Atoms & Water

Dev Honors - Atoms and Water Quiz

Chapter 2-1 Atoms

Atomic

• What is it? The number of protons in an atom's nucleus.

• What determines the atomic number? The number of protons. This number is unique to each element and identifies it.

Atomic Mass

• How is it calculated? It is the sum of the number of protons and neutrons in an atom's nucleus. For an element, it's typically the weighted average of the masses of its isotopes.

• What can be determined from this number? The total number of protons and neutrons in an atom. When rounded to the nearest whole number, it gives the mass number of the most common isotope.

Subatomic Particles

• What are they? Particles smaller than an atom that make up an atom: protons, neutrons, and electrons.

• Identify them in diagrams

  • Protons: Positively charged, located in the nucleus.

  • Neutrons: Neutral charge, located in the nucleus.

  • Electrons: Negatively charged, orbit the nucleus in electron shells/energy levels.

• What properties do they have? (See table below)

Bohr Models

• Be able to identify the different parts of an atom in one A Bohr model shows the central nucleus (containing protons and neutrons) surrounded by electrons orbiting in specific energy shells or levels.

Isotopes / Radioactive isotopes

• What is an isotope? Atoms of the same element (same number of protons) that have different numbers of neutrons, and therefore, different mass numbers.

• How do you know it is an isotope? It will have the same atomic number but a different mass number (e.g., carbon-12 and carbon-14).

• What is a radioactive isotope? An isotope with an unstable nucleus that decays over time, emitting radiation (particles and energy).

• What can radioactive isotopes be used for?

  • Medical diagnosis and treatment: Tracers for medical imaging (e.g., PET scans), cancer therapy.

  • Scientific research: Dating fossils (carbon-14 dating), tracing chemical reactions in biological systems.

  • Industrial applications: Sterilization of medical equipment, power generation (nuclear reactors).

Isotopes of Nitrogen

Ions

• What is an ion? An atom or molecule that has gained or lost one or more electrons, resulting in a net electrical charge.

• What properties do they have? They are electrically charged (either positive or negative), which influences their interactions with other ions and molecules.

• How are they formed? By an atom either gaining electrons (forming a negatively charged anion) or losing electrons (forming a positively charged cation).

Bonding

• Why do atoms form bonds? To achieve a stable electron configuration, typically resembling a noble gas (full outer electron shell).

Ionic Bonds

• What are they? Chemical bonds formed by the electrostatic attraction between oppositely charged ions, typically occurring when one atom transfers one or more electrons to another atom.

• Give examples Sodium chloride (NaCl), Magnesium oxide (MgO), Potassium iodide (KI) .

• Be able to identify Look for bonds between a metal (which tends to lose electrons and form cations) and a nonmetal (which tends to gain electrons and form anions).

Covalent Bonds

• What are they? Chemical bonds formed by the sharing of one or more pairs of electrons between two atoms.

• Give examples Water (H2O), Methane (CH4), Oxygen gas (O2), Carbon dioxide (CO2).

• Be able to identify Look for bonds between two nonmetal atoms.

Compounds vs elements - What is the difference?

• Element: A pure substance consisting of only one type of atom (e.g., Oxygen, Hydrogen, Gold). Cannot be broken down into simpler substances by ordinary chemical means.

• Compound: A substance formed when two or more different elements are chemically bonded together in fixed proportions (e.g., Water (H2O), Carbon Dioxide (CO2), Salt (NaCl)). Can be broken down into simpler substances (elements) by chemical reactions.

Chapter 2-2 Polarity of Water (Still a Neutral Molecule as a Whole)

Electronegativity

• Why is it a polar molecule? Oxygen is more electronegative than hydrogen, meaning it pulls the shared electrons in the covalent bonds closer to itself. This creates a partial negative charge near the oxygen atom and partial positive charges near the hydrogen atoms, making the molecule have distinct poles.

• What kinds of bonds hold water together? Within a single water molecule, hydrogen and oxygen are held together by polar covalent bonds.

Hydrogen Bonds

• What are they? Weak attractive forces that form between the partial positive charge on a hydrogen atom in one polar molecule (like water) and the partial negative charge on a highly electronegative atom (like oxygen or nitrogen) in another polar molecule.

• Why do they form? Due to the unequal sharing of electrons in polar covalent bonds (electronegativity difference) which creates partial charges, allowing for electrostatic attraction between different molecules.

Cohesion/Adhesion/Surface Tension/Capillary Action

• What is cohesion? The attraction between water molecules themselves, due to hydrogen bonding.

• What is adhesion? The attraction between water molecules and other surfaces (different polar molecules).

• What is surface tension? The property of a liquid's surface that resists an external force, caused by the strong cohesive forces between water molecules at the surface, which pull inward.

• What is capillary action? The ability of water to flow in narrow spaces against the force of gravity, due to the combined effects of cohesion (water molecules sticking to each other) and adhesion (water molecules sticking to the walls of the narrow tube).

• What property of water causes all of these? Hydrogen bonding (leading to water's polarity).

• What are some examples of these in nature?

  • Cohesion: Water molecules forming droplets on a leaf; insects walking on water.

  • Adhesion: Water sticking to the inside of a glass tube; water climbing up the roots of a plant.

  • Surface tension: A water strider walking on the surface of a pond; drops of water forming a dome shape on a penny.

  • Capillary action: Water movement up a plant stem; absorption of water by a paper towel.

Universal Solvent

• Solute - The substance that is dissolved in a solvent.

• Solvent - The substance, often a liquid, that dissolves another substance (the solute) to form a solution. Water is considered the universal solvent due to its ability to dissolve a wide range of substances, making it essential for various chemical reactions and biological processes.

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Cohesion: Causes water molecules to be drawn together, which is why drops of water form beads on a smooth surface. Produces surface tension, allowing insects and spiders to walk on a pond’s surface.

Adhesion: Attraction b/w molecules of different substances

Capillary Action: Adhesion b/w water molecules drags other molecules upwards, acting as a natural pump

Heat Capacity: Amount of heat energy required to increase a substance’s temperature. Water has a high heat capacity. Gradual changes in water temp protect sea organisms from drastic changes.

Water is the universal solvent.

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pH scale - Goes up to 14, 7 is neutral

Acidic - Anything below 7 

H+ means acidity

Above 7 = Basic or alkaline - Gives off OH-, absorbs H+

Cell pH should be 6.5 and 7.5 in order to maintain homeostasis

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Organic = Carbon-based

Carbon bonds to:

Hydrogen, oxygen, sulfur, phosphorus, nitrogen, and other carbon atoms.

These elements make up macromolecules

Macromolecules: Made from smaller molecules called monomers

Polymer - Chain of monomers

Four main groups of macromolecules - lipids, proteins, carbs, nucleic acids

Carbohydrates: Structure - CHO. Contains C, H, and O, usually in a ratio of 1:2:1

Example: Glucose - C6H12O6

Carbohydrates are a source of energy for life. Others like plants, fungus, and some animals use carbs for structural purposes

Monosaccharides: Glucose, fructose, ribose, deoxyribose.

Disachoride: Sucrose, lactose - When two sugar molecules bond together

Polysaccharide: When three or more sugar molecules bond together - starch, cellulose - large macromolecule formed from monosaccharides, includes starches, cellulose, and glycogen.

Cellulose - structural walls in plants

Plant starch - energy source, flour, bread, pasta

Chitin - Structural, exoskeleton, arthropods, cell walls, mushrooms

Glycogen - animal starch - energy storage

Dehydration Synthesis and Hydrolysis

Dehydration Synthesis - Joining the sugars to form a disaccharide - causes it to lose a water molecule - one loses a H and the other loses an OH

Hydrolysis - split water - fills gaps w water

Fat

Composed of: Glycerol heads and fatty acid tails

Lipids can be used to store energy - some lipids are important parts of biological membranes and waterproof coverings.

Two key times (triglycerides, phospholipids)

Saturated fat - completely saturated with hydrogen no double bonds

Unsaturated fat - contains one double bond

Polyunsaturated fat - contains more than one double bond

Fatty acid tails are hydrophobic

Glycerol heads are hydrophilic

Saturated fats have no more room for hydrogen no double bonds, while unsaturated fats only one double bond have room. Saturated fats solidify at room temperature, unsaturated fats do not.

Polyunsaturated fat - contains more than one double bond

Proteins/polypeptide

Functions:

Structural support

Protection

Transport

Catalysis (Enzymes)

Defense

Regulation

Movement

The composition of a protein relative amounts of each amino acid present

The sequence of amino acids in the chain determines the protein structure and function

Monomers = amino acids

Amino acids have carboxyl and amino groups-they function as both acid and base. The R group varies in each amino acid… everything else is the same. 

On the left side, there is an amino group of H3N+, and on the right there is a carboxyl group of COO-. Carbon at the center. Above that, there is a R side chain

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Regulation of Chemical Reactions

Allosteric Enzymes: Have two binding sites (1 active, 1 allosteric)

Allosteric site is not an active site, but another site that influences the shape of the active site

Feedback Inhibition - This is when an end product of a reaction acts as an allosteric inhibitor

Competitive Inhibition - A substance that mimics the substrate occupies the active site to inhibit the enzyme from working

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H2CO3 (Carbonic Acid)

Chemical reactions either

Release energy : cellular respiration

Absorb energy : Photosynthesis

Exergonic - Releases energy

Endergonic - Absorbs energy

Activation energy: Amount of energy ended to start a chemical reaction

Catalysts: SUbstance that speeds up the rate of a chemical reaction, works by lowering a reaction’s activation energy

Enzymes: Biological catalysts

Factors regulating enzyme activity:

Temperature

pH

Concentration of substrate

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Denature - When an enzyme changes shape

Substrates - The reactants that bind to a enzyme

Active site - Place where the substrates can bind on the enzyme