Please help me, I really need it, God Bless you <3

Answer:

b. the development of new vaccine prevents disease from spreading

Answer:

the option A is right matter keeps it's chemical makeup like size shape volume and state

An element is a substance that cannot be broken down into any other substance.

I hope this answer helps you..

Answer: Well, 365 days is about how long it takes for Earth to orbit all the way around the Sun one time. It's not exactly this simple though. An Earth year is actually about 365 days, plus approximately 6 hours.

Answer:  A

Explanation:  10^-7 means that the decimal point is 7 digits to the left (the "-" sign) of the 2.  Move the decimal point left seven times, putting a "0" for each step. and then place the decimal point.  A "0" is added to the left of the decimal point for clarity.

2.98x10^-7

1st)  0.298x10^-6

2nd)  0.0298x10^-5

etc, for 7 times

0.000000298

The scientific notation for 2.98 x 10^-7 will be .000000298. The correct option is A.

Scientific notation is a method of writing extremely large or extremely small numbers.

When a quantity between 1 and 10 is multiplied by a power of 10, it is written in scientific notation.

The proper scientific notation format is a x 10^b, where an is a number or decimal number with an absolute value greater or equal one and less than ten.

The b is the power of ten required for scientific notation to be mathematically equivalent to the original number.

A positive exponent indicates that the decimal point has been moved that many places to the right.

A negative exponent indicates that the decimal point has been shifted that many places to the left.

As in the given number, 2.98 x 10^-7 the exponent is negative so the decimal will shift seven times to left of the digit making it .000000298.

Thus, the correct option is A.

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Answer:

1. to purify sugar , I think it is correct answer

Explanation:

hope it is helpful for you

thank you

Answer:

1. To purify sugar

=lime and carbon dioxide

2. To purify petroleum products

=hydrogen

The equations for the preparation of C₂H₅Br from alcohol using PX₃ and HX are shown in the attachment below.

a) Preparation of C₂H₅Br from alcohol using PX₃

In PX₃, X refers to the halides (F, Cl, Br etc.). Since the desired ethyl halide is ethyl bromide (C₂H₅Br) , then X in PX₃ will be Br. Therefore, PBr₃ will be used in the reaction as shown in the attachment below.

b) Preparation of C₂H₅Br from alcohol using HX

Also, In HX, X refers to the halides (F, Cl, Br etc.). Since the desired ethyl halide is ethyl bromide (C₂H₅Br), then X in HX will be Br. Therefore, HBr will be used in the reaction as shown in the attachment below.

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Answer:

It is melting which is a physical change.

Explanation:

[tex].[/tex]

The process is a physical change because the chocolate and marshmallow melted.

You included no options but this is a physical change because the question mentioned that the chocolate melted.

A physical change occurs when the state of matter changes but the chemical properties remain the same. Physical changes include:

In conclusion therefore, the chocolate and marshmallow melted and so underwent a physical change.

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Answer: 69.152% → 63^Cu

30.848% → 65^Cu

Explanation:

As you know, the average atomic mass of an element is determined by taking the weighted average of the atomic masses of its naturally occurring isotopes.

Simply put, an element's naturally occurring isotopes will contribute to the average atomic mass of the element proportionally to their abundance.

Explanation:

Answer: Using the science method helps other because It helps you put together experiments, and use data to find conclusions and interpret them.

Explanation: Hope this helps!

Answer:

A spider

B termite

C 2nd

D grassy environment

E the clams will grow in numbers  

Explanation:

Answer:a- spider b-lizard c- the second one (II) d- you can literally find it in your backyard or a field e- the number of clams will increase

Explanation:

Answer:

lead

Explanation:

As we know the formula

[tex]\boxed{\sf Density=\dfrac{Mass}{Volume}}[/tex]

[tex]\\ \sf\longmapsto Volume=\dfrac{Mass}{Density}[/tex]

Answer:

Option 1

Explanation:

Option number 1 is the most compact one which indicates it is a solid

Answer:density

Explanation:

it’s how’s how dens the ball is

The number of atoms will be 3.131 x [tex]10^{25}[/tex],  7.8286 x [tex]10^{24[/tex], and 7.8286 x [tex]10^{24[/tex] atoms respectively.

There are 6.022 x [tex]10^{23}[/tex] atoms in 1 mole of every substance.

52 moles of Ar will contain 52 x 6.022 x [tex]10^{23}[/tex] = 3.131 x [tex]10^{25}[/tex] atoms

52 u of He = 52/4 = 13 moles of He.

13 moles of he = 13 x 6.022 x [tex]10^{23}[/tex] = 7.8286 x [tex]10^{24[/tex] atoms

52 g of He = 52/4 = 13 moles of He.

13 moles of he = 13 x 6.022 x [tex]10^{23}[/tex] = 7.8286 x [tex]10^{24[/tex] atoms

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1. The number of atoms in 52 mole of Ar is 3.13×10²⁵ atoms

2. The number of atoms in 52 u of He is 7.83×10²⁴ atoms

3. The number of atoms in 52 g of He is 7.83×10²⁴ atoms

1 mole of substance = 6.02×10²³ atoms

1 mole of Ar = 6.02×10²³ atoms

Therefore,

52 mole of Ar = 52 × 6.02×10²³

52 mole of Ar = 3.13×10²⁵ atoms

4 u of He = 1 mole

Thus,

52 u of He = 52 / 4

52 u of He = 13 moles

From Avogadro's hypothesis,

1 mole of He = 6.02×10²³ atoms

Therefore,

13 moles of He = 13 × 6.02×10²³

13 moles of He = 7.83×10²⁴ atoms

Thus,

52 u of He = 7.83×10²⁴ atoms

4 g of He = 1 mole

Thus,

52 g of He = 52 / 4

52 g of He = 13 moles

From Avogadro's hypothesis,

1 mole of He = 6.02×10²³ atoms

Therefore,

13 moles of He = 13 × 6.02×10²³

13 moles of He = 7.83×10²⁴ atoms

Thus,

52 g of He = 7.83×10²⁴ atoms

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Answer:

Density of the rectangular object = 4 / 6 = 0.67g/cm³

Explanation:

First find the volume of the rectangular object.

Volume of the rectangular object = 3 x 2 x 1 = 6cm³.

Density of an object = mass of the object / volume of the object

Therefore,

Density of the rectangular object = 4 / 6 = 0.67g/cm³

Answer:

I think he was right but not explaining

Explanation:

I think it is C cause.... the volume of a material is the amount of matter that matterial can hold. it should the the amount of space the whole material takes up.

so C is the answer.

pls make this the brainliest.

not because it is, but because I asked.

Answer:

yyreyytryrryrtryryyye

Explanation:

Answer:

130 gram

Explanation:

first subtract 180 to 100

then the answer is 80

now add 80 to 250

the answer is 330

lastly subtract 330 with 250

the final answer is 130

Explanation:

just trying.....hope that helps

Answer:D.the train must be able to maintain a speed of 250km/h.

Explanation:

Density, which is the mass per unit volume, is a constant for a material, and does not depend on the size of the sample tested

[tex]Density = \mathbf{\dfrac{m}{v}} = \rho = \mathbf{Constant \ for \ the \ material}[/tex]

The steps taken to arrive at the above statement are as follows:

The density of a substance is its mass per unit volume. Mathematically, density can be expressed as follows;

[tex]Density = \mathbf{\dfrac{Mass}{Volume}}[/tex]

Let m₁ represent the mass and let v₁ represent the volume, of an object. Let m₂ represent the mass of double the the object, so that we have;

m₂ = 2 × m₁

The volume of m₂, v₂ = 2 × v₁

The ratio of the difference in the change in mass to the change in volume between the samples, m₁ and m₂, is given as follows;

[tex]\dfrac{\Delta m}{\Delta v} = \dfrac{m_2 - m_1}{v_2 - v_1} = \dfrac{2 \times m_1 - m_1}{2 \times v_1 - v_1} = \dfrac{m_1}{v_1} = \rho_1[/tex]

Therefore as Δv = v₂ - v₁ approaches zero, that is as the mass m₁ approaches m₂, we have;

[tex]\lim \limits_{\Delta v \to 0} \dfrac{\Delta m}{\Delta v} =\mathbf{ \dfrac{dm}{dv}}[/tex]

Which gives;

[tex]\mathbf{\lim \limits_{\Delta v \to 0} \dfrac{\Delta m}{\Delta v} } = \dfrac{dm}{dv} = \mathbf{\dfrac{Mass \ of \, sample}{Volume \ of \, sample}} = \mathbf{Density, \ \rho}[/tex]

Therefore, the rate of change of mass to volume of a sample to the volume of the sample is constant which gives that the mass of a sample is directly proportional to the volume of the sample and the ratio of the mass of the sample to the volume of the sample is a constant equal to the density of the substance

Which gives that the density of a substance which is the mass/volume is constant for all masses of the substance and does not depend on the size of the sample tested

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Answer:

Jupiter

Explanation:

Fifth in line from the sun, Jupiter is, by far, the largest planet in the solar system.

Ans 1:

Ammonia is not collected over water since it is highly soluble in water

Ans 2:

Ammonia gas is lighter than air and hence collected by the downward displacement of air.

Ans 3:

The carbon dioxide is very cold as it comes out of the extinguisher, so it cools the fuel as well.

Ans 4:

H₂SO₄ is not used in the preparation of carbon dioxide Because the calcium sulphate formed is insoluble in water. So, CO₂ will not form.

Ans 5:

The opening of hard glass test tube is slanted down during laboratory preparation of ammonia gas because Ammonia gas is not collected in the gas jar by upward displacement of air because it is lighter than air

Ans 6:

Magnesium is reactive enough to be combusted and oxidized in a reaction with carbon dioxide:

The magnesium strip burns brightly in the air, but continues to burn in the carbon dioxide environment

-TheUnkownScientist

Answer:

Gold is a Chemical element