MS-PS1-2: Using Property Data to Decide If a Chemical Reaction Occurred
In plain English: MS-PS1-2 is the NGSS middle school performance expectation that asks students to analyze data on the properties of substances before and after they interact, such as density, melting point, boiling point, solubility, flammability and odor, and decide whether a chemical reaction made new substances. It is usually taught in grade 6, 7 or 8 physical science.
Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
Clarification Statement: Examples of reactions could include burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride.
Assessment Boundary: Assessment is limited to analysis of the following properties: density, melting point, boiling point, solubility, flammability, and odor.
Next Generation Science Standards · Disciplinary Core Idea: Matter and Its Interactions · Official standard
Students analyze data on the properties of substances before and after they interact and decide whether a chemical reaction happened. A substance is one kind of matter, such as water, iron or table sugar, with the same makeup all through it. A property is a trait you can observe or measure. Some properties are the same for any amount of a substance, so they act like a fingerprint: density (mass divided by volume), melting point (the temperature at which a solid turns to liquid), boiling point (the temperature at which a liquid boils), solubility (how well a substance dissolves in water), flammability (whether it burns) and odor (smell). In a chemical reaction, the starting substances change into new substances with different properties. In a change of state or when substances are only mixed or dissolved, the substances stay the same and so do their properties.
The NGSS Clarification Statement says: "Examples of reactions could include burning sugar or steel wool, fat reacting with sodium hydroxide, and mixing zinc with hydrogen chloride." The Assessment Boundary says: "Assessment is limited to analysis of the following properties: density, melting point, boiling point, solubility, flammability, and odor." Every data table on this page uses only those six properties. Sodium hydroxide and hydrogen chloride are corrosive and burning needs an open flame, so students see the four official examples as video and data only. Their hands-on work uses Epsom salt, castile soap, salt, sugar, water and glass marbles, with goggles on. Reference values are rounded; class data are invented and labeled. Students do the practice: they compute densities, compare tables, and argue from the data.
Learning Objectives
By the end of this lesson, students will be able to:
Name the six properties used in this standard (density, melting point, boiling point, solubility, flammability and odor) and explain why they can identify a substance
Compute density from mass and volume, including volume found by water displacement
Compare property data before and after substances interact and decide whether new substances formed
Tell a chemical reaction apart from a change of state, dissolving or mixing, using property data
Write a claim, evidence and reasoning statement that cites at least two properties
Prior Knowledge Required
Students should already be comfortable with:
Identifying materials by their properties 5-PS1-3
Testing whether mixing two substances makes a new substance 5-PS1-4
Dividing decimals to find a unit rate, such as grams per milliliter 6.RP.A.2
Show two clear cups: one with plain water and one with water in which a spoonful of sugar has fully dissolved. Ask:
Warm-Up Prompt
"The sugar seems to disappear. Did it turn into a new substance, or is it still sugar? What could you measure or test, without tasting, to find out?"
List students' ideas. Steer toward letting the water evaporate and testing what is left. Tell students that today they will decide such questions with data, not with how things look.
Direct Instruction15-20 minutes
The test for a reaction. Measure the properties of each starting substance. Let them interact. Then separate what is left and measure the same properties again. If several properties are clearly different from those of every starting substance, new substances formed: a chemical reaction occurred. Density is mass ÷ volume, in g/cm³ for solids or g/mL for liquids (1 mL = 1 cm³). Bubbles or a color change can be a sign to look closer, but the decision on this page always rests on the six properties. Show the four official examples on video, then analyze their data. Diagram 1 compares the densities and Diagram 2 shows the steps.
Burning sugar (official example, video)
Before: table sugar has a density of 1.59 g/cm³, melts near 186 °C, dissolves easily in water and has no odor. After strong heating in a flame, a black solid is left. It does not dissolve in water, does not melt in the flame and has a burnt odor.
Result: Solubility, melting and odor all changed, so the black solid is a new substance (mostly carbon): a chemical reaction occurred.
Burning steel wool (official example, video)
Before: steel wool is mostly iron: density 7.9 g/cm³, melting point 1,538 °C, does not dissolve in water. Thin strands burn with sparks. After: a dark, brittle powder with a density of 5.2 g/cm³ and a melting point near 1,600 °C. It does not burn again.
Result: Density, melting point and flammability changed, so the powder (iron oxide) is a new substance: a reaction with oxygen in the air.
Fat and sodium hydroxide (official example, video)
Before: solid fat (lard) has a density of 0.92 g/cm³, melts at about 35 °C, does not dissolve in water and has a mild fatty odor. Sodium hydroxide dissolves in water and melts at 318 °C. After heating them together: soap, with a density of about 1.05 g/cm³, which dissolves in water and does not melt until well above 200 °C.
Result: The soap's density, solubility and melting point match neither starting substance, so soap is a new substance. This reaction is how soap is made.
Zinc and hydrogen chloride (official example, video)
Before: zinc has a density of 7.1 g/cm³, melts at 420 °C, does not dissolve in water and does not burn as a lump. Hydrogen chloride, dissolved in water, has a sharp, choking odor. After: a gas with no odor that burns with a small pop, and, once the water evaporates, a white solid (density 2.9 g/cm³, melting point 290 °C) that dissolves easily in water.
Result: The gas (hydrogen) is flammable, and the white solid (zinc chloride) differs in density, melting point and solubility from zinc. Two new substances formed.
Dissolving is not a reaction (contrast)
10.0 g of table salt (density 2.16 g/cm³, melting point 801 °C) dissolves in 100 mL of water. After the water evaporates, 4.32 g of the crystals are measured in vegetable oil (salt does not dissolve in oil): the oil level rises by 2.00 mL.
Result: Density = 4.32 g ÷ 2.00 cm³ = 2.16 g/cm³, the same as before. The crystals dissolve again and melt at 801 °C. Same properties, same substance: no reaction.
After each example, ask: "Which properties changed? Did we compare with every starting substance? Is the difference bigger than a measuring error?" Point out that in the steel wool and zinc examples more than one property changed: one property alone can be misleading.
Guided Practice15 minutes
Pairs analyze teacher-reference data (rounded; this reaction needs heat and a catalyst, so it is data only). Two clear liquids, A and B, are mixed and heated, and a new layer of liquid, C, is separated. Students first compute each density from 50.0 mL samples, then compare.
Guided practice data: liquids A, B and C (teacher reference)
Liquid
Mass of 50.0 mL (g)
Boiling point (°C)
Solubility in water
Odor
Flammability
A (before)
39.5
78
mixes completely
sharp
burns
B (before)
52.5
118
mixes completely
sharp, like vinegar
hard to light
C (after)
45.0
77
only a little dissolves
fruity
burns
Compute the densities: A = 39.5 ÷ 50.0 = 0.79 g/mL, B = 52.5 ÷ 50.0 = 1.05 g/mL, C = 45.0 ÷ 50.0 = 0.90 g/mL.
Compare C with A. The boiling points (77 °C and 78 °C) are almost the same. Is that enough to say C is just A?
Now compare density, solubility and odor. C differs from A and from B in all three.
Write a claim with two pieces of evidence: "Liquid C is a new substance because its density (0.90 g/mL) and its solubility differ from both A and B."
Independent Practice10-15 minutes
Each student analyzes a new invented data set. A white solid, M, is added to a clear liquid, N. Afterward, the liquid is poured off and allowed to evaporate, leaving a white solid, P.
Independent practice data (invented)
Sample
Mass (g)
Volume (cm³)
Melting point (°C)
Solubility in water
Odor
Solid M (before)
12.0
4.4
breaks down before melting
does not dissolve
none
Liquid N (before)
11.0
10.0
freezes below 0
mixes completely
sharp
Solid P (after)
6.3
3.0
772
dissolves easily
none
Students compute the three densities (about 2.7, 1.1 and 2.1 g/cm³), decide whether P is a new substance, and write a claim, evidence and reasoning paragraph that cites at least two properties.
Closure5 minutes
Exit ticket: "An iron nail rusts in damp air. Name two of the six properties you would measure on the nail and on the rust, and say what results would show that rust is a new substance." Return to the warm-up: dissolved sugar can be recovered with the same properties, so dissolving did not make a new substance.
Differentiation Strategies
For Struggling Students
Give a before-and-after table with a "same or different?" column for each property, so students compare one property at a time
Provide the density formula on a card, with one worked line: 12.0 g ÷ 4.0 cm³ = 3.0 g/cm³
Use a sentence frame: "A new substance (did / did not) form, because its ___ and ___ (changed / stayed the same)."
For Advanced Students
Ask students to decide how large a density difference must be before they trust it, given that their balance reads to 0.1 g and their cylinder to 0.5 mL
Have students find a case on this page where one property barely changed but a reaction still happened, and explain why several properties are checked
Ask students to design a fair test that shows soap scum is a new substance, naming the control and the properties measured
Assessment Guidance
What to Look For
Check that students compare the after-substance with every starting substance, not just one, and that they cite at least two properties. Look for correct density work (mass ÷ volume, with units) and for volume by displacement taken as the rise in the water level. Listen for students who call dissolving, melting or mixing a reaction, or who use bubbles or color alone as proof.
02
Classroom Activities
3 Activities
1
Soap Scum Lab: A Safe Reaction and a Control
25 minPairs
Pairs test whether mixing castile soap solution with Epsom salt solution makes a new substance, the soap scum that forms in hard water. A second station, dissolving sugar and letting it dry, is the control: a change that should not make a new substance.
Procedure
Safety: wear goggles, do not taste anything, and waft (wave the air toward your nose) instead of sniffing a cup directly. Wash hands at the end.
Station 1, before: stir 5 mL of castile soap into 50 mL of distilled water in one cup, and 1 teaspoon of Epsom salt into 50 mL of distilled water in another. Record solubility and odor for each. Shake the soap cup gently: it makes suds.
Station 1, after: pour the Epsom salt solution into the soap solution and stir. A white, curdy solid forms. Scoop some into a cup of fresh water and stir for 1 minute. Record its solubility and odor.
Station 2 (control): dissolve 1 teaspoon of sugar in 20 mL of water, spread a few drops on a dark plate, and leave it overnight. Test the dried crystals the next day.
Sample Data (invented)
Soap: dissolves, mild soapy odor, makes suds. Epsom salt: dissolves, no odor. White solid: does not dissolve even in fresh water, faint soapy odor. Dried sugar crystals: dissolve again, no odor.
Discussion Questions
Both starting substances dissolve, but the white solid does not. What does that tell you?
Why is it important to test the white solid in fresh water, not in the mixture?
What did the sugar station show, and why is it called a control?
Modification for Distance Learning
Students watch a teacher video of both stations, record the observations in the data table, and post a claim with two pieces of evidence.
2
Density Fingerprint Lab
20 minGroups of 3-4
Groups show that density does not depend on the amount of a substance, which is why it can identify one. They measure the mass and volume of 5, 10 and 15 glass marbles, then use density to judge invented before-and-after samples.
Procedure
Fill a 50 mL graduated cylinder to 15.0 mL with water. Tilt it and slide 5 marbles in gently. Read the new level: the rise is the volume of the marbles.
Find the mass of the 5 marbles on the balance. Repeat with 10 and 15 marbles, starting from fresh water each time.
Compute density = mass ÷ volume for each trial.
Sample Data (invented)
5 marbles: 27.4 g, 10.5 mL. 10 marbles: 54.9 g, 21.0 mL. 15 marbles: 82.1 g, 31.5 mL. Each density is about 2.61 g/cm³, close to the density of glass.
Discussion Questions
The mass and the volume both grew, so why did the density stay about the same?
A sample taken after a reaction has a density of 2.6 g/cm³, and one of the starting substances is this glass. Is that enough to prove no new substance formed? What else would you test?
Challenge Variation
Groups predict, then measure, the density of 3 marbles, and explain why the result is less precise than with 15.
3
Reaction or Not? Data Card Sort
20 minGroups of 3-4
Groups sort eight invented data cards into "new substance formed" and "no new substance", then write the two strongest pieces of evidence on each card.
The Eight Cards (invented data)
A solid that melts at 44 °C is warmed until liquid, then cooled. The solid melts at 44 °C again.
Two liquids that boil at 100 °C and 118 °C are mixed. A new liquid separates that boils at 35 °C and has a strong odor that neither starting liquid had.
A gray solid (density 1.5 g/cm³, melting point 842 °C) is heated in air. A white powder forms with a density of 3.3 g/cm³ that does not melt below 2,500 °C.
A purple solid dissolves in water. After evaporation the solid left dissolves again and has the same density, 2.7 g/cm³.
A shiny solid that does not dissolve in water is dropped into a liquid. Later the liquid is evaporated, leaving a white solid that dissolves easily in water and melts far below the shiny solid's melting point.
A liquid that boils at 56 °C is mixed with water. The two liquids are separated again, and they boil at 56 °C and 100 °C.
A white powder with no odor is mixed with water and gives off a gas with a strong, sharp odor.
An aluminum can is crushed flat. The metal still has a density of 2.70 g/cm³ and still does not dissolve in water.
Discussion Questions
Cards 2, 3, 5 and 7 show new substances, and cards 1, 4, 6 and 8 do not. Which property was the strongest evidence on each card?
Card 3 tells you two property values after the change. Why is that stronger than one?
Modification for Distance Learning
Put the eight cards on a shared slide with two columns. Each student drags the cards into place and adds a comment naming the evidence.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: Density Before and After in Four Changes
Densities from the worked examples, drawn to scale. In the three reactions the substance afterward has a different density from the starting one (for zinc, less than half). When salt is dissolved and dried again, the density does not change, because no new substance formed.
Diagram 2: How to Decide If a Chemical Reaction Occurred
Measure the six properties (density, melting point, boiling point, solubility, flammability, odor) before, let the substances interact, separate them and measure again. Several clear differences from every starting substance mean new substances formed.
04
Homework Assignment
~30 min
MS-PS1-2 Homework: Analyzing Property Data for Chemical Reactions
Directions: All values are rounded reference values or invented data. Show each density calculation with units (1 mL = 1 cm³). End every problem with a claim that names at least two properties as evidence.
Part 1: Comparing Properties (Problems 1-3)
Tin is a silvery metal. When it is heated strongly in air (teacher reference data), a white powder forms. A tin sample has a mass of 29.2 g and a volume of 4.0 cm³ and melts at 232 °C. A sample of the white powder has a mass of 20.85 g and a volume of 3.0 cm³ and melts at about 1,630 °C. (a) Compute both densities. (b) The densities differ by only a little. Which property gives the strongest evidence, and does it show that a new substance formed?
Liquid R (density 0.80 g/mL, boiling point 82 °C, sharp odor, burns) is mixed with liquid S (density 1.00 g/mL, boiling point 100 °C, no odor, does not burn). The mixture has a density of 0.92 g/mL. The teacher then separates the mixture into two liquids, which boil at about 82 °C and 100 °C and have the same odors as R and S. Did a chemical reaction occur? Explain why the density of the mixture alone could mislead you.
Ice has a density of 0.92 g/cm³ and liquid water has a density of 1.00 g/cm³. A student says, "The density changed when the ice melted, so melting made a new substance." Use melting point and boiling point to respond to the student, and explain what kind of change melting is.
Part 2: Arguing from Data and Planning (Problems 4-6)
A sheet of paper burns, leaving gray ash (teacher video). Before: the paper burns easily, does not dissolve in water and has no odor. After: the ash does not burn, part of it dissolves in water, and the air smells of smoke. Write a claim, evidence and reasoning response: did a new substance form?
Plan an investigation to find out whether dissolving lemonade drink powder in water makes a new substance. Name the materials (household only), the steps, two of the six properties you would compare, and one safety rule. Say what result would show that no new substance formed.
In a teacher video, iron powder and yellow sulfur powder are heated together. Before: iron has a density of 7.9 g/cm³ and melts at 1,538 °C; sulfur has a density of 2.1 g/cm³, melts at 115 °C and has a faint odor. After: a dark solid with a mass of 24.0 g and a volume of 5.0 cm³, no odor and a melting point of 1,194 °C. (a) Compute the density of the dark solid. (b) Compare it with both starting substances. (c) Did a chemical reaction occur?
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Density and Data Work
Every density is mass ÷ volume with correct units and rounding
Correct method with one calculation or unit error
Comparing Properties
Compares the after-substance with every starting substance, using at least two of the six properties
Compares only one property or only one starting substance
Claim, Evidence, Reasoning
Clear claim (reaction or not), specific data as evidence, and reasoning that new substances have new properties
Claim stated but evidence is general or reasoning is missing
05
Quiz: 20 Questions
Interactive, with answers
Instructions
All data are rounded reference values or invented for practice. Density is mass ÷ volume, and 1 mL = 1 cm³. 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
Which result is the best evidence that a new substance formed when two substances interacted?
Answer: B
Melting point is a property that identifies a substance, so a new melting point means a new substance. Choice D changes only the size and shape, and choice C describes what was done, not a property. Choice A could happen from packing or dissolving and is not one of the six properties.
Question 2 of 20 · Multiple Choice
A metal sample has a mass of 26.7 g and a volume of 3.0 cm³. What is its density?
Answer: B
Density = mass ÷ volume = 26.7 ÷ 3.0 = 8.9 g/cm³. Choice A divides volume by mass. Choice C subtracts the volume from the mass, and choice D multiplies them.
Question 3 of 20 · Multiple Choice
A stick of butter melts at about 32 °C. It is melted, poured into a mold and cooled in the refrigerator. The new solid melts at about 32 °C. What do the data show?
Answer: C
The melting point is the same before and after, so the butter is the same substance: melting and freezing are changes of state. Choices A and D treat a change of shape or state as a reaction. Choice B has no property data to support it.
Question 4 of 20 · Multiple Choice
Fresh milk has a mild smell. After two weeks in the refrigerator, the milk has a strong sour odor. What is the best conclusion from the odor alone?
Answer: C
Odor is one of the six properties, and a new odor suggests a new substance (bacteria change the sugar in milk into an acid). One property is weaker evidence than several, so more tests would make the claim stronger. Choice A is wrong because odor is a property. Choice D has no data to support it.
Question 5 of 20 · Multiple Choice
Liquid X does not burn, and liquid Y does not burn. After they are mixed, a liquid separates out that catches fire easily. Which property gives the evidence, and what does it show?
Answer: A
Neither starting liquid burns, but the new liquid does, so its flammability is new: a new substance formed. Choice C names the right property but the wrong conclusion, since mixing alone cannot make a liquid that burns out of two that do not. Choices B and D name properties that were not given.
Question 6 of 20 · Multiple Choice
Copper has a density of 8.96 g/cm³ and melts at 1,085 °C. After copper is heated in air, a black powder forms with a density of 6.3 g/cm³ that melts at 1,326 °C. Which conclusion do the data support?
Answer: D
Two properties, density and melting point, are clearly different, so the black powder is a new substance (copper oxide). Choice B uses color, which is not one of the six properties analyzed here. Choice C uses the state, and choice A guesses about makeup without property evidence.
Question 7 of 20 · Multiple Choice
A solid is dissolved in water and the water is left to evaporate. Which result would show that NO reaction happened?
Answer: C
Matching density and melting point mean the recovered solid is the same substance, so dissolving did not make anything new. Choices A, B and D each describe a changed property (odor, solubility, flammability), which would be evidence of a new substance.
Question 8 of 20 · Multiple Choice
Vegetable oil is shaken with water and the two liquids separate. A 30.0 mL sample of the top layer has a mass of 27.6 g. Reference densities: water 1.00 g/mL, vegetable oil 0.92 g/mL, rubbing alcohol 0.79 g/mL, corn syrup 1.38 g/mL. What is the top layer?
Answer: D
27.6 ÷ 30.0 = 0.92 g/mL, which matches vegetable oil, so the oil is unchanged and no new substance formed. Choice B assumes the water stays on top, but water is denser than oil. Choice C would need 0.79 g/mL (23.7 g). Corn syrup was never added.
Question 9 of 20 · Multiple Choice
Before a change, a liquid has a density of 1.00 g/mL. After, a liquid has a density of 1.01 g/mL, the same boiling point and the same odor. What is the best conclusion?
Answer: B
A difference of 0.01 g/mL is about the size of a measuring error with classroom tools, and the boiling point and odor did not change, so there is no evidence of a new substance. Choice A trusts a tiny difference over two properties that match. Choice C reverses the logic: unchanged properties point to the same substance.
Question 10 of 20 · Multiple Choice
Before an interaction, liquid V has a sharp odor and boils at 118 °C, and solid W has no odor. Afterward, a liquid is recovered that has a sharp odor and boils at 118 °C. What do the data show?
Answer: D
The recovered liquid matches V in both odor and boiling point, so it is most likely V that did not react. Choice C compares it with only one starting substance, W, and forgets to check V. Choice A treats any odor as new. Choice B has no data: nothing shows W's melting point.
Question 11 of 20 · Multiple Choice
Solid R dissolves in water, and liquid S mixes with water. When R is added to S, a solid forms that does not dissolve even in a large amount of fresh water. What does the solubility evidence show?
Answer: A
The new solid's solubility differs from both starting substances, so it is a new substance. Choice C ignores that R dissolves while the new solid does not. Choice B is false, since R itself dissolves. Choice D is wrong because solubility is one of the six properties.
Question 12 of 20 · Multiple Choice
Which data show that NO new substance formed?
Answer: A
Grinding changes only the size of the pieces; the melting point and solubility are the same, so it is still salt. Choices B, C and D each describe a new property (odor, density, flammability), which is evidence of a new substance.
Question 13 of 20 · Multiple Choice
A solid has a mass of 15.6 g. When it is placed in a graduated cylinder, the water level rises from 20.0 mL to 22.0 mL. What is the density of the solid?
Answer: B
The volume is the rise, 22.0 - 20.0 = 2.0 mL = 2.0 cm³, so density = 15.6 ÷ 2.0 = 7.8 g/cm³. Choice A divides by the final reading, 22.0 mL. Choice C divides by the starting reading, 20.0 mL. Choice D divides the volume by the mass.
Question 14 of 20 · Multiple Choice
Before mixing, solid J has a density of 1.3 g/cm³ and melts at 160 °C. After mixing it with a liquid and drying, a sample of solid has a mass of 3.9 g and a volume of 3.0 cm³ and melts at 160 °C. What is the sample's density, and what does it show?
Answer: A
Density = 3.9 ÷ 3.0 = 1.3 g/cm³. Both the density and the melting point match solid J, so the sample is still J and no new substance formed. Choice B divides volume by mass (3.0 ÷ 3.9) and choice D multiplies them. Choice C has the right density but the wrong conclusion.
Question 15 of 20 · Short Answer
Magnesium is a light, silvery metal. A sample of magnesium has a mass of 17.4 g and a volume of 10.0 cm³. After magnesium burns (teacher video), a sample of the white powder has a mass of 17.9 g and a volume of 5.0 cm³. Compute both densities. Do they support the claim that a reaction occurred?
Magnesium: 17.4 ÷ 10.0 = 1.74 g/cm³. Powder: 17.9 ÷ 5.0 = 3.58 g/cm³. The powder's density is about twice that of magnesium, so it is a different substance (magnesium oxide). Yes, the data support the claim that a chemical reaction occurred.
Question 16 of 20 · Short Answer
Plan a test, using only safe household materials, to find out whether mixing castile soap solution with salt water makes a new substance. Name two properties you would compare and what result would show a reaction.
Sample plan: wear goggles; dissolve soap in one cup of water and table salt in another; record solubility and odor of each; mix them and look for any solid; take any solid out, put it in fresh water and stir; record its solubility and odor. A solid that does not dissolve in fresh water, or a new odor, would show a new substance. If nothing new appears and the properties match the starting substances, no reaction occurred. Accept any safe plan that compares two of the six properties before and after.
Question 17 of 20 · Short Answer
Epsom salt crystals have a density of 1.68 g/cm³ and dissolve easily in water. A large spoonful is dissolved in a cup of water. The solution boils at about 100.5 °C instead of 100 °C and has a density of 1.04 g/mL. After the water evaporates, the crystals left behind have a density of 1.68 g/cm³ and dissolve easily again. Did dissolving make a new substance? Explain.
No. The solution's boiling point and density are different from pure water because it is a mixture of water and Epsom salt. When the substances are separated again, the crystals have the same density (1.68 g/cm³) and solubility as before. Properties must be compared on the separated substances, and those did not change.
Question 18 of 20 · Short Answer
Use the invented data to write a claim, evidence and reasoning response. Before: liquid G (density 1.20 g/mL, boiling point 105 °C, no odor, does not burn) and liquid H (density 1.00 g/mL, boiling point 100 °C, no odor, does not burn). After mixing, a top layer K separates: density 0.85 g/mL, boiling point 64 °C, strong odor, burns easily.
Claim: a chemical reaction occurred and K is a new substance. Evidence: K's density (0.85 g/mL) and boiling point (64 °C) differ from both G and H, it has a strong odor when neither starting liquid has one, and it burns while neither G nor H does. Reasoning: each substance has its own set of properties, so a liquid with four new properties must be a new substance.
Question 19 of 20 · Short Answer
A student mixes two liquids and sees bubbles. The student writes, "Bubbles mean a chemical reaction happened." Explain why this is not enough evidence, and name the property data that would decide the question.
Bubbles can also come from a change of state (boiling) or from a gas that was already dissolved, as when a soda bottle is opened, so they do not prove a new substance. To decide, collect the gas and the liquid left behind and compare their properties with the starting substances: for example, whether the gas burns (flammability), its odor, and the density or boiling point of the liquid. New properties would show a reaction.
Question 20 of 20 · Short Answer
Aluminum foil has a density of 2.70 g/cm³. After a reaction, a student scrapes two solid samples from the foil. Sample X: 10.8 g and 4.0 cm³. Sample Y: 11.9 g and 3.0 cm³. Compute both densities and decide which sample is a new substance.
X: 10.8 ÷ 4.0 = 2.70 g/cm³, the same as aluminum, so X is leftover aluminum. Y: 11.9 ÷ 3.0 ≈ 3.97 g/cm³, clearly different, so Y is a new substance (aluminum oxide has a density of about 3.95 g/cm³). Testing a second property, such as melting point, would make the claim stronger.
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does MS-PS1-2 mean?
MS-PS1-2 asks students to analyze data on the properties of substances before and after they interact, and decide whether a chemical reaction happened. If the substances afterward have different properties, new substances formed. The code means Middle School, Physical Science, core idea 1 (Matter and Its Interactions), performance expectation 2.
Which properties does MS-PS1-2 use?
The Assessment Boundary limits assessment to six properties: density, melting point, boiling point, solubility, flammability and odor. Each one is the same for any amount of a pure substance, so together they act like a fingerprint. Color, temperature change and bubbles can prompt a closer look, but they are not the properties this standard assesses.
What grade is MS-PS1-2 taught in?
It is a middle school standard for grades 6-8, and schools place it in whichever year holds their chemistry unit. Students need to divide decimals to compute density and read a data table. It builds on the grade 5 standards about identifying materials and mixing substances.
What is the difference between a physical change and a chemical reaction?
In a physical change, such as melting, freezing, dissolving or grinding, the substance stays the same, so its identifying properties stay the same once it is separated and back in its original state. In a chemical reaction, new substances form with new properties. The test is to compare property data before and after.
Is dissolving a chemical reaction?
Usually not. When sugar or salt dissolves, the solution has a different density and boiling point from pure water, but that is because it is a mixture. When the water evaporates, the solid left has the same properties as before. Always compare properties of the separated substances.
Are the official MS-PS1-2 example reactions safe for students to do?
Not as student labs. The Clarification Statement names burning sugar or steel wool, fat reacting with sodium hydroxide, and zinc mixed with hydrogen chloride. Burning needs an open flame, and sodium hydroxide and hydrochloric acid are corrosive, so this page uses videos and data tables for them. Students can safely do hands-on tests with household materials, such as soap and Epsom salt, with goggles on.
How do you find the density of an odd-shaped solid?
Find its mass on a balance, then find its volume by displacement: read the water level in a graduated cylinder, add the solid, and read again. The rise in milliliters is the volume in cubic centimeters. For a solid that dissolves in water, such as salt, use a liquid it does not dissolve in, such as vegetable oil.
Why should students compare more than one property?
One property can mislead. Two different substances can have nearly the same boiling point, and a small difference in density may only be a measuring error. When several properties change, compared with every starting substance, the evidence for a new substance is much stronger.
How is MS-PS1-2 usually assessed?
Students usually get a table of property data for substances before and after an interaction and must say whether a reaction occurred and which data support the claim. Some tasks ask students to compute a density first or to explain why a change such as dissolving is not a reaction. Strong answers cite specific values for at least two properties.
How does MS-PS1-2 connect to other science standards?
MS-PS1-1 gives the particle picture: a reaction rearranges atoms into new molecules or structures, which is why properties change. MS-PS1-5 shows that atoms and mass are conserved in reactions. In high school, HS-PS1-2 explains the outcome of reactions using the periodic table.
07
Related Standards
5 standards
These standards connect to MS-PS1-2: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
5-PS1-3Prerequisite
Make observations and measurements to identify materials by their properties
Lesson coming soon
5-PS1-4Prerequisite
Investigate whether mixing two or more substances makes new substances
Lesson coming soon
Alongside
MS-PS1-1Parallel
Model the atoms that make up simple molecules and extended structures
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