A system is a part of the <em>physical</em> universe defined <em>arbitrarily</em> for observation purposes.
Boundaries are a part of the <em>physical</em> universe that are around the system.
In a scientific sense, a system is a part of the <em>physical</em> universe whose boundaries, that is, the limit between the system and its surroundings, are defined <em>arbitrarily</em> for observation purposes.
A system contains at least a model, represented in a phenomenological way, and it can be isolated (no mass nor energy interactions), closed (no mass interactions) or open.
The surroundings are a part of the <em>physical</em> universe that are around the system.
An example is a coffee-maker, where coffee-maker the system and air represents the surroundings, the coffee-maker receives energy from a heat source to warm up itself and releases part of such energy to the air.
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Answer:
propagation of disturbances—that is, deviations from a state of rest or equilibrium—from place to place in a regular and organized way. Most familiar are surface waves on water, but both sound and light travel as wavelike disturbances, and the motion of all subatomic particles exhibits wavelike properties.
Explanation:
<span>The symbol for the element whose atoms have 40 electrons each is Zr. This is the element zirconium. In the atoms of a pure element, the number of positively charged protons is normally equal to the number of negatively charged electrons. Hence, the number of electrons in the atom can be inferred from the atomic number, which corresponds to the number of protons in an atom. The atomic number of zirconium is 40.</span>
Lithium's atomic weight is 6.94 g/mol.

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Answer:
12.62 L
Explanation:
First, we have to calculate the moles corresponding to 18.0 g of oxygen gas (MW 32.0).
18.0 g × (1 mol/32.0 g) = 0.563 mol
Then, we can find the volume occupied by 0.563 moles of oxygen at STP (273,15 K, 1.00 atm) using the ideal gas law.
P × V = n × R × T
V = n × R × T / P
V = 0.563 mol × 0.0821 atm.L/mol.K × 273.15 K / 1.00 atm
V = 12.62 L