Key relationship
V=1 kg/ρ(T); maximum freshwater density occurs near 3.986°C.
Physics · Class 11
Explore water near 4°C
Water contracts when warmed from 0°C to about 4°C and expands when warmed further. Its density maximum explains why lakes can retain denser liquid below a colder surface.
Open the interactive experiment →Explore water near 4°C
நீர் 0°C முதல் 4°C வரை சூடாகும்போது சுருங்கும்; 4°Cக்கு மேல் சூடாகும்போது விரியும். 4°C அருகே அடர்த்தி அதிகம்.
Key notes, relationships and model limits
Remember
Water contracts when warmed from 0°C to about 4°C and expands when warmed further. Its density maximum explains why lakes can retain denser liquid below a colder surface.
Common trap
Water does not expand monotonically throughout the 0–10°C interval.
Model limits
Empirical freshwater density approximation over 0–20°C near atmospheric pressure; no ice, salinity or pressure effects. The small volume change is physical, so inspect the readout.
What you will learn
Recognize the anomalous expansion region and link density to volume.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
The model gives density about 999.868 kg/m³ at 0°C and nearly 1000 kg/m³ at 4°C. One kilogram therefore occupies slightly less volume at 4°C.
Why this matters
The model connects explore water near 4°c with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Where is liquid freshwater volume smallest for a fixed mass?
- At 0°C
- Near 4°C
- At 20°C
Read the explanation
The density is largest there, and volume at fixed mass is inversely proportional to density.
Course connection: Class XI Chapter 10. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.