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Marat540 [252]
4 years ago
6

Which of these is an example of a physical change ?

Chemistry
1 answer:
Gre4nikov [31]4 years ago
8 0
It's 1. Melting a substance. The rest are chemical changes
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Calculate the energy of a photon with a frequency of 2.36 x 10-19 Hz.
OlgaM077 [116]

Answer:

Explanation:

energy for photon is calculated in same wasy as for electromagnetic radiation

energy for electromagnetic radiation = hf

where f is the frequency of photon

h is Planck's constant = h = 4.14 × 10−15 eV · s.

thus

energy of photon = 4.14 × 10−15 eV · s *  2.36 x 10-19 Hz

energy of photon = 9.77 * 10−(-15+ -19) eV

energy of photon = 9.77 * 10−34eV        answer

6 0
3 years ago
What is the minimum amount of heat required to completely melt 40.0 grams of ice at its melting point?
elena55 [62]
If 20.0 grams of ice takes about 6680j...then 40.0 grams of ice would take ___ .
6 0
3 years ago
You are part of a team of scientists and engineers in charge of launching a new spacecraft to venus. What are two ways in which
kap26 [50]

Answer: A barrier should be created to overcome the atmosphere of the Venus, while launching spacecraft to Venus.

Explanation:

The atmosphere of Venus consists of 96.5% carbon dioxide, other composition includes nitrogen and other gases in trace amounts. The large amount of carbon dioxide in the atmosphere can extinguish the missile of the launcher of spacecraft thus it will become difficult in launch of spacecraft to the Venus.

8 0
3 years ago
What should be the temperature of the solvent before adding it to the sample to be recrystallized?
Serhud [2]

Answer:

Near the boiling point of the solvent

Explanation:

The process of recrystallization is hinged on the fact that the amount of solute that can be dissolved by a solvent increases with temperature. The process involves creation of a solution by dissolving a solute in a solvent at or near its boiling point.  At the boiling point of the solvent, the solute has a greater solubility in the solvent; not much volume of  the hot solvent is required to dissolve the solute.

Before the solution is later cooled, you can now filter out insoluble impurities from the hot solvent. The quantity of the original solute drops appreciably because impurities have been removed. At this lower temperature, the solution becomes saturated and the solute can no longer be held in solution hence it forms pure crystals of solute, which can be recovered.

Recrystallization must be carried out using the proper solvent. The solute must be relatively insoluble in the solvent at room temperature but more soluble in the solvent at elevated temperature.

3 0
3 years ago
Can someone help me please .
lyudmila [28]

Sure. Whith what do you need help?

4 0
3 years ago
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