Answer:The first task of a nuclear weapon design is to rapidly assemble a supercritical mass of fissile uranium or plutonium. A supercritical mass is one in which the percentage of fission-produced neutrons captured by another fissile nucleus is large enough that each fission event, on average, causes more than one additional fission event. Once the critical mass is assembled, at maximum density, a burst of neutrons is supplied to start as many chain reactions as possible. Early weapons used a modulated neutron generator codenamed "Urchin" inside the pit containing polonium-210 and beryllium separated by a thin barrier. Implosion of the pit crushed the neutron generator, mixing the two metals, thereby allowing alpha particles from the polonium to interact with beryllium to produce free neutrons. In modern weapons, the neutron generator is a high-voltage vacuum tube containing a particle accelerator which bombards a deuterium/tritium-metal hydride target with deuterium and tritium ions. The resulting small-scale fusion produces neutrons at a protected location outside the physics package, from which they penetrate the pit. This method allows better control of the timing of chain reaction initiation.
Explanation:
A chemical reaction occurs when substances change. Photosynthesis is the process by which plants produce food.
1) A chemical reaction is a process by which substances can be changed into other substances. Hence, in a chemical reaction, new substances are formed.
2) Photosynthesis is the process by which plants produce food using carbon dioxide and water in the process of sunlight and chlorophyll. Glucose is produced during photosynthesis and the energy produced and stored as starch.
3) Valence electrons show the kind of bond that an atom can form. Reaction between two atoms that have many valence electrons is most likely covalent. An ionic bond is formed between an atom that has few valence electrons and an atom that has many valence electrons.
4) A carbohydrate is a compound that comprises of hydrogen and oxygen in a ratio of 2:1. The compound that is a carbohydrate is C3H6O3.
5) Rocks contain iron. Iron oxides form when cyanobacteria produce oxygen via photosynthesis.
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D. Making the reactant particles larger
<h3><u>Answer;</u></h3>
exceeds evaporation over land
Precipitation<u> exceeds evaporation over land </u>
<h3><u>Explanation;</u></h3>
- <em><u>In order to maintain earths water balance, evaporation exceeds precipitation over oceans but precipitation exceeds evaporation over land.</u></em>
- Water evaporates into the atmosphere from the ocean and to a much lesser extent from the continents. Winds transport this moisture-laden air, often great distances, until conditions cause the moisture to condense into clouds and to precipitate and fall.
- Most precipitation originates by evaporation from the oceans. Over time, water evaporated from the oceans is replenished by inflow of freshwater from rivers and streams.
Because of the crystal structure of the ice, ice has lower density than liquid water. So the volume of the ice of same mass is greater than water. When melting, the volume will decrease.
