This chapter explores the concept of temperature and how it is measured. You will learn why our sense of touch alone is not reliable for determining how hot or cold something is. The chapter introduces different types of thermometers and how to use them correctly. You will also discover the various temperature scales and how to convert between them. By the end of this chapter, you will understand the importance of accurate temperature measurement in everyday life and science.
What you'll learn
1Understand what temperature is and why it is important
2Learn how to measure temperature using different types of thermometers
3Identify the different temperature scales and their uses
4Convert temperatures between Celsius and Fahrenheit scales
5Use a clinical thermometer to measure body temperature
6Use a laboratory thermometer to measure the temperature of various substances
7Recognize the normal and abnormal ranges of body temperature
Chapter at a glance
01Understanding Temperature and Heat
02Measuring Temperature with Thermometers
03Temperature Scales and Conversions
04Temperature Scales and Conversions
05Clinical and Laboratory Thermometers
06Abnormal Body Temperature and Safety
Detailed chapter notes
01
Understanding Temperature and Heat
Temperature is a measure of how hot or cold a body is. It tells us the degree of hotness or coldness of a substance. We often use our sense of touch to judge if something is hot or cold, but this can be unreliable. For example, if you dip your right hand in warm water and your left hand in cold water, and then place both hands in lukewarm water, your right hand will feel the lukewarm water as cold, while your left hand will feel it as warm. This shows that our sense of touch can be misleading. Therefore, we need a more reliable way to measure temperature.
Temperature measures how hot or cold a body is
Our sense of touch can be unreliable for judging temperature
We need accurate tools to measure temperature
02
Measuring Temperature with Thermometers
A thermometer is a device used to measure temperature. There are two main types of thermometers: clinical thermometers and laboratory thermometers. Clinical thermometers are used to measure body temperature, while laboratory thermometers are used for measuring the temperature of various substances in experiments. Both types of thermometers have a scale marked with temperature units, usually in degrees Celsius (°C). The liquid inside the thermometer, which is often mercury or alcohol, expands when heated and contracts when cooled, causing the level of the liquid to rise or fall in the thermometer tube.
Thermometers measure temperature
Clinical thermometers measure body temperature
Laboratory thermometers measure the temperature of substances
Thermometers use a scale marked in degrees Celsius
03
Temperature Scales and Conversions
There are three main temperature scales: Celsius, Fahrenheit, and Kelvin. The Celsius scale is commonly used in scientific work and everyday life. The Fahrenheit scale is used in some countries, particularly the United States. The Kelvin scale is used in scientific studies and is the SI unit of temperature. To convert a temperature from Celsius to Fahrenheit, you can use the formula: Fahrenheit = (Celsius × 9/5) + 32. To convert from Fahrenheit to Celsius, you can use the formula: Celsius = (Fahrenheit - 32) × 5/9. The Kelvin scale starts at absolute zero, which is the lowest possible temperature. To convert from Celsius to Kelvin, you add 273.15 to the Celsius temperature.
Celsius, Fahrenheit, and Kelvin are the main temperature scales
Fahrenheit = (Celsius × 9/5) + 32
Celsius = (Fahrenheit - 32) × 5/9
Kelvin = Celsius + 273.15
04
Clinical and Laboratory Thermometers
Clinical thermometers are designed to measure body temperature accurately. They usually have a range from 35°C to 42°C, which covers the normal and feverish body temperatures. Digital clinical thermometers are now commonly used as they are easier to read and do not contain mercury, which is toxic. Laboratory thermometers have a wider range, typically from -10°C to 110°C, and are used to measure the temperature of various substances in experiments. When using a laboratory thermometer, it is important to ensure that the bulb is fully immersed in the substance and that the thermometer is read while it is still in the substance.
Clinical thermometers measure body temperature
Digital clinical thermometers are safer and easier to read
Laboratory thermometers have a wider temperature range
Proper use of a laboratory thermometer ensures accurate readings
05
Abnormal Body Temperature and Safety
The normal body temperature of a healthy human adult is around 37.0°C. However, this can vary slightly from person to person. A temperature below 35°C or above 42°C is considered abnormal and can be dangerous. High fever can be a sign of infection or illness, while very low body temperature can indicate hypothermia. It is important to use thermometers correctly to ensure accurate readings. Always follow the instructions provided with the thermometer and handle it carefully to avoid damage or injury. Digital thermometers should be cleaned and disinfected after each use to prevent the spread of germs.
Normal body temperature is around 37.0°C
Abnormal body temperature can be dangerous
High fever and very low body temperature require medical attention
Proper use and care of thermometers ensure accurate and safe measurements
Want the complete chapter resources?Topic notes, quizzes and flashcards for Temperature and its Measurement.
A thermometer is the device used to measure temperature. Barometer measures pressure, speedometer measures speed, and ammeter measures electric current.
Question 02
What is the liquid used in most common thermometers?
AMercury
BWater
CAlcohol
DOil
Show answer
Answer: (A) Mercury
Mercury is the most common liquid used in thermometers because it expands and contracts uniformly with temperature changes.
Question 03
What is the freezing point of water on the Celsius scale?
A0°C
B32°C
C100°C
D212°C
Show answer
Answer: (A) 0°C
Water freezes at 0°C on the Celsius scale by definition.
Question 04
Which of the following is used to measure human body temperature?
AClinical thermometer
BLaboratory thermometer
CRoom thermometer
DDigital thermometer
Show answer
Answer: (A) Clinical thermometer
A clinical thermometer is specifically designed to measure human body temperature.
Question 05
What is the normal body temperature of a healthy human adult?
A35.0 °C
B37.0 °C
C39.0 °C
D40.0 °C
Show answer
Answer: (B) 37.0 °C
The normal body temperature of a healthy human adult is taken to be 37.0 °C.
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Temperature is a measure of the hotness or coldness of a body. It tells us how hot or cold a body is. A device that measures temperature is called a thermometer. There are two common types of thermometers: clinical thermometers, used to measure body temperature, and laboratory thermometers, used for various other purposes. Temperature is measured in different scales, such as the Celsius scale (°C), Fahrenheit scale (°F), and Kelvin scale (K).
Sample question3 marks
Q2. What are the two main types of thermometers mentioned in the chapter, and what is each used for?
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Model answer
The two main types of thermometers mentioned are clinical thermometers and laboratory thermometers. Clinical thermometers are used to measure human body temperature, while laboratory thermometers are used for measuring a wide range of temperatures in various experiments and settings.
Sample question3 marks
Q3. What are the three most-used scales of temperature? Name their units and symbols.
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Model answer
The three most-used scales of temperature are: (a) the Celsius scale, with the unit degree Celsius denoted by °C, (b) the Fahrenheit scale, with the unit degree Fahrenheit denoted by °F, and (c) the Kelvin scale, with the unit kelvin denoted by K.
Sample question3 marks
Q4. What is the difference between a clinical thermometer and a laboratory thermometer?
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Model answer
A clinical thermometer is used specifically for measuring human body temperature and has a temperature range from 35°C to 42°C. It has a kink to prevent the mercury from falling back and is designed to be used digitally. A laboratory thermometer, on the other hand, is used for a wide range of temperature measurements and has a broader range, typically from -10°C to 110°C. It is used for scientific experiments and does not have a kink.
Sample question3 marks
Q5. What is considered the normal body temperature of a healthy human being?
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Model answer
The normal body temperature of a healthy human being is typically around 37.0 °C or 98.6 °F. However, it can vary slightly from person to person and can be influenced by factors such as age, time of day, and activity level.
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The normal body temperature of a healthy human adult is around 37.0°C. However, this can vary slightly from person to person.
What is the difference between a clinical thermometer and a laboratory thermometer?
A clinical thermometer is used to measure body temperature and has a range from 35°C to 42°C. A laboratory thermometer has a wider range, typically from -10°C to 110°C, and is used to measure the temperature of various substances in experiments.
Why is our sense of touch not reliable for judging temperature?
Our sense of touch can be misleading because it is relative. For example, if you dip your right hand in warm water and your left hand in cold water, and then place both hands in lukewarm water, your right hand will feel the lukewarm water as cold, while your left hand will feel it as warm.
How do you convert a temperature from Celsius to Fahrenheit?
To convert a temperature from Celsius to Fahrenheit, you can use the formula: Fahrenheit = (Celsius × 9/5) + 32.
What is the SI unit of temperature?
The SI unit of temperature is the Kelvin (K). The Kelvin scale is used in scientific studies and starts at absolute zero, which is the lowest possible temperature.
Why are digital thermometers preferred over mercury thermometers?
Digital thermometers are preferred over mercury thermometers because they are easier to read, do not contain toxic mercury, and are safer to use. They also provide accurate and quick readings.