At stp (standard temperature and pressure), the temperature is T=0 C=273 K and the pressure is p=1.00 atm. So we can use the ideal gas law to find the number of moles of helium:

where p is the pressure (1.00 atm), V the volume (20.0 L), n the number of moles, T the temperature (273 K) and

the gas constant. Using the numbers and re-arranging the formula, we can calculate n:
In an uniform circular motion, the direction of the net force on the object is radially inward, passing through the center of the circle.
Direct current (DC) is the flow of electric charge in only one direction. It is the steady state of a constant-voltage circuit. Most well-known applications, however, use a time-varying voltage source. Alternating current (AC) is the flow of electric charge that periodically reverses direction.
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Explanation:
Igneous - metamorphic - sedimentary
A rock cycle provides the cyclic transformation of one rock type to another in nature.
There are three main types of rock involved in the rock cycle;
- igneous rocks are derived from the cooling and solidification of molten magma
- metamorphic rocks are changed rocks subjected to intense pressure and temperature
- sedimentary rocks are derived from rock sediments that have been lithified.
The history of the rock in Monticello begins with igneous rock formation. Basalt is an igneous rock that forms from the cooling and solidification of molten magma. Under intense pressure and temperature regimes, they are changed to metamorphic rocks.
Agents of denudation such as wind, water and glacier weathers the rock and disintegrates it. They are then carried into basins where they are deposited. Here they form sedimentary rock.
The process still goes on as the sedimentary rock gets taken into depth, they can either melt to form igneous rock or be changed to metamorphic rocks.
learn more:
metamorphic process brainly.com/question/869769
sedimentary rocks brainly.com/question/9131992
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A liquid requires enthalpy of vaporization to transform into vapor or gas at its boiling point. Here the element absorbs heat from surroundings or heat source.
This energy is used in breaking the forces of attraction among the atoms and molecules of the element. The molecules get separated to higher distances. The energy is converted in to the kinetic energy of the molecules in gaseous form and into the internal energy in terms of the temperature of the gas.