The question requires us to calculate the mass of a block, given its density (7.8 g/cm~3) and dimensions (length = 5.0 cm; width = 6.0 cm and height = 2.0 cm).
Considering that the volume of the block can be calculated following the basic formula for volume (volume = length x width x height), we can obtain the volume of the object from the dimensions given and then use the definition of density to calculate the mass from the density and volume of the block.
First, we'll calculate the volume of the block:
[tex]\begin{gathered} \text{Volume = length}\times\text{ width }\times\text{ height} \\ \text{Volume = }(5.0cm)\times(6.0cm)\times(2.0cm) \\ \text{Volume = 60 }cm^3 \end{gathered}[/tex]Next, we must consider the definition of density (mass per volume of an object) to calculate the mass of the block:
[tex]\begin{gathered} \text{density = }\frac{mass}{\text{volume}}\to\text{mass = density}\times volume \\ \end{gathered}[/tex][tex]\begin{gathered} \text{mass = (7.8g/}cm^3)\times(60cm^3) \\ \text{mass = }468g \end{gathered}[/tex]Therefore, the mass of the block is 468g.
Howmany molecules of iron (iii) oxide canbe produced from 13.5 molesFe
Calculations:
Balanced Reaction :
[tex]2Fe+3O_2\Rightarrow2Fe_2O_3[/tex]1. by stoichiometry,• 2 moles of Fe : 2 moles of iron (iii) oxide
• then 13.5 moles Fe : x
X = 13.5 *2 /2 = 13.5 moles of Fe
• This means that 13.5 mole of Fe2O3 will be produce.
2. Calculate number of molecules by Avogardo principles.No. of molecules = Moles * Avogardo Number
[tex]\begin{gathered} Fe_2O_{3\text{ }}Molecules\text{ = 13.5 moles }\cdot6.022\cdot10^{23} \\ \text{=8.1297}\cdot10^{24} \end{gathered}[/tex]• This means that there are 8.1297 x10^24molecules of Fe2O3 from 13.5 moles Fe.
3.21 X 10^54 atoms of nitrogen=___ moles of nitrogen.
Answer:
[tex]5.33\text{ }\times\text{ 10}^{30\text{ }}\text{ moles}[/tex]Explanation:
Here, we want to get the number of moles of nitrogen
Mathematically:
[tex]1\text{ mole of nitrogen = 6.02 }\times\text{ 10}^{23}\text{ atoms}[/tex]3.21 * 10^54 atoms of nitrogen will contain:
[tex]\frac{3.21\times10^{54}}{6.02\text{ }\times\text{ 10}^{23}}\text{ = 5.33 }\times\text{ 10}^{30\text{ }}\text{ moles}[/tex]What is the pH of a solution where [OH-] = 5.6 × 10-4 M?
The pH value indicates the concentration of H+ ions in the solution. We are given the value of the concentrations of the OH- ions, so we can find the pOH using the following equation:
[tex]pOH=-log\lbrack OH^-\rbrack[/tex]The sum of pH and pOH will always be equal to 14, so we find the pH by clearing it from the following relationship:
[tex]pH+pOH=14[/tex]So, pOH value will be:
[tex]pOH=-log\lbrack5.6\times10^{-4}\rbrack=3.3[/tex]The pH will be:
[tex]\begin{gathered} pH=14-pOH \\ pH=14-3.3=10.7 \end{gathered}[/tex]The pH of the solution will be 10.7
Determine the molarity of a solution with a volume of 707. mL and 0.610 mol of solute dissolved.Answer: ____ M
Molarity or molar concentration is a measure of the concentration of a chemical species, of a solute in a solution, using as units, number of moles, and volume in liters. The formula for Molarity is:
M = n/V
Where:
n = number of moles, 0.610 moles
V = volume in Liters, 0.707
Now we add these values into the formula:
M = 0.610/0.707
M = 0.863 M is the molarity
Determine the molar mass of an unknown monoprotic acid to two decimal places if 16.98 mL of a 0.086 M NaOH solution were used to titrate 0.236 g of the unknown acid
1 ) Chemical equation
[tex]\text{NaOH + HX}\rightarrow H_2O+Na^++X^-[/tex]HX represents the unknown acid.
2) Moles of NaOH in the reaction
[tex]M=\frac{\text{moles of solute}}{\text{liters of solution}}[/tex]Convert mL into L
[tex]L=16.98mL\cdot\frac{1L}{1000mL}=0.01698L[/tex]Plug in known values in the equation and solve for moles.
[tex]0.086M=\frac{\text{moles of NaOH}}{0.01698L}[/tex][tex]\text{mol NaOH= 0.086M}\cdot0.01698L=0.00146028\text{ mol NaOH}[/tex]3) Moles of the unknown acid that reacted with 0.00146028 mol NaOH
Molar ratio
1 mol NaOH: 1 mol HX
[tex]\text{mol HX=0.00146028 mol NaOH}\cdot\frac{1\text{ mol HX}}{1\text{ mol NaOH}}=0.00146028\text{ mol HX}[/tex]4) Molar mass of the unknown monoprotic acid
[tex]\text{Molar Mass=}\frac{\text{mass of solute (g)}}{moles\text{ of solute}}[/tex]Plug in known values and solve
[tex]\text{Molar Mass}=\frac{0.236\text{ g HX}}{0.00146028\text{ mol HX}}=161.61\text{ g/mol}[/tex]The molar mass of the unknown monoprotic acid is 161.61 g/mol
.
when 14.12 moles of mercury (ll) oxide decomposes, how many moles of oxygen gas will form ?
ANSWER
The number of moles of oxygen formed is 7.06 moles
EXPLANATION
Given that
The number of moles of mercury (II) oxide is 14.12 moles
Follow the steps below to find the number of moles of oxygen
Step 1; Write the balanced equation for the decomposition of the reaction
[tex]\text{ 2HgO }\rightarrow\text{ 2Hg}_{(s)}\text{ + O}_{2(g)}[/tex]In the reaction above, 2 moles HgO decompose to produce 2 moles Hg and 1 mole O2
Step 2; Find the number of moles of oxygen using a stoichiometry ratio
Let x represents the number of moles of oxygen
[tex]\begin{gathered} \text{ 2 moles HgO }\rightarrow\text{ 1 mole O}_2 \\ \text{ 14.12 moles HgO}\rightarrow\text{ x mole O}_2 \\ \text{ cross multiply} \\ \text{ 2 moles HgO }\times\text{ x mole O}_2\text{ }=\text{ 1 mole O}_2\times\text{ 14.12 moles HgO} \\ \text{ Isolate x} \\ \text{ x = }\frac{1\text{ mole O}_2\times14.12moles\cancel{HgO}}{2moles\cancel{HgO}} \\ \text{ x = }\frac{14.12}{2} \\ \text{ x = 7.06 moles} \end{gathered}[/tex]Therefore, the number of moles of oxygen formed is 7.06 moles
If there are 1.1 moles of SeCl6 how many moles of Cl2 will be produced? Use up to one decimal point
ANSWER
There are 3.3 moles of Cl2 in 1.1 moles of SeCl6
EXPLANATION
Given that
The number of moles of SeCl6 is 1.1 moles
Firstly, write a balanced equation of the reaction
[tex]\text{ SeCl}_6\text{ }\rightarrow\text{ Se + 3Cl}_2[/tex]In the reaction above, 1 mole SeCl6 gives 3 moles Cl2
Let x be the number of moles of Cl2
[tex]\begin{gathered} \text{ 1 mole SeCl}_6\text{ }\rightarrow\text{ 3 moles Cl}_2 \\ \text{ 1.1 mole SeCl}_6\text{ }\rightarrow\text{ x moles Cl}_2 \\ \text{ cross multiply} \\ \text{ 1 mole SeCl}_6\times\text{ x moles Cl}_2\text{ = 1.1 mole SeCl}_6\text{ }\times\text{ 3 moles Cl}_2 \\ \text{ Isolate x } \\ \text{ x = }\frac{1.1moles\cancel{SeCl_6}\times\text{ 3 moles Cl}_2}{1mole\cancel{SeCl_6}} \\ \\ \text{ x = 1.1 }\times\text{ 3} \\ \text{ x = 3.3 moles} \end{gathered}[/tex]Therefore, there are 3.3 moles of Cl2 in 1.1 moles of SeCl6
I really need help on this problem for chemistry, please help!
answer and explanation
we are given the balanced reaction and so we begin by calculating the number of mols of each reactant
for Al
mols = mass/Molar mass
= 22.0g / 26.98g/mol
= 0.82 mols
for oxygen
mols = mass / Molar mass
= 26.0g / 16.00g/mol
= 1.6 mols
theerefore
a. the limiting reagent is Al
b. theoretical yield will be determine using the limiting reagent.
from the balanced reaction we see that the mol ratio between aluminum and aluminum oxide is 4:2
therefore
2/4 x0.82 = 0.41 mols of aluminum oxide will form
the mass will be
mass = n x M
= 0.41 mols x 101.96g/mol
= 41.8 grams
c. percentage yield is:
actual yield/ theorectical yield x 100
= 40.0/41.8 x 100%
= 95.7 %
Which compound BH3 or BO3 would have polar covalent bonds? How do you know?These are the options in photo
To solve this problem, let's find the electronegativity difference that we have between each pair of elements. If we look for the electronegativity of B, H and O we might find these values:
B: 1.5 O: 3.4 H: 2.1
So the two bonds that are present in our molecules have a difference of:
O ---- B = 3.4 - 1.5 = 1.9
H ----- B = 2.1 - 1.5 = 0.6
We have two types of covalent bonds, polar and non-polar. When the electronegativity difference is between 1.5 and 0.4 the bond is covalent polar, when it is less that 0.4 is non-polar and when it is higher than 1.5 it is ionic.
In our case, the electronegativity difference between O and B is 1.9, it seems that it would be an ionic bond. But that's not an option. The difference between H and B is 0.6, the polarity of that bond is weak compared to the polarity of the bond between O and B (if we consider that it is covalent).
So the answer to our problem is the first one:
BO₃ would have polar covalent bonds because
Select the correct structure thatcorresponds to the name.2-hexyneA.CH3CH₂CH₂C=CCH3B. CH3C CCH₂CH₂CH3C. both
Answer
c. both
explanation
both structures have a triple bond on the second carbon and the have 6 carbons in the carbon chain
Select the statements that are true about electronegativity between elements, and their type of bond.A.If the difference is over 1.0, an ionic bond will form.B.If the difference in electronegativity is 0 to 0.5, the bond will be polar covalent.C.If the difference in electronegativity is from 0.6 to 1.7, the bond will be polar and covalent.
Answer:
C. If the difference in electronegativity is from 0.6 to 1.7, the bond will be polar and covalent.
Explanation:
Let's see the type of bondings based on the electronegativity differences between atoms:
[tex]\begin{gathered} less\text{ than 0.4 : Nonpolar covalent.} \\ 0.4\text{ - 1.7 :}Pola\text{r covalent.} \\ Greater\text{ than 1.7: Ionic.} \end{gathered}[/tex]So based on this, the answer would be C. If the difference in electronegativity is from 0.6 to 1.7, the bond will be polar and covalent.
Calcium reacts with Aluminum chloride to form Calcium chloride and Aluminum. If you react 100 grams of Aluminum chloride with Calcium, how many grams of Aluminum are produced?
38.95 g of Al is produced on reacting 100 g of Aluminium chloride with Calcium.
We need to write a balanced equation for the reaction. This is illustrated below:
2AlCl₃ + 3Ca —> 3CaCl₂ + 2Al
Molar Mass of AlCl₃
= 27 + (3x35.5)
= 27 + 106.5 = 133.5g/ mol
Mass of AlCl₃ from the balanced equation
= 2 x 133.5g
= 267g
Molar mass of Al= 26
Mass of Al from balanced equation= 2×26
= 52
Molar Mass of CaCl₂ = 40 + (2 x 35.5)
= 40 + 71 = 111g/mol
Mass of CaCl₂ from the balanced equation
= 3 x 111 = 333g
From the equation,
133.5g of AlCl₃ produced 52g of Al
Therefore, 100g of AlCl₃ will produce
= (100 x 52)/133.5
= 38.95g of Al
So, 38.95 g of Al is produced on reacting 100 g of Aluminium chloride with calcium.
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What coefficients would correctly balance this equation?_Ag2S → _Ag +_ S₂
In order to properly balance an equation, we need to make sure that the same amount of elements on the reactants side matches the number of elements on the products side, we can do that by increasing the number in front of each molecule, the so called stoichiometric coefficient. In the reaction from the question we can properly balance by adding the following stoichiometric coefficients
For our question, we have:
2 Ag2S -> 4 Ag + S2
How many L of solution do you have if you dissolve 5 moles of salt in enough water to make a 0.5 M solution?
10L
Explanations:The formula for calculating the molarity of a solution is expressed as:
[tex]molarity=\frac{moles}{volume}[/tex]Given the following parameters
• Moles of salt = 5 moles
,• Molarity of solution = 0.5M
Substitute the given parameters into the formula
[tex]\begin{gathered} volume=\frac{moles}{molarity} \\ volume=\frac{5moles}{0.5M} \\ volume=10L \end{gathered}[/tex]Hence the required volume of the solution is 10L
6. A sample of nitrogen gas weighs 130 g. Write the chemical formula for nitrogen gas. Howmany molecules of elemental nitrogen is this? How many atoms of nitrogen are in this sample?
Chemical formula for nitrogen gas is N₂.
To find the number of molecules in the given sample, we have to convert the mass of the sample to moles by using the molecular mass of elemental nitrogen (N₂).
[tex]130gN_2\cdot\frac{1molN_2}{28gN_2}=4.64molN_2[/tex]Now, we have to use Avogadro's number (6.022x10^23) that indicates the number of molecules in one mole of substance:
[tex]4.64molN_2\cdot\frac{6.022\times10^{23}molecules}{1molN_2}=2.79\times10^{24}molecules[/tex]It means that there are 2.79x10^24 molecules of elemental nitrogen.
To find the number of atoms we just have to multiply the number of molecules by 2, which is the number of atoms of nitrogen per molecule of elemental nitrogen:
[tex]2.79\times10^{24}molecules\cdot\frac{2atoms}{1molecule}=5.59\times10^{24}atoms[/tex]There are 5.59x10^24 atoms of nitrogen in the sample.
Which of the following is not an empirical formula?H2O2HOH2OH3O
An empirical formula is the simplest form of a formula, that is, the subscripts are simplified.
Therefore, the answer is H2O2 because it's not the simplest form.
When reacting 5.00 g of MgCl2 with 15.0 g of AgNO3 , what is the limiting reagent based on the following equation?MgCl2 (aq) + 2 AgNO3(aq) --> 2 AgCl (s) + Mg(NO3)2 (aq)
Answer:
[tex]AgNO_3\text{ is the limiting reagent}[/tex]Explanation:
Here, we want to get the limiting reactant
The limiting reactant is the reactant that would produce less amount of the solid precipitate
Firstly, we need to get the number of moles of each of the reactants
To get this, we divide their masses by the molar masses
The molar mass of magnesium chloride is 95 g/mol
The number of moles would be:
[tex]\frac{5}{95}\text{ = 0.053 mol}[/tex]Now, from the equation of reaction, 1 mole of MgCl2 produced 2 moles of AgCl
Then: 0.053 mole of MgCl2 will produce 2 * 0.053 mol = 0.106 mol AgCl
For AgNO3, the molar mass is 170 g/mol
The number of moles would be:
[tex]\frac{15}{170}\text{ = 0.088 mol}[/tex]Now, looking at the equation of reaction:
2 moles of AgNO3 produce 2 moles of AgCl
0.088 mol AgNO3 will also produce 0.088 mol AgNO3
Now, looking at the values of the number of moles of AgCl produced, we can see that AgNO3 produces less of the product
This means that AgNO3 is the limiting reactant
10.Which of the following elements is correctly matched with the number of electrons it needs to become stable?Select one:a. Sulfur (S) .. 6b. Hydrogen (H) .. 2c. Chlorine (Cl) .. 1d. Aluminum (Al) .. 3
Chlorine (Cl). Option C is correct
Explanations:For an elements to be stable, it must attain its octet configuration that is the total number of electron in its outermost shell is must be 8 electrons.
For sulphur (atomic number of 16) with an electronic configuration 1s^2 2s^2 2p^6 3s^2 3p^4. This shows that sulphur needs 2 electrons to complete its shell making the first option incorrect.
For hydrogen (atomic number of 1) will need one electron to attain duplet rule making the option B is incorrect.
For chlorine element (atomic number of 17), with electronic configuration 1s^2 2s^2 2p^6 3s^2 3p^5. This shows that chlorine will need 1 more electron to make it stable
what is the percent composition of h and o in H2O2
Percent compositions:
[tex]\begin{gathered} Hydrogen:\frac{2}{34}\times100=5.9\% \\ \\ Oxygen:\frac{32}{34}\times100=94.1\% \end{gathered}[/tex]I would like some help to solve this problem number 1
A chemical equation is known to be balanced if the total number of moles of elements at the reactant is equal to that of the product.
For the reaction between sodium chloride (NaCl) and potassium nitrate (KNO₃), the balanced reaction is given as;
[tex]\text{NaCl}+\text{KNO}_3\rightarrow KCl+NaNO_3[/tex]You can see that the reactant ions exchange places to form new products (potassium chloride and sodium nitrate). This shows that the equation is a double displacement reaction
How many moles are in 91.5 grams of Helium?
In order to find the number of moles with a given mass of Helium, we need to use its molar mass, which is 4.0026g/mol, therefore we will have:
4.0026g = 1 mol of Helium
91.5g = x moles of Helium
x = 22.86 moles of Helium in 91.5 grams
A compound of molecular mass 28 has a molecular formula CxHy. What is the value of x and y if its empirical formula is CH?
Answer
x = 2, y = 2
Explanation
The empirical formula is the simplest whole number ration that defines constituent atoms in a species.
The molecular formula is always a multiple of the empirical formula.
Since the empirical formula of the compound i given to be CH, ithen its molecula formula is:
[tex]Molecular\text{ }formula=n\times(empirical\text{ }formula)[/tex]From the periodic table, the molar masses of (H = 1.00784, C = 12.011)
Thus, the molecular formula is
[tex]\begin{gathered} Molecular\text{ }formula=28\text{ }g\text{/}mol=n(12.011+1.00784)\text{ }g\text{/}mol \\ \\ n=\frac{28}{12.011+1.00784}=\frac{28}{13.01884}=2.150729251\approx2 \end{gathered}[/tex](CH)n = (CH)₂ = C₂H₂
Therefore, CxHy = C₂H₂. The value of x and y is 2 and 2 respectively.
The value of x and y if its empirical formula is CH is x = 2, y = 2
PLEASE HELP
Balance the chemical reaction
using an atom inventory.
What is the coefficient for
oxygen?
4NH3 + ? O2 ---> ?NO + ? H2O
The balance chemical equation will be 4NH3 + 5 O2 → 4NO + 6H2O and the coefficient for water will be 5.
The given unbalanced chemical equation is :
4NH3 + O2 → NO + H2O
It can be seen that number of nitrogen atom in reactant side is 4. By multiplying by 4 as the coefficient of NO , multiplying by 5 as the coefficient of oxygen and multiplying by 6 as the coefficient of H2O. The equation will be balanced.
The balanced chemical equation will be :
4NH3 + 5O2 →4 NO + 6H2O
Therefore, the the coefficient for water will be 5.
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The Croatian seismologist, Andrija Mohorovicic, discovered a boundary change in the Earth's layers. Please explain how he discovered this using two to three sentences using your best grammar.
The Croatian seismologist, Andrija Mohorovicic, discovered a boundary change in the Earth's layers because he noticed that P-waves were refracted at the boundary.
Who is a seismologist?Seismologists are described as Earth scientists, specialized in geophysics, who study the genesis and the propagation of seismic waves in geological materials.
Andrija Mohorovicic realized that as one crosses the boundary the predominant mineral composition of the rock changes, and the minerals on the mantle side enable seismic waves to travel faster.
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which best corresponds to a strong base?I need to know
Assuming that the question is considering quantity of OH- ions as strength of base, the most basic compound will be the last one, as it has more OH- being released into the reaction, but the definition of strong base is a base that totally dissociates, but for the purpose of the question, letter D corresponds to a strong base.
Is there any difference(s) in observation and molarity of the strong base when phenolphthalein or methyl orange is used? If Yes / No account for this reason.
Yes, the molarity in both the cases will be different if the indicator is changed from methyl orange to phenolphthalein or from phenolphthalein to methyl orange.
Since molarity is defined as the Molar concentration, also known as molarity, amount concentration, or substance concentration, is a unit used to describe the amount of a substance in a solution expressed as a percentage of the volume of the solution or it is the number of moles of solute divided by volume of solution in liters.
So on changing indicator, the number of moles changes as the molar mass is changing, so the molarity and other observations will get changed too and may increase or decrease.
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Using the Gay-Lussac LawIf I have 7.7 moles of gas at a pressure of 0.09 atm at a temperature of 56 C°, what is the volume of the container that the gas is in?
ANSWER
EXPLANATION
Given that;
The number of moles of the gas is 7.7 moles
The pressure of the gas is 0.09 atm
The temperature of the gas is 56 degrees Celcius
Follow the steps below to find the volume of the gas in the container
Step 1; Convert the temperature to degrees Kelvin
[tex]\text{ T K = t}\degree C\text{ + 273.15}[/tex][tex]\begin{gathered} \text{ T K = 56 + 273.15} \\ \text{ T K = 329.15K} \end{gathered}[/tex]Step 2; Apply the ideal gas equation
[tex]\text{ PV = nRT}[/tex][tex]\begin{gathered} \text{ Recall, that R = 0.08205 L atm mol}^{-1}K^{-1} \\ \text{ 0.09 }\times\text{ V = 7.7 }\times\text{ 0.08205 }\times\text{ 329.15} \\ \text{ 0.09V = 207.95} \\ \text{ Divide both sides by 0.09} \\ \text{ V = }\frac{\text{ 207.95}}{\text{ 0.09}} \\ \text{ V = 2310.58 Liters} \end{gathered}[/tex]Therefore, the volume of the container is 2310.58 liters
A piece of sodium metal reacts completely with water. The hydrogen gas generated is collected over water at 25oC. The volume of the gas is 252mL measured at 1.00atm. Calculate the number of grams of hydrogen that was collected
The mass or number of grams of hydrogen that was collected in the experiment is 0.02 g.
What is the number of moles of hydrogen gas collected at the given conditions of temperature and pressure?The number of moles of hydrogen gas collected at the given conditions of temperature and pressure is calculated using the ideal gas equation as follows:
PV = nRT
Where;
P is pressure = 1.00 atm
V is volume = 252 mL or 0.252 L
n is the number of moles = ?
R is molar gas constant = 0.082 L.atm/K.mol
T is temperature = 273 + 25 K
T = 298 K
n = PV/RT
n = 1 * 0.252 / (298 * 0.082)
n = 0.01 moles
1 mole of hydrogen gas has a mass of 2.0 g
mass of 0.01 moles of hydrogen = 2 * 0.01
Mass of 0.01 moles of hydrogen = 0.02 g
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Which models of the atom include a structure that is mostly made of empty space?RutherfordThomsonBohrQuantum mechanical
Rutherford's models
Explanations:What is the electron cloud model?There are known as the region where electrons are found especially in the nucleus.
According to the five basic atomic models which have contributed to the structure of the atom itself, the Rutherford's models of the atom include a structure that is mostly made of empty space compared to thomson that proposed the plum pudding model of the atom
I need to know the answer to this science problem . Please and thank you
Step 1 - Understanding the types of heat transfer
There are three types of heat transfer: conduction, convection and irradiation. Let's see how each one works:
a) Conduction: is when a very hot substance enters in contact with a cooler substance. The atoms in the hotter substance are moving with a greater velocity and will therefore collide with the atoms of the cooler substance.
b) Convection: it happens especially in liquids and air (fluids). The liquid is warmed up at the bottom first, via conduction. The heated bottom thus changes its density: it becomes less dense, and go up. This process repeats itself several times, warming the whole liquid.
c) Irradiation: when something is put near a heat source, but do not touch it directly. In this case, there's no direct atom collision, but indirect: the rapid atoms of the heat source collide with atoms in the air which then collide with the atoms in the object that is being heated.
Step 2 - Discovering the type of heat transfer in each scenario
In the first scenario, the water at the bottom is in direct contact with the pan. Therefore, water molecules will directly collide with "pan" molecules (probably aluminum atoms or other materials). But there's also convection. The water is not heated only by conduction.
In the second scenario, the hands are near the Bunsen burner, but not directly touching it. What is happening here is then heat irradiation, not conduction.
In the third scenario, the hand is touching the object (the handle of the pan). Even though handles are made of material that poorly conduct heat, it will increase its temperature, at least a little bit. When we touch it, we can feel it is hotter than before. In this case, only conduction is involved (from the handle to our hand). In this case atoms are directly colliding and this is the only source of heat.
Finally, in the last scenario, we also have a case of irradiation: the pan with water is near the heat source, but not directly touching it.
Step 3 - How to set an experiment
In science in general, anytime we want to investigate some effect it is good manners to investigate a system controling all other effects. We want to investigate a variable at a time.
Therefore, while both scenario 1 and 3 involve conduction, scenario 1 also involves convection, which could be a problem to a experiment intending to study conduction only.
The best experiment would be then scenario 3, hands touchind the handle of pan siting in a Bunsen burner.