Copper wire is not an example of a pure element because although it's made by pure elements, it's not one itself. It's made by factories.
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The excited atom is positive when then neutral has no charge
The melting of solid wax to form liquid wax and the evaporation of liquid wax to form wax vapor are physical changes. The burning of the wax vapor is a chemical change.
Answer:
<em>Rigid plates that move around Earth's surface is called tectonic plates. </em>
Explanation:
Lithosphere is rigid and relatively cold and is the outer surface of the planet. The convective motions of maintenance break the lithosphere into plates.
This place that a form can move in any direction, can move towards each other, can move away and push each other which is the reason for formation of mountains for shifting of continents for making of ocean basin.
Answer:
= 25 g
Explanation:
Using the formula;
A = A₀ (1/2)^(t/h)
where A is the final amount,
A₀ is the initial amount of the substance,
t is the time and
h is the half-life of the substance,
In this case; the half life of U-238 h is equal to 4.47 billion years.
A = A₀ (1/2)^(t/h)
A = 50 (1/2)^(4.5 / 4.47)
= 24.88
<u> = 25 g</u>