chapter 2 lecture

Exploration of the relationship between rising atmospheric carbon dioxide and coral reefs.
- Will rising atmospheric carbon dioxide harm coral reefs?

Chemical Composition:
- Chemicals are the raw materials for all living and non-living organisms.
- Matter is defined as anything that occupies space and has mass (weight).
- Elements:
- Definition: Fundamental substances that cannot be broken down into simpler substances by chemical means.
- Natural elements discovered: approximately 92, but only a few exist in pure form.
- Four key elements in the human body: Oxygen, Carbon, Hydrogen, Nitrogen (96.3% of body mass).
- Discussion of trace elements (e.g., Iron, Iodine, Fluoride) which are crucial for health in minute quantities (example: Iron deficiency leading to anemia, Iodine deficiency leading to goiter).

Compounds:
- Definition: A substance formed when two or more different elements combine in fixed ratios (e.g., sodium chloride, NaCl, formed from sodium and chlorine).
- Compounds are more prevalent than pure elements in nature.
- Essential to recognize key compounds discussed in class for exams.

Atoms:
- Smallest units of matter that retain the properties of an element.
- Structure includes:
- Nucleus: Contains protons and neutrons.
- Electrons orbiting the nucleus, held in place by the positive charge of protons.
- Calculating Atomic Numbers and Mass Numbers:
- Atomic Number = Number of Protons
- Mass Number = Sum of Protons and Neutrons.
- Example calculation: Atom with 2 protons and 2 neutrons has an Atomic Number of 2 and a Mass Number of 4.

Isotopes:
- Atoms with the same number of protons but different mass numbers due to varying numbers of neutrons.
- Example with Carbon isotopes: Carbon-12, Carbon-13, and Carbon-14.
Radioactive Isotopes:
- Definition: Isotopes that decay spontaneously, emitting particles and energy.
- Applications in medicine: Used in PET scans for diagnostic imaging.
- Ethical implications of radioactivity due to potential harm from uncontrolled exposure (e.g., damage to DNA).

Chemical Activity:
- Involves the outermost electrons or valence electrons of atoms.
- Types of Bonds:
- Covalent Bonding (strongest): Sharing of electrons.
  - Examples: H₂ (hydrogen molecule) and O₂ (oxygen molecule) forming bonds for full outer shells.
- Ionic Bonding: Transfer of electrons (Sodium giving away an electron to Chlorine to form NaCl).
- Hydrogen Bonds (weakest): Important for water molecules, enabling properties of cohesion and adhesion.

Water as a Fundamental Molecule:
- Water's unique V-shaped structure contributes to its properties.
- Cohesion and Adhesion:
- Cohesion: Attraction between like molecules.
- Adhesion: Attraction between different types of molecules.
- Water exhibits high surface tension due to hydrogen bonding.
Thermal Properties:
- Heat capacity due to hydrogen bonds, moderating Earth's climate.
- Evaporative Cooling: The phenomenon where the surface of the liquid cools as the molecules with the greatest kinetic energy escape into the gas phase.

Chemical Reactions:
- Rearrangement of atoms in reactants to form products (Law of conservation of mass).
- Example: Photosynthesis as a fundamental biochemical reaction.
Reactants and Products Defined:
- Reactants are the starting materials, and products are the formed substances after the reaction.

Global Climate Change:
- Carbon dioxide (CO₂) as a primary product of fossil fuel combustion.
- High levels linked to ocean acidification, affecting coral reefs.
Ocean acidification leads to impacts on marine life, particularly organisms that build shells (e.g., corals).
Importance of maintaining healthy ecosystems for biodiversity.

This chapter has provided a comprehensive introduction to key principles of chemistry relevant to biology, particularly focusing on the crucial role of water and the implications of environmental changes such as increased carbon dioxide levels.