SME
Grade 7 Science · Problem type
Heating curve of water
Use this for “What is the temperature 30 minutes into heating the ice, and what state is it in?”
Chart
Melting point = 0 °C
Boiling point = 100 °C
Time = 4 + 16 + 20 + 108 = 148 min
At 30 min the water is at 50 °C
This is an example. Type your own values to start a new problem.
t
Time heating
example · min
T
Temperature
worked out (not typed) · °C
Formulas
T
=
the
temperature
on
the
curve
at
t
(temperature
=
the
temperature
on
the
curve
at
time
heating)
50 = the temperature on the curve at 30
Assumptions
•
Ice at −40 °C is heated at a steady rate on a hot plate.
•
While it melts or boils the temperature stays flat: the heat changes the state instead of warming it.
•
Melting takes 16 minutes here; boiling all the water away takes 108, because turning liquid into gas takes far more energy.
•
Drag the point along the curve.
Step-by-step
WE KNOW
t = 30 min (time heating)
FIND
temperature (T)
Step 1 · Find temperature (T)
Use T = the temperature on the curve at t (temperature = the temperature on the curve at time heating)
The water warms 5 °C a minute from 0 °C, starting at 20 minutes.
T
=
5
×
(30
−
20)
T
=
5
×
10
T
=
50
°C
(liquid
water,
warming)
Check
Put the numbers back in. Both sides should match.
50 = 5 × (30 − 20) ✓
Topic check
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