Answer:
<em>What quantity dictates the speed of a reaction?</em> The activation energy
Explanation:
According to the collision theory, when molecules collide, they must overcome an energy barrier for the reaction to take place. This energy, known as activation energy, is represented by the difference in energy between the initial state and the transition state. The higher the activation energy, the slower the reaction. That's why catalysts reduce the activation energy to accelerate the reaction.
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances.
Particle
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Answer:
Explanation:
The standard system of measurement is what is popularly referred to as SI unit (or international system of units). For example, the SI unit for length is basically in meters (m), which is convertible to millimeter (mm), centimeter (cm) or even kilometer (km).
If there is no standard system of measurement,
1) Scientists will not be able to compare data as every scientist will use a unit that suits him/herself which might make data incomparable as some units might be difficult to convert to other units or there conversion methods might even be debatable.
2) There might be a general lack of understanding of the research work done by a scientist/scientists in the scientific community. This is because the standard system of measurement affords scientists to communicate properly with the same or convertible units and based on 1. above, if scientists use any unit that isn't agreed upon, different/unknown/debatable units might make understanding of research works incomprehensible.
