HS-ESS2-5NGSS*ScienceEarth and Space ScienceGrades 9-12
HS-ESS2-5: Investigating Water and Its Effects on Earth Materials
In plain English: HS-ESS2-5 is the NGSS high school performance expectation that asks students to plan and conduct investigations of the properties of water and of how water changes Earth materials and surface processes. Students test mechanical effects such as frost wedging and stream erosion and chemical effects such as dissolving minerals, and link them to the water and rock cycles. It is usually taught in Earth and Space Science.
Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes.
Clarification Statement: Emphasis is on mechanical and chemical investigations with water and a variety of solid materials to provide the evidence for connections between the hydrologic cycle and system interactions commonly known as the rock cycle. Examples of mechanical investigations include stream transportation and deposition using a stream table, erosion using variations in soil moisture content, or frost wedging by the expansion of water as it freezes. Examples of chemical investigations include chemical weathering and recrystallization (by testing the solubility of different materials) or melt generation (by examining how water lowers the melting temperature of most solids).
Next Generation Science Standards · Disciplinary Core Idea: Earth's Systems · Official standard
Students plan and conduct investigations of the properties of water and use the results as evidence of how water breaks down, dissolves, moves and deposits Earth materials. The NGSS Disciplinary Core Idea behind this performance expectation lists the properties that matter: water can absorb, store and release large amounts of energy, transmit sunlight, expand when it freezes, dissolve and transport materials, and lower the viscosities and melting points of rocks. In this lesson students measure several of these properties directly (expansion on freezing, dissolving, carrying sediment) and analyze data for the others (energy storage, melting points).
The official Clarification Statement reads: "Emphasis is on mechanical and chemical investigations with water and a variety of solid materials to provide the evidence for connections between the hydrologic cycle and system interactions commonly known as the rock cycle. Examples of mechanical investigations include stream transportation and deposition using a stream table, erosion using variations in soil moisture content, or frost wedging by the expansion of water as it freezes. Examples of chemical investigations include chemical weathering and recrystallization (by testing the solubility of different materials) or melt generation (by examining how water lowers the melting temperature of most solids)." NGSS lists no Assessment Boundary for HS-ESS2-5, so this lesson keeps the focus that statement sets: classroom investigations, with water lowering the melting temperature of rock handled through published approximate data rather than a lab. Every data set on this page is invented for teaching unless a value is marked as a standard property of water.
Learning Objectives
By the end of this lesson, students will be able to:
Describe the properties of water that let it change Earth materials: expansion on freezing, energy storage, dissolving and transporting materials, and lowering melting points of rock
Plan an investigation of water and Earth materials with a testable question, one independent variable, a measured dependent variable, controlled variables, repeated trials and safety steps
Conduct mechanical and chemical investigations (frost wedging, stream table, solubility) and record quantitative data
Analyze investigation data to explain how water weathers, erodes and deposits Earth materials
Connect investigation results to the water cycle and the rock cycle
Prior Knowledge Required
Students should already be comfortable with:
The water cycle driven by sunlight and gravity MS-ESS2-4
The rock cycle: weathering, erosion, deposition and melting MS-ESS2-1
States of matter and how adding or removing thermal energy changes them MS-PS1-4
Density as mass divided by volume, and reading a balance and a graduated cylinder
Independent, dependent and controlled variables in an experiment
Show three short scenes (photos or a quick description) and give pairs two minutes to answer the prompt.
Warm-Up Prompt
"A plastic water bottle left in a freezer bulges and splits. A pinch of rock salt stirred into a cup of water disappears. A gravel driveway on a slope loses its gravel after a heavy storm. For each scene, what did the water do to the solid, and what property of water made it possible?"
Collect answers on the board in two columns, mechanical (the solid is broken or moved but not changed chemically) and chemical (the solid dissolves or reacts). Push students to name a property, not just an action: "water expands when it freezes", "water dissolves many minerals", "moving water carries particles". Tell students that today they will turn each scene into an investigation they can measure.
Direct Instruction20 minutes
Part 1: The properties of water that shape Earth. Walk through the table. The values in the middle column are standard properties of water, rounded; the rock melting temperatures are approximate published values.
Properties of water and their effects on Earth materials
Property of water
Value used in this lesson
Effect on Earth materials and surface processes
Expands when it freezes
Liquid water 1.000 g/cm³; ice 0.917 g/cm³, so ice takes up about 9% more volume
Frost wedging: ice in cracks pries rock apart (mechanical weathering)
Absorbs and stores a lot of energy
Specific heat 4.18 J/(g·°C), about 5 times that of dry sand (about 0.80 J/(g·°C)); freezing releases 334 J/g
Wet ground and water bodies change temperature slowly; freezing and thawing take time
Dissolves many minerals (polar molecule)
About 36 g of halite dissolves in 100 g of water at 20°C; gypsum about 0.24 g; calcite far less in pure water
Chemical weathering; minerals recrystallize when the water evaporates
Moves and carries particles
Faster, steeper flow carries more and larger grains
Erosion, transport and deposition by streams
Cohesion and adhesion
Water molecules cling to each other and to mineral surfaces
Soil moisture changes how much rain soaks in and how much runs off
Lowers melting temperature of rock
Granite begins to melt near 950°C dry, near 650°C when water-saturated (mid-crust pressures)
Magma forms where water is added to hot rock, as above subduction zones
Part 2: From a property to an investigation. Work the examples. For each one, name the property, the Earth material and what would be measured.
Frost wedging (mechanical)
A crack in a granite boulder holds 180 g of water on a fall evening. Overnight it all freezes. What volume does the ice need? Use 0.917 g/cm³ for ice.
Result: V = 180 g ÷ 0.917 g/cm³ ≈ 196 cm³, about 16 cm³ more than the 180 cm³ of liquid water, so the ice presses on the crack walls
Planning: soil moisture and erosion
A group plans to test how initial soil moisture affects erosion. Each tray gets 400 g of dry soil. How much water makes the 10%, 20% and 30% trays (water mass as a percent of dry soil mass)? Name the variables.
Result: 40 g, 80 g and 120 g of water. Independent: moisture; dependent: dry mass of soil washed off; controlled: soil type, tray size, slope, spray volume and time
Dissolving and recrystallization (chemical)
A dish holds 250 g of water with as much halite dissolved as it can hold at 20°C. Then 50 g of the water evaporates at the same temperature. How much halite crystallizes?
Result: 250 g holds 90 g; 200 g holds 72 g; so 90 - 72 = 18 g of halite crystals form
Melt generation (data analysis)
Using the table values for granite, by how many degrees does water lower the temperature at which granite begins to melt, and what fraction of the dry value is that?
Result: 950 - 650 = 300°C lower, about 32% of the dry melting temperature
Stream table (transport and deposition)
Invented results: at 0.50 L/min for 10 minutes, 42 g of sediment reached the delta; at 1.00 L/min for 10 minutes, 118 g did. Compare sediment carried per liter of water.
Result: 42 g ÷ 5.0 L = 8.4 g/L and 118 g ÷ 10 L = 11.8 g/L: doubling the flow carried about 2.8 times as much sediment
After the examples, use Diagram 1 to show why ice in a crack pushes outward, and stress the conclusion students should draw: the same property that splits a freezer bottle can split rock, but only when water gets into the crack and then freezes. Ask what would have to happen again and again for a crack to keep growing.
Guided Practice15-20 minutes
Pairs critique and rewrite a flawed plan. Project it and ask each pair to find at least three problems before sharing.
Flawed Plan to Fix
"Question: Does freezing break sandstone? Plan: Soak one sandstone block in water and put it in the freezer for 5 nights, taking it out each morning. Leave a second, dry block on the shelf. At the end, look at both blocks and see which one looks more broken."
Problems to draw out: two things differ between the blocks (water and freezing), so a difference cannot be pinned on either one; "looks more broken" is not a measurement; there is one block per condition; and nothing says how long the block thaws or how wet it is. A strong rewrite uses four groups (wet and frozen, dry and frozen, wet at room temperature, dry at room temperature), at least three samples per group, the mass before and after (dried the same way) as the dependent variable, and fixed soak time, freeze time and thaw time. Pairs write their rewrite with a data table and a safety note (wipe up water on the floor; handle frozen samples with gloves). This plan is the one groups carry out in Activity 1.
Independent Practice15 minutes
Students analyze invented results from a heating investigation. Three cups, each with 200 g of material, sat under the same lamp for 15 minutes.
Invented heating data, 200 g of each material, same lamp, 15 minutes
Material
Start (°C)
End (°C)
Change (°C)
Water
21.0
25.0
4.0
Dry sand
21.0
41.0
20.0
Wet sand
21.0
30.5
9.5
Tasks: (1) Use Q = m × c × ΔT to find the energy absorbed by the water (c = 4.18 J/(g·°C)) and by the dry sand (c = 0.80 J/(g·°C)). (2) Are the two amounts close? What does that suggest about why their temperature changes are so different? (3) Explain where wet sand fits and why. (4) Name one variable the investigators controlled and one they should add to make the comparison fairer. Expected: about 3,340 J and 3,200 J, within about 4% of each other, so both absorbed similar energy and water's higher specific heat explains its smaller temperature change; wet sand warmed less than dry sand because the water in its pores absorbs energy too.
Closure5-10 minutes
Exit ticket: (1) Name one property of water and one Earth material it changes. (2) Write one testable question about water and rock that you could answer in this classroom, and name its independent and dependent variables. (3) Is your investigation mechanical or chemical? How do you know?
Differentiation Strategies
For Struggling Students
Give a planning frame with blanks: "I will change ___. I will measure ___ using ___. I will keep ___, ___ and ___ the same. I will run ___ trials."
Pair each property of water with a picture card of its effect (split rock, salt crust, delta) before students plan
Provide data tables with column headings and units already filled in
For Advanced Students
Ask students to estimate how many freeze-thaw cycles their sample would need to lose half its mass if the loss per cycle stayed constant, and to explain why that assumption may fail
Have students design a stream table test that separates the effect of slope from the effect of flow speed, and explain why the two are linked
Ask students to research how water released from a subducting plate leads to volcanoes, and to connect it to the granite melting data (beyond this standard in depth)
Assessment Guidance
What to Look For
In plans, look for one independent variable, a dependent variable that is measured with a unit (grams, millimeters, milliliters) rather than "see what happens", at least three controlled variables and repeated trials. In analysis, look for students who cite numbers from their data and connect them to a specific property of water. A student who writes "the ice is heavier so it pushes" has the right event but the wrong property: ice has the same mass as the water it came from and takes more volume because it is less dense.
02
Classroom Activities
3 Activities
1
Frost Wedging in the Freezer
25 min, plus 5 short freeze-thaw checksPairs
Pairs measure how much water expands when it freezes, then carry out the four-group freeze-thaw plan from Guided Practice with porous brick or sandstone chips. This is the frost-wedging investigation from the Clarification Statement.
Part A: How Much Does Water Expand?
Pour water into a narrow plastic tube (a centrifuge tube or a straw sealed at one end with clay) until it is about two-thirds full, leaving room above the water for the ice, and mark the level. Leave any cap loose. Measure the water column in millimeters
Stand the tube upright in the freezer overnight, then measure the ice column
Sample invented result: 80.0 mm of water became 87.2 mm of ice, an increase of 7.2 mm, or 9.0%. Compare your class results with the value predicted from the densities
Part B: Freeze-Thaw Cycles
Weigh three sets of chips per condition (about 120 g per set): wet and frozen, dry and frozen, wet at room temperature, dry at room temperature. Soak wet sets for 1 hour. Put each set in a labeled zip-top bag
One cycle = freezer overnight, thaw for 8 hours. Run 5 cycles
After the last cycle, pour off loose flakes, dry the chips for 2 days, and weigh again
Sample invented result after 5 cycles: wet and frozen chips lost 1.8 g of 120.0 g (1.5%); dry and frozen chips lost 0.1 g (about 0.08%)
Discussion Questions
In the sample data, the wet and frozen chips lost 18 times as much mass as the dry and frozen chips. What does that tell you about the role of water, as opposed to cold alone?
Why does the plastic tube show the expansion mainly as extra height?
Which Earth materials would you expect to be damaged most by frost wedging, and what property of the rock would you test next?
Modification for Distance Learning
Students freeze water in a capped plastic bottle at home, mark the level before and after, and share photos. The class pools the height measurements and compares the mean increase with the 9% prediction. Remind students never to freeze glass containers.
2
Stream Table: Slope, Erosion and Deposition
30 minGroups of 3-4
Groups carry out a stream table investigation of how slope affects the amount of sediment moving water erodes, carries and deposits. This is the stream transportation and deposition investigation from the Clarification Statement.
Setup
A stream table, or a plastic paint tray or length of rain gutter, filled with a damp mix of sand and some fine gravel, with an empty pool area at the low end
A bucket or cup with a small hole that delivers 0.75 L/min (check with a graduated cylinder and a stopwatch); a catch basin; a coffee filter to collect the delta sediment
Blocks to raise the upper end by 2, 4 or 6 cm
Procedure
Smooth the sand to the same shape before each trial and cut the same starting channel
Run water for 5 minutes. Sketch the channel and note where the coarse grains and the fine grains settle
Scoop the delta sediment into a filter, dry it and weigh it. Run three trials per height
Sample invented means: 26 g at 2 cm, 55 g at 4 cm, 97 g at 6 cm (shown in Diagram 2)
Discussion Questions
In the sample data, raising the upper end from 2 cm to 4 cm more than doubled the sediment. Why might steeper flow carry more than a proportional amount?
Where did the coarse grains settle compared with the fine grains, and why?
Which variables were hardest to keep the same between trials?
Safety
Water on the floor is a slip hazard: work over a tray or towels and mop up spills right away. Keep water away from outlets and electrical cords.
3
Dissolve and Recrystallize
25 min, plus evaporation over 2-3 daysPairs
Pairs test the solubility of three minerals in water, recover dissolved mineral by evaporation, and model acidic water with vinegar. This is the chemical weathering and recrystallization investigation from the Clarification Statement.
Part A: Solubility Test
Weigh 5.0 g each of rock salt (halite), crushed gypsum and small calcite chips. Add each to its own cup of 100 g of room-temperature water
Stir for 5 minutes, pour through a pre-weighed coffee filter, dry the filter and weigh the solid left
Pour the halite liquid into a shallow dish and let it evaporate for 2-3 days. Weigh and describe the crystals
Sample invented results: halite 0.0 g left (all 5.0 g dissolved); gypsum 4.8 g left (0.2 g dissolved); calcite 5.0 g left (no change measurable on a 0.1 g balance). About 5.0 g of cubic halite crystals formed in the dish
Part B: Acidic Water
Natural water is often slightly acidic. White vinegar is a much stronger acid, so it shows the effect of acidic water within one day
Put 10.00 g of calcite chips in 100 mL of white vinegar and 10.00 g in 100 mL of tap water. After 24 hours, rinse, dry and weigh
Sample invented result: the chips in vinegar lost 0.88 g (8.8%) and fizzed; the chips in water showed no measurable change
Discussion Questions
Only halite dissolved completely in plain water. What would happen to a halite layer exposed at the surface in a rainy climate?
Where in nature does water evaporate and leave dissolved minerals behind as crystals?
Why is vinegar a model and not a copy of rainwater? What does the model exaggerate?
Safety
Wear safety goggles. Use only white household vinegar, no stronger acids. Do not taste any sample. Wash hands after handling minerals.
Variation: Melt Generation Data
Water lowering the melting temperature of rock cannot be tested safely in class. Give groups the approximate granite values from the Direct Instruction table and a simple temperature-depth sketch, and ask them to mark the depths where wet granite, but not dry granite, would begin to melt.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Frost Wedging and the Expansion of Freezing Water
Water that seeps into a crack expands by about 9% when it freezes and pushes on the crack walls. The rock panels are a sketch; the bars at the bottom are drawn to scale from the densities of liquid water (1.000 g/cm³) and ice (0.917 g/cm³).
Diagram 2: Stream Table Results (Invented Class Data)
Invented means of three trials from Activity 2, drawn to scale. Every trial used the same sand mix, starting channel, flow rate and run time; only the height of the upper end changed. Steeper flow eroded and carried more sediment to the delta.
04
Homework Assignment
~30 min
HS-ESS2-5 Homework: Water, Rock and Soil
Directions: Show your calculations with units. When you plan, name the independent variable, the dependent variable and how you will measure it, at least three controlled variables, the number of trials and one safety step. All data sets are invented for practice. Use ice = 0.917 g/cm³, liquid water = 1.000 g/cm³, halite solubility = 36 g per 100 g of water at 20°C.
Part 1: Properties of Water (Problems 1-2)
A glass jar holds 250 mL when full. Predict, without trying it, whether 235 g of water sealed in the jar and frozen would still fit as ice. Show the calculation, then explain how the same property affects rock in a mountain climate.
A 1,500 g puddle of water at 0°C sits on a rock ledge. (a) How much energy must it lose to freeze completely? Water releases 334 J/g as it freezes. (b) How much energy would the same water lose cooling by 10°C as a liquid (c = 4.18 J/(g·°C))? (c) Use your answers to explain why a wet rock surface can stay near 0°C for hours on a freezing night.
Part 2: Planning Investigations (Problems 3-4)
Plan an investigation to answer: "Does water temperature affect how fast rock salt dissolves?" Use water no hotter than 50°C. Include a data table with units and explain how your result connects to chemical weathering.
A student plans this test: "Put halite powder in 100 mL of warm water and a calcite chunk in 50 mL of cold water. Watch which one disappears." List every problem with the plan and rewrite it so it compares only the two minerals.
Part 3: Analyzing Results (Problems 5-6)
Invented data: three 150.0 g samples were soaked and put through 10 freeze-thaw cycles. Sandstone (porosity 20%) ended at 139.2 g, limestone (porosity 8%) at 146.7 g, and granite (porosity 1%) at 149.8 g. Find the percent mass lost by each, describe the pattern, and explain it using a property of water and a property of the rock.
Invented data: four soil trays with 0%, 10%, 20% and 30% initial moisture each received 1,000 mL of sprayed "rain" on the same slope. Runoff was 180, 260, 350 and 470 mL, and the soil washed off was 22, 29, 41 and 63 g. (a) What percent of the rain ran off each tray? (b) Describe the relationship between initial moisture and erosion. (c) Explain it in terms of where the water goes. (d) Suggest one change that would make the conclusion stronger.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
No Credit (0 pts)
Calculations
Correct values with units and work shown
Correct method with one error or missing units
Missing or incorrect
Investigation Plans
One independent variable, measured dependent variable, 3+ controls, trials and safety
Plan is testable but missing one element
Plan is not testable
Data Analysis
Pattern described with numbers from the data
Pattern described without numbers
No pattern described
Explanation
Names the property of water and links it to the Earth material or process
Link is partly correct or vague
No link to a property of water
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Work through the questions in order. Several questions give invented data to analyze or ask you to plan part of an investigation. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
Two identical sealed steel pipes sit outside through a night at -10°C. One is full of water and splits open; the other is full of air and is undamaged. Which explanation fits this evidence?
Answer: B
Water takes more volume as ice than as liquid, because ice (0.917 g/cm³) is less dense than liquid water, so the ice presses on the walls. The air-filled pipe is the control: it faced the same cold, so choice A cannot explain why only one pipe split. Choice C reverses the densities: denser ice would take less room, not more.
Question 2 of 20 · Multiple Choice
A crack holds 45.0 g of liquid water. If all of it freezes, about what volume will the ice occupy? Use 0.917 g/cm³ for ice.
Answer: C
V = m ÷ ρ = 45.0 g ÷ 0.917 g/cm³ ≈ 49.1 cm³. Choice A multiplies by the density instead of dividing, which would make ice smaller than the water. Choice B ignores the expansion, and choice D adds 9 cm³ instead of about 9%.
Question 3 of 20 · Multiple Choice
A group will test whether flow rate affects how much sediment reaches the delta of a stream table. Which variable must stay the same in every trial?
Answer: A
Slope also changes how fast water moves, so it must be controlled or its effect would mix with the effect of flow rate. Choice B is the independent variable, the one the group changes on purpose. Choice C is the dependent variable they measure. Choice D confuses repeated trials with controlled variables: repeating a flawed test does not fix it.
Question 4 of 20 · Multiple Choice
A student tests whether the number of freeze-thaw cycles (0, 3, 6 or 9) affects soaked sandstone samples. What is the dependent variable?
Answer: D
The dependent variable is what the student measures to see the effect: how much of each sample breaks off, found by drying and weighing before and after. Choice A is the independent variable, the one the student changes on purpose. Choices B and C are variables to keep the same.
Question 5 of 20 · Multiple Choice
At 20°C, about 36 g of halite dissolves in 100 g of water. What is the most halite that 40 g of water can dissolve at 20°C?
Answer: A
Solubility scales with the amount of water: 36 g × (40 g ÷ 100 g) = 14.4 g. Choice B ignores that there is less than 100 g of water. Choice C divides 36 by 0.4 instead of multiplying. Choice D divides 40 by 36 and has no meaning here.
Question 6 of 20 · Multiple Choice
Which observation is evidence of chemical weathering rather than only mechanical weathering?
Answer: C
The calcite was dissolved by the water, carried away in solution and then recrystallized as the water evaporated, so the mineral changed from solid to dissolved and back: a chemical process. Choices A and B break or wear rock into smaller pieces of the same material, which is mechanical weathering. Choice D is mass movement of soil, not a chemical change.
Question 7 of 20 · Multiple Choice
In a stream table, water carrying gravel, sand and silt flows out of the channel into a still pool. Where do students find most of the gravel?
Answer: B
Water slows as it enters the pool and can no longer carry the largest, heaviest grains, so gravel settles first near the mouth, then sand, while silt travels farthest. Choice C reverses the sorting: heavy grains need the fastest water to keep moving. Choice D confuses gravel with fine clay and silt, which can stay suspended.
Question 8 of 20 · Multiple Choice
Approximate data: dry granite begins to melt near 950°C, and water-saturated granite near 650°C at mid-crust pressures. At a depth where the rock is at 720°C, which prediction fits the data?
Answer: D
720°C is above the 650°C melting temperature of water-saturated granite but below the 950°C of dry granite, so only the wet granite begins to melt. Choice C reverses the effect: adding water lowers the melting temperature, it does not raise it.
Question 9 of 20 · Multiple Choice
How much energy does it take to warm 2.0 kg of water by 5.0°C? Use c = 4.18 J/(g·°C).
Answer: A
Q = m × c × ΔT = 2,000 g × 4.18 J/(g·°C) × 5.0°C = 41,800 J. Choice C leaves the mass in kilograms while c is per gram. Choice B uses the specific heat of dry sand (0.80) instead of water. Choice D multiplies by an extra factor of 10.
Question 10 of 20 · Multiple Choice
A student reports: "Tray A: dry soil at a 10° slope. Tray B: soaked soil at a 20° slope. Both got 500 mL of spray. Tray B lost more soil, so wet soil erodes more." What is the main problem with this conclusion?
Answer: C
Two variables differ between the trays, so the larger loss in Tray B could come from the steeper slope, the wetter soil or both. The fix is to keep the slope the same and change only moisture. Choice B would add a third uncontrolled variable.
Question 11 of 20 · Multiple Choice
Why should each stream table condition be run three times rather than once?
Answer: D
Repeated trials show the spread of results and give a mean that one odd trial (a collapsed bank, a clogged spout) cannot dominate. Choice B misunderstands investigations: trials test a hypothesis, they do not guarantee it. Choice C would add an uncontrolled variable.
Question 12 of 20 · Multiple Choice
A piece of chalk (calcite) with a mass of 8.00 g sits in vinegar for 24 hours. Rinsed and dried, it has a mass of 6.80 g. What percent of its mass was lost?
Answer: B
Mass lost = 8.00 - 6.80 = 1.20 g, and 1.20 ÷ 8.00 = 0.15 = 15%. Choice A reports the mass lost in grams as if it were a percent. Choice C is the percent that remains. Choice D divides by the final mass instead of the starting mass.
Question 13 of 20 · Multiple Choice
A dish holds 150 g of water with as much halite dissolved as it can hold at 20°C (54 g). If 25 g of the water evaporates at 20°C, about how much halite crystallizes?
Answer: C
The 125 g of water left can hold 36 × 1.25 = 45 g, so 54 - 45 = 9.0 g comes out as crystals. Choice B is the halite still dissolved, not the amount that crystallizes. Choice A assumes all the halite comes out, and choice D confuses the mass of water with the mass of salt.
Question 14 of 20 · Multiple Choice
Which statement best links the water cycle to the rock cycle, based on investigations like the ones in this lesson?
Answer: A
The stream table, freeze-thaw and dissolving tests each show one step: water breaks rock, dissolves minerals, moves sediment and deposits it, which supplies material for sedimentary rock. Choice B ignores dissolving and stream transport. Choice D is wrong because evaporation leaves minerals where the water evaporates, such as dry lake beds and shallow seas, not on distant mountains.
Question 15 of 20 · Short Answer
Plan an investigation to test whether breaking calcite into smaller pieces changes how fast it weathers chemically in vinegar. Name the independent variable, the dependent variable and how you will measure it, three controlled variables, the number of trials and one safety step.
Independent variable: piece size, for example one whole 10 g chip, 10 g of small chips and 10 g of coarse powder. Dependent variable: mass lost in a fixed time, measured by rinsing, drying and weighing on a balance (or the mass of the cup and vinegar every 5 minutes as gas escapes). Controls: same total mass of calcite from the same source, same volume and brand of vinegar, same temperature and same time. Trials: at least three per size. Safety: goggles, household vinegar only. Smaller pieces expose more surface to the liquid, so the prediction is faster mass loss.
Question 16 of 20 · Short Answer
Invented stream table data: after 5 minutes of flow, a curved channel was 1.8 cm deep on the outside of its bend and 0.4 cm deep on the inside, where a small sand bar formed. Explain the difference using how water moves around the bend, and predict how the bend will change if the flow continues.
Water moves faster along the outside of a bend, so it has more energy to erode the bank and bed there, which makes that side deeper. On the inside the water slows and drops sediment, building the sand bar. If the flow continues, the outside bank keeps eroding and the inside keeps filling, so the bend grows more curved and shifts outward, which is how river meanders migrate.
Question 17 of 20 · Short Answer
Town A has air temperatures that cross 0°C on about 80 days a year. Town B stays below 0°C for five months in a row and crosses 0°C on about 15 days a year. In which town would you expect faster frost wedging of exposed rock, and why?
Town A. Frost wedging needs repeated cycles: liquid water must seep into a crack, freeze and expand, then melt so water can seep deeper before the next freeze. A crack that stays frozen for months does not widen further after the first freeze. More freeze-thaw cycles in Town A mean more times the ice pries the crack open.
Question 18 of 20 · Short Answer
In a class test, halite dissolved completely in plain water, gypsum dissolved slightly, and calcite showed no measurable change. Yet large caves form in limestone, which is mostly calcite. Explain how, and name a variable you could test in class to support your explanation.
Rainwater and groundwater pick up carbon dioxide from the air and soil and become slightly acidic (carbonic acid). Calcite reacts with acidic water much faster than it dissolves in pure water, and caves form over thousands of years as this water flows through cracks. A class test: change the acidity of the water (plain water, carbonated water, vinegar) and measure the mass lost by identical calcite chips over the same time.
Question 19 of 20 · Short Answer
A group measures the dry sediment reaching the delta in three trials at one slope: 52 g, 47 g and 60 g. A second slope gave a mean of 57 g. Find the mean and range of the first slope, and decide whether the group can claim the second slope moved more sediment.
Mean = (52 + 47 + 60) ÷ 3 = 53 g; range = 60 - 47 = 13 g. The difference between the means (57 - 53 = 4 g) is smaller than the spread within the first set of trials, so the data do not support a clear difference. The group should run more trials or control the setup more tightly before making the claim.
Question 20 of 20 · Short Answer
Invented data: dry sand holds a pile slope of about 34°, damp sand (about 8% water) can hold nearly vertical walls, and waterlogged sand slumps to about 15°. Explain the pattern using a property of water, and connect it to what can happen to hillsides after long, heavy rain.
In damp sand, thin films of water between grains pull them together (cohesion and adhesion, surface tension), so the sand holds steep walls. Dry sand has no water films. When the sand is waterlogged, the pores fill, the films disappear and water pushes the grains apart, so the sand flows. Hillsides behave the same way: soil that becomes saturated after long, heavy rain can lose strength and slide, which is one way water drives erosion and mass movement.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-ESS2-5 mean?
HS-ESS2-5 asks high school students to plan and conduct their own investigations of the properties of water and use the results to explain how water changes Earth materials and surface processes. "HS" is high school, "ESS2" is the Earth's Systems core idea, and "5" is the fifth performance expectation in that group. The emphasis is on doing the investigation, not only learning facts about water.
Is HS-ESS2-5 taught in Earth science or in chemistry?
It is usually taught in Earth and Space Science, often in a unit on weathering, erosion and the rock cycle. Schools that use an integrated course sequence may place it in a combined Earth, chemistry or environmental course. The solubility and energy parts connect well with chemistry, but the goal is always the effect of water on Earth materials.
Which properties of water should students investigate?
The NGSS core idea lists water's capacity to absorb, store and release energy, to transmit sunlight, to expand on freezing, to dissolve and transport materials, and to lower the viscosities and melting points of rocks. A good unit lets students measure at least two directly, such as expansion on freezing and dissolving, and work with data for the rest.
What is the difference between a mechanical and a chemical investigation here?
A mechanical investigation shows water breaking or moving material without changing what it is made of, such as frost wedging or a stream table. A chemical investigation shows material dissolving, reacting or recrystallizing, such as testing how much of a mineral dissolves or evaporating a solution to grow crystals. The Clarification Statement asks for both kinds.
How can we study frost wedging without waiting for winter?
Use a classroom or cafeteria freezer. Water in capped plastic tubes shows the expansion overnight, and soaked brick or sandstone chips in zip-top bags can go through one freeze-thaw cycle per day. Five cycles are usually enough to see mass loss in porous samples. Never freeze water in glass.
Do we need a commercial stream table?
No. A plastic paint tray, a length of rain gutter or a shallow storage bin with a hole at the low end works. Fill it with a sand and fine gravel mix, raise one end with blocks, and deliver water from a cup or jug with a small hole so the flow rate can be measured with a graduated cylinder and a stopwatch.
Does HS-ESS2-5 have an Assessment Boundary?
No. NGSS lists no Assessment Boundary for HS-ESS2-5, so the Clarification Statement guides the scope: mechanical and chemical investigations with water and solid materials. Melting of rock is treated with published approximate data rather than a lab, and phase diagrams or pressure calculations go beyond this standard.
How is HS-ESS2-5 assessed?
It is usually assessed through performance tasks: students write or critique an investigation plan, collect or analyze data, and explain the result in terms of a property of water. State science tests differ in format, so check your state's released items. Recall of facts alone does not show the performance expectation.
What safety steps do these labs need?
Goggles for any work with vinegar or crushed minerals, household white vinegar only (no stronger acids), no tasting of samples, plastic rather than glass in the freezer, and prompt cleanup of spilled water, which is a slip hazard. Keep water away from outlets.
What mistakes do students make when planning these investigations?
A frequent one is changing more than one variable between conditions. Others are a dependent variable that is only "look and see" instead of a measured mass or length, a single trial per condition, and the idea that ice is heavier than water. Ask students to state their measurement and its unit before they start.
07
Related Standards
6 standards
These standards connect to HS-ESS2-5: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-ESS2-4Prerequisite
Model the cycling of water through Earth's systems, driven by sunlight and gravity
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