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3 years ago

_____________________ held that all matter is made up of four “elements”— earth, air, fire, and water.

Chemistry

1 answer:

Novosadov [1.4K]3 years ago

4 0

Answer:

Democritus

Explanation:

He spoke about matter was made of tiny particles which moved in empty space

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Which of the following is the composition of an isotope of calcium (atomic number 20)?

ivolga24 [154]

20 protons

20 electrons ( as much elctrons as protons because there has to be same positive and negative to have a neutral atom)

And the number of neutrons depends of the mass number but in that case, I think that it's a Calcium atom (Ca) and so there are 20 netrons.

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3 years ago

Read 2 more answers

Which element has the same number of energy levels as aluminum (Al) and the same number of valence electrons as calcium (Ca)? A.

Rudik [331]

The answer to this question would be: <span>D. Magnesium

The </span><span>number of energy levels of aluminum is 3 which was why it was put on the 3rd row. The valence of calcium is 2 which is why it was put in the 2nd column. If you look at the periodic table, the answer should be clear that it was magnesium.</span>

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3 years ago

DNA bases are attached to _____.

horsena [70]

Answer:

sugar molecules......

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3 years ago

Does it take more, less, or the same amount of heat to melt 1.0 kg of ice at 0°C, or to bring 1.0 kg of liquid water at 0°C to t

Murljashka [212]

Answer : It takes less amount of heat to metal 1.0 Kg of ice.

Solution :

The process involved in this problem are :

$(1):H_2O(s)(0^oC)\rightarrow H_2O(l)(0^oC)\\\\(2):H_2O(l)(0^oC)\rightarrow H_2O(l)(100^oC)$

Now we have to calculate the amount of heat released or absorbed in both processes.

<u>For process 1 :</u>

$Q_1=m\times \Delta H_{fusion}$

where,

$Q_1$ = amount of heat absorbed = ?

m = mass of water or ice = 1.0 Kg

$\Delta H_{fusion}$ = enthalpy change for fusion = $3.35\times 10^5J/Kg$

Now put all the given values in $Q_1$ , we get:

$Q_1=1.0Kg\times 3.35\times 10^5J/Kg=3.35\times 10^5J$

<u>For process 2 :</u>

$Q_2=m\times c_{p,l}\times (T_{final}-T_{initial})$

where,

$Q_2$ = amount of heat absorbed = ?

m = mass of water = 1.0 Kg

$c_{p,l}$ = specific heat of liquid water = $4186J/Kg^oC$

$T_1$ = initial temperature = $0^oC$

$T_2$ = final temperature = $100^oC$

Now put all the given values in $Q_2$ , we get:

$Q_2=1.0Kg\times 4186J/Kg^oC\times (100-0)^oC$

$Q_2=4.186\times 10^5J$

From this we conclude that, $Q_1$ that means it takes less amount of heat to metal 1.0 Kg of ice.

Hence, the it takes less amount of heat to metal 1.0 Kg of ice.

5 0

3 years ago

Oxygen decays to form nitrogen. 15 8 O → 15 7 N + 0 1 e This type of nuclear decay is called

Natasha2012 [34]

The type of nuclear decay in which Oxygen decays to form nitrogen is beta plus decay.

<h3>What is a beta plus decay?</h3>

A beta plus decay is a type of decay in which a proton in an element disintegrates to produce a neutron resulting in a decrease in the atomic number of the radioactive element.

In the given equation below:

$^{15}_{7}O \rightarrow ^{15}_{7}N + ^{0}_{1}e$

Oxygen decays to form nitrogen due to a decrease in atomic number.

This is an example of beta plus decay.

In conclusion, oxygen decays to form nitrogen beta plus decay.

Learn more about beta plus decay at: brainly.com/question/12448836

#SPJ1

5 0

2 years ago