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The tonne (t) is an SI-compatible unit of mass equal to a megagram (Mg), or 10 3 kg. The unit is in common use for masses above about 10 3 kg and is often used with SI prefixes. For example, a gigagram ( Gg ) or 10 9 g is 10 3 tonnes, commonly called a kilotonne .
By Landauer's principle, the minimum amount of energy required at 25 °C to change one bit of information 3–7×10 −21 J Energy of a van der Waals interaction between atoms (0.02–0.04 eV) [11] [12] 4.1×10 −21 J The "kT" constant at 25 °C, a common rough approximation for the total thermal energy of each molecule in a system (0.03 eV) [13]
Mass–energy equivalence states that all objects having mass, or massive objects, have a corresponding intrinsic energy, even when they are stationary.In the rest frame of an object, where by definition it is motionless and so has no momentum, the mass and energy are equal or they differ only by a constant factor, the speed of light squared (c 2).
If a first body of mass m A is placed at a distance r (center of mass to center of mass) from a second body of mass m B, each body is subject to an attractive force F g = Gm A m B /r 2, where G = 6.67 × 10 −11 N⋅kg −2 ⋅m 2 is the "universal gravitational constant". This is sometimes referred to as gravitational mass.
The enthalpy of fusion is the amount of energy required to convert one mole of solid into liquid. For example, when melting 1 kg of ice (at 0 °C under a wide range of pressures), 333.55 kJ of energy is absorbed with no temperature change. The heat of solidification (when a substance changes from liquid to solid) is equal and opposite.
The calorie is defined as the amount of thermal energy necessary to raise the temperature of one gram of water by 1 Celsius degree, from a temperature of 14.5 °C, at a pressure of 1 atm. For thermochemistry a calorie of 4.184 J is used, but other calories have also been defined, such as the International Steam Table calorie of 4.1868 J.
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Mg 2+ is the coordinating metal ion in the chlorophyll molecule, and in plants where the ion is in high supply about 6% of the total Mg 2+ is bound to chlorophyll. [4] [88] [89] Thylakoid stacking is stabilised by Mg 2+ and is important for the efficiency of photosynthesis, allowing phase transitions to occur. [90]