What is calorie (thermochemical)?
The thermochemical calorie is a unit of energy equal to approximately 4.184 joules. It is used in chemistry and physics to express small heat quantities, particularly in thermochemical experiments.
Real-world uses
The thermochemical calorie (4.184 J) is used in chemistry for expressing heats of reaction, specific heat capacities of substances, and calorimetry experiments. It appears in older scientific literature and some chemistry textbooks, particularly in calorimetric calculations.
History
The calorie was first defined by Nicolas Clément in 1824 as the heat needed to raise 1 gram of water by 1°C. The thermochemical calorie (exactly 4.184 J) was later standardized for precise scientific use, distinguishing it from other calorie definitions.
Common mistakes
Confusing the small calorie (cal, 4.184 J) with the large Calorie/kilocalorie (Cal/kcal, 4,184 J) used in food labelling. Also, several slightly different definitions of the calorie exist (thermochemical, 15°C, IT), which differ by fractions of a percent.
What is electronvolt?
An electronvolt is a unit of energy equal to the work done on an electron by a potential difference of one volt, approximately 1.602 × 10⁻¹⁹ joules. It is used in atomic physics, particle physics, and quantum mechanics.
Real-world uses
The electronvolt is the standard energy unit in particle physics, atomic physics, and semiconductor science. X-ray photon energies are measured in keV; visible light photons in eV (about 1.8–3.1 eV); nuclear reactions in MeV; and particle accelerator energies in GeV or TeV.
History
The electronvolt came into use in the early 20th century with the development of quantum mechanics and experimental atomic physics. As physicists began measuring energies of electrons and photons, the eV provided a convenient unit far smaller than the joule but appropriate for subatomic-scale phenomena.
Common mistakes
Confusing the electronvolt with a unit of voltage—it is a unit of energy equal to the kinetic energy gained by one electron accelerated through a potential difference of one volt (1 eV = 1.602 × 10⁻¹⁹ J). Also mixing up the scale prefixes (keV, MeV, GeV, TeV) when discussing different physical phenomena.
When is this conversion used?
Converting calorie (thermochemical) to electronvolt is useful in the energy domain when comparing values across different measurement standards or applying formulas that require a specific unit.
Worked examples
1 calorie (thermochemical) = 2.611447e+19 electronvolt
1 electronvolt = 1.602177e-19 joule
How to convert calorie (thermochemical) to electronvolt
To convert calorie (thermochemical) to electronvolt, multiply the value by 2.611447e+19.
To convert electronvolt back to calorie (thermochemical), multiply by 3.829294e-20.
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
Quick reference: calorie (thermochemical) to electronvolt
| calorie (thermochemical) | electronvolt |
|---|---|
| 0.1 | 2.611447e+18 |
| 0.5 | 1.305724e+19 |
| 1 | 2.611447e+19 |
| 2 | 5.222895e+19 |
| 5 | 1.305724e+20 |
| 10 | 2.611447e+20 |
| 25 | 6.528618e+20 |
| 50 | 1.305724e+21 |
| 100 | 2.611447e+21 |
| 250 | 6.528618e+21 |
| 500 | 1.305724e+22 |
| 1,000 | 2.611447e+22 |
Common values
| calorie (thermochemical) | electronvolt | |
|---|---|---|
| A food calorie (1 kcal) | 1,000 calorie (thermochemical) | 2.611447e+22 electronvolt |
| A AA battery | 2,237.09369025 calorie (thermochemical) | 5.842052e+22 electronvolt |
| Boiling a kettle | 100,382.40917782 calorie (thermochemical) | 2.621434e+24 electronvolt |
| Daily human diet (2000 kcal) | 2,000,000 calorie (thermochemical) | 5.222895e+25 electronvolt |
| 1 gallon of gasoline | 31,491,395.79349904 calorie (thermochemical) | 8.223812e+26 electronvolt |
Available Energy units
More calorie (thermochemical) conversions
- Convert calorie (thermochemical) to joule
- Convert calorie (thermochemical) to kilojoule
- Convert calorie (thermochemical) to kilowatt hour
- Convert calorie (thermochemical) to kilocalorie (dietary)
- Convert calorie (thermochemical) to watt hour
- Convert calorie (thermochemical) to megajoule
- Convert calorie (thermochemical) to electronvolt
- Convert calorie (thermochemical) to British thermal unit
- Convert calorie (thermochemical) to therm (US)
Assumption: calorie means thermochemical calorie, and therm means US therm.