AP Chemistry Unit Weights
Exam score weighting guides where to focus your study time.
IMF & Properties is King
At 18-22%, intermolecular forces and properties is the largest unit. Master polarity, hydrogen bonding, London dispersion forces, and their effect on boiling points, solubility, and viscosity.
Equilibrium + Acids/Bases = 26%
Together these units make up over a quarter of the exam. Deeply understand Le Chatelier's principle, ICE tables, Ka/Kb relationships, and buffer calculations.
Don't Neglect Electrochemistry
Students often skip this unit since it seems hard. But it's 7-9% and the FRQs are very predictable — cell notation, Nernst equation, and electrolysis calculations appear nearly every year.
Key Concepts by Unit
What you must understand deeply — not just memorize.
- Electron configuration: Aufbau principle, Hund's rule, and Pauli exclusion. Exceptions: Cr, Cu, Mo.
- Periodic trends: Atomic radius decreases across a period (increasing nuclear charge). Ionization energy increases across a period.
- Photoelectron spectroscopy: PES peaks map to subshells; intensity = number of electrons in subshell.
- First principles: All periodic trends arise from two forces — nuclear attraction and electron-electron repulsion (shielding).
- VSEPR: Electron geometry vs. molecular geometry. Lone pairs compress bond angles more than bonding pairs.
- Bond polarity: Electronegativity difference determines polarity. Symmetrical polar bonds cancel out (CO₂ nonpolar, H₂O polar).
- Resonance: Delocalized electrons — the true structure is an average. Ozone, benzene, nitrate.
- Formal charge: Assign to determine best Lewis structure. Minimize magnitude, negative charge on most electronegative atom.
- ICE tables: Initial → Change → Equilibrium. The workhorse of equilibrium problems.
- Q vs. K: If Q < K, reaction proceeds forward; if Q > K, reaction shifts reverse.
- Le Chatelier: Adding reactant shifts forward. Increasing pressure favors fewer moles of gas. Increasing temp shifts endothermic direction.
- First principles: Equilibrium is dynamic — forward and reverse reactions still occur, just at equal rates. It's not "reactions stopped".
- pH = -log[H⁺]. For strong acids, [H⁺] = molarity. For weak acids, set up Ka expression.
- Buffer equation: pH = pKa + log([A⁻]/[HA]) — Henderson-Hasselbalch. Buffer works best when pH ≈ pKa.
- Titration curves: Equivalence point pH depends on salt formed. Strong-strong = pH 7; weak acid + strong base = pH > 7.
- Kw = Ka × Kb = 1.0×10⁻¹⁴ at 25°C. Conjugate pairs are linked.
- Cell notation: Anode (oxidation) | solution || solution | cathode (reduction). Salt bridge allows ion flow.
- Standard cell potential: E°cell = E°cathode − E°anode. Positive E°cell means spontaneous.
- Nernst equation: E = E° − (RT/nF)ln(Q). At 25°C: E = E° − (0.0592/n)log(Q).
- ΔG° = −nFE°. Links thermodynamics to electrochemistry. Spontaneous if ΔG° < 0 and E° > 0.
AP Chemistry Formula Reference
All formulas provided on the AP exam — but you need to know what they mean and when to use them.
| Formula | What It Means | When to Use |
|---|---|---|
| PV = nRT | Ideal gas law: pressure × volume = moles × R × temp (K) | Any gas behavior problem; combined gas law situations |
| pH = -log[H⁺] | pH is the negative log of hydrogen ion concentration | Acid-base calculations, titrations, buffer problems |
| Ka × Kb = Kw | Conjugate acid-base pair product equals water's Kw | Finding Ka of conjugate acid from Kb of base |
| ΔG° = -RT ln K | Links Gibbs energy to equilibrium constant | Predicting spontaneity from K; finding K from ΔG° |
| ΔG° = ΔH° - TΔS° | Gibbs energy: enthalpy minus entropy contribution | Determining spontaneity at any temperature |
| ΔH°rxn = Σ ΔH°f(products) - Σ ΔH°f(reactants) | Hess's Law via formation enthalpies | Any enthalpy of reaction calculation |
| E = E° - (0.0592/n) log Q | Nernst equation at 25°C: cell potential under non-standard conditions | Galvanic cells with non-standard concentrations |
| ln[A]t = -kt + ln[A]0 | First-order integrated rate law | Radioactive decay, first-order kinetics |
| t½ = 0.693/k | Half-life for first-order reactions | Decay problems, time for half to react |
| q = mcΔT | Heat = mass × specific heat × temperature change | Calorimetry problems |
AP Chemistry Practice Questions
AP-style multiple choice with instant explanations.
Free Response Question (FRQ) Strategy
FRQs are 50% of your score. Master the format.
Long FRQ: Show Every Step
Long FRQs are worth 10 points. Write out every step even if you think it's obvious. Partial credit is generous — you can get 7/10 even with an arithmetic error if your setup is correct.
Short FRQs: Be Precise
Short FRQs (4 pts each) often ask to "justify" or "explain." Vague answers get zero. Write the specific chemical reasoning: e.g., "increasing [H⁺] shifts equilibrium right via Le Chatelier's principle."
"Because the rate increases"
Never say something "because it increases/decreases" — that's circular. Always explain why at the particle level: activation energy, effective collisions, concentration effect.
Particulate Diagrams
AP Chem frequently shows particulate-level diagrams. Practice interpreting molecules, ions, and phases at the particle level. Know what aqueous vs. molecular solutions look like.
Consider the equilibrium: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH° = −92 kJ/mol. At 500°C, Kp = 6.0 × 10⁻². A sealed flask initially contains N₂ at 2.0 atm and H₂ at 4.0 atm with no NH₃.
Using an ICE table, set up the expression for Kp in terms of the change in pressure x. You do not need to solve for x.
The system reaches equilibrium. Then the temperature is increased to 600°C. Predict whether K increases, decreases, or stays the same. Justify your answer using Le Chatelier's principle.
At equilibrium at 500°C, more N₂ is added to the flask. (i) Predict the direction the reaction will shift. (ii) Predict whether the final mole fraction of NH₃ is greater than, less than, or equal to its value before N₂ was added. Justify each response.
A 25.0 mL sample of 0.150 M propanoic acid (Ka = 1.3 × 10⁻⁵) is titrated with 0.150 M NaOH solution.
Calculate the pH of the solution after 12.5 mL of NaOH has been added. Show all work.
Explain why the solution described in part (a) resists pH change when small amounts of strong acid or strong base are added.
- Equilibrium ICE Table: Set up ICE, solve for x, find Kc or Kp. Use small-x approximation when K is very small.
- Acid-Base Titration: Calculate pH before/during/at equivalence point. Henderson-Hasselbalch for buffer region.
- Electrochemistry: Write cell notation, calculate E°cell, find ΔG°, apply Nernst equation.
- Kinetics: Determine rate law from data, find rate constant, integrated rate law graph analysis.
- Thermodynamics: Calculate ΔH from Hess's Law, find ΔG at non-standard conditions, predict spontaneity.
AP Chemistry Prep Checklist
Check off what you've mastered. Track your readiness.
AP Chemistry — My Progress
Track your practice scores and see your estimated AP score (1–5).
AP Physics 1 Unit Weights
Physics 1 is algebra-based. Focus on conceptual understanding and proportional reasoning.
Forces = 20% of Exam
Newton's Second Law (ΣF = ma) is the foundation of almost every mechanics problem. Mastering free body diagrams and net force analysis will earn you the most points.
Energy Conservation
Energy is the most powerful tool in physics. "Work-energy theorem" and "conservation of energy" solve problems that would be impossible with kinematics alone.
Rotation is NOT Optional
Many students skip rotation. But rotational kinematics, torque, and angular momentum make up 10-16%. The concepts mirror linear mechanics — treat them as a translation.
Key Concepts by Unit
Deep understanding over memorization — AP Physics tests application, not recall.
- Big Five equations connect v, v₀, a, t, Δx. Each has one variable missing — pick the equation that matches what you know.
- Projectile motion: Horizontal and vertical components are independent. vₓ is constant; vy changes at 9.8 m/s² downward.
- Graphs: Slope of position-time = velocity. Slope of velocity-time = acceleration. Area under v-t = displacement.
- First principles: Kinematics is purely descriptive — it tells you HOW objects move, not WHY.
- Free body diagrams: Draw every force acting ON the object. Never include forces the object exerts on others.
- Net force = ma. If ΣF = 0, acceleration = 0 (equilibrium). Object can still be moving at constant velocity.
- Friction: Static (fs ≤ μsN) keeps objects at rest. Kinetic (fk = μkN) acts while sliding. μk < μs always.
- Newton's 3rd Law: Forces come in equal-and-opposite action-reaction pairs on different objects. Never add them together in the same FBD.
- Work-energy theorem: Wnet = ΔKE. All forces do work; only conservative forces have potential energy.
- Conservation of energy: Total mechanical energy constant if only conservative forces. Add heat losses for friction.
- Impulse-momentum: J = Δp = FΔt. Impulse equals change in momentum.
- Collisions: Momentum always conserved. Kinetic energy conserved only in perfectly elastic collisions.
AP Physics Formula Reference
| Formula | What It Means | When to Use |
|---|---|---|
| v = v₀ + at | Velocity after constant acceleration for time t | Missing displacement; find final velocity |
| Δx = v₀t + ½at² | Displacement with initial velocity and acceleration | Missing final velocity |
| v² = v₀² + 2aΔx | Relates velocity to displacement without time | Missing time variable |
| ΣF = ma | Net force equals mass times acceleration | All force problems; the cornerstone equation |
| W = Fd cos θ | Work = force × displacement × cosine of angle between them | Calculating work done by a force |
| KE = ½mv² | Kinetic energy of a moving object | Energy conservation problems |
| PE = mgh | Gravitational potential energy near Earth's surface | Energy conservation; height problems |
| p = mv | Momentum = mass × velocity | Collisions and impulse problems |
| J = FΔt = Δp | Impulse equals change in momentum | Force over time; collision duration |
| τ = rF sin θ | Torque = lever arm × force | Rotational equilibrium and dynamics |
AP Physics Practice Questions
FRQ Strategy for AP Physics
Experimental Design FRQ
AP Physics 1 includes experimental design questions worth 12 points. Practice identifying variables, explaining controls, describing measurements, and analyzing data with uncertainty.
Paragraph-Length Response
New to AP Physics 1: a 4-point paragraph response. Write like a physicist: claim → evidence → reasoning. One clear paragraph beats three vague ones.
No Units = Lost Points
Every numerical answer needs units. Every time. Graders deduct for missing units even if your number is right. Circle or highlight units in your answer.
A 2 kg block is released from rest at the top of a ramp that is 3 m high and 5 m long (measured along the ramp). The coefficient of kinetic friction between the block and ramp is μk = 0.1. g = 10 m/s².
Draw a free-body diagram showing all forces on the block while it is sliding down the ramp. Label each force.
Calculate the speed of the block at the bottom of the ramp using energy methods. Show all work clearly.
A student wants to determine the spring constant k of an unknown spring using only: a ruler, a known mass set (with values in kg), a stand with a clamp, and the spring.
Describe a procedure to determine k. Include: what measurements to take, how to record them, and how to calculate k from the data.
Describe how to use a graph of the data to determine k. What should be on each axis, and how is k found from the graph?
Identify one source of systematic error in this experiment and explain how it would affect the measured value of k.
AP Physics 1 Prep Checklist
AP Physics — My Progress
Track your practice scores and see your estimated AP score (1–5).
AP Biology Unit Weights
Evolution is 20% — Master It
Natural selection, Hardy-Weinberg equilibrium, phylogenetics, and speciation are tested more heavily than any other unit. Understand the logic of evolution, don't just memorize facts.
Gene Expression = Modern Biology
Transcription, translation, operons, epigenetics, and CRISPR. AP Bio is increasingly focused on molecular mechanisms. Know every step of the central dogma cold.
Key Concepts by Unit
- Photosynthesis: Light reactions (thylakoid) → NADPH + ATP. Calvin cycle (stroma) → G3P using CO₂. Light reactions split water; oxygen is a byproduct.
- Cellular respiration: Glycolysis (cytoplasm) → Krebs cycle (matrix) → ETC (inner membrane). Net: ~30-32 ATP per glucose.
- Chemiosmosis: H⁺ gradient across membrane drives ATP synthase. The same mechanism in chloroplasts and mitochondria.
- First principles: Both processes are about moving electrons to lower energy states. Energy is captured when electrons "fall" to more electronegative atoms.
- Transcription: DNA → mRNA via RNA polymerase. Promoters, enhancers, and silencers regulate when and how much.
- Translation: mRNA → protein at ribosomes. tRNA anticodons match codons; start codon AUG, stop codons UAA/UAG/UGA.
- Operons (prokaryotes): lac operon (inducible — sugar turns on genes) vs. trp operon (repressible — amino acid turns off genes).
- Eukaryotic regulation: Histone modification (acetylation loosens chromatin), methylation, miRNA, alternative splicing.
- Hardy-Weinberg: p² + 2pq + q² = 1 and p + q = 1. Equilibrium requires no selection, mutation, migration, drift, or non-random mating.
- Types of selection: Directional (one extreme favored), stabilizing (middle favored), disruptive (both extremes favored).
- Speciation: Allopatric (geographic barrier) vs. sympatric (same location, e.g., polyploidy in plants).
- Phylogenetics: Parsimony — simplest tree explaining data is preferred. Shared derived characters (synapomorphies) define clades.
AP Biology Practice Questions
FRQ Strategy for AP Biology
Data Analysis FRQs
AP Bio loves graphs, bar charts, and data tables. Practice describing patterns (not just reading numbers), identifying controls, calculating percent change, and evaluating experimental design.
Write Mechanistically
Say HOW, not just WHAT. Instead of "more ATP is produced," write "electrons from NADH pass through Complex I, III, IV, creating a proton gradient that drives ATP synthase to synthesize ATP."
Don't Say "It Wants To"
Organisms don't "want" to do anything. Evolution doesn't "try" to create better organisms. Lose anthropomorphic language — it costs points. Write in terms of selection pressures and fitness.
In a population of 1000 mice, 360 are white (homozygous recessive, bb) and 640 are dark (B_). Assume the population is in Hardy-Weinberg equilibrium.
Calculate the frequencies of both alleles and the expected number of heterozygous individuals. Show all work.
Suppose owls preferentially prey on white mice because they are more visible in dark forests. Predict and explain what would happen to the allele frequencies over 10 generations. Name the type of selection occurring.
Name TWO other conditions required for Hardy-Weinberg equilibrium that are NOT natural selection. For each, explain what would happen if that condition were violated.
The following DNA template strand corresponds to part of a gene: 3'-TACGCAATGGCTCGAAAG-5'
Write the sequence of the mRNA transcribed from this template strand. Label the 5' and 3' ends.
Use the mRNA sequence from part (a) to determine the first four amino acids in the polypeptide. The first codon AUG codes for Met.
A mutation changes the 6th base of the template strand from A to T (so the mRNA codon changes from CGU to CAU). Predict and explain the effect on the protein.
AP Biology Prep Checklist
AP Biology — My Progress
Track your practice scores and see your estimated AP score (1–5).
AP Calculus AB Unit Weights
The Fundamental Theorem
The Fundamental Theorem of Calculus connects derivatives and integrals — they are inverses. This is the single most important idea in all of calculus. Every other concept builds from it.
Integration = 32% of Exam
Units 6 and 8 together are nearly a third of your score. Master u-substitution, the Fundamental Theorem, area between curves, and accumulation functions.
Key Concepts — The Big Ideas
- Limit definition: lim(x→a) f(x) = L means f(x) gets arbitrarily close to L as x approaches a. The function doesn't need to equal L at a.
- L'Hôpital's Rule: If limit gives 0/0 or ∞/∞, take derivative of numerator and denominator separately, then re-evaluate.
- Continuity: f is continuous at a if (1) f(a) exists, (2) the limit exists, and (3) they're equal. All three conditions must hold.
- IVT: If f is continuous on [a,b] and k is between f(a) and f(b), then there exists c in (a,b) where f(c) = k.
- Definition: f'(x) = lim(h→0) [f(x+h)-f(x)]/h. The derivative is the instantaneous rate of change — the slope of the tangent line.
- Chain rule: d/dx[f(g(x))] = f'(g(x)) · g'(x). Work from outside in. "Derivative of outside times derivative of inside."
- Implicit differentiation: Differentiate both sides with respect to x; treat y as a function of x, so dy/dx appears whenever you differentiate y.
- Optimization: Set f'(x) = 0 to find critical points. Use second derivative or first derivative sign test to classify as max/min.
- FTC Part 1: d/dx ∫ₐˣ f(t)dt = f(x). The derivative of an accumulation function gives back the integrand.
- FTC Part 2: ∫ₐᵇ f(x)dx = F(b) - F(a) where F is any antiderivative. Net change = final - initial.
- u-substitution: Let u = inside function, du = derivative × dx. Rewrite integral entirely in terms of u. The chain rule in reverse.
- Area between curves: ∫[top - bottom]dx. Always integrate the upper function minus the lower. Set up limits at intersection points.
Essential Derivatives & Integrals
| Function f(x) | Derivative f'(x) | Notes |
|---|---|---|
| xⁿ | nxⁿ⁻¹ | Power rule — most used rule in calculus |
| sin x | cos x | Trig derivatives cycle: sin→cos→-sin→-cos |
| cos x | -sin x | Note the negative sign |
| eˣ | eˣ | e is the unique base where f = f' |
| ln x | 1/x | Domain: x > 0 |
| tan x | sec² x | Memorize this one |
| f(g(x)) | f'(g(x)) · g'(x) | Chain rule — most common mistake is forgetting g'(x) |
| Integrand | Antiderivative | Notes |
|---|---|---|
| xⁿ (n≠-1) | xⁿ⁺¹/(n+1) + C | Reverse power rule |
| 1/x | ln|x| + C | Note absolute value |
| eˣ | eˣ + C | eˣ is its own antiderivative |
| sin x | -cos x + C | Note negative sign |
| cos x | sin x + C | |
| sec² x | tan x + C | Reverse of tan derivative |
AP Calculus Practice Questions
AP Calculus AB Prep Checklist
FRQ Strategy for AP Calculus
FRQs are 50% of your score — 3 with calculator, 3 without.
Show All Work
AP Calculus graders give credit for process, not just answers. Write every step: set up, integrate/differentiate, evaluate. Even a wrong final answer earns most points if the method is correct.
No Calculator? Exact Answers
On the no-calculator FRQ sections, leave answers in exact form: ln(3), π/4, √2. Never approximate unless the problem says to. Rounding prematurely loses points.
Forgetting the Constant of Integration
Every indefinite integral needs + C. On differential equations, forgetting C means you found one particular solution, not the general solution — major point loss on the setup.
FRQ Types That Appear Every Year
Area/volume integrals; rates (slope fields / differential equations); motion on a line (position, velocity, acceleration from graphs); accumulation (FTC applied to real context).
A particle moves along the x-axis so that its velocity at time t is given by v(t) = t² − 4t + 3 for 0 ≤ t ≤ 4. The particle is at position x = 5 when t = 0.
Find all values of t in [0, 4] where the particle changes direction. Justify your answer.
Find the total distance traveled by the particle from t = 0 to t = 4.
Find the position of the particle at t = 4.
Let f(x) = 3 − x² and g(x) = x + 1. Let R be the region enclosed by the graphs of f and g.
Find the x-coordinates of the points of intersection of f and g. Show the work leading to your answer.
Find the area of region R.
Write, but do not evaluate, an integral expression for the volume of the solid generated when R is rotated about the x-axis.
AP Calculus — My Progress
Track your practice scores and see your estimated AP score (1–5).
AP Statistics Unit Weights
Inference is 50%+ of the Exam
Units 6, 7, and 8 together cover confidence intervals and hypothesis tests — more than half the exam. Know when to use each test (z, t, chi-square, F) and be able to write full conclusions in context.
Context is Non-Negotiable
Every single answer must reference the context of the problem. Never write "the mean is 42" — write "the mean exam score of students is 42 points." Graders require context for full credit.
Key Concepts by Unit
- Shape, center, spread: Always describe distributions with all three. Shape: symmetric/skewed left or right. Center: mean or median. Spread: range, IQR, or standard deviation.
- Outlier rule: Q1 − 1.5×IQR and Q3 + 1.5×IQR. Points outside this range are outliers.
- Normal distribution: 68-95-99.7 rule. Z-score = (x − μ)/σ. Z-table gives area to the LEFT.
- Skewness and center: In right-skewed data, mean > median. In left-skewed, mean < median. Median is resistant to outliers.
- Law of Large Numbers: As sample size increases, sample mean approaches population mean. Does NOT say results "balance out."
- Central Limit Theorem: For n ≥ 30 (or any n if population is normal), the sampling distribution of x̄ is approximately normal with mean μ and std dev σ/√n.
- Binomial distribution: Fixed n trials, binary outcome, constant p, independent trials. Mean = np, SD = √(np(1-p)).
- First principles: A sampling distribution is NOT data — it's the distribution of a statistic across all possible samples.
- Four steps: (1) State hypotheses, (2) Check conditions, (3) Calculate test statistic and p-value, (4) Make conclusion in context.
- p-value: The probability of getting a result at least as extreme as observed, IF H₀ is true. It is NOT the probability H₀ is true.
- Type I error: Rejecting a true H₀ (false positive). Type II error: Failing to reject a false H₀ (false negative). Power = 1 - P(Type II).
- AP-required phrase: "We (reject/fail to reject) H₀. There (is/is not) convincing evidence that [context statement in terms of population]."
- Formula: statistic ± (critical value) × (standard error). Always: point estimate ± margin of error.
- Interpretation: "We are 95% confident the true [parameter] is between [L] and [U]." Not "there's a 95% chance" — the parameter is fixed.
- Increasing width: Higher confidence level OR smaller sample size → wider interval. More precision requires larger n.
- Conditions for z-interval: (1) Random sample, (2) n ≥ 30 or normal population, (3) n ≤ 10% of population (independence).
AP Statistics Practice Questions
Investigative Task (Question 6)
The Investigative Task
Question 6 is a multi-part, open-ended problem worth more points than any other FRQ. It often introduces a new concept or variant you haven't seen before — that's intentional. You're being tested on statistical reasoning, not just recall.
Score Points Even When Lost
The investigative task is designed to be hard. Most students don't complete it fully. Focus on parts (a) and (b) first — they're usually more accessible. Partial credit adds up: a 5 out of 6 is excellent.
Always Write a Conclusion
Every inference question needs a conclusion sentence. State: reject/fail to reject H₀, what that means in context, and acknowledge what could go wrong (Type I/II error). This earns "E" (essentially correct) vs. "P" (partially correct).
Conditions Must Be Verified
Simply saying "the conditions are met" is worth zero. You must show the work: "The sample is random (given). n=50 ≥ 30, so CLT applies. 50 < 10% of all students (independence condition met)."
A teacher claims the average exam score for her class is 80 points. A random sample of 25 students from this class has a mean of 77 points with a standard deviation of 10 points.
Conduct a one-sample t-test at α = 0.05 to determine if there is convincing evidence that the true mean is less than 80. Include all four steps.
Step 2 — Conditions (1 pt): (1) Random sample ✓ (stated); (2) n = 25 < 10% of class population (independence); (3) n = 25 < 30, but assume approximately normal distribution. Conditions met — proceed with t-test.
Step 3 — Test statistic & p-value (1 pt): t = (x̄ − μ₀)/(s/√n) = (77 − 80)/(10/√25) = −3/2 = −1.5. df = 24. p-value = P(t < −1.5 | df=24) ≈ 0.073.
Step 4 — Conclusion (1 pt): Since p = 0.073 > α = 0.05, we fail to reject H₀. There is NOT convincing evidence that the true mean exam score is less than 80 points. Must use "fail to reject" (not "accept") and state conclusion in context.
A school district wants to estimate the proportion of students who regularly eat breakfast. They survey 120 randomly selected students and find that 78 reported eating breakfast that morning. A researcher claims the true proportion is 0.70.
Construct a 95% confidence interval for the true proportion of students who eat breakfast. Interpret the interval in context.
Using your interval from part (a), does the interval provide convincing evidence against the researcher's claim that p = 0.70? Explain.
A classmate suggests that if the sample size were increased to 480 students, the interval would be more useful. Explain what would happen to the interval and why.
AP Statistics Prep Checklist
AP Statistics — My Progress
Track your practice scores and see your estimated AP score (1–5).