Temperature - Introduction
Temperature is a physical property to tell you about the coldness and hotness of a body. Celsius, Kelvin or Fahrenheit are the scales to use for recording temperature, and these scales have a correlation to convert one reading into another scale reading.
In the notes, Vedantu has provided a detailed explanation about temperature, thermometers and examples of temperature measurement. Also, physics experts at Vedantu have offered you the relation between temperature and kinetic energy. Students can learn more about the topic from Vedantu online class for physics, where you study each concept with the help of 3-D illustrations and examples.
Vedantu Notes on Temperature
Vedantu gives you correct and helpful content to boost your knowledge, also ease the process to retain the concepts for a long duration. Various subject matter experts for physics have made these resources to provide you with in-depth knowledge to gain good marks in the examination.
Experts of physics at Vedantu have made sure to provide you with easy notes on temperature, including the use of thermometers, units of temperature and absolute zero. Students also get to learn about the difference between hotness and temperature.
Temperature Scales with Vedantu
There are three temperature scales to study in this chapter; each scale is different and has different upper and lower fixed points, and widely preferred temperature scales are Celsius and Fahrenheit. Vedantu notes give you exposure to the new and exciting examples that help you understand the significance of each scale in measuring temperature.
Vedantu has explained the relationship between these scales to convert one reading into another scale. For example, in India, we use a Celsius scale that has 0 oC as the lower fixed point, which is the freezing point of water, and 100 oC as the upper fixed point, which is the boiling point of water. All the basic details are necessary to learn about different thermometers, and experts have made sure to add them into the notes. Also, you can join Vedantu online tuition classes for physics to study these thermometers or scales with the help of expert teachers.
Register at Vedantu to Learn Smartly
Register to Vedantu pro classes to start studying under the guidance of the subject matter experts of various subjects. They not only just teach you about the applications of a particular concept but also provide one-on-one support to clear all your doubts.
Sign up to Vedantu classes with your valid email id and enjoy learning smartly.
More About Temperature
In Physics, temperature refers to the physical properties of matter, which quantitatively expresses the hotness or coldness of a body. Before the evolution of the concept of temperature, we used to judge temperature on the basis of human perception - whether an object is hot or cold was mostly judged by human touch. However, this is not accurate. For example, during a cold morning, a wooden table might seem warmer than a metal cycle rod. However, both have an equal temperature based on the external atmosphere. Metal, being a better conductor of heat, draws heat out of your body faster, making it cooler than the wood (a poor conductor of heat). A simple temperature definition in science is the physical quantity measured using a thermometer. However, the temperature is related closely to the kinetic energies of the molecules and atoms inside an object.
Temperature and Kinetic Energy
The kinetic energy of an object, as per physics, is the energy that an object possesses due to its motion. Every molecule or atom has kinetic energy. Even in solids, when the molecules are tightly packed, all of them contain vibrational energy. Temperature is referred to as the average kinetic energy of all molecules. When a substance absorbs heat, the molecules start to move faster. This increases its kinetic energy. As a result, the temperature of the substance starts to increase. Eventually, the movement of molecules can result in the separation of the molecules as they start moving farther away from one another. For example, in solids, when the temperature increases, the molecules start moving faster, and this leads to the expansion of the solid. Eventually, if the temperature rises to the melting point of the solid, it can change its state as well. The sum of all kinetic energy in a body is called heat. Heat is a form of energy, and it can get transferred from one body to another.
Example of Temperature
Many people often think of temperature as energy, which is not true. Temperature is just a measurement that shows the average kinetic energy of one atom or molecule. Hence, when we say something is hot or cold, we are generally using another reference point to define the hotness and coldness of a body. For example, if we say that the coffee is hotter than the ice-cream, we are using the ice-cream as a reference point to determine the temperature of the coffee. During weather reports, temperature and humidity are shown in two different columns. This is because hot and humid days are considered hotter than hot and dry days because of human perception rather than temperature changes. If the temperature of a day is the same, but the humidity is high, then a person might feel hotter since humid days do not evaporate sweat as fast as dry days do. Evaporation of sweat helps us stay cooler.
What is the Absolute Zero?
(Image will be uploaded soon)
Absolute zero is the lowest possible temperature. It has been marked at 0 Kelvin or -273.15 degrees Celsius or -460 degrees Fahrenheit. At absolute zero temperature, there is no heat energy present in a substance. At this temperature, the particles present in a perfect crystal will remain motionless, that is all kinetic energy in the particle will become zero. Absolute zero is theoretically possible, but practically, we have not reached absolute zero temperatures yet. However, we have been able to reach close to absolute zero by using cryocoolers and dilution refrigerators.
Units of Temperature
Since temperature is a physical quantity, it has units that represent it. The SI unit of temperature is Kelvin. However, we also use two other units to measure temperature - Celsius, and Fahrenheit. The units of temperature are related in this manner:
oC = 5/9 (oF - 32)
K = oC + 273
How do Thermometers Measure Temperature?
Thermometers are generally used to measure the temperature of a body. A thermometer has two important components - a temperature sensor like the bulb of a mercury-in-glass thermometer and a numerical scale. The mercury thermometer works on the principle of thermal expansion. Thermal expansion is the change in the volume of a substance due to the change in temperature. Since mercury is sensitive to temperature changes, it is used in thermometers. An increase in the temperature is quickly registered as the mercury inside the thermometer expands and rises upwards. The numeric scale in the thermometer gives the measurement of the temperature. There are three kinds of thermometers - Celsius Thermometers, Fahrenheit thermometers, and Kelvin Thermometers.
(Image will be uploaded soon)
Temperature Scales
Since thermometers have to be of a specific length, each thermometer has a fixed scale. Celsius thermometers are easy to manufacture as the fixed scale used for them is set at the freezing point and boiling point of water. Celsius thermometers have a lower fixed point set at 0 oC (freezing point of water) and 100 oC (boiling point of water). Fahrenheit thermometers have a lower fixed point at 32 oF and an upper fixed point at 212 oF. Kelvin thermometers have a lower fixed point at 273 oK and an upper fixed point at 373 oK. From these fixed points, we can derive the relationship between Celsius, Fahrenheit, and Kelvin too
\[\frac{C}{100}\] = \[\frac{F-32}{180}\] = \[\frac{K-273}{100}\]
FAQs on Temperature
1. What is temperature in simple terms?
Temperature is a measure of how hot or cold something is. Scientifically, it represents the average kinetic energy (or movement energy) of the particles within an object. The faster these particles move, the higher the temperature we measure.
2. How is temperature different from heat?
This is a common point of confusion. Heat is the total energy of all the moving particles in a substance, while temperature is the measure of the *average* energy of those particles. For instance, a small cup of boiling water has a very high temperature, but a large, warm lake has far more heat because it contains vastly more water molecules, even though they are moving slower.
3. What are the main scales used to measure temperature?
The three most common temperature scales are:
- Celsius (°C): Used globally for most purposes. In this scale, water freezes at 0°C and boils at 100°C.
- Fahrenheit (°F): Primarily used in the United States. Water freezes at 32°F and boils at 212°F.
- Kelvin (K): The standard scale used in science. It starts at absolute zero and does not use degrees.
4. How does a basic thermometer work?
Most traditional thermometers operate on the principle of thermal expansion. They contain a liquid (like alcohol) in a glass tube. When the temperature rises, this liquid gets warmer and expands, causing it to rise up the tube. When it gets colder, the liquid contracts and falls. The tube is marked with a scale (like Celsius or Fahrenheit) to give a reading.
5. What is absolute zero?
Absolute zero is the lowest possible temperature that can exist. It is defined as 0 Kelvin (-273.15°C or -459.67°F). At this temperature, particles have the minimum possible energy and their motion almost completely stops. It is a theoretical limit that has never been fully reached.
6. Why does a metal chair feel colder than a wooden one, even if they are in the same room?
This happens because of differences in thermal conductivity, not temperature. Both chairs are at the same room temperature. However, metal is a good thermal conductor, so it quickly pulls heat away from your body when you touch it, making it feel cold. Wood is a poor conductor (an insulator), so it transfers heat much more slowly, and therefore doesn't feel as cold.
7. What are some important effects of temperature in our daily lives?
Temperature plays a crucial role in many everyday phenomena:
- It determines the state of matter (e.g., ice melting into water).
- It causes materials to expand and contract, a factor engineers consider when building bridges and railway tracks.
- It affects the speed of chemical reactions, which is why we refrigerate food to slow down spoilage.
- It drives our planet's weather patterns and climate.
8. What is the normal human body temperature?
The commonly accepted average normal human body temperature is around 37°C (98.6°F). However, this can vary slightly from person to person and can change based on the time of day, activity level, and age. Doctors use a clinical thermometer to measure it accurately.
