Physical and chemical change

Answer;

The above statement is true

upon heating a copper sample will expand, leading to a lower density

Explanation;

-The density of solids decreased with increase in temperature and vice versa. The increase in temperature causes the volume of the solid to increase which as a result decreases the density as Density=Mass/Volume. The temperature of a body is the average kinetic energy of the molecules present in it.

In other words; The temperature of a body is the average kinetic energy of the molecules present in it. Therefore; when heat is supplied ( or temperature is increased) the average kinetic energy increases which increases the volume and thus density decreases.

1. Different ideas from different scientists (such as schleiden and schwann)

2. B. Describe and examine cells

3. Sorry i don't remember this

hope this helps :)

Final answer:

The development of the cell theory was a collaborative effort by different scientists, including Schleiden, Schwann, and Virchow, and the invention of the microscope allowed for cells to be examined and described, making 'A. different ideas from different scientists' and 'B. examine and describe cells' the correct answers for the respective questions. The nucleus contains directions for cell growth and reproduction, so 'C. nucleus' is the correct answer for the third question.

Explanation:

The development of cell theory involved different ideas from different scientists. Scientists like Schleiden, Schwann, and Virchow contributed to the theory that all organisms are made of cells, all life functions occur within cells, and all cells come from other cells. Hence, the correct answer to the first part of the question is A. different ideas from different scientists.

The invention of the microscope, including the advanced electron microscope in the 1950s, allowed scientists to examine and describe cells. They were able to see organelles and other structures inside cells for the first time. Therefore, the answer to the second part of the question is B. examine and describe cells.

As for the cell part containing directions for cell growth and reproduction, the correct answer is C. nucleus. The nucleus of a cell contains DNA, which holds the hereditary material and instructions for cell growth, function, and reproduction.

Answer:

8.10 days  

Explanation:

The half-life of gold-198 (2.70 days) is the time it takes for half the gold to decay.  

After one half-life, half (50 %) of the original amount will remain.

After a second half-life, half of that amount (25 %) will remain, and so on.

We can construct a table:

No. of half-lives  Fraction remaining

            1                       [tex]\frac{1}{2}[/tex]  

            2                      [tex]\frac{1}{4}[/tex]

            3                     [tex]\frac{1}{8}[/tex]  

Thus, the gold will decay to ⅛ of its original mass after three half-lives.

∴ Time required = 3 × 2.70 days = 8.10 days

The exact time it would take for a 180 G sample of AU-198 to decay to 1/8 of its original mass depends on the half-life of AU-198, which isn't provided here. However, theoretically, it would take three half-lives for a substance to decay to 1/8 of its original mass.

The question is asking for the time it will take for a 180 G sample of AU-198 to decay to 1/8 it's original mass. AU-198 represents gold-198, which is a radioactive isotope of gold.

In radioactive decay problems, the time it takes for a substance to decay is dependent on the half-life of the substance. Without the specific half-life of AU-198 provided, we can only describe the general formula for calculating decay time.

The half-life of a radioactive isotope is the time it takes for half of the atoms in a sample to decay. This process is exponential, meaning after each half-life, half of the remaining atoms will decay.

To decay to 1/8 of the original mass, the substance has to go through 3 half-lives (since 1/2^3 = 1/8). So, the total time it would take for a sample to decay to 1/8 of its original mass would be 3 times the half-life of this isotope.

Once you obtain the half-life value of AU-198, simply multiply it by 3 to get the answer. Remember that the unit of your answer should be in the same unit as the half-life is given.

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Unbalanced force acts on it

Answer: The density of a substance is 2 g/mL

Explanation:

To calculate the mass of solution, we use the equation:

[tex]\text{Density of substance}=\frac{\text{Mass of substance}}{\text{Volume of substance}}[/tex]

We are given:

Mass of a substance = 40 g

Volume of a substance = 20 mL

Putting values in above equation, we get:

[tex]\text{Density of a substance}=\frac{40g}{20mL}=2g/mL[/tex]

Hence, the density of a substance is 2 g/mL

The density of a substance that has a mass of 40g and a volume of 20mL is 2g/mL.

HOW TO CALCULATE DENSITY:

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Answer:

Stars are made of gas.

Star color is related to temperature.

Explanation:

Stars are big ball of gases mainly hydrogen and helium. Stars can be bigger than sun or smaller. They appear as flat circles but are spheres. The brightness of star depends on their size and distance but not on their shape. Color of star is related to temperature. A blue color star is hotter than a yellow star. A red star is a cool star.

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Sample b 10 mL of water and sample c 20 mL of water have the same boiling point ,therefore option (b) and option (c) are correct .

The boiling point is defined as the temperature at which a liquid’s saturated vapor pressure equals the atmospheric pressure surrounding it.

The boiling point of water is the temperature at which the liquid water vapor pressure is equal to the pressure surrounding the body, and the body transforms into a vapor.

The boiling point is the temperature for a particular liquid to boil at.

For example, the boiling point for water, at a pressure of 1 a t m, is 100 degrees Celsius.

Sample b 10 mL of water and sample c 20 mL of water have the same boiling point ,hence option (b) and option (c) are correct .

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Helium- 2

Aluminum- 3

Fluorine- 7

Sodium- 1

Hope I helped.

The correct match of each element with its valence electron is as follows:

Valence electron is any of the electrons in the outermost shell of an atom capable of forming bonds with other atoms.

The number of valence electrons possessed by the atoms of an element determines the chemical reactivity of such element and it's groups on the periodic table.

According to this question, the appropriate valence electron has been assigned to each element based on their group on the periodic table.

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The volume of O2 gas  that is produced from  2.80 L of CO2 at STP is  1.40 L

write a balanced chemical equation

2Na2O2 + 2CO2 → 2Na2CO3 +O2

by use of mole ratio between CO2:O2 which is 2:1 the number of liters of O2 produced is therefore= 2.8 x 1/2 =1.40 Liters

Answer: The volume of [tex]O_2[/tex] produced will be 1.4 liters.

Explanation:

AT STP, the conditions are:

1 mole of a gas occupies 22.4 liters of volume.

The balanced chemical equation for the reaction follows:

[tex]2Na_2O_2+2CO_2\rightarrow 2Na_2CO_3+O_2[/tex]

By Stoichiometry of the reaction:

2 moles of carbon dioxide produces 1 mole of oxygen gas, which means that

44.8 liters of carbon dioxide gas produces 22.4 liters of oxygen gas.

So, 2.8 liters of carbon dioxide gas will produce = [tex]\frac{22.4}{44.8}\times 2.8=1.4liters[/tex] of oxygen gas.

Hence, the volume of [tex]O_2[/tex] produced will be 1.4 liters.

I think the answer is B

The correct answer is option B which is fusion occurs in the sun.

When you are asked a question like this, you can always ask yourself this question. Can I change it back after this change? For example, if you are burning wood, you cannot bring it back to wood after you burn it, therefore, it is a chemical change. However, if you boil and evaporate water, you can make the water condense again back into its liquid form. In this case, you cannot bring the tomato back to its raw state. Therefore, cooking raw tomatoes is a chemical change.

The answer to your question is,

C. Cloud of dust and gas in space.

-Mabel <3

a nebula is a  cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter.

therfore your answer would be C  cloud of dust and gas in space

question answered by

(jacemorris04)

Alkali metals are rarely found in pure form because they are so reactive.

Alkali metals are in Group 1 of the Periodic Table.

They need to lose only one valence electron to reach a filled valence shell

Thus, they readily react wirh water and other chemicals in the earth to form compounds.

molarity (M) = mol / Liters

molarity = ?

mol of LiNO3 = 0.50 mol

Volume = 6.50 L

molarity = 0.50 mol / 6.50 L

molarity = 0.0769 mol/L

Hope this help!

Molarity is calculated by taking the ratio of no. of moles of solute to the volume of solution in liter. The molarity of the solution containing 0.50 mol of the solute in 6.50 L of solution is 0.07 M.

Molarity is a term used to represent the concertation of a solution. Mathematically it is the ratio of no. of moles of solute to the volume of solution in liters.

Given that the no. of moles of solute is 0.50 and the volume is 6.50 L. Molarity of this solution is calculated as follows;

Molarity = no.of moles/ volume in L

             = 0.50 mol / 6.50 L

             = 0.07 mol/L

Hence, molarity of the given solution is 0.07 molar.

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electrical energy and mechanical energy

Answer : The excess reactant in the combustion of methane in opem atmosphere is [tex]O_{2}[/tex] molecule.

Solution : Given,

Mass of methane = 23 g

Molar mass of methane = 16.04 g/mole

The Net balanced chemical reaction for combustion of methane is,

[tex]CH_4(g)+2O_2(g)\rightarrow CO_2(g)+2H_2O(g)[/tex]

First we have to calculate the moles of methane.

[tex]\text{ Moles of methane}=\frac{\text{ Given mass of methane}}{\text{ Molar mass of methane}}[/tex] = [tex]\frac{23g}{16.04g/mole}[/tex] = 1.434 moles

From the above chemical reaction, we conclude that

1 mole of methane react with the 2 moles of oxygen

and 1.434 moles of methane react to give [tex]\frac{2moles\times 1.434moles}{1moles}[/tex] moles of oxygen

The Moles of oxygen = 2.868 moles

Now we conclude that the moles of oxygen are more than the moles of methane.

Therefore, the excess reactant in the combustion of methane in open atmosphere is [tex]O_{2}[/tex] molecule.

Answer:

NaCI and H20

To simplify it.

Answer:

The products are NaCl and H₂O

Explanation:

The complete question is:

"Hydrochloric acid, or HCl, reacts with solid NaOH. What are the products of this chemical reaction?

HCl and NaCl

NaCl and H2O

NaOH and HCl

NaOH and H2O"

Neutralization reactions are the reactions between an acid and a base, producing salt and water. It is the type of reaction that happens in this case.

An acid and a base are strong when fully ionized, that is, in the ionization process they completely transform into positive cations or ions and negative anions or ions. So, a strong acid is an acid that completely dissociates into hydrogen ions and anions in solution.

In this case, both the HCl acid and the NaOH base are strong, completely dissociating as follows:

HCl → H⁺ + Cl⁻

NaOH → Na⁺ + OH⁻

So you have:

H⁺ + Cl⁻ + Na⁺ + OH⁻ → ?

The hydroxide anions and the hydrogen cations will neutralize each other to produce water.

H⁺ + OH⁻ → H₂O

So the sodium Na anions and Cl cations will form the NaCl salt.

Finally, the balanced chemical equation is

HCl + NaOH → NaCl +  H₂O

The answer should be "A. Electrical Conductivity". I really hope I helped! Have a great day!

Answer:

Homeostasis is the maintenance of a stable internal environment despite changing external conditions.

Explanation:

In other words the answer is D. (:

Homeostasis is the maintenance of a stable internal environment despite changing external conditions. Thus option D is correct.

Homeostasis is the natural process of  cell response to its environment to remain as the steady state between internal conditions and outer environment.

In this process cell maintains temperature, fluid, sugar balance through it For Example when the outside climate is cold we start shivering and get energy from ATP to regulate our body temperature.

The primary components of homeostasis are  stimulus from a change in the environment, the receptor which react to the change by informing the control unit.

The control unit which communicates the change in the body, The effector receives the information and acts on the change.

Thus option D is correct.

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Air is not a compound because oxygen and nitrogen stay seperately in air instead of reacting nitric oxide which is toxic. Same thing apply to other gases. Of course there are also few compound inside the air. However, air you breathe in generally is mixture made up of different non reacting gases and gas compounds.

mark brainliest plssss

Answer: Air is a mixture

Explanation:

Mixture is a substance which has two or more components which do not combine chemically and do not have any fixed ratio in which they are present. Example: Air

Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Carbon [tex](C)[/tex] , Oxygen [tex](O)[/tex]

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water [tex]CO_2[/tex]

Thus Air is a mixture as it is composed of various gases which are not chemically bonded.

Answer:

D. 0.044 m3

Explanation:

it would be B because warm humid air+cool land=fog

Answer: B) Use headlights and drive slowly if you encounter dense fog.

Explanation: Fog begins to form when water vapor condenses into liquid water droplets that are suspended in the air. This happens when the air has a lot of moisture and when the temperature is low (because in this way the water in the air condenses). So if a weather station predicts that warm humid air will pass over much cooler land, the precaution must be to use healights and drive slowly because it will probably be dense fog.

Answer is: there are two compounds with molecular formula C₂H₆O, one alcohol and one ethar.

Alcohol with molecular formula C₂H₆O is ethanol or ethyl alcohol (C₂H₅OH).

Ethanol is a volatile, flammable, colorless liquid with characteristic odor.

Ether with molecular formula C₂H₆O is dimethyl ether (CH₃OCH₃).

Dimethyl ether is a colorless gas.

Answer:

Alcohol :CH₃-CH₂-OH (ethanol)

Ether: H₃C-O-CH₃  (dimethyl ether)

Explanation:

Alcohols are compounds containing the hydroxyl or the -OH functional group i.e. R-OH where R is an alkyl or aryl group

Ethers are compounds with a general structure, R-O-R' where R and R' are once again either alkyl or aryl groups.

The given compound has a molecular formula: C₂H₆O

Structure with 'alcohol' -OH functional group

CH₃-CH₂-OH ------- ethanol

Structure with ether functionality:

H₃C-O-CH₃     ---------dimethyl ether

D: is the anwser that your looking for

Answer:

A variable or alteration to one part that affects an entire system

Explanation:

In both glasses have juices of same mass. But the temperature is different due to which the kinetic energy of molecules in both glasses is different.

As kinetic energy is directly proportional to temperature.

To make the kinetic energy of the molecules equal she should:

               or

The answer would be "C" increase glass a by 15 degrees