Which of the following is an example of a chemical change? *
A Nitrogen and oxygen mix to form air
Salt dissolves in a glass of water
Hydrogen and oxygen to form water
a solid changes to a liquid

Answer: A

Explanation:

The white Dwarfs are a group of stars that are extremely bright and hot. Hence option A is correct.

Stars are defined as any large gaseous heavenly body that emits light as a result of its own internal energy sources. Stars are celestial bodies that generate their own energy through the fusing of gases. They resemble bright orbs that burn gas and produce energy. Our solar system's star, the Sun, generates energy through the fusion reaction in which helium transforms into hydrogen.

When a white dwarf first forms, it is extremely hot, but because it has no energy source, it will gradually cool as it emits its energy into space. This implies that the color temperature of its radiation, which is initially high, will gradually decrease and turn red. After using up all of their nuclear fuel, stars like the Sun become white dwarfs.

Thus, the white Dwarfs are a group of stars that are extremely bright and hot. Hence option A is correct.

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Answer:

both have internal organization dog only has living cells both use energy dogs only produce offspring computers only lack genetic material

Answer:

It's most probably

A non metal

Answer:

Tissue level of organization

Explanation:

The various levels of the organization of life are as follows:

Cells: a cell is the basic unit of ife

Tissues; A tissue is a group of cells with a common origin. performing similar functions.

Organ: an organ is a group of tissues with varied or similar function that work together to perform a specific function.

System: a system is a group of different organs that work together in the body to perform a specific function.

Since, the leaf is an organ in the plant that performs the function of photosynthesis, the group of dermal cells found on the leaf are in the tissue level of organization, they perform the function of protection for the leaf.

Answer:

E = 3.035× 10-¹⁹J = 1.9eV

f = 4.58 × 10¹⁴Hz

Explanation:

wavelength = 6.55 × 10-⁷m

c = 3 × 10⁸m/s

f = ?

E = ?

a) f = c/wavelength

f = 3 × 10⁸/6.55 × 10-⁷

f = 4.58 × 10¹⁴Hz

b) E = hc/wavelength

E = 6.626×10-³⁴ × 3 × 10⁸/ 6.55 × 10-⁷

E = 3.035 × 10-¹⁹J

1ev = 1.6 × 10-¹⁹J

Therefore E = 3.035/1.6 = 1.9eV

Explanation:

speed of light = wavelength * frequency

frequency =speed of light/wavelength

Let frequency = F

Speed of light = 3.0 *10^8

wavelength = 6.55 * 10^-5 cm = 6.55 * 10^-7m

Therefore F= 3.0 *10^8m/s *6.55 * 10^-7m

F = 196.5Hz

Energy = Planck's constant * frequency

Let energy be E

Planck's constant = 6.63 * 10^-34Joule/ seconds

E = 6.63 * 10^-34 * 196.5Hz

E=1.3027 * 10^-31 J

Answer:

naci

Explanation:

The molar concentration of the CH₃COOH soluttion is 0.33 M

We'll begin by writing the balanced equation for the reaction. This is given below:

CH₃COOH + NaOH —>CH₃COONa + H₂O

From the balanced equation above,

The mole ratio of the acid, CH₃COOH (nA) = 1

The mole ratio of the base, NaOH (nB) = 1

From the question given above, the following data were obtained:

Volume of acid, CH₃COOH (Va) = 15 mL

Molarity of base, NaOH (Mb) = 0.2 M

Volume of base, NaOH (Vb) = 24.55 mL

MaVa / MbVb = nA/nB

(Ma × 15) / (0.2 × 24.55) = 1

(Ma × 15) / 4.91 = 1

Cross multiply

Ma × 15 = 4.91

Divide both side by 15

Ma = 4.91 / 15

Therefore, the molar concentration of the acid, CH₃COOH is 0.33 M

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Answer:

Sustancia  Masa (g)  Composición (% m/m)

Proteínas      5,5                  4,4

Azúcares      5,0                  4,0

Sodio            0,06               0,048

Potasio         0,15                 0,12

Explanation:

Para calcular la composición porcentual en masa de las sustancias debemos usar la siguiente ecuación:

[tex] \%_{m/m} = \frac{m_{s}}{m_{sol}} \times 100 [/tex]

En donde:

[tex]m_{s}[/tex] es la masa de la sustancia

[tex]m_{sol}[/tex] es la masa del yogurt = 125 g

Para las proteínas:

[tex] \%_{m/m} = \frac{m_{s}}{m_{sol}} \times 100 = \frac{5,5 g}{125 g} \times 100 = 4,4 \% [/tex]

Para los azúcares:

[tex] \%_{m/m} = \frac{5,0 g}{125 g} \times 100 = 4,0 \% [/tex]

Para el sodio:

[tex] \%_{m/m} = \frac{0,06 g}{125 g} \times 100 = 0,048 \% [/tex]

Para el potasio:

[tex] \%_{m/m} = \frac{0,15 g}{125 g} \times 100 = 0,12 \% [/tex]

Espero que te sea de utilidad!    

Answer:

F.1s 2s 2p 3s 3p 4s3d104p

The element in the first configuration is F and the element in the second option is calcium Ca. The configuration in option c is of cerium Ce and it is cadmium in option D. The configuration in E is mendelevium and F is zinc.

An electronic configuration represents the filling of electrons in various energy level. Electrons fill from the lowest energy levels to the highest energy level.

The first configuration have a total of 9 electrons. The 9th element is fluorine. The second configuration given is of 20 electrons. That is 18 electrons of argon plus 2 electrons in 4s. The 20th element is calcium.

The third configuration have 58 electrons and the element is cerium Ce. The configuration given in option D is of cadmium with 48 electrons and that in option E is mendelevium with 101 electrons.

In the last option, the configuration contain a total of 30 electrons. 3o th element in periodic table is zinc, Zn.

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Answer:

I don't think u finished the question -

Answer:

See explanation

Explanation:

Crystals can be made from methanol by recrystallizing the plant extract from methanol.

The methanol/water system is heated rapidly using a hot plate and the plant extract dissolves in the heating solution until a clear solution is obtained.

The solution is now cooled rapidly. The interior of the flask used for the re crystallization may even by scratched to assist the quick formation of crystals. Large crystals of plant compounds may be obtained using this method. This process should be carried out in a fume hood because of the toxicity of methanol.

Answer:

indian ocean

Explanation:

Answer:

The pressure when the stopcock is opened is opened is 87.783 cm

Explanation:

The given parameters of the question are;

The volume of the vessel of chlorine = 400 cc

The pressure of the vessel of chlorine = 80 cm

The volume of the vessel of chlorine = 250 cc

The pressure of the vessel of chlorine = 100 cm

Daltons law of Partial Pressures states that the total pressure exerted by a volume of a mixture of gases is equal to the partial pressures exerted by the individual gases in the mixture with respect to the given volume

Therefore;

The total volume of the mixture = 400 cc + 250 cc = 650 cc

The partial pressure exerted by the chlorine gas in the total volume is given by Boyles law as follows;

P₁·V₁ = P₂·V₂

P₂ = P₁·V₁/V₂

Where;

P₁ = 80 cm = The pressure in volume V₁ = 400 cc

P₂ₓ = The partial pressure of chlorine in volume V₂ = 650 cc

Substituting, we have;

P₂ₓ = 80 × 400/650 ≈ 49.321 cm

Similarly, the partial pressure exerted by the nitrogen gas in the total volume is given by Boyles Law as follows;

P₂ₐ = P₁·V₁/V₂

Where;

P₁ = 100 cm = The pressure in volume V₁ = 250 cc

P₂ₐ = The partial pressure of nitrogen in volume V₂ = 650 cc

Substituting, we have;

P₂ₐ = 100× 250/650 ≈ 38.462 cm

The pressure of the combined gas, P, when the stopcock is opened is opened is given by Dalstons Law of partial pressure as P = P₂ₐ + P₂ₓ

Therefore, the pressure, P when the stopcock is opened is opened = 49.321 cm + 38.462 cm = 87.783 cm

Answer:

15 grams

Explanation:

Answer:

Ionic compounds conduct electricity when molten (liquid) or in aqueous solution (dissolved in water), because their ions are free to move from place to place. Ionic compounds cannot conduct electricity when solid, as their ions are held in fixed positions and cannot move

Explanation:

Answer:

In thermodynamics, the Joule–Thomson effect describes the temperature change of a real gas or liquid when it is forced through a valve or porous plug while keeping it insulated so that no heat is exchanged with the environment. This procedure is called a throttling process or Joule–Thomson process

Answer:

Explanation:

Glaciers are melting, sea levels are rising, cloud forests are dying, and wildlife is scrambling to keep pace. It has become clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than at any time in the last 800,000 years.

We often call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place. While many people think of global warming and climate change as synonyms, scientists use “climate change” when describing the complex shifts now affecting our planet’s weather and climate systems—in part because some areas actually get cooler in the short term.

Climate change encompasses not only rising average temperatures but also extreme weather events, shifting wildlife populations and habitats, rising seas, and a range of other impacts. All of those changes are emerging as humans continue to add heat-trapping greenhouse gases to the atmosphere, changing the rhythms of climate that all living things have come to rely on.

What will we do—what can we do—to slow this human-caused warming? How will we cope with the changes we've already set into motion? While we struggle to figure it all out, the fate of the Earth as we know it—coasts, forests, farms, and snow-capped mountains—hangs in the balance.

Answer:

argon is an inert gas

Explanation:

an inert gas is when a chemical helium, xenon, neon, krypton, radon are also inert gases

Answer: Q4=1 Q5=2

Explanation:

Best of luck.

Answer:

4. '4' "pathogens can interfere with normal life functions."

5. '2' "synthesizing antibodies that mark these organisms to be destroyed."

Explanation:

Answer:

Mesosphere

Stratosphere

Thermosphere

Troposphere

Exosphere

Explanation:

The exosphere refers to the farthest region of the atmosphere that gradually fades into space.

The troposphere is the lowest layer of atmosphere. It is the layer where weather changes occur.

The thermosphere is right above the mesosphere but just below the exosphere. It is the layer where photoionization/photodissociation of molecules occurs thereby creating ions. This largely owes to interaction of molecules in this layer with ultraviolet radiation.

The stratosphere is composed of gases. Prominent among them is ozone which serves as a blanket against the sun's ionizing radiation.

The mesosphere lies above the stratosphere but just below the thermosphere. Temperature decreases steadily with height in the mesosphere.

The 5 layers of the atmosphere are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

The atmosphere has been consisted of the 5 layers that protect the earth. The layers have been present at the height that and each layer has consisted of different constituents.

The layers of the atmosphere can be described as:

The 5 layers of the atmosphere are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

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Answer:

Excess fertilizer alters the soil by creating too high of a salt concentration, and this can hurt beneficial soil microorganisms. Over- fertilization can lead to sudden plant growth with an insufficient root system to supply adequate water and nutrients to the plant

Explanation:

Answer:

0.249087

Explanation:

1.5 x 10^23 atoms x 1 mole / 6. 022 x 10^23 atoms

= 0.249087

Answer:

1. Potassium, K.

2. Calcium, Ca.

3. Gallium, Ga.

4. Carbon, C.

5. Bromine, Br.

6. Barium, Ba.

7. Silicon, Si.

8. Gold, Au.

Explanation:

Atomic radius can be defined as a measure of the size (distance) of the atom of a chemical element such as hydrogen, oxygen, carbon, nitrogen etc, typically from the nucleus to the valence electrons. The atomic radius of a chemical element decreases across the periodic table, typically from alkali metals (group one elements such as hydrogen, lithium and sodium) to noble gases (group eight elements such as argon, helium and neon). Also, the atomic radius of a chemical element increases down each group of the periodic table, typically from top to bottom (column).

Additionally, the unit of measurement of the atomic radius of chemical elements is picometers (1 pm = 10 - 12 m).

1. Li or K: the atomic radius of lithium is 167 pm while that of potassium is 243 pm.

2. Ca or Ni: the atomic radius of calcium is 194 pm while that of nickel is 149 pm.

3. Ga or B: the atomic radius of gallium is 136 pm while that of boron is 87 pm.

4. O or C: the atomic radius of oxygen is 48 pm while that of carbon is 67 pm.

5. Cl or Br: the atomic radius of chlorine is 79 pm while that of bromine is 94 pm.

6. Be or Ba: the atomic radius of berryllium is 112 pm while that of barium is 253 pm.

7. Si or S: the atomic radius of silicon is 111 pm while that of sulphur is 88 pm.

8. Fe or Au: the atomic radius of iron is 156 pm while that of gold is 174 pm.

The atoms in each pair which has the larger atomic radius is;

Definition:

Atomic radius is simply the distance from the centre of the nucleus to the outermost shell containing electrons.

In other words, the atomic radius is the distance from the center of the nucleus to the point up to which the electron cloud density is maximum.

Trend:

The atomic radius of atoms generally decreases from left to right across a period. The atomic radius of atoms generally increases from top to bottom within a group.

It is on this basis that atoms with the larger atomic radius are determined

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Answer:

Oldest

Explanation:

toxicity

Answer:

Oldest

toxicity

Explanation:

Answer:

1) crust

2)mantle

3) asthenosphere

4)core

5) hydrosphere

Explanation:

Hope this helps, Let me know if i am wrong( i dont think i am but, yeah...), OH! and GOOD LUCK!  :D ;P.

b. ₈¹⁸O²⁻ , ₉¹⁹F⁻ , ₁₀²⁰Ne

The Atomic Number (Z) indicates the number of protons and electrons in an atom of an element.

Atomic number = number of protons = number of electrons ⇒ neutral number

Atomic mass is the sum of protons and neutrons

Atomic Number (Z) = Atomic mass (A) - Number of Neutrons

Atomic mass = 18

Atomic number = 8 , gain 2 electron ⇒ total 10 electrons

Configuration : 1s², 2s², 2p⁶ (10 electrons)

Neutrons : 18 - 8 = 10

Atomic mass = 19

Atomic number = 9 , gain 1 electron ⇒ total 10 electrons

Configuration : 1s², 2s², 2p⁶ (10 electrons)

Neutrons : 19 - 9 = 10

Atomic mass = 20

Atomic number = 10

Configuration : 1s², 2s², 2p⁶ (10 electrons)

Neutrons : 20 - 10 = 10