1. Chapter 2: The Chemistry of Life

2. Basic Chemistry
ATOM: The basic building block of all matter; the smallest particle of an element that still retains properties of that element
All atoms have a Nucleus, which is the central part of the atom; it contains protons; and has an overall positive charge.
PROTON: (+)ve charged subatomic particles located in the nucleus; charge of +1
NEUTRON: (-/+) neutral (no charge) subatomic particles located in the nucleus; charge of 0.
Protons and neutrons have about the same mass.
ELECTRON: (-) Negatively charged subatomic particles located in electron orbitals around the nucleus; their mass is tiny, about 1/1840 the mass of a proton; charge or -1

3. Atoms have equal numbers of protons and electrons, their overall charge is zero (neutral)

4. ELEMENT – Matter containing only one type of atom.
SYMBOL
ATOMIC NUMBER
The number of protons
ATOMIC MASS
The number of protons + neutron

7. ISOTOPES
Atoms of the same element that have different numbers of NEUTRONS.

8. Chemical Bonds
When two or more ELEMENTS chemically combined by bonding.

9. Chemical Bonds IONIC BONDS
An attraction between atoms where electrons transferred

10. Ions A form of an atoms where electrons are either lost or gained.
Ions have either a positive or negative charge.

11. Sodium Chloride (NaCl): An Ionic Bond

12. Chemical Bonds COVALENT BONDS
Two atoms SHARE electrons (this forms very strong bonds).
Example: Water (H2O) = 2 hydrogen + 1 oxygen
MOLECULE – two or more ATOMS covalently bonded.

13. Water (H-O-H): A covalent bond

14. Properties of Water Water covers ¾ of Earth’s Surface
Water is the single most abundant compound in most living things.

15. The Water Molecule
Water has several important physical properties:
It is a liquid at temperatures found over much of Earth’s surface.
Water expands as it freezes.
Water is more dense than ice, so ice floats. Which allows for fish and plant life to survive below the ice.

16. The Water Molecule Overall, water is a neutral molecule.
However, a water molecule is polar.
Although the entire molecule has equivalent numbers of protons and electrons, the electrons are unevenly distributed.

17. The Water Molecule
The oxygen has a strong pull on the electrons near the oxygen making the probability of finding those electrons near the oxygen greater than finding them near the hydrogen atoms.
This gives the oxygen end of the water molecule a slightly negative charge and the hydrogen ends of the water molecule a slightly positive charge.
This uneven distribution of charge on a molecule is called polarity.
When large numbers of water molecules get together, hydrogen bonding occurs.

18. Properties of Water
COHESION – an attraction between molecules of the same substance.
An example of cohesion is called surface tension- water molecules on the surface of a body of water cling tightly together and allow small organisms to survive on its surface.
ADHESION – an attraction between molecules of different substances.
Cohesion and adhesion work together to produce capillary action.

19. The water molecule
ADHESION – an attraction between molecules of different substances.
Cohesion and adhesion work together to produce capillary action.
Adhesive forces cause the water to climb up the inside of the alls of the tubes, and cohesive forces allow the water molecules to cling to each other as it crawls up the tube.

20. Solutions and Suspensions

21. Solution and Suspensions
Water is often found as a - a material composed of substances
that are
mixture
two or more
physically mixed together.
Example:
1) Dissolving sugar into hot tea
2) Dissolving salt into hot water

22. Solution and Suspensions
Two types of mixtures can be made with water:
Solution – a mixture where a substance is evenly mixed in another substance.
The substance in the smallest amount, which is
is called the
The substance in the greatest amount, which
dissolved
solute.
dissolves the solute
solvent.

23. Solution and Suspensions
Water
has the ability to dissolve many substances and thus is called the
General Solubility Rule:
universal solvent.
- Like dissolves like
Polar substances dissolve polar substances

24. MIXTURE – mixed but not chemically combined.
SOLUTION – uniform mixture
SOLVENT – dissolves other substances.
SOLUTE – dissolves in the solvent.
SUSPENSION – temporarily mixed

25. Acids, Bases, pH Water can react and divide/dissolve into two ions:
H2O  H OH
Scientists have devised a scale to measure the amount of hydrogen ions that exist in solutions called pH. - +

26. Acids, Bases, pH The pH scale ranges from 0-14.
When a solution has an equal number of H and OH ions such as water, it is assigned a neutral pH, which is 7 on the pH scale.
When a solution has a high H concentration then it is assigned an acidic pH, which is a number less than 7 on the pH scale.
When a solution has a low H concentration then it is assigned a basic pH, which is a number greater than 7 on the pH scale. + - - + +

28. Acids, Bases, pH
The pH inside human cells must be kept close to neutral, between 6.5 and 7.5. If a chemical with a lower or higher pH enters the cell, it could disrupt chemical reactions there and thus disrupt the cell’s homeostasis.

29. Acids, Bases, pH
Therefore, cells contain weak acids or bases called buffers which work to prevent changes in pH inside cells that are too acidic or too basic.
For example, the skin has a surface film that is acidic and it acts as a buffer against strong bases like Clorox.