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earnstyle [38]
3 years ago
5

Why are chemical changes considered “unseen”?

Chemistry
2 answers:
atroni [7]3 years ago
6 0
<span>The correct answer here is that the reason chemical changes can be considered unseen, is because the alterations made within an element when it undergoes a chemical change occurs within the very atoms of the cell itself. In contrast with this, a physical change (such as a solid changing to a liquid through melting) does not change the element itself, but just it's physical form, so this can be seen easily to the human eye.</span>
enot [183]3 years ago
5 0

Answer is: chemical changes are considered "unseen", because they occur at the atomic level.

There are two types of substance changes: chemical and physical.

In chemical change (chemical reaction) new substances are formed, the atoms are rearranged (atoms are invisible to human eyes).

Physical property can be observed and measured without any changes in molecular composition. The same substance is present before and after the psysical change, just with different form or state of matter, this changes are seen by human eyes because of change of color or state of matter.

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A sample of nitric acid contains both H3O ions and NO3 ions. This sample has a pH
bearhunter [10]

Answer : The name of positive ion present in this sample is, hydronium ion.

Explanation :

For formation of a neutral ionic compound, the charges on cation and anion must be balanced.

The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.

Ion : An ion is formed when an atom looses or gains electron.

When an atom looses electrons, it will form a positive ion known as cation.

When an atom gains electrons, it will form a negative ion known as anion.

As per question, hydronium ion or hydrogen ion is having an oxidation state of +1 called as H_3O^{+} or H^+ cation and nitrate ion NO_3^{-} is an anion with oxidation state of -1.

Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral HNO_3.

Hence, the name of positive ion present in this sample is, hydronium ion.

4 0
4 years ago
At room temperature and pressure, 0.4 g of neon will occupy what volume<br> of gas?
LekaFEV [45]

Answer:

"One mole of any gas has a volume of 24 dm3 or 24,000 cm3 at rtp (room temperature and pressure). This volume is called the molar volume of a gas."

Explanation:

Divide the mass of neon.

8 0
3 years ago
A gas has a volume of 75mL at a pressure of 200.0 kPa. What will be the new volume be in mL if the pressure is decreased to 60.0
devlian [24]

Answer:

The new pressure will be

1000 L, rounded to one significant figure.

Explanation:

Boyle's law states that when a gas is held at a constant temperature and mass in a closed container, the volume and pressure vary inversely. The equation to use is  p1v1=p2v2

3 0
4 years ago
Read 2 more answers
Which energy transformation occurs in an<br> electric motor?
vivado [14]

Answer:

Electrical energy to mechanical energy

Explanation:

In an electric motor, the energy transformation that is involve is a move from from electrical energy to mechanical energy.

For every system, according to the law of conservation of energy "energy is neither created nor destroyed but transformed from one form to another".

  • An electric motor converts electrical energy to mechanical energy
  • The electrical energy passes through and electromagnet set up.
  • This then cause the motion to rotate.
  • Therefore, electrical energy is transformed to mechanical energy.
5 0
3 years ago
In the mathematical equation showing that volume (V) divided by temperature (T) remains equal to a constant (k), volume and temp
NARA [144]

Answer:

Directly  

Explanation:

\dfrac{V}{T} = k

If V increases, then T must also increase to keep the same ratio.

If V decreases, then T must also decrease to keep the same ratio.

V and T are directly proportional, because a change in one always causes a change in the other and the changes are in the same ratio. The constant k is called the proportionality constant.

7 0
3 years ago
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