Plan four dilution steps

Make one paper plan containing four successive 1:10 dilution steps and one conditional prediction about signal. Your assigned starting concentration is 1000 units/mL. It is an illustrative input for calculation, not a measurement of a real solution. You will not obtain a solution, prepare a sample or run an assay in this lesson.

The supplied record has a starting-stock row and four step rows. The stock row is given. You calculate the four rows after it, show the calculations and keep the concentration unit. The table and prediction become one PDF, unless I already collected the same work on paper.

Yesterday's allocation discussion separated supplied facts from assumptions. Today's record makes a similar distinction: the starting value is supplied, the resulting concentrations are calculated, and the signal statement depends on an assumption. You do not need a completed debate response to begin.

Concentration is the amount of a substance per volume of solution, stated with a unit. The assigned unit, units/mL, is read as “units per milliliter.” Keep that exact illustrative unit. No particular substance or conversion to another unit is supplied.

Stock means the starting solution used for a dilution calculation. Here, the stock row is only a paper-planning input. It does not mean a real stock solution has been made or measured.

A sample is the portion being diluted. A solvent is the liquid added to dilute it. These words describe parts of the plan; they are not instructions to obtain materials. After the first step in a serial plan, the preceding step supplies the next sample.

Total volume, also called final volume, counts sample and solvent together. A dilution factor is final volume divided by sample volume, using the same volume unit for both. For today's ratio, you can compare parts directly: ten total parts divided by one sample part gives a factor of 10.

Serial dilution means a series in which the preceding mixture supplies the sample for the next step. Each row therefore depends on the row just before it.

A standard has a known concentration and is used as a reference. This lesson does not supply measured standards or require a standard curve. A signal is a test's measured response, and an assay is a test. You are not running an assay; your signal statement will be a prediction under a stated assumption.

For this lesson's 1:10 rule, count one part of the preceding sample plus nine parts solvent. The total is ten parts, including the sample. The planned concentration is therefore the preceding concentration divided by 10.

Resulting concentration = preceding concentration ÷ 10.

Dividing by nine would count the solvent alone instead of the final total. Starting again from 1000 for every row would also change the plan: it would not describe four successive steps using the preceding row.

Begin with the given starting-stock row. In Step 1, use that row as your input. In Step 2, use your Step 1 result. Continue the same way for Steps 3 and 4. Show the division and write units/mL with each resulting concentration. Five displayed rows mean one starting row and four steps, not five steps.

You may work on paper or in a document. A calculator is useful, but the written calculation should still let another reader see which preceding value and divisor you used. No actual sample volume is assigned; do not invent milliliter amounts or a laboratory preparation to fill a perceived gap. The given parts ratio is enough for this paper calculation.

The worked model starts at 800 ng/mL and uses four 1:2 steps. The unit ng/mL means nanograms per milliliter. One sample part plus one solvent part makes two total parts, so that example divides its preceding concentration by 2 each time.

The model shows how to label a starting row, use the preceding result and retain a unit. Its starting value, factor and unit differ from your assigned record. Do not copy 800, the model results or ng/mL into the assigned 1000 units/mL, 1:10 plan. The model is support, not another task to submit.

Use this assumption, which is also printed beside your response field:

For this classroom model, assume signal increases with concentration within its useful range. Your prediction is conditional on that assumption. It is not a measured result or a rule for every assay format.

Write one sentence predicting signal change across your four steps and explaining how the planned concentration change supports it. A conditional prediction depends on an assumption. Make that dependence clear; do not write that a test actually produced the predicted response.

These calculations cannot show what was actually mixed, establish a test result or diagnose a patient. No unknown sample, standard curve, patient result or assay execution is part of today's work.

Check that you have one given starting row and four completed step rows, a calculation and units in each result, and one prediction using the stated assumption. A partner may help check your reasoning, but a partner response is not required. Guided notes and the optional denominator explanation are support, not additional submissions.

Submit one PDF containing your table and prediction to Wk4 Data table: Concentration and serial dilution by September 17 at 11:59 PM. If I collected this work on paper, do not upload a second copy. The assignment is 5 points in Daily Work. Your notebook can hold the developing plan; it does not require a second upload.

This local task practices ratio and concentration reasoning connected to the Serial Dilutions resource for PLTW Medical Interventions Activity 1.1.5, ELISA. Completing this paper plan does not by itself complete that official activity or authorize an assay. The next lesson introduces antigen-antibody binding and an ELISA model; today's prediction is not its test result.

The required input, calculation rule, blank record and signal assumption are supplied in this lesson. If an official reference needs sign-in, use your authorized myPLTW access; that does not prevent you from using the supplied materials to complete this local paper plan.

References already used for this lesson:

• PLTW Activity 1.1.5: ELISA, the official activity reference.
• PLTW Serial Dilutions resource, the related official resource.
• myPLTW, the existing authorized access route.
• ELISA background, background on the test and why a model prediction is not a measured result.
• Today's portal lesson, with the required record and separate model.