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3 years ago

Which is a sign of a chemical change?

Physics

2 answers:

zalisa [80]3 years ago

7 0

Answer: a sign of chemical change is when a new substance is created.

Explanation:

When iron sits out in the rain it will begin to rust. Rust is a sign of chemical change because it did not exist before the iron became wet.

Molodets [167]3 years ago

5 0

Answer: When chemical change occurs you will see like, the change of color or bubbles will form, the temperature will change, and maybe the odor too.

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8. Three grams of Bismuth-218 decay to 0.375 grams in one hour. What is the half-

Evgen [1.6K]

Answer: 0.333 h

Explanation:

This problem can be solved using the Radioactive Half Life Formula:

$A=A_{o}.2^{\frac{-t}{H}}$ (1)

Where:

$A=0.375 g$ is the final amount of the material

$A_{o}=3 g$ is the initial amount of the material

$t=1 h$ is the time elapsed

$H$ is the half life of the material (the quantity we are asked to find)

Knowing this, let's substitute the values and find $h$ from (1):

$0.375 g=(3 g)2^{\frac{-1h}{H}}$ (2)

$\frac{0.375 g}{3 g}=2^{\frac{-1h}{H}}$ (3)

Applying natural logarithm in both sides:

$ln(\frac{0.375 g}{3 g})=ln(2^{\frac{-1 h}{H}})$ (4)

$-2.079=-\frac{1 h}{H}ln(2)$ (5)

Clearing $H$ :

$H=\frac{-1h}{-2.079}(0.693)$ (6)

Finally:

$h=0.333 h$ This is the half-life of the Bismuth-218 isotope

4 0

4 years ago

Movement of a stationary object it's called what?

kumpel [21]

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3 years ago

The gold has a density of 19300 kg/m3 calculate the mass of one gold bar 1= 2.54cm

icang [17]

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If you decrease the distance between successive crests of a wave, this changes

AlexFokin [52]

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Answer:

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Explanation:

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