, they contain particles within them called subatomic particles that are even smaller!
The subatomic particles that make up atoms are:
1) protons
2) neutrons
3) electrons

5. Nucleus Protons are positively (+) charged particles
Neutrons are particles with no charge
Protons and neutrons have about the same mass
Together, these subatomic particles make up the nucleus of an atom
The nucleus is the center of the atom

6. Electrons Electrons are negatively (-) charged particles
Electrons have 1/1840 the mass of a proton
Electrons can be found in a “cloud” around the nucleus and they are in constant motion
They are attracted to the positively charged nucleus (opposites attract!!), but they stay outside of the nucleus because of all of the energy of their motion

7. Charge of an Atom
Atoms have an equal number of protons and electrons so the positive and negative charges balance out
This means that atoms are electrically neutral

8. The Atom’s Family

9. The Atoms Family 2nd Verse:
Together they make gases,
And liquids like molasses,
And all the solid masses,
The Atoms Family
Chorus
3rd Verse:
Neutrons can be found,
Where protons hang around;
Electrons they surround
1st Verse: They’re tiny and they’re teeny, Much smaller than a beany, They never can be seeny, The Atoms Family Chorus: They are so small (snap, snap) They’re round like a ball (snap, snap) They make up the air. They’re everywhere. Can’t see them at all (snap, snap)

10. EXTRA CREDIT OPPORTUNITY
The Atom’s Family
EXTRA CREDIT OPPORTUNITY
Either by yourself, with a partner, or a small group, perform the Atom’s Family song and video tape it! You can then save the video clip on a flash drive, CD, or your school account. The video needs to be school appropriate and the more creative, the more extra credit points! You can earn up to 10 extra credit points.

11. Elements
An element is a pure substance that is made completely of only one type of atom
There are more than 100 known elements but only about 24 are found in living things

12. Elements
Atomic symbol- the symbols used to represent an element (one or two letters)
i.e. Carbon’s atomic symbol is: C
Atomic number- the number of protons in the nucleus of an element
i.e. Carbon’s atomic number is : 6

13. Isotopes
Isotopes are atoms of the same element that have a different number of neutrons
i.e. Carbon atoms (which always have 6 protons) can have
six, seven, and even eight neutrons!

14. i.e. carbon-12, carbon-13, carbon 14
Isotopes cont…
Mass Number- the total number of protons and neutrons in the nucleus of an atom
We identify the isotopes according to their mass number (Figure 2-3, p. 35)
i.e. carbon-12, carbon-13, carbon 14
Atomic Mass- the weighted average of the masses of an element’s isotopes (the abundance of each isotope in nature is considered when this average is calculated)

15. Radioactive Isotopes
Some isotopes have unstable nuclei that break down at a constant rate over time
This radiation can be dangerous, but can also be important!
Can determine the age of rocks based on the isotopes found in them
Radiation can be used to detect and treat cancer
Can kill bacteria that cause food to spoil
Can be used as “tracers” within living things to “trace” the movements of substances within them

16. i.e. the chemical formula for water is H2O
Chemical Compounds
A compound is a substance that is formed by the chemical combination of 2 or more elements in definite proportions
A compound can be represented by a chemical formula
i.e. the chemical formula for water is H2O
Water has 2 hydrogen atoms for every 1 oxygen atom so these atoms combine in a 2:1 ratio

17. Properties of Compounds
The physical and chemical properties of a compound are very different from the properties of the elements that make it
i.e. hydrogen and oxygen are both gases at room temperature by themselves, but when they are together, they form liquid water

18. Chemical Bonds
The atoms within a compound are held together by chemical bonds
These bonds are the result of interactions between the electrons that surround each atom
Valence electrons- the electrons that are in the outer electron shell of an atom that can form bonds with other atoms
There are 2 main types of chemical bonds:
1) Ionic Bonds
2) Covalent Bonds

19. Ionic Bonds
An ionic bond is formed when one or more electrons are transferred from one atom to another
If an atom loses electrons, it becomes positively charged (there are more protons than electrons)
If an atom gains electrons, it becomes negatively charged (there are more electrons than protons)
Ions – Atoms that are positively or negatively charged
See p. 37, Figure 2-4 A

20. Covalent Bonds
A covalent bond is formed when electrons are shared between atoms
The electrons can move around the nuclei of both atoms
When only one electron is shared, it is a single covalent bond. When four are shared, it’s a double bond and when six are shared it’s a triple bond.
As a result of sharing electrons, the atoms are joined together and a molecule is formed
See p. 37, Figure 2-4 B

21. Molecules Molecules are the smallest unit of most compounds
They are formed when two or more atoms are bonded together

22. Van der Waals Forces Some atoms have the ability to attract electrons
Some have a stronger ability than others
When atoms share electrons in a covalent bond, the sharing is not always equal
This means that a molecule may have regions that are slightly positive and slightly negative
This can play a role in the properties of a molecule (i.e. water molecule)

23. Van der Waals Forces
When molecules are close together, a slight attraction can develop between these regions that are oppositely charged
These intermolecular (between molecules) forces are called Van der Waals forces
These forces are not as strong as ionic or covalent bonds, but they can still hold molecules together
See p.39