Ch. 2 Intro Chem 2022

Plant Growth Experiment
- Independent variables could be water and sunlight.
Testing Protein Bars on Workout Ability
- Controlled variables include:
  - Type of protein bar
  - Duration of workout
  - Workout intensity
  - Participant’s diet
Cat Scratching Experiment
- Control setup would include using a non-treated area to compare results.
Dormant Bacteria as Alive?
- Yes, they are considered alive if they can resume metabolic activity after dormancy.

Difference between Atom, Element, Compound
- Atom: Smallest unit of matter.
- Element: Pure substance that cannot be broken down (e.g., hydrogen, nitrogen).
- Compound: Combination of two or more different elements in fixed ratios (e.g., H2O, CO2).
Components of an Atom
- Protons (+), Neutrons (0), Electrons (-).
Elements Comprising 96% of Living Matter
- Oxygen (O) and Carbon (C).

Isotope Definition
- Atoms with the same number of protons but different numbers of neutrons.
Example of Potential Energy
- A drawn bow ready to shoot an arrow.
Potential Energy in C6H12O6
- Stored in chemical bonds.
Importance of Covalent vs. Ionic Compounds in Biology
- Covalent compounds are generally more relevant due to stability in biological systems.

Importance of Electronegativity
- Determines how electrons are shared/bonded between atoms.
Bond Types and Examples
- H2O: Polar covalent
- KCl: Ionic
- C6H12O6: Polar covalent
- N2: Nonpolar covalent
- Ba(OH)2: Ionic
Identifying Cations and Anions
- Cations: e.g., Na+
- Anions: e.g., Cl-

Hydrogen Bond vs. Ionic/Covalent Bonds
- Hydrogen bonds are weaker and occur between polar molecules, unlike strong ionic or covalent bonds.
Weakest Attraction in Chemistry
- Van der Waals interactions.
Analogy for Dynamic Equilibrium
- A balanced scale where weights can be added or removed but overall balance is maintained.

Example of a Chemical Reaction
- 6CO2 + 6H2O → C6H12O6 + O2 (Photosynthesis)
Dynamic Equilibrium Analogy
- Water flowing in and out of a bucket at the same rate keeps the water level constant.

Relationship
- Ants use formic acid to inhibit competing plant growth, allowing Duroia trees to thrive.

Subatomic Particles
- Protons, Neutrons, Electrons and their significance in chemical bonding.
Types of Bonds
- Understanding covalent, ionic, and hydrogen bonds and their importance in life.

Matter
- Has mass, occupies space, affected by gravity.
Energy
- Moves matter; exists as potential or kinetic energy.
- Capable of doing work; involved in conversions (e.g., sound, light).

Key Elements
- 25 elements in total; main ones are O, C, H, N contributing to 96% of biological matter.
  - Approx. 4% consists of P, S, Ca, K, and trace elements (e.g., Fe, I).
  - Mnemonic: CHNOPS.

Body Mass Composition
- Oxygen (65.0%), Carbon (18.5%), Hydrogen (9.5%), Nitrogen (3.3%), other elements in smaller percentages.
- Trace elements are less than 0.01% of mass, include B, Cr, Co, Fe, etc.

Atoms as Units of Matter
- Smallest unit retaining elemental properties.
- Subatomic Particles
  - Neutrons: mass of 1, located in nucleus, charge 0
  - Protons: mass of 1, located in nucleus, charge +1
  - Electrons: negligible mass, located in shells, charge -1

Elemental Notation
- Example:
  - Helium: ( \text{He} )
  - Mass number: 4, Atomic number: 2

Definition of Isotopes
- Vary in number of neutrons, same number of protons.
- Radioactive isotopes: used as tracers but can be harmful if exposure is uncontrolled.

Strongest Bonds
- Covalent Bonds
  - Electron sharing:
    - Polar: unequal sharing
    - Nonpolar: equal sharing (e.g., O2, H2)

Ionic Bonds
- Formed between two ions with opposite charges; subject to environmental factors (e.g., water).

Hydrogen Bonds
- Formed when H atom of one polar covalent molecule bonds to electronegative atom in another molecule.

Description
- Fleeting attractions between atoms/molecules; weakest bond observable in nature (e.g., gecko feet).

Types of Bonds
- Covalent, Ionic, and Hydrogen bonds are crucial for cellular functions and chemical reactions in living systems.

Molecular shapes
- Impact biological interaction (e.g., endorphin and morphine).

Chemical Reactions
- Reactants turn into products; can be reversible.
- Chemical equilibrium: balance of forward and reverse reactions.