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brilliants [131]

3 years ago

13

Chemical reactions happen when _____. a.atoms attract or repel one another b.heat is created by friction c. two or more substanc

es are mixed substances are heated or d.cooled

1 answer:

melomori [17]3 years ago

5 0

Answer:

A

Explanation:

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Lesson Four: Significant Figures in Calculations

MArishka [77]

Answer:

a) significant figures b) decimal places

Multiplying/dividing ex: 1.33 * 4.4932 = 5.98 because the first component only has three sig figs while the second has five.

Adding/subtracting ex: 12.13 + 53.5763 = 65.71 we ignore the whole numbers and focus only on the decimal places. The first component only has two while the second has four. Hope this helps!

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3 years ago

If a body was lying on their back when they died, and was moved to their front after 12 hours, where would one see the skin disc

My name is Ann [436]

Answer:the parts of the body which is nearest to the ground ie thier back will show discoloration

Explanation:

If the body remains at a position for long hours, the parts of the body which is nearest to the ground can develop a skin discoloration as a result of pooling of blood in the tissues and this is called livor mortis, which tends to be permanent from 8Hours upwards.

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3 years ago

Is glass breaking physical or a chemical

serg [7]

Answer:

<h2>physical </h2>

Explanation:

I hope this helps

3 0

3 years ago

A sample of paper from an ancient scroll was found to contain 39.5% 14C content as compared to a present-day sample. The t1/2 fo

nirvana33 [79]

Answer

7665 years

Procedure

Let N₀ be the amount of carbon-14 present in a living organism. According to the radioactive decay law, the number of carbon-14 atoms, N, left in a dead tissue sample after a certain time, t, is given by the exponential equation:

N = N₀e^(-λt)

where λ is the decay constant which is related to half-life (T1/2) by the equation:

$\lambda=\frac{ln(2)}{t_{\frac{1}{2}}}$

Here, ln(2) is the natural logarithm of 2.

The percent of carbon-14 remaining after time t is given by N/N₀.

Using the first equation, we can determine λt.

The half-life of carbon-14 is 5,720 years, thus, we can calculate λ using the second equation, and then find t.

$\lambda=\frac{ln(2)}{5720}=1.211\times10^{-4}$

Solving the second equation for t, and using the λ we have just calculated we will have

t= 7665 years

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1 year ago

2,6 -dimetil nonano<br> 4 etil-2,2dimetil-4-propo:0ctano

Svetllana [295]

Answer:

it will be 26 %t _4

Explanation:

do the math and tst

7 0

3 years ago