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Grade 6 (age 11-12)

grade 6 Physical & Chemical Changes

Physical & Chemical Changes

Changes in matter come in two kinds: physical and chemical. A physical change alters only the shape or state while the substance stays the same, like folding paper or water freezing. A chemical change makes a completely new substance, like wood burning or iron rusting. Tap the physical and chemical buttons and the two kinds come into view side by side.

Two Kinds of Change

💡 What is Physical Change?
①Only shape or state changes; substance stays the same
②Ice melts into water — both are still H₂O
③Tearing paper still leaves paper
④Sugar dissolved in water is still sugar

Physical vs Chemical

Comparison

Physical vs Chemical Change
CategoryPhysicalChemical
PropertiesUnchangedCompletely different
Reversible?Yes (water→ice)No (ash→paper ✕)
New substanceNoYes
Example 1Ice meltsPaper burns
Example 2Sugar dissolvesIron rusts
Example 3Tearing paperCooking egg

Find Changes Around You

🏠 Physical Changes Around Us
①Laundry drying (water → vapor)
②Steam on a window (vapor → water)
③Salt dissolving in water
④Beads breaking
⑤Only shape/state changes; substance stays the same
🔥 Chemical Changes Around Us
①Food spoiling (decomposition by bacteria)
②Iron rusting (Fe + O₂ → iron oxide)
③Candle burning shorter
④Rice cake browning when toasted
⑤A new substance forms, different from the original

Summary

Physical Change
Shape/state changes → substance properties unchanged
Reversible (ice ↔ water ↔ vapor)
Chemical Change
Substance itself changes → new substance formed
Irreversible (paper→ash, iron→rust)
🎯 Key Points
①Physical: only shape/state changes (same substance)
②Chemical: substance itself changes
③Physical change is reversible
④Chemical change is not reversible
⑤Test: "Is a new substance formed?"

Examples and Unit Test

Example 1
Is ice melting into water a physical change or a chemical change, and why?
1
Ice and water are the same substance (H₂O); only the shape and state change.
2
No new substance forms and it can be reversed, so it is a physical change.
▸ Physical change (ice and water are both H₂O; no new substance)
A physical change alters only shape or state, not the substance. Ice ↔ water ↔ vapor.
Example 2
Burning paper makes ash and carbon dioxide and cannot be turned back into paper. What change is this, and what is the test?
1
When paper burns, new substances that were not there before (ash, carbon dioxide) form.
2
A new substance forms and it cannot be reversed, so it is a chemical change.
▸ Chemical change / test: did a new substance form?
The test is whether a new substance formed. A chemical change cannot be reversed.
Unit-test style
Which statement about changes in matter is correct?
①Sugar dissolving in water is a chemical change
②Paper burning into ash is a chemical change
③A physical change cannot be reversed
④No new substance forms in a chemical change
⑤Iron rusting is a physical change
▸ ② Paper burning into ash is a chemical change
1
Burning paper forms new substances (ash and carbon dioxide), so it is a chemical change.
2
Sugar dissolving is a physical change (①), physical changes can be reversed (③), chemical changes form new substances (④), and iron rusting is a chemical change (⑤).
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