Body Temperature

3.1 Body Temperature
SCIENCE • Form 4 • Chapter 3: Techniques of Measuring the Parameters of Body Health

3.1 Body Temperature

Body temperature is an essential parameter indicating our general state of health. It measures the degree of hotness and coldness of our body, ensuring that body organs and systems function at optimal levels.

Learning Objectives

  • State the definition of temperature and human body temperature.
  • Identify the four types of thermometers used to measure temperature and describe their specific functions and measuring ranges.
  • Describe the correct techniques for measuring body temperature using clinical, laboratory, rectal, and infrared thermometers.
  • Explain the function of the kink in a clinical thermometer compared to a laboratory thermometer.
  • State the normal human body temperature value.
  • Identify the factors that cause human body temperature to rise above normal reading.

Types of Thermometers and Their Features

Compare the functions, measuring ranges and key structural differences of the four thermometers.

Four types of thermometers and their features A comparison diagram showing a clinical thermometer with a kink, a laboratory thermometer without a kink, a rectal thermometer with a short rounded bulb, and an infrared thermometer aimed at a forehead. Clinical 35°C – 42°C Has a kink Laboratory -10°C – 110°C No kink Rectal For infants < 3 months Infrared Non-contact Quick reading

Short Explanation

Definition

Temperature is a measurement of the degree of hotness and coldness of a substance. Body temperature is the measurement of the degree of hotness and coldness of our body.

The normal human body temperature is 36.9°C. A body temperature above 37°C may indicate a fever, while a body temperature that drops below normal due to extreme cold exposure can lead to death.

Homeostasis. The skin and the endocrine system are important to regulate body temperature. Homeostasis is the mechanism that regulates body temperature so that it remains in a balanced and stable state.

Four Types of Thermometers

Comparison of the four types of thermometers used to measure temperature.
Thermometer Function Measuring range Accuracy Kink
Clinical Measures body temperature 35°C to 42°C 0.1°C Yes
Laboratory Measures the temperature of liquids -10°C to 110°C 1°C No
Rectal Measures body temperature through the rectum; usually for infants less than 3 months old Body range — —
Infrared Measures body temperature without contact; quick reading Body range — —

Measuring Body Temperature with the Correct Technique

Each thermometer has a specific technique that must be followed for an accurate reading.

Clinical Thermometer

  1. Ensure the temperature is lower than 35°C before use. If it exceeds 35°C, shake the thermometer until the reading is below 35°C.
  2. Place the thermometer under the armpit or in the mouth for about 2 to 3 minutes, or until a 'beep' sound is heard for a digital clinical thermometer.
  3. Pull out the thermometer and record the reading.

Function of the kink. The kink in the clinical thermometer ensures that the mercury does not go down quickly after it is removed from the mouth or armpit, providing a more accurate reading.

Laboratory Thermometer

A laboratory thermometer is not suitable to measure body temperature because it lacks a kink in the mercury tube. When removed from the mouth or armpit, the temperature reading drops quickly, causing an inaccurate reading. If used to measure body temperature, the reading must be taken while the thermometer is still in the mouth or under the armpit.

Rectal Thermometer

  1. Usually used for infants less than 3 months old. Ensure the thermometer is labelled for rectal use.
  2. Clean the tip with alcohol.
  3. Dab petroleum jelly on the tip to ease insertion into the infant's rectum.
  4. Raise the infant's legs.
  5. Insert 1.5 – 2.5 cm of the thermometer into the infant's rectum.
  6. Leave it until a 'beep' sound is heard.
  7. Record the temperature.

Infrared Thermometer

  1. Can be used without any physical contact with the individual.
  2. Aim at the forehead at a distance of about 5 cm from the individual. Do not aim directly or indirectly at the eyes.
  3. Record the temperature.

Factors That Can Cause Body Temperature to Be Above Normal Reading

An elevated body temperature above 37°C may be caused by several factors.

1. Infection

Caused by bacteria or viruses.

2. Exposure to extreme heat

Heat stroke or extreme sunburn.

3. Exercise

Vigorous exercise.

Try to Answer First

Answer in your mind, then press “Check Answer”.

1

What is the purpose of the kink found in a clinical thermometer?

Answer: The kink ensures that the mercury does not go down quickly after being removed from the mouth or armpit, allowing a more accurate reading to be taken.
2

Why must a rectal thermometer tip be dabbed with petroleum jelly before insertion?

Answer: To make it easier and smoother for the thermometer to be inserted into the infant's rectum.
3

State three main categories of factors that cause body temperature to exceed the normal reading.

Answer: Infection (bacteria or virus), exposure to extreme heat (heat stroke or extreme sunburn), and exercise (vigorous exercise).

Common Mistakes

  • !Reading a laboratory thermometer after removing it from the armpit or mouth, which causes the mercury to drop rapidly and produce an inaccurate reading.
  • !Forgetting to shake a mercury clinical thermometer below 35°C before taking a measurement.
  • !Aiming the infrared thermometer directly into or near the eyes instead of aiming at the forehead from a safe distance of about 5 cm.
  • !Inserting the rectal thermometer deeper than 1.5 – 2.5 cm into an infant's rectum.

Concept Misunderstandings

Misconception

A laboratory thermometer can easily replace a clinical thermometer under normal procedures.

Correct Concept

A laboratory thermometer lacks a kink in its mercury tube, causing the reading to drop immediately upon removal from the body; hence, the reading must be recorded while it remains inside the mouth or armpit.

Misconception

Any rise in body temperature is always caused by a viral or bacterial infection.

Correct Concept

An increase in body temperature can also be triggered non-infectiously by environmental heat, such as heat stroke or sunburn, or by vigorous physical exercise.

Misconception

Normal human body temperature is 37.5°C.

Correct Concept

Normal body temperature is 36.9°C; a reading exceeding 37°C indicates a fever.

Summary

  • Body temperature indicates the balance of hotness and coldness in the body, with a normal reading of 36.9°C regulated by homeostasis.
  • Clinical thermometer: 35°C to 42°C, has a kink, 0.1°C accuracy.
  • Laboratory thermometer: -10°C to 110°C, lacks a kink, 1°C accuracy.
  • Rectal thermometer: inserted 1.5 – 2.5 cm with petroleum jelly for infants under 3 months.
  • Infrared thermometer: non-contact, aimed at the forehead at approximately 5 cm distance.
  • Elevated body temperature above 37°C is caused by infections, extreme heat exposure, or vigorous exercise.

Short Activity

A. Objective Quiz

1 Which part of the clinical thermometer prevents the mercury level from falling rapidly when removed from the body?

2 At what distance should an infrared thermometer be aimed from an individual's forehead?

B. Fill in the Blanks

3 The normal human body temperature is °C.

 

4 When using a rectal thermometer on an infant, insert to 2.5 cm of the thermometer into the rectum.

 

C. Drag and Drop: Match the Thermometer to Its Feature

Drag each thermometer to its correct feature or function. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.

Thermometer
Clinical thermometer
Laboratory thermometer
Rectal thermometer
Infrared thermometer
Feature / Function
1 Measures temperature in the range of 35°C to 42°C and contains a kink
2 Measures liquids in the range of -10°C to 110°C and has no kink
3 Inserted into the rectum, usually for infants less than 3 months old
4 Measures body temperature quickly without physical contact

C. Match the Thermometer to Its Feature

Write the correct thermometer next to each feature or function.

Feature / Function Thermometer
1. Measures temperature in the range of 35°C to 42°C and contains a kink  
2. Measures liquids in the range of -10°C to 110°C and has no kink  
3. Inserted into the rectum, usually for infants less than 3 months old  
4. Measures body temperature quickly without physical contact  

Answer choices: Clinical thermometer • Laboratory thermometer • Rectal thermometer • Infrared thermometer

Keywords

Temperature Body Temperature Clinical Thermometer Laboratory Thermometer Rectal Thermometer Infrared Thermometer Kink Homeostasis Fever Heat Stroke

Body Temperature

3.1 Body Temperature
SCIENCE • Form 4 • Chapter 3: Techniques of Measuring the Parameters of Body Health

3.1 Body Temperature

Body temperature is an essential parameter indicating our general state of health. It measures the degree of hotness and coldness of our body, ensuring that body organs and systems function at optimal levels.

Learning Objectives

  • State the definition of temperature and human body temperature.
  • Identify the four types of thermometers used to measure temperature and describe their specific functions and measuring ranges.
  • Describe the correct techniques for measuring body temperature using clinical, laboratory, rectal, and infrared thermometers.
  • Explain the function of the kink in a clinical thermometer compared to a laboratory thermometer.
  • State the normal human body temperature value.
  • Identify the factors that cause human body temperature to rise above normal reading.

Types of Thermometers and Their Features

Compare the functions, measuring ranges and key structural differences of the four thermometers.

Four types of thermometers and their features A comparison diagram showing a clinical thermometer with a kink, a laboratory thermometer without a kink, a rectal thermometer with a short rounded bulb, and an infrared thermometer aimed at a forehead. Clinical 35°C – 42°C Has a kink Laboratory -10°C – 110°C No kink Rectal For infants < 3 months Infrared Non-contact Quick reading

Short Explanation

Definition

Temperature is a measurement of the degree of hotness and coldness of a substance. Body temperature is the measurement of the degree of hotness and coldness of our body.

The normal human body temperature is 36.9°C. A body temperature above 37°C may indicate a fever, while a body temperature that drops below normal due to extreme cold exposure can lead to death.

Homeostasis. The skin and the endocrine system are important to regulate body temperature. Homeostasis is the mechanism that regulates body temperature so that it remains in a balanced and stable state.

Four Types of Thermometers

Comparison of the four types of thermometers used to measure temperature.
Thermometer Function Measuring range Accuracy Kink
Clinical Measures body temperature 35°C to 42°C 0.1°C Yes
Laboratory Measures the temperature of liquids -10°C to 110°C 1°C No
Rectal Measures body temperature through the rectum; usually for infants less than 3 months old Body range — —
Infrared Measures body temperature without contact; quick reading Body range — —

Measuring Body Temperature with the Correct Technique

Each thermometer has a specific technique that must be followed for an accurate reading.

Clinical Thermometer

  1. Ensure the temperature is lower than 35°C before use. If it exceeds 35°C, shake the thermometer until the reading is below 35°C.
  2. Place the thermometer under the armpit or in the mouth for about 2 to 3 minutes, or until a 'beep' sound is heard for a digital clinical thermometer.
  3. Pull out the thermometer and record the reading.

Function of the kink. The kink in the clinical thermometer ensures that the mercury does not go down quickly after it is removed from the mouth or armpit, providing a more accurate reading.

Laboratory Thermometer

A laboratory thermometer is not suitable to measure body temperature because it lacks a kink in the mercury tube. When removed from the mouth or armpit, the temperature reading drops quickly, causing an inaccurate reading. If used to measure body temperature, the reading must be taken while the thermometer is still in the mouth or under the armpit.

Rectal Thermometer

  1. Usually used for infants less than 3 months old. Ensure the thermometer is labelled for rectal use.
  2. Clean the tip with alcohol.
  3. Dab petroleum jelly on the tip to ease insertion into the infant's rectum.
  4. Raise the infant's legs.
  5. Insert 1.5 – 2.5 cm of the thermometer into the infant's rectum.
  6. Leave it until a 'beep' sound is heard.
  7. Record the temperature.

Infrared Thermometer

  1. Can be used without any physical contact with the individual.
  2. Aim at the forehead at a distance of about 5 cm from the individual. Do not aim directly or indirectly at the eyes.
  3. Record the temperature.

Factors That Can Cause Body Temperature to Be Above Normal Reading

An elevated body temperature above 37°C may be caused by several factors.

1. Infection

Caused by bacteria or viruses.

2. Exposure to extreme heat

Heat stroke or extreme sunburn.

3. Exercise

Vigorous exercise.

Try to Answer First

Answer in your mind, then press “Check Answer”.

1

What is the purpose of the kink found in a clinical thermometer?

Answer: The kink ensures that the mercury does not go down quickly after being removed from the mouth or armpit, allowing a more accurate reading to be taken.
2

Why must a rectal thermometer tip be dabbed with petroleum jelly before insertion?

Answer: To make it easier and smoother for the thermometer to be inserted into the infant's rectum.
3

State three main categories of factors that cause body temperature to exceed the normal reading.

Answer: Infection (bacteria or virus), exposure to extreme heat (heat stroke or extreme sunburn), and exercise (vigorous exercise).

Common Mistakes

  • !Reading a laboratory thermometer after removing it from the armpit or mouth, which causes the mercury to drop rapidly and produce an inaccurate reading.
  • !Forgetting to shake a mercury clinical thermometer below 35°C before taking a measurement.
  • !Aiming the infrared thermometer directly into or near the eyes instead of aiming at the forehead from a safe distance of about 5 cm.
  • !Inserting the rectal thermometer deeper than 1.5 – 2.5 cm into an infant's rectum.

Concept Misunderstandings

Misconception

A laboratory thermometer can easily replace a clinical thermometer under normal procedures.

Correct Concept

A laboratory thermometer lacks a kink in its mercury tube, causing the reading to drop immediately upon removal from the body; hence, the reading must be recorded while it remains inside the mouth or armpit.

Misconception

Any rise in body temperature is always caused by a viral or bacterial infection.

Correct Concept

An increase in body temperature can also be triggered non-infectiously by environmental heat, such as heat stroke or sunburn, or by vigorous physical exercise.

Misconception

Normal human body temperature is 37.5°C.

Correct Concept

Normal body temperature is 36.9°C; a reading exceeding 37°C indicates a fever.

Summary

  • Body temperature indicates the balance of hotness and coldness in the body, with a normal reading of 36.9°C regulated by homeostasis.
  • Clinical thermometer: 35°C to 42°C, has a kink, 0.1°C accuracy.
  • Laboratory thermometer: -10°C to 110°C, lacks a kink, 1°C accuracy.
  • Rectal thermometer: inserted 1.5 – 2.5 cm with petroleum jelly for infants under 3 months.
  • Infrared thermometer: non-contact, aimed at the forehead at approximately 5 cm distance.
  • Elevated body temperature above 37°C is caused by infections, extreme heat exposure, or vigorous exercise.

Short Activity

A. Objective Quiz

1 Which part of the clinical thermometer prevents the mercury level from falling rapidly when removed from the body?

2 At what distance should an infrared thermometer be aimed from an individual's forehead?

B. Fill in the Blanks

3 The normal human body temperature is °C.

 

4 When using a rectal thermometer on an infant, insert to 2.5 cm of the thermometer into the rectum.

 

C. Drag and Drop: Match the Thermometer to Its Feature

Drag each thermometer to its correct feature or function. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.

Thermometer
Clinical thermometer
Laboratory thermometer
Rectal thermometer
Infrared thermometer
Feature / Function
1 Measures temperature in the range of 35°C to 42°C and contains a kink
2 Measures liquids in the range of -10°C to 110°C and has no kink
3 Inserted into the rectum, usually for infants less than 3 months old
4 Measures body temperature quickly without physical contact

C. Match the Thermometer to Its Feature

Write the correct thermometer next to each feature or function.

Feature / Function Thermometer
1. Measures temperature in the range of 35°C to 42°C and contains a kink  
2. Measures liquids in the range of -10°C to 110°C and has no kink  
3. Inserted into the rectum, usually for infants less than 3 months old  
4. Measures body temperature quickly without physical contact  

Answer choices: Clinical thermometer • Laboratory thermometer • Rectal thermometer • Infrared thermometer

Keywords

Temperature Body Temperature Clinical Thermometer Laboratory Thermometer Rectal Thermometer Infrared Thermometer Kink Homeostasis Fever Heat Stroke