Chemistry

Question 1

Describe the three subatomic particles.

Answer 1

Protons: Positively charged, found in the nucleus.

Neutrons: No charge, found in the nucleus.

Electrons: Negatively charged, orbit the nucleus.

Question 2

Distinguish between the atomic number and the mass number of an element.

Answer 2

Atomic Number: Number of protons in an atom.

Mass Number: Sum of protons and neutrons in the nucleus.

Question 3

Distinguish between ionic bonds, polar covalent bonds, and non-polar covalent bonds and provide examples of each.

Answer 3

Ionic Bond: Electron transfer (e.g., NaCl).

Polar Covalent Bond: Unequal electron sharing (e.g., H₂O).

Non-Polar Covalent Bond: Equal electron sharing (e.g., O₂).

Question 4

Given the electronegativity of two atoms, predict the type of bond they will form.

Answer 4

Large difference (>1.7) → Ionic bond.

Moderate difference (0.5–1.7) → Polar covalent bond.

Small difference (<0.5) → Non-polar covalent bond.

Question 5

Describe the difference between CO₂ and H₂O that accounts for their different physical and chemical properties.

Answer 5

CO₂: Linear, non-polar, gas at room temp.

H₂O: Bent shape, polar, liquid at room temp due to hydrogen bonding.

Question 6

Draw a water molecule surrounded by 4 other water molecules and distinguish between hydrogen bonds and covalent bonds.

Answer 6

Covalent Bonds: Hold H and O within a single water molecule.

Hydrogen Bonds: Weak attractions between adjacent water molecules.

Question 7

Describe the properties of water that contribute to Earth’s suitability for life.

Answer 7

High heat capacity

Solvent properties

Cohesion & adhesion

Ice floats (lower density when frozen)

Question 8

Cohesion

Answer 8

Water molecules stick together (surface tension).

Question 9

Adhesion

Answer 9

Water sticks to other surfaces (capillary action).

Question 10

Hydration

Answer 10

Water surrounds solutes

Question 11

Solute

Answer 11

Dissolved substance

Question 12

Solvent

Answer 12

Dissolving agent (liquid)

Question 13

Molarity

Answer 13

Concentration of a solution

Question 14

Specific heat

Answer 14

Energy to change temp

Question 15

Heat of vaporization

Answer 15

Energy to turn liquid to gas

Question 16

Evaporative cooling

Answer 16

Heat loss via evaporation

Question 17

Hydrophilic

Answer 17

Water-attracting

Question 18

Hydrophobic

Answer 18

Water-repelling

Question 19

Explain why it takes longer to heat a cup of water than a cup of oil.

Answer 19

Water has a higher specific heat capacity, requiring more energy to raise its temperature compared to oil.

Question 20

Describe what happens when a crystal of sucrose dissolves in water.

Answer 20

Water molecules surround sucrose molecules, forming hydrogen bonds and separating them into solution.

Question 21

Describe the relationship between the density of water and temperature and explain how this has impacted the evolution of life on Earth.

Answer 21

Water is less dense as a solid (ice floats).

This prevents lakes/oceans from freezing solid, allowing aquatic life to survive.

Question 22

Provide examples of the role of weak bonds in biological molecules.

Answer 22

Hydrogen bonds: Hold DNA strands together.

Ionic interactions: Stabilize protein structure.

Question 23

Describe the exclusion of hydrophobic molecules by water molecules.

Answer 23

Water forms hydrogen bonds with itself, pushing non-polar molecules together (e.g., oil droplets in water).

Question 24

What are isotopes, and how are they useful in research and medicine?

Answer 24

Isotopes are atoms of the same element with different numbers of neutrons, meaning they have different mass numbers but the same chemical properties.

Usefulness: Isotopes help in medical imaging, cancer treatment, and understanding biological and geological processes.

Question 25

How do you draw the electron configuration of the first 17 elements?

Answer 25

Follow 2-8-8 rule

Use atomic number