Sci8 Q2W6D3: Metals, Nonmetals & Metalloids - Sorting by Properties

Day 3: Metals, Nonmetals & Metalloids — Sorting by Properties

Today you will classify elements into metals, nonmetals, and metalloids using clear, test-ready evidence: conductivity, luster, malleability/brittleness, typical state, and reactivity patterns. You will connect position on the periodic table to likely behavior and practice writing short explanations that earn points on quizzes. By the end, you can justify a classification with two properties and a location clue, read simple data tables to decide a class, and explain why “borderline” elements show mixed behavior—useful in electronics and materials.

• Subject: Science 8
• Grade: 8
• Day: 3 of 4

By the end of the lesson, you will be able to:

1. Classify an element as metal, nonmetal, or metalloid using 2 properties + 1 position clue.
2. Interpret a simple data table (conductivity, luster, malleability, state) and justify the class in 3 sentences.
3. Explain why metalloids show mixed behavior and name one real-life application.

• Conductivity — ability to carry electric current or heat.
• Luster — surface shine (metallic vs. dull).
• Malleability/Brittleness — can be shaped into sheets/wires vs. breaks easily.
• Metals — usually shiny, conductive, malleable; mostly left/center of the table.
• Nonmetals — usually dull, poor conductors; many are gases at room temperature; upper right.
• Metalloids — border “staircase” elements with mixed properties; useful as semiconductors.
• Alloy — mixture of metals (or metal + other) to improve properties.

Warm-up: Answer first; check keys.

1. Where do most metals sit on the periodic table?
Show Answer
Left and center regions (including the transition block).
2. Which broad class often includes gases at room temperature?
Show Answer
Nonmetals.
3. What nickname describes elements along the staircase between metals and nonmetals?
Show Answer
Metalloids (semimetals).

How to use this section: Work through each checkpoint. You’ll see a mini-goal, guided discussion, real-life tie-in, mini-summary, and three guiding questions with hidden answers.

Checkpoint 1 — What Makes a Metal?

Mini-goal: Recall the core properties that define metals and why they matter.

Guided discussion: Most metals are solid at room temperature (except mercury). They are shiny (metallic luster), malleable (flatten into sheets), and ductile (drawn into wires). Their key feature is conductivity: free-moving electrons allow heat and electric current to pass easily. On the periodic table, metals dominate the left and center, including the transition metals. Reactivity varies—alkali metals are very reactive; some (gold, platinum) are less reactive. In compounds, metals often lose electrons to form positive ions. For test items, pair a property with a use: “Aluminum conducts and is light—good for wires and cans.”

Real-life tie-in: Buildings, vehicles, electrical cables, cookware, and coins rely on metals’ strength and conductivity.

Mini-summary: Metals: shiny, conductive, shapeable; mostly left/center; often form positive ions.

1. Name two physical properties typical of metals.
Show Answer
High conductivity; malleable/ductile; metallic luster.
2. Which room-temperature liquid metal is a common exception?
Show Answer
Mercury (Hg).
3. In compounds, do metals usually gain or lose electrons?
Show Answer
Usually lose electrons → positive ions.

Checkpoint 2 — What Makes a Nonmetal?

Mini-goal: Identify the properties of nonmetals and recognize their diversity.

Guided discussion: Nonmetals cluster on the upper right of the table. Many are gases (e.g., oxygen, nitrogen, chlorine); a few are solids (carbon, sulfur); bromine is a liquid. Compared with metals, nonmetals are poor conductors (insulators) and have dull surfaces. Solids are usually brittle—they snap rather than bend. Chemically, nonmetals tend to gain electrons in reactions with metals, forming negative ions. Their molecules can also share electrons to form covalent compounds (like water and carbon dioxide). Their diversity is a strength: life depends on nonmetals (C, H, O, N, P, S) forming complex molecules.

Real-life tie-in: Air, water, plastics, medicines, and disinfectants depend on nonmetals’ ability to form many compounds and to resist electric flow.

Mini-summary: Nonmetals: often gases, dull, brittle, poor conductors; upper right; often gain electrons.

1. Give one state of matter that is common among nonmetals at room temperature.
Show Answer
Gas (e.g., O₂, N₂, Cl₂).
2. How do solid nonmetals usually break?
Show Answer
They are brittle—snap or crumble.
3. Do nonmetals typically form positive or negative ions when reacting with metals?
Show Answer
Negative ions (they gain electrons).

Checkpoint 3 — The Staircase: What Are Metalloids?

Mini-goal: Explain why metalloids show mixed behavior and where to find them.

Guided discussion: Metalloids sit along a “staircase” boundary between metals and nonmetals. Common examples are boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te). Their properties are in-between: some shine like metals yet break like nonmetals; they usually conduct electricity poorly when cold but better when warmed or doped with a tiny amount of another element. This tunable conductivity is called semiconductivity and powers computer chips and solar cells. On tests, link position + a mixed property: “Si near the staircase; semiconductive → metalloid.”

Real-life tie-in: Phones, computers, and panels that convert sunlight to electricity depend on silicon-based semiconductors.

Mini-summary: Metalloids: staircase location; mixed properties; useful semiconductors.

1. Name two metalloids.
Show Answer
Silicon (Si), Boron (B), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te) — any two.
2. How does a semiconductor’s conductivity compare to a metal’s?
Show Answer
Lower than metals but can be increased by temperature or doping.
3. What location clue signals a metalloid?
Show Answer
On/near the staircase border between metals and nonmetals.

Checkpoint 4 — Property Tests You Can Read Fast

Mini-goal: Use quick tests—conductivity, luster, malleability/brittleness, and state—to make a justified classification.

Guided discussion: Imagine a data table for four unknown samples. Column A shows electric bulb brightness (conductivity), Column B shows surface look (shiny/dull), Column C shows hammer test (bends/breaks), Column D shows room-temperature state (solid/liquid/gas). A strong answer pairs two properties: “Bright bulb + bends → metal,” “Dull + breaks + gas → nonmetal,” “Weak bulb + shiny but breaks → metalloid.” When time is short, prioritize conductivity and malleability because together they separate metals from the other two classes quickly. Use state as extra support—gases point to nonmetals—but remember exceptions (Hg is a liquid metal; C is a solid nonmetal).

Real-life tie-in: Engineers choose wire materials by conductivity and shapeability; materials scientists choose semiconductors by controlled, in-between conductivity.

Mini-summary: On tests, cite two strong properties; use state as support; note exceptions clearly.

1. Which two tests best separate metals from others?
Show Answer
Electrical/thermal conductivity and malleability/ductility.
2. If a solid is shiny but snaps under a small bend, what class is likely?
Show Answer
Metalloid (mixed behavior) or brittle nonmetal—use conductivity to decide.
3. Why is “state” alone not enough for classification?
Show Answer
There are exceptions (e.g., Hg is a liquid metal; C is a solid nonmetal).

Checkpoint 5 — Position Clues that Strengthen Your Claim

Mini-goal: Combine properties with periodic table location for a high-scoring justification.

Guided discussion: After testing, use the map. If the symbol is on the left/center, a “metal” claim gains support; if it is on the upper right, “nonmetal” strengthens; if it touches the staircase, “metalloid” becomes likely. Add group hints: Group 1 and 2 are metals with strong conductivity; Group 17 includes reactive nonmetals; the transition block in the center contains metals with high strength and often bright colors in compounds. Your explanation should read like: “Sample X is a metal because it conducts electricity well and bends into wire; it also lies in the left-center of the periodic table.” Notice how the position is extra evidence, not the only proof.

Real-life tie-in: Safety sheets and product labels often list element symbols; knowing the region helps you predict behavior before you ever touch the material.

Mini-summary: State two properties first, then add a location clue to secure the mark.

1. Which side of the table supports a “metal” claim?
Show Answer
Left/center (including the transition block).
2. What region supports a “nonmetal” claim?
Show Answer
Upper right.
3. Where are metalloids usually found?
Show Answer
Along the staircase boundary between metals and nonmetals.

Checkpoint 6 — From Properties to Products

Mini-goal: Link class to common uses and materials choices.

Guided discussion: Metals are chosen for wires, frames, cookware, and tools because they conduct and can be shaped. Alloys (steel, brass) tune strength and resistance to corrosion. Nonmetals are chosen for insulation, disinfectants, fuels, and life molecules because they resist flow of charge and form covalent structures. Metalloids are chosen for chips, solar cells, and sensors because their conductivity can be controlled. When test questions ask “Why is material X used for Y?” answer with class → property → use: “Copper is a metal; high conductivity → ideal for wiring.”

Real-life tie-in: Choosing the wrong class wastes money or risks safety, like using a brittle nonmetal where a malleable metal is needed.

Mini-summary: Class predicts use: metals (conduct/shape), nonmetals (insulate/bond covalently), metalloids (semiconduct).

1. Which class best fits a cooking pan? Why?
Show Answer
Metal—good heat conduction and strength.
2. Which class best fits a computer chip? Why?
Show Answer
Metalloid—semiconducting behavior (e.g., silicon).
3. Which class best fits a greenhouse gas molecule, and why is this not a metal use?
Show Answer
Nonmetal—molecular compounds (e.g., CO₂) form from nonmetals sharing electrons.

1. Classify & justify: Aluminum foil.
   Show Answer

   Metal — conducts heat/electricity, malleable (sheets), left/center location.
2. Data read: Dull, brittle solid; poor conductor.
   Show Answer

   Nonmetal — classic properties.
3. Border case: Shiny, brittle, weak conductor; staircase location.
   Show Answer

   Metalloid — e.g., Si or Ge behavior.
4. Use logic: Material for solar cells.
   Show Answer

   Metalloid (silicon) — semiconductivity.
5. Counterexample: A liquid metal at room temp.
   Show Answer

   Mercury (Hg) — still a metal despite being liquid.

1. Give a two-property + one-location justification that carbon is a nonmetal.
   Show Answer

   Dull/brittle solid; poor conductor; upper-right region (Group 14 nonmetal).
2. Choose a metal and write one use explained by conductivity or malleability.
   Show Answer

   Example: Copper—wires due to excellent conductivity.
3. Explain why silicon is preferred over aluminum for chips.
   Show Answer

   Si is a semiconductor (tunable conductivity); Al is a good metal conductor but not controllable for logic.
4. From data: “bright bulb, bends easily.” Classify.
   Show Answer

   Metal.
5. From data: “dim bulb, shiny, snaps when bent.” Classify.
   Show Answer

   Metalloid.
6. From data: “no glow, dull, gas.” Classify.
   Show Answer

   Nonmetal.
7. Name two metalloids and one device using them.
   Show Answer

   Si, Ge — used in diodes, transistors, solar cells.
8. Why do metals often form positive ions?
   Show Answer

   They tend to lose outer electrons during bonding.
9. State one exception you must remember about “state” when classifying.
   Show Answer

   Mercury is a liquid metal; bromine is a liquid nonmetal.
10. Create a one-sentence rule of thumb to classify quickly.
    Show Answer

    “Good conductor + bends → metal; poor conductor + brittle → nonmetal; in-between + staircase → metalloid.”

1. Multiple choice: Which is most likely a metal?
   A) dull, brittle, gas B) shiny, bends, bright bulb C) dull, breaks, dim bulb D) shiny, brittle, dim bulb
   Show Answer

   B.
2. True/False: All metals are solids at room temperature.
   Show Answer

   False (Hg is liquid).
3. Fill-in: Elements with mixed behavior near the staircase are called ______.
   Show Answer

   Metalloids.
4. Short answer: Give two properties that separate nonmetals from metals.
   Show Answer

   Poor conductivity and brittleness/dullness (vs. malleable, shiny metals).
5. Multiple choice: Best material for high-speed wiring?
   A) sulfur B) silicon C) copper D) phosphorus
   Show Answer

   C (metal with high conductivity).
6. True/False: A metalloid always has higher conductivity than a metal.
   Show Answer

   False—usually lower; but tunable.
7. Fill-in: Many nonmetals form ______ compounds by sharing electrons.
   Show Answer

   Covalent.
8. Short answer: Why is silicon used in solar cells?
   Show Answer

   Semiconductivity allows controlled conversion of light to electricity.
9. Multiple choice: Which pair are both nonmetals?
   A) C & S B) Na & S C) Al & Si D) Fe & Cl
   Show Answer

   A.
10. True/False: Shiny appearance alone proves a sample is a metal.
    Show Answer

    False—check conductivity and malleability too.
11. Fill-in: Metals tend to form ______ ions in reactions with nonmetals.
    Show Answer

    Positive.
12. Short answer: Name one metalloid and one property that is “in between.”
Show Answer
Germanium—shiny but brittle; moderate, tunable conductivity.
13. Multiple choice: Which evidence best supports “nonmetal” for sulfur?
    A) bends into wire B) bright bulb C) brittle and dull D) strong magnetism
    Show Answer

    C.
14. True/False: The staircase location guarantees metalloid behavior for every element touching it.
Show Answer
False—there are exceptions; use properties too.
15. Fill-in: Pair class → use: Metal → wires; Nonmetal → ______; Metalloid → chips.
Show Answer
Insulators (or molecular substances like disinfectants, plastics).

1. Device Detective: List 5 home devices and match each to a material class that makes it work.
2. Alloy Lab (Paper): Compare steel vs. pure iron—benefits, risks, typical uses (80–120 words).
3. Semiconductor Story: In 100 words, explain how doping changes silicon’s conductivity.
4. Property Poster: Create a quick-reference chart: tests → class decision rules (use #2563eb accents).
5. Local Materials Walk: Photograph places or objects only and label which class their key material belongs to.

Notebook Task: Choose one metal, one nonmetal, and one metalloid you meet in daily life. In 6–8 sentences, justify each classification with two properties and one location clue, then explain how class guided its use. End with one rule of thumb you will use on tests.

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