A homogenous mixture is uniform and thus hard to recognize as a mixture. An example is water!
Potassium is placed where it is based on its properties and it's reactivity. It's also placed there based on it's atomic number.
When water freezes into ice, some of the properties have change. What stays the same.
Answer: 1: Ice Melting is a physical change. When liquid water (H2O) freezes into a solid state (ice), it appears changed; However, this change is only physical as the the composition of the constituent molecules is the same: 11.19% hydrogen and 88.81% oxygen by mass.
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Equation for the standard formation of solid sodium orthosilicate:
4 Na(s) + Si(s) + 2 O₂(g) → Na₄SiO₄(s)
