Investigate water’s mechanical and chemical roles

How can moving water and dissolved substances change Earth materials differently?

Submit: An evidence record, explanation and revision.

Related lesson: Plate Tectonics and Earth History

This is a teacher-led extension beyond the short lesson. The task supplies a performance opportunity; completion alone does not certify mastery, full NGSS coverage or state alignment.

Build the idea

Water can move sediment mechanically and participate in chemical processes that dissolve or alter minerals. Transport depends on flow and particle properties; dissolution depends on material and solution conditions. One classroom model cannot reproduce a whole landscape or geological timescale.

Evidence and model inputs

Two-part investigation: A, compare sediment movement on identical shallow trays with the same water volume delivered gently versus more quickly; B, compare equal masses and sizes of safe classroom chalk in water and dilute household vinegar in open cups. Vinegar models an acidic solution but is more acidic than ordinary rain; chalk composition must be recorded and may not match natural limestone exactly.

Keep actual observations, published findings and invented model cases labeled separately. If a source or required equipment is unavailable, pause that part with a teacher; do not invent results.

Materials and preparation

Shallow trays, safe sediment, water, measuring cup, timer, chalk, dilute household vinegar, open cups and goggles.

Grade-level scope

Teacher-supervised household-scale materials only; no strong acids, hot liquids or sealed gas-producing containers.

Do the work

1. Teacher approves goggles, trays, open cups and small quantities; no tasting, sealed reactions or disposal of sediment into drains.
2. Plan repeated A trials with matched slope, sediment and volume; measure transported sediment by a consistent safe method.
3. Plan B trials with equal liquid volume, material size, temperature and duration; record fizzing, visible changes and mass only after consistent drying if measured.
4. Separate evidence of mechanical transport from evidence of chemical interaction; identify limitations of each proxy.
5. Connect the observations to erosion, carbonate weathering and movement of material through the rock cycle, then propose a better-controlled follow-up.

Learner worksheet

Write on paper or type here and print. Entries stay in this page’s memory and are lost when you leave or reload; they are not saved or submitted.

Check your reasoning

1. Why keep total water volume fixed in A?
2. Does fizzing alone measure all dissolved mass?
3. Is vinegar identical to rainwater?
4. Why include both parts?

Teacher review guide

Review the actual deliverable and discuss the reasoning. For each criterion, use 0 when evidence is absent or fundamentally incorrect, 1 when partly supported with a material error or omission, and 2 when accurate, supported and complete for the stated task. Maximum 8 points is a task score, not a proficiency certification. Give feedback and allow revision.

1. Plans controlled mechanical and chemical investigations.
2. Collects actual repeated observations.
3. Connects properties and processes with Earth-material changes.
4. Evaluates model differences and measurement limitations.

Sources and standard reference

• Official NGSS HS-ESS2-5 performance expectation — inspect the practice, core idea, crosscutting concept and assessment boundary.

Instructional text and hypothetical cases are original. Linked source readings supply published evidence where specified. Teachers should judge fit with their course and state requirements.