PRE-AP CHEMISTRY
Day 2 — Developing a Model of Matter
Lesson 1.2.A + Classification of Matter
Hsinchu County American School · Science Department
IN THE NEWS
Today's Hook
“From Curbside to Countertop: Consumer Recycling
Goes High-Tech”
2026 consumer technology roundup
AI-powered smart bins now use cameras and sensors to identify and separate
plastics, paper, and metal at high speed inside people's homes — before the
material ever reaches the curb.
IMAGE PLACEHOLDER
DISCUSS
These machines have milliseconds to figure out what something is made of before sorting
it. What clues do YOU use to figure out what a material is made of — and could you sort
a mixed pile of classroom objects the same way?
Suggested image: photo of a smart recycling bin / AI sorting
system, or a curbside recycling bin sorted into materials
Today's Plan
01
Hook & Discussion
7 min
02
Connect to Day 1
3 min
03
New Vocabulary
5 min
04
Mini-Lecture: Classifying Matter
15 min
05
POGIL: Classification of Matter
30 min
06
Handout 1.2.A: Developing a Model of Matter
25 min
07
Debrief & Exit Ticket
5 min
VOCABULARY
New Words & Terminology
Pure substance
Fixed composition — always made of the same particles (element or compound)
Element
A pure substance that cannot be broken down into simpler substances
Compound
Two or more elements chemically combined in a fixed ratio
Mixture
Two or more substances physically combined — can be separated
Homogeneous
Uniform throughout — you can't see the individual parts
Heterogeneous
Non-uniform — individual parts are visibly distinguishable
Particle diagram
A drawing using dots/circles to represent atoms or molecules
CONTENT DELIVERY
The Classification Tree of Matter
Matter splits into Pure Substances and Mixtures
Pure substances split into Elements and Compounds
Mixtures split into Homogeneous and Heterogeneous
IMAGE PLACEHOLDER
Example: saltwater = homogeneous mixture
Example: sand + water = heterogeneous mixture
Suggested image: classification-of-matter tree diagram (matter → pure substances/mixtures →
element/compound, homogeneous/heterogeneous)
CONTENT DELIVERY
Reading a Particle Diagram
Each colored dot = one type of atom
Dots touching/bonded = a compound (fixed ratio)
Same-color dots only = an element
IMAGE PLACEHOLDER
Different substances not bonded, physically mixed = a mixture
We'll use this convention all year — get comfortable with it now
Suggested image: example particle diagram: element (one color of dots) vs.
compound (two colors bonded) vs. mixture (two colors unbonded, mixed)
HANDS-ON
Today's Activities
1. POGIL — Classification of Matter
2. Handout 1.2.A — Developing a Model of Matter
~30 min
~25 min
• Examine each sample/image with your partner
• Observe the demonstration
• Sort using the classification tree
• Draw a particle-level model to explain it
• Justify each placement in writing
• Trade diagrams with another group for feedback
BEFORE YOU GO
Exit Ticket
INDIVIDUAL WRITTEN RESPONSE
Classify each as element, compound, homogeneous mixture, or heterogeneous mixture:
(1) oxygen gas (2) trail mix (3) carbon dioxide (4) apple juice (no pulp)
Justify one answer in a full sentence.
See you next class!
Day 3 — Applying the Shared Model of Matter