Temperature and its Measurement · Lesson 4 of 5
Measuring Water and Air Temperature
“Apply careful thermometer reading to water, a room and daily weather records.”
• Set up and read a laboratory thermometer correctly in warm water. • Explain why the bulb position, eye position and timing affect a reading. • Interpret repeated readings during melting and boiling and compare classmates’ results. • Record and analyse maximum and minimum air temperatures over several days. • Compare room and water readings in a sustained investigation.
Read the temperature of warm water
Put comfortably warm water in a beaker and lower a laboratory thermometer until its bulb is surrounded by water. Keep it upright and clear of the beaker’s bottom and sides. Watch the liquid column rise and wait until it stops moving before recording the top of the column. Read at eye level while the bulb remains in the water. The position of the column can change when the thermometer is lifted into cooler air.
Activity 7.5 asks students to compare their warm-water readings. If your values differ, do not immediately assume one thermometer is broken. Check whether you used the same water, waited for a steady column, kept the bulb clear of the beaker, read at eye level, and measured before the water cooled appreciably.
Problem
A student notes 42 °C while the bulb is in warm water. After lifting the thermometer, the liquid falls toward 30 °C. Which value belongs to the water?
- 1.The bulb was in contact with the water when the 42 °C reading was taken.
- 2.After removal the thermometer began responding to its new surroundings.
- 3.Record the steady in-water reading, 42 °C, assuming the instrument was used and read correctly.
The ice and boiling-water demonstration uses hot equipment. Observe from a safe distance under the teacher’s supervision; do not touch the apparatus.
Observe ice and boiling water
The chapter asks students to observe thermometers in crushed ice and in boiling water, then read them again after a while. Ice can remain at a steady temperature while it melts; boiling water can also show a steady temperature while it boils. These observations prepare a question about what a substance is doing even though its thermometer reading is staying steady. Record the values you actually see instead of assuming that every place produces an identical boiling-water number.
In Shillong, the chapter’s five readings of boiling water range from 97.8 °C to 98.1 °C. They cluster near 98 °C. Slight differences among students may arise because an instrument was held differently, the level was read from a different eye position, or the column had not settled. The table supports comparing recorded results and checking the method; it does not make 98 °C a universal boiling-water reading.
| Student | Boiling-water reading (°C) |
|---|---|
| Phiban | 97.8 |
| Shemphang | 98.0 |
| Onestar | 97.9 |
| Kloi | 98.0 |
| Bandarisha | 98.1 |
Problem
Five students record 97.8, 98.0, 97.9, 98.0 and 98.1 °C for the same boiling-water setup. What should you notice?
- 1.The lowest is 97.8 °C and highest is 98.1 °C.
- 2.The difference is 98.1 − 97.8 = 0.3 °C; the readings are close but not identical.
- 3.Discuss measurement method and reading before concluding that every student observed a different physical event.
Measure the air around us
A room thermometer hung in a laboratory, clinic or hospital provides an approximate room-temperature reading. Weather reports usually list the day’s maximum and minimum air temperatures. The maximum is the highest reported value for that day; the minimum is the lowest. These are air measurements, not body temperatures and not necessarily the temperature of water sitting in the room.
The highest air-temperature reading reported for a stated day and place.
The lowest air-temperature reading reported for a stated day and place.
Record the maximum and minimum for the same place over ten successive days, noting the date and unit each time. Compare days instead of judging a season from one reading. The values usually change because weather depends on several factors. In general the chapter notes rising temperatures as summer approaches and falling temperatures toward winter.
| Date | Maximum air temperature (°C) | Minimum air temperature (°C) |
|---|---|---|
| Day 1 | Record from report | Record from report |
| Day 2 | Record from report | Record from report |
| Day 3 | Record from report | Record from report |
Problem
One day has a maximum of 29 °C and a minimum of 17 °C. What can we conclude?
- 1.The reported highest air temperature is 29 °C.
- 2.The reported lowest is 17 °C.
- 3.The spread between these reported values is 29 − 17 = 12 °C. This does not say the air stayed at either value all day.
Weather stations monitor air temperature with other weather information to help make forecasts. Anna Mani, an Indian scientist, designed and built many weather-measuring instruments and also studied wind and solar energy. Her work is a reminder that accurate readings depend on reliable instruments as well as careful observers.
Compare water with its surroundings
For a longer classroom investigation, hang a room thermometer and place a beaker of water nearby with a laboratory thermometer positioned correctly in it. Take readings in the first period, at lunch and in the last period, and repeat over two weeks. The two readings answer different questions: one concerns air, the other water. Record both with their times before looking for patterns; do not assume that nearby things must always have identical readings.
| Day and time | Room air (°C) | Beaker water (°C) | Observation |
|---|---|---|---|
| Day 1, first period | Record | Record | Note conditions |
| Day 1, lunch | Record | Record | Note conditions |
| Day 1, last period | Record | Record | Note conditions |
Quiz
When should a liquid-column laboratory thermometer be read in a beaker of water?
Which setup is correct?
What did repeated observation of ice while melting and water while boiling show in the chapter?
In the Shillong table, what is the spread between 97.8 °C and 98.1 °C?
A weather report lists 32 °C maximum and 21 °C minimum. What does maximum mean here?
Why should the room and beaker thermometers in the classroom investigation be recorded separately?
Practice Problems
- Sketch a correctly positioned laboratory thermometer in a beaker and label three precautions for obtaining a reading.
- Describe the likely change in the liquid column after a thermometer is removed from warm water and explain when to record the water temperature.
- Use the five Shillong boiling-water readings to find the lowest, highest and spread; give two possible reasons readings might differ.
- Explain what to observe when checking crushed ice and boiling water twice, and state the safety requirement.
- Create a ten-day record template for maximum and minimum air temperatures and write two questions it could answer.
- Design a table for comparing classroom air and beaker water three times daily over two weeks. Explain what a persistent difference would tell you about the two measurements.
Key Takeaways
• Keep the laboratory bulb immersed, upright and clear of the beaker; read the settled column at eye level. • Melting ice and boiling water can show steady readings during observation. • Close measurements can differ, so inspect the method and instrument. • Weather reports give maximum and minimum air temperatures that can vary from day to day. • Room air and beaker water are distinct measurements worth recording side by side.