Classifying Matter by Its Properties

Overview

This is a self-contained, no-technology substitute packet in which students explore how physical properties — density, magnetism, electrical and thermal conductivity, solubility, state, and luster — are used to identify and classify matter, and how a pure substance differs from a mixture. Working alone with a pencil, students read a short original passage, study an original particle-model diagram, and analyze an original data table of five "unknown" samples that have already been measured. They sort the samples, decide which property distinguishes look-alikes, tell observation from inference, and write an evidence-based explanation. No lab materials and no hazards are involved.

Accessible version of the student activity

The full student activity is reproduced below in plain, screen-reader-friendly HTML. It reflows on phones and at 200% zoom. Write your answers on the printed packet.

Start (5 minutes) — Notice & Wonder

1. Imagine a bin holding a copper penny, a rubber eraser, a glass marble, and a paper clip. Write one thing you notice that could help you sort them into groups, and one thing you wonder about telling them apart.
2. A property is a trait you can observe or measure. Name two properties you could use to sort a pile of coins, buttons, and beads into groups.

Build (5–10 minutes) — Read the science

Matter is anything that has mass and takes up space. Every kind of matter has physical properties — traits you can observe or measure without changing what the substance is made of. We use them to identify and sort, or classify, matter. Useful physical properties include:

• Density — how much mass is packed into a certain volume (mass ÷ volume). A pure substance has the same density no matter how big the piece is.
• Magnetism — whether a magnet is attracted to it (iron and steel are; copper, aluminum, and glass are not).
• Electrical and thermal conductivity — how easily electricity or heat passes through (most metals conduct well; plastic, wood, and glass do not).
• Solubility — whether it dissolves in water (like salt) or does not (like sand).
• State — solid, liquid, or gas at room temperature.
• Luster — how shiny it is (metals are usually shiny; nonmetals often dull).

Matter can also be sorted by what it is made of. A pure substance is made of only one kind of particle throughout, so its properties are the same everywhere. A mixture combines two or more substances that are physically blended but not chemically joined; the parts keep their own properties and can often be separated using a property — for example, a magnet can pull iron out of sand. Note: a property is a clue about a substance, not the substance itself.

Word bank

physical property

a trait you can observe or measure without changing what the matter is made of.

density

the amount of mass in a given volume (mass ÷ volume).

conductivity

how easily heat or electricity passes through a material.

solubility

whether a material dissolves in a liquid such as water.

pure substance

matter made of only one kind of particle throughout.

mixture

two or more substances physically blended but not chemically joined.

3. Using Figure 1, explain in one sentence how you can tell the mixture apart from the pure substance just by looking at the particles.

Apply (20–25 minutes) — Use the data

A lab team measured five unknown solid samples and recorded their physical properties. All samples were solid at room temperature.

4. Classify each sample as M (metal) or N (nonmetal) — metals are usually shiny and conduct electricity — for samples W, X, Y, Z, and Q, then name the one property you relied on most.
5. Samples X and Z share density, magnetism, conductivity, and luster. Which single property in the table tells them apart, and how?
6. Observation vs. inference — mark O (directly measured/seen) or I (a reasoned conclusion):
   • a) Sample W has a density of 7.9 g/cm³.
   • b) A magnet sticks to Sample W.
   • c) Sample W is probably iron or steel because it is magnetic and shiny.
   • d) Sample X is not a metal because it is dull and does not conduct.
7. W and Y are both shiny metals that conduct electricity. Name one property from Table 1 that could tell W from Y, and explain how you would use it.
8. A scientist grinds up part of Sample Z and finds different specks dissolve at different rates and a few dark grains can be pulled out with a magnet. Is this ground-up Z best described as a pure substance or a mixture? Justify with the evidence.

Explain (5–10 minutes) — Claim, Evidence, Reasoning

Question 9. A student claims, "Sample W and Sample Q are the same metal." Using Table 1, decide whether the data support or do not support that claim. Write a claim, back it with two pieces of evidence from the table, and explain your reasoning.

Sentence stems you may use: "The data do / do not support the idea that…"; "One piece of evidence is… (from Table 1)."; "A second piece of evidence is…"; "This matters because a pure substance has the same properties everywhere, so…"

Close (5 minutes) — ACE

• Articulate: explain one physical property (density, magnetism, conductivity, solubility, state, or luster) in your own words.
• Connect: point to one row of Table 1 where that property helped you sort a sample.
• Extend: give a new example of using that property to sort or identify something in everyday life.

Continue (optional, ~15 minutes) — Early finisher

Design a step-by-step plan to separate a stirred-together mixture of salt, sand, and iron filings, using a different physical property at each step (magnetism, solubility, filtering). Name the property at each step, then predict which material comes out first and explain why.

Turn in

Hand in the whole packet with your name, class period, and date, with questions 1–9 and the ACE box answered. Include the optional plan if you did it.