Q1. Draw and label a simplified model of an atom.

Background

Topic: Atomic Structure

This question tests your understanding of the basic structure of an atom, including the arrangement and labeling of subatomic particles.

Key Terms:

• Atom: The smallest unit of an element that retains its properties.

• Proton: Positively charged particle found in the nucleus.

• Neutron: Neutral particle found in the nucleus.

• Electron: Negatively charged particle found in orbitals around the nucleus.

Step-by-Step Guidance

1. Start by drawing a central circle to represent the nucleus of the atom.

2. Inside the nucleus, label and indicate protons (p+) and neutrons (n0).

3. Draw one or more rings (energy levels) around the nucleus to represent electron shells.

4. Place and label electrons (e-) on these rings.

5. Make sure to clearly label each particle and indicate their charges.

Try drawing your model before revealing the answer!

Q2. Define and differentiate the following terms: element/compound, neutron/proton/electron, atomic number/mass number, covalent bond/ionic bond/hydrogen bond, isotope/ion.

Background

Topic: Basic Chemistry Vocabulary

This question checks your understanding of foundational chemistry terms and your ability to distinguish between related concepts.

Key Terms:

• Element: A substance made of only one kind of atom.

• Compound: A substance made of two or more different elements chemically bonded.

• Neutron: Neutral subatomic particle in the nucleus.

• Proton: Positively charged subatomic particle in the nucleus.

• Electron: Negatively charged subatomic particle in orbitals.

• Atomic Number: Number of protons in an atom.

• Mass Number: Total number of protons and neutrons.

• Covalent Bond: Atoms share electrons.

• Ionic Bond: Atoms transfer electrons, forming ions.

• Hydrogen Bond: Weak attraction between a hydrogen atom and an electronegative atom.

• Isotope: Atoms of the same element with different numbers of neutrons.

• Ion: Atom with a net electric charge due to loss or gain of electrons.

Step-by-Step Guidance

1. Write a brief definition for each term listed.

2. For each pair or set, note the main difference(s) between the terms (e.g., element vs. compound: one type of atom vs. multiple types bonded).

3. Use examples where helpful (e.g., NaCl for a compound, O2 for an element).

4. For bonds, describe how electrons are involved in each type.

5. For isotope vs. ion, focus on what changes (neutrons vs. electrons).

Try defining and differentiating each term before revealing the answer!

Q3. Explain how the atomic number, mass number, and number of neutrons relate. If you know two, how can you determine the third?

Background

Topic: Atomic Structure Calculations

This question tests your understanding of how to use atomic number and mass number to find the number of neutrons in an atom.

Key Formula:

Step-by-Step Guidance

1. Recall that the atomic number tells you the number of protons in the atom.

2. Remember that the mass number is the sum of protons and neutrons.

3. To find the number of neutrons, subtract the atomic number from the mass number:

4. If you know any two of these values, rearrange the formula to solve for the third.

Try applying the formula to an example before revealing the answer!

Q4. Be able to find information on a periodic table.

Background

Topic: Periodic Table Usage

This question tests your ability to use the periodic table to find atomic number, symbol, mass number, and other element information.

Key Terms:

• Atomic Number: Number of protons (usually above the symbol).

• Element Symbol: One- or two-letter abbreviation.

• Atomic Mass: Average mass of all isotopes (decimal number).

Step-by-Step Guidance

1. Locate the element on the periodic table using its symbol or name.

2. Identify the atomic number (usually at the top of the box).

3. Find the atomic mass (usually a decimal number below the symbol).

4. Note the element's group (column) and period (row) for additional properties.

Practice finding these values before revealing the answer!

Q5. Compare and contrast two isotopes of an element.

Background

Topic: Isotopes

This question tests your understanding of what makes isotopes similar and different.

Key Terms:

• Isotope: Atoms of the same element with different numbers of neutrons.

• Atomic Number: Same for all isotopes of an element.

• Mass Number: Varies between isotopes.

Step-by-Step Guidance

1. Choose an element (e.g., Carbon) and identify two isotopes (e.g., Carbon-12 and Carbon-14).

2. List what is the same: atomic number (number of protons), chemical properties.

3. List what is different: number of neutrons, mass number, atomic mass.

4. Explain how these differences affect the isotope's properties (e.g., stability, radioactivity).

Try comparing two isotopes before revealing the answer!

Q6. Determine how many electrons are in the outer shell (valence shell) of a given atom.

Background

Topic: Electron Configuration

This question tests your ability to use the periodic table to determine the number of valence electrons in an atom.

Key Terms:

• Valence Electrons: Electrons in the outermost shell.

• Group Number: For main group elements, indicates number of valence electrons.

Step-by-Step Guidance

1. Find the element's position on the periodic table.

2. For main group elements (Groups 1, 2, 13–18), the group number helps determine valence electrons (e.g., Group 16 elements have 6 valence electrons).

3. Write out the electron configuration if needed to confirm the number of electrons in the outer shell.

4. Remember that the maximum number of valence electrons is 8 (octet rule).

Try determining valence electrons for an element before revealing the answer!

Q7. Draw a single water molecule, labeling the atoms and showing covalent bonds. Add two other water molecules nearby in correct orientation, showing hydrogen bonds.

Background

Topic: Molecular Structure and Bonding

This question tests your ability to represent water's molecular structure and the interactions between molecules.

Key Terms:

• Covalent Bond: Atoms share electrons (within a water molecule).

• Hydrogen Bond: Weak attraction between hydrogen of one molecule and oxygen of another.

• Polarity: Water is a polar molecule.

Step-by-Step Guidance

1. Draw one water molecule (H2O) with an oxygen atom (O) in the center and two hydrogen atoms (H) bonded to it.

2. Label the covalent bonds between O and each H.

3. Draw two more water molecules nearby, oriented so that the hydrogen of one is near the oxygen of another.

4. Use dashed lines to indicate hydrogen bonds between the hydrogen of one molecule and the oxygen of another.

5. Label all atoms and bonds clearly.

Try sketching the molecules and bonds before revealing the answer!

Q8. List emergent properties of water. Explain these properties at a molecular level, including how they relate to polarity or hydrogen bonding. Give biologically relevant examples of each property.

Background

Topic: Properties of Water

This question tests your understanding of water's unique properties and their molecular basis.

Key Terms:

• Cohesion: Water molecules stick together.

• Adhesion: Water molecules stick to other substances.

• High Specific Heat: Water resists temperature change.

• High Heat of Vaporization: Takes a lot of energy to evaporate water.

• Expansion upon Freezing: Ice is less dense than liquid water.

• Versatile Solvent: Water dissolves many substances.

Step-by-Step Guidance

1. List at least four emergent properties of water (e.g., cohesion, adhesion, high specific heat, expansion upon freezing).

2. For each property, explain how hydrogen bonding or polarity is responsible.

3. Provide a biological example for each property (e.g., cohesion enables water transport in plants).

4. Relate each property back to the molecular structure of water.

Try listing and explaining these properties before revealing the answer!

Q9. Distinguish between cohesion and adhesion.

Background

Topic: Properties of Water

This question tests your understanding of the difference between two key properties of water.

Key Terms:

• Cohesion: Attraction between like molecules (water to water).

• Adhesion: Attraction between unlike molecules (water to other substances).

Step-by-Step Guidance

1. Define cohesion and give an example (e.g., water droplets forming beads).

2. Define adhesion and give an example (e.g., water climbing up a glass tube).

3. Explain how hydrogen bonding contributes to both properties.

Try explaining the difference before revealing the answer!

Q10. Explain the relationships of a solute, a solvent, and a solution.

Background

Topic: Solutions and Mixtures

This question tests your understanding of the components of a solution.

Key Terms:

• Solute: Substance dissolved in a solution.

• Solvent: Substance that dissolves the solute (often water).

• Solution: Homogeneous mixture of solute and solvent.

Step-by-Step Guidance

1. Define solute, solvent, and solution.

2. Describe how a solute dissolves in a solvent to form a solution.

3. Give a biological example (e.g., salt water, blood plasma).

Try explaining these relationships before revealing the answer!

Q11. Distinguish between hydrophobic and hydrophilic substances. Decide if a substance is hydrophobic or hydrophilic based on its chemical description.

Background

Topic: Water Interactions

This question tests your ability to classify substances based on their affinity for water.

Key Terms:

• Hydrophilic: "Water-loving"; interacts well with water (usually polar or charged).

• Hydrophobic: "Water-fearing"; does not interact well with water (usually nonpolar).

Step-by-Step Guidance

1. Recall that polar or charged molecules are hydrophilic (e.g., sugars, salts).

2. Nonpolar molecules (e.g., oils, fats) are hydrophobic.

3. When given a chemical description, look for polarity or charge to classify the substance.

Try classifying a substance before revealing the answer!

Q12. What ions result when water dissociates?

Background

Topic: Water Chemistry

This question tests your understanding of water's dissociation and the resulting ions.

Key Formula:

Step-by-Step Guidance

1. Recall that water can break apart (dissociate) into ions.

2. Identify the two ions formed: hydrogen ion () and hydroxide ion ().

3. Understand that this process is reversible and occurs in all aqueous solutions.

Try writing the dissociation equation before revealing the answer!

Q13. What is the pH scale based on? What are acids and bases? How do pH units relate to powers of ten? If pH changes by two or three units, what’s the difference in protons?

Background

Topic: Acids, Bases, and pH

This question tests your understanding of the pH scale, acids, bases, and the logarithmic nature of pH.

Key Formula:

Step-by-Step Guidance

1. Recall that the pH scale measures the concentration of hydrogen ions () in a solution.

2. Acids have a pH less than 7 (higher ); bases have a pH greater than 7 (lower $\mathrm{[H^+]}$).

3. Each pH unit represents a tenfold change in concentration.

4. If pH changes by 2 units, changes by times; by 3 units, times.

Try calculating the change in before revealing the answer!

Q14. What’s the effect of a buffer? Why are buffers important for organisms?

Background

Topic: Buffers and Homeostasis

This question tests your understanding of how buffers help maintain pH stability in biological systems.

Key Terms:

• Buffer: Substance that minimizes changes in pH by accepting or donating H+ ions.

• Homeostasis: Maintenance of stable internal conditions.

Step-by-Step Guidance

1. Define what a buffer does in a solution (resists pH changes).

2. Explain how buffers work (accept or donate H+ as needed).

3. Describe why stable pH is important for biological processes (e.g., enzyme function).

4. Give an example of a biological buffer (e.g., bicarbonate in blood).

Try explaining the role of buffers before revealing the answer!