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Questions and Answers
What are the building blocks of elements?
Atoms
Which of the following subatomic particles are positively charged?
Atoms are electrically neutral.
True
A _____ is formed when two or more atoms of different elements combine chemically.
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What type of bond forms when electrons are shared between atoms?
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Which of these statements about ionic bonds is true?
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What is the pH scale used to measure?
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What is a characteristic of strong acids?
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What is the primary solvent in biological systems?
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Match the following terms with their definitions:
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Hydrogen bonds are the strongest type of chemical bonds.
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Study Notes
Composition of Matter
- Atoms: Building blocks of elements. Each element differs in its atomic structure.
- Subatomic Particles: Protons (p+), neutrons (n0), and electrons (e-).
- Nucleus: Contains protons (positively charged) and neutrons (neutral).
- Orbiting the Nucleus: Electrons (negatively charged) orbit the nucleus.
- Electrically Neutral Atoms: Number of protons = Number of electrons.
- Ions: Atoms that have gained or lost electrons. Anions: negatively charged, Cations: positively charged.
Molecules and Compounds
- Molecule: Two or more atoms of the same element chemically combined.
- Compound: Two or more atoms of different elements chemically combined to form a molecule.
Chemical Bonds and Chemical Reactions
- Electron Shells: Electrons are distributed around the atom's nucleus in shells (orbitals).
- Stable Atoms: First shell holds 2 electrons, subsequent shells hold 8 electrons for stability.
- Chemical Bonds: Atoms gain, lose, or share electrons to achieve a stable valence shell.
- Leads to stable state and formation of molecules.
Ionic Bonds
- Formed by complete electron transfer between atoms.
- Achieve stability through electron transfer.
- Result in ions with opposite charges (anions and cations).
- Opposing charges attract, leading to bond formation.
Covalent Bonds
- Atoms achieve stability through shared electrons.
- Electrons are shared in pairs.
- Single covalent bonds share one pair of electrons.
- Double covalent bonds share two pairs of electrons.
- Examples: C-C, C-H, O-O, O-H, N-H.
Nonpolar Covalent Bonds
- Electrons are shared equally between atoms.
- Electrically neutral as a molecule.
- Example: Carbon dioxide (CO2).
Polar Covalent Bonds
- Electrons are not shared equally between atoms.
- Molecule has a positive and negative side (pole).
- Example: Water (H2O).
Hydrogen Bonds
- Form between atoms in molecules with polar covalent bonds.
- Weak chemical bonds.
- Hydrogen is attracted to the negative portion of a polar molecule.
- Responsible for surface tension of water.
- Important for intramolecular bonds (e.g., protein structure).
Patterns of Chemical Reactions
- Synthesis Reaction (A + B → AB): Atoms or molecules combine. Energy is absorbed for bond formation. Anabolic activities.
- Decomposition Reaction (AB → A + B): Molecule is broken down. Chemical energy is released. Catabolic activities.
- Exchange Reaction (AB + C → AC + B or AB + CD → AD + CB): Involves synthesis and decomposition reactions, bonds are made and broken.
- Most chemical reactions are reversible.
Biochemistry: Chemical Composition of Living Matter
- Inorganic Compounds: Mostly lack carbon or are small. Examples: CO2, H2O, NH3, NaCl, Calcium.
- Organic Compounds: Contain carbon, tend to be larger. Examples: Glucose (C6H12O6), lipids, proteins.
Inorganic Compounds in Biological Systems
- Water: Important for biological processes due to its ability to form hydrogen bonds.
- High heat capacity: Absorbs or releases a lot of heat without drastic temperature changes.
- Polarity/solvent properties: Universal solvent, essential for chemical reactions, nutrient transport, and waste removal.
- Capillary action: Ability to flow in narrow spaces against gravity.
- High surface tension: Cohesive forces between water molecules, allowing some insects to walk on water.
- Chemical reactivity: Important reactant in chemical reactions, especially hydrolysis (breakdown of large molecules with water).
- Cushioning/protection: Fluids protect organs like heart, brain, and developing fetuses.
Salts
- Ionic compounds containing cations (other than H+) and anions (other than OH-).
- Examples: Calcium salts (bones and teeth), phosphorus salts (bones, teeth, nucleic acids).
- Easily dissolve in water.
- Dissociation forms electrolytes (ions that conduct electricity).
- Electrolyte balance crucial for body function and cell viability.
Acids
- Substances that release H+ (protons).
- Taste sour and are corrosive.
- Strong acids ionize completely (e.g., HCl).
- Weak acids ionize partially (e.g., carbonic acid) and act as buffers.
Bases
- Substances that accept H+ (protons), releasing OH- to form water.
- Taste bitter and feel slippery.
- Strong bases dissociate completely (e.g., NaOH).
- Weak bases, like HCO3-, can accept H+ ions.
Neutralization Reaction
- Exchange reaction between acids and bases, forming water and a salt.
- Acid + base → H2O + salt
- Example: NaOH + HCl → H2O + NaCl.
The pH Concept
- Measures proton (H+) activity in a solution.
- pH value is calculated as -Log10 [H+].
- Range: 0 (very acidic) to 14 (very basic).
- pH 7 is neutral.
- Each pH unit represents a 10-fold change in [H+]:
- Decrease of 1 pH unit = 10-fold increase in [H+].
- Increase of 1 pH unit = 10-fold decrease in [H+].
Buffers
- Biological systems require a narrow range of H+ concentration.
- Buffers prevent sudden changes in H+ concentration.
- Weak acids and weak bases act as buffers.
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Description
Explore the fundamental concepts of the composition of matter in this quiz. Test your understanding of atoms, molecules, compounds, and chemical bonds. Whether it's identifying subatomic particles or understanding ionic charges, this quiz covers the essentials of chemistry.
