Matter Shift Slides
Science Investigation • Grade 6-8 Chemistry
Module 03 • Transformations of Matter
MATTER SHIFT
Mastering Physical vs. Chemical Changes at the Macro and Atomic Levels
Particle Models
Arrangements & Bonds
Reaction Evidence
4 Observable Clues
Mass Conserved
Every Atom Accounted For
Foundational Concept
What Happens When Matter Changes?
Slide 02
PHYSICAL CHANGE
Form Changes, Identity Remains
The substance may look different in shape, state, or size, but its fundamental chemical formula is untouched.
Key Test: Are the original molecules still present? YES!
CHEMICAL CHANGE
Bonds Break, New Identity Forms
Chemical bonds shatter and atoms regroup. Brand-new substances emerge with completely different properties.
Key Test: Was an entirely new substance produced? YES!
The Diagnostic Question: Did the change merely dress up the original substance, or build a new one?
Deep Dive • Part 1
Physical Changes: Same Molecules
Slide 03
Phase Changes
Melting, freezing, boiling, condensing, sublimating. Only thermal kinetic energy and particle spacing change!
H2O (s) → H2O (l) → H2O (g)
Shape & Size
Cutting, shredding, tearing, crushing, grinding. Mass and molecules are conserved; only geometry alters.
Crushed soda can • Torn paper
Dissolving & Mixtures
Salt or sugar dissolving into water. Solute particles disperse evenly among solvent particles without reacting.
Reversible via evaporation!
Key Takeaway: Physical changes are frequently reversible because no atomic bonds were broken!
Everyday Science
Physical Changes in Action
Slide 04
Metal Recycling
Aluminum cans are shredded, compacted, melted into liquid ingots, and rolled into sheets.
Atomic State: 100% pure Al atoms throughout the entire process!
Culinary Prep
Chopping onions, grinding coffee beans, melting butter, whipping cream into peaks.
Atomic State: Particle sizes and states shift; chemical nutrients stay identical.
Frost Wedging
Water seeps into rock crevices, expands upon freezing, and shatters boulders into gravel.
Atomic State: Rock minerals are fractured mechanically with zero chemical decay.
Observation: In each scenario, matter changed shape, phase, or distribution without changing identity.
Deep Dive • Part 2
Chemical Changes: Atoms Rearrange
Slide 05
The Molecular Mechanism of a Reaction
During a chemical reaction, existing chemical bonds between atoms are severed, atoms reorganize, and new chemical bonds form. The resulting substance possesses distinct chemical and physical properties.
1. Reactants
Iron (Fe) + Oxygen (O2)
Shiny silver metal + invisible odorless gas
2. Chemical Bond Shift
→ Electrons Shared & Transferred →
Bonds break & new bonds forge
3. New Product
Rust (Fe2O3)
Brittle, reddish-brown, non-conductive solid
Irreversibility Principle: Chemical changes cannot be undone by simple physical acts like filtering or cooling!
Observable Clues
4 Signs of a Chemical Reaction
Slide 06
1. Gas Production
Bubbles, fizzing, or smoke without boiling. A new gaseous molecule is created!
Example: Vinegar + Baking Soda → CO2
2. Unexpected Color Shift
A spontaneous, dramatic change in color due to different electron absorption.
Example: Sliced apples turning brown; rust
3. Temperature or Light Shift
Energy released (exothermic: flames, warmth) or absorbed (endothermic: sudden cold).
Example: Burning campfire; chemical cold packs
4. Precipitate Formation
Two transparent liquids mix and create an insoluble solid that clouds the solution.
Example: Lead nitrate + potassium iodide → yellow solid
Critical Scientist Check: Boiling water bubbles, but it is physical (heat source applied). True reaction gas appears spontaneously!
Atomic Blueprint
Particle-Level Comparison
Slide 07
Physical: Ice Melting Bonds Preserved
Solid Ice Lattice
H2O
H2O
H2O
→
Liquid Water Flow
H2O
H2O
Molecules spread apart and roll over one another, but each molecule remains one Oxygen atom covalently bonded to two Hydrogen atoms.
Chemical: Electrolysis Bonds Shattered
2 H2O Molecules
→
2 H2 + 1 O2 Gases
Electric current fractures intramolecular bonds! Hydrogen atoms pair into H2 gas and Oxygen atoms pair into O2 gas.
Molecular Verdict: Physical = changes spacing & motion. Chemical = reorganizes atomic attachments.
Universal Scientific Law
Conservation of Matter
Slide 08
Mass of Reactants = Mass of Products
No Atoms Lost • No Atoms Created
The Apparent Mystery
Burning a 10 kg Wooden Log
After the fire dies down, the pile of ash weighs only 0.5 kg. Did 9.5 kg of matter vanish from the universe?
The Atomic Reality
Matter Escaped into the Air!
The missing 9.5 kg transformed into carbon dioxide gas, water vapor, and particulate smoke carried into the atmosphere!
In a Closed System: If the log and oxygen are sealed in a glass chamber, total mass before fire = total mass after fire!
Core Rule: Atoms are immortal in everyday chemical and physical changes—they merely trade partners!
Everyday Science
Chemical Changes in Nature & Food
Slide 09
Maillard Reaction
Heat fuses amino acids and sugars in dough, synthesizing hundreds of aromatic flavor molecules.
Permanent: A baked loaf cannot be separated back into raw eggs and flour!
Acid Precipitation
Atmospheric nitric and sulfuric acids react with calcium carbonate in limestone monuments.
Permanent: Solid rock dissolves into soluble calcium ions and CO2 gas.
Copper Patina
Atmospheric oxygen, water, and CO2 react with copper metal over decades.
Permanent: Shiny copper transforms into a protective green mineral shell.
Key Connection: Chemical reactions power our bodies, shape landscapes, and cook our food!
Diagnostic Guide
Physical vs. Chemical Decision Matrix
Slide 10
Feature Under Test
Physical Change
Chemical Change
Substance Identity
Unchanged (Original molecules remain)
New substance formed
Chemical Bonds
Intact (Only spacing/speed changes)
Broken & reformed
Reversibility
Usually straightforward (melt/freeze)
Difficult or impossible physically
Observable Evidence
Change in phase, size, or shape
Gas, color change, heat/light, precipitate
Golden Rule: If you can still extract the starting material without a chemical reaction, it is physical!
Interactive Diagnostic
Classroom Challenge: Call the Shift!
Slide 11
Case 1 • Snap Glowstick
You bend a plastic glowstick, crack the vial, and it glows brightly in the dark.
Observable Clue: Intense production of light energy with no heat.
Answer: Chemical! Chemiluminescent reaction between hydrogen peroxide and phenyl oxalate ester.
Case 2 • Sweet Iced Tea
Granulated white sugar is stirred into warm tea until it completely vanishes.
Observable Clue: The solid crystals disappear, but the liquid tastes sweet.
Answer: Physical! Sugar molecules (sucrose) dispersed among water molecules; no bonds broken.
Case 3 • Effervescent Tablet
An antacid tablet dropped into water roars with fizzing bubbles and cools the glass.
Observable Clue: Rapid bubbling without heat, plus temperature drop.
Answer: Chemical! Citric acid and sodium bicarbonate react to create carbon dioxide gas!
Debrief Question: How does distinguishing physical from chemical changes protect engineers and consumers?
Essential Takeaways
The Master Principles
Slide 12
1. Molecule Identity is the Dividing Line
If molecular identity is preserved, the change is physical. If atoms reorganize into new molecules with distinct properties, it is chemical.
2. Trust Observable Evidence
Look for the 4 core signs of chemical change: gas bubbling, unexpected color shift, temperature/light change, and precipitate formation.
3. Matter is Always Conserved
In every physical and chemical change in the universe, mass remains constant. Atoms are rearranged, never created or destroyed!
Next Step: Prepare your lab notebooks for our station-based transformation experiment!
