D870 Physical Chemistry I, catalog number CHEM 3040, is the three-CU course sitting where physics and chemistry meet: atomic and molecular structure, thermodynamics and kinetics treated quantitatively. It is the course where chemical explanations become derivations, and the students who find it hardest are usually not weak at chemistry. They are out of practice at algebra, at rearranging relationships and at tracking what a symbol means, and those are repairable in days rather than months.
Where the explanations become derivations
Physical chemistry asks you to hold a quantity and its meaning at once. Enthalpy, entropy and free energy are not three synonyms for energy: one tracks heat exchanged at constant pressure, one tracks how many ways a system can be arranged, and the third combines them to say which direction a process will run at a given temperature. Almost every difficulty students report in the thermodynamics section is a symbol whose meaning has become detached, and the fix is to write the definition beside the symbol every time until it stops being necessary.
Kinetics is the second block and it rewards clean method. A rate law is an experimental result rather than something read off a balanced equation, and it is determined by seeing how rate responds when concentrations change. Once the order is known, the integrated form tells you how concentration evolves in time, and a plot chosen to linearise that form is the standard analysis: the straight line confirms the order and its gradient gives the constant. Temperature dependence then connects kinetics back to energy through the barrier a reaction has to cross.
Structure is the third block and it is where quantisation returns. Electrons in atoms and molecules occupy states with discrete energies, which is why spectra are lines and why bonding produces some arrangements and not others. At this level the expectation is usually qualitative reasoning supported by quantitative relationships rather than full derivation, but the reasoning has to be genuine: saying that electrons occupy orbitals is not an explanation of anything.
Planning the work from your Course of Study
The scoring detail sits in your Course of Study rather than in the public catalog, and it matters more here than in most courses because physical chemistry deliverables vary widely: a derivation, a data analysis, a written explanation or a problem set can each be scored differently. Each aspect is judged on its own and needs a 2, so a correct final number cannot rescue an aspect asking for the reasoning that produced it.
The word budget, worked. Take five scored aspects and directions asking for about 1,500 words alongside your working. Reserve 100 words for setting up the problem and 90 for a close, leaving roughly 1,310, or 260 an aspect. Then move 60 words from each descriptive aspect into the aspects asking you to justify a method or interpret a result, since in this subject the algebra takes no words and the reasoning takes all of them.
The study budget, worked. Fifty hours, and the first five should go to algebra rather than to chemistry: rearranging relationships, logarithms and exponentials, and reading a graph as a relationship. Then fifteen hours on thermodynamics, fifteen on kinetics, ten on structure and five on mixed problems. Students who skip the algebra block spend those five hours later anyway, distributed as friction across every topic.
Solve symbolically before substituting numbers. It is the single habit that most reduces errors in this course, because it keeps the meaning of each quantity visible until the last step.
A structure that fits a physical chemistry deliverable
Where the task directions prescribe a format, follow it. Where they do not, this arrangement suits a quantitative analysis or a derivation-based explanation.
| Section | What belongs in it | What earns the aspect |
|---|---|---|
| System and question | What the system is, what is held constant and what is being determined | Scored for specifying conditions, which govern which relationship applies |
| Assumptions | Ideal behaviour, constant temperature, closed system and anything else assumed | Scored explicitly in this subject; unstated assumptions read as errors |
| Relationships used | The expressions applied, with every symbol defined | Scored for justification of why each applies here |
| Derivation | Algebra shown symbolically to the point of substitution | Scored for visible reasoning rather than for a final value |
| Data and analysis | Measurements, the plot chosen to linearise, the fit and what the gradient means | Scored for interpreting parameters physically |
| Result | The value with units and appropriate precision | Scored for units and precision as much as for the number |
| Interpretation | What the result says about the system, including its sign | Scored for meaning; a value with no interpretation leaves the aspect thin |
| Limitations | Where the assumptions break and how far the conclusion extends | Scored for judgment; ideal treatments have known boundaries |
State the sign convention you are using once, early. Physical chemistry results change meaning entirely with a sign, and a reader who cannot tell which convention you adopted cannot award the interpretation aspect.
Evidence craft in quantitative chemistry
Written work here is judged on whether the reasoning can be followed and checked.
- Define every symbol, including subscripts, and state the units of each quantity.
- Say what is held constant. Almost every relationship in thermodynamics applies under specific conditions and is wrong outside them.
- Keep the algebra symbolic until the final substitution, so an error is visible rather than buried.
- Show the plot you used to determine a rate order or an activation barrier, with axes labelled by the quantities actually plotted.
- Report values with units and a precision the data support, and interpret the sign explicitly.
- Cite reference data, constants and any experimental values you compare against, in APA where directions require it.
- State the ideal assumptions you relied on and where a real system would deviate.
The most efficient check in this subject is dimensional. Before evaluating anything, confirm that the expression has the units of the quantity you are looking for. It catches most algebraic slips in seconds and it is the habit that separates students who finish problem sets from students who fight them.
What separates Competent from a return or a retake
Aspects score independently, and returns here usually concern assumptions left unstated or results left uninterpreted.
- Conditions and assumptions are stated before any relationship is applied.
- Symbols are defined and units carried throughout.
- Algebra is visible and substitution happens once.
- Graphical analysis uses a linearising plot with labelled axes.
- Results carry units, precision and a stated sign convention.
- Interpretation says what the value means for the system.
Performance assessment work can be revised and resubmitted with no grade penalty, so a return costs time rather than standing, and in a six-month flat-rate term that time is the budget. Where any part of the course is assessed by a proctored objective assessment, we prepare only, never sit it and never ask for portal credentials.
Six mistakes that cost time in D870
- Reading a rate law off a balanced equation. Rate laws are experimental results, and this assumption is wrong more often than it is right.
- Substituting numbers immediately. Early numbers hide errors and make checking impossible.
- Losing track of what a symbol means. Most thermodynamic confusion is a definition that slipped rather than a concept that failed.
- Ignoring conditions. Constant pressure and constant volume treatments differ, and applying the wrong one produces a confidently wrong answer.
- Skipping the algebra refresher. The mathematics is the barrier for most students, and five hours early saves twenty later.
- Quoting a value without its sign meaning. A negative free energy change says something specific, and reporting the number alone leaves the aspect unanswered.
How support works on this course
Send your topic list or task directions with the scoring detail from your Course of Study. What comes back is a diagnostic that separates the mathematics from the chemistry, worked problems solved symbolically so the structure is visible, and written work that states conditions and assumptions the way this subject requires.
For most students the fastest gain is the algebra block: rearrangement, logarithms and reading a linear fit as a physical relationship. It is unglamorous, it takes a few hours, and it changes how the rest of the course feels.
Where a data analysis is part of your deliverable, we work through the linearising plot and the interpretation of its gradient with your own numbers, so the method transfers to the next problem rather than solving only this one.
Teacher candidates get a specific dividend from this course. Physical chemistry is where the explanations behind school chemistry actually live, so the reasoning you build here is what lets you answer the question a bright student asks after the simplified version has been given, which is a different and better position than knowing the simplified version alone.
Questions students ask about D870
Is D870 the same course as CHEM 3040?
How much mathematics does D870 need?
Can a rate law be predicted from the balanced equation?
Physical chemistry blocked by the algebra rather than the chemistry?
Send your topic list or task directions. You get a diagnostic that separates the two, symbolic worked solutions and written work that states its conditions properly.
Where D870 sits in WGU's programs
The July 2026 catalog places this code in 3 current WGU programs. Open a program page for the complete standard path and term positions. The live Degree Plan remains authoritative after transfer credit, substitutions, and mentor planning.
The assessments, one by one
The public catalog does not publish this course's PA/OA identity or task count. WGU Tutors publishes at most one PA manual per course and only from a WGU-controlled public rubric. Until that source exists, PA help begins from the student's real Course of Study and OA support remains preparation only.