How Can We Measure Temperature
4 Minutes
Temperature and thermometers for kids: learn how heat relates to moving molecules and explore three measuring scales. An English science lesson.
- How kinetic energy of moving molecules changes water temperature
- Where Celsius, Fahrenheit, and Kelvin temperature scales are used
- Freezing and boiling points of water across all three scales
What this lesson teaches
Temperature is the term used to describe both the heat and the coldness of an object. It depends directly on the motion of the molecules inside matter and is measured using a standard instrument called a thermometer.
How molecular motion creates heat
The molecules inside any object are always in motion because of an energy known as kinetic energy. When water in a vessel is heated, the kinetic energy of its molecules increases, causing them to move faster and collide with one another. These collisions produce heat energy, so heating the water further makes the molecules collide even faster, causing the heat energy and the temperature of the water to rise. Cooling the water does the opposite by decreasing kinetic energy, which slows down the molecules, reduces collisions, and makes the temperature drop.
The thermometer as a measuring instrument
A thermometer is the standard instrument used to measure temperature. People often see it when doctors place a glass stick-like tool into a patient's mouth to check for a fever. This instrument allows temperature to be measured accurately across three different scales known as Celsius, Fahrenheit, and Kelvin.
Where each temperature scale is used
- Celsius is used in daily weather reports, such as when announcing that the weather is 30 degrees Celsius or 45 degrees Celsius in Chennai.
- Fahrenheit is used by doctors to check body temperature and find out whether someone has a fever of 100 degrees Fahrenheit or 105 degrees Fahrenheit.
- Kelvin is used in space research and by scientists and other experts, such as when measuring the temperature of the sun at 5,778 Kelvin.
Freezing and boiling points of water
- On the Celsius scale, the freezing point of water is 0 degrees Celsius and the boiling point is 100 degrees Celsius, with 100 divisions counted by tens.
- On the Fahrenheit scale, the freezing point of water is 32 degrees Fahrenheit and the boiling point is 212 degrees Fahrenheit, with 180 divisions counted by nines.
- On the Kelvin scale, the freezing point of water is 273 Kelvin and the boiling point is 373 Kelvin, with 100 divisions counted by tens.