12A - Energy by Muna Al Dulaimy

Thank you so much ( 5 points for Najla-Maryam-Jawaher) (3 points for Laian-Noor-Aya-Nawal) plese,check the Ans.for 2 Najla Naseraldeen 12A

2020-09-22 16:16:22 UTC

The .................... is the heat required to melt one mole of solid substance.
A) molar enthalpy of vaporization
b) molar enthalpy of deposition
c) molar enthalpy of fusion
d) molar enthalpy of combustion
A swimming pool, 20.0 m ✕ 12.5 m, is filled with water to a depth of 3.73 m. If the initial temperature of the water is 18.4°C, how much heat must be added to the water to raise its temperature to 29.0°C? Assume that the density of water is 1.000 g/mL.
A) 5.02x10^8 j
B)4.15x10^8 j
C)9.63x10^8 j
D)9.35x10^ j

Answers:
Maryam Hasan: C and B
Aya Khalil : c
Noor.A: c
Laian: C, B
jawaher: C , B
sada: c
Nawal:c,b
Asma O: C,B
Ghazlan :c
Yara:c
Maitha : c
maryem yasser : C
FM: C
Afnan D: C&B
ShouG A: C, B

Thank you Maryam Hasan-Aya-Noor-Nijla-Laian (5 points) Thank you Jawaher but ,please correct your answer Maryam Hasan AlZaabi

maryamalzaabi304 — 2020-09-22 17:10:43 UTC

Which of the following is an endothermic reaction, explain why.

Answers:
Najla: I think it the first one because the reactant are absorbing energy to make a product which result in the upper curve shown in the figure #1 on the left.
Aya Khalil : first one is endo thermic because it absorb heat from the surrounding so the potential energy of the product is greater than the potential energy of the reactant
Noor.A: The first graph represent an endothermic reaction, since the amount of energy in the product is greater than the amount of energy in the reactant.
Laian: the first graph is endothermic, because its absorbing heat /energy, the potential energy of the products is bigger than the potential energy of the reactants.
jawaher: the first one is endothermic, because as shown below the energy in the product is greater than the energy in the reactant. (i fixed it and thank you miss)
Rawan: The first graph because the amount of products is greater than reactants and the the endothermic is (absorbed) so it will be always positive, and shown in graph .
yara: the endothermic is the first one because the heat is absorbing energy also because the amount of energy in the product is greater than the amount of energy in the reactant.
Asma o : the first one is endothermic ,because the energy in the product is greater than the energy in the reactant.
Maitha Fadhel : endothermic is the first one , as the product energy is much greater than the energy in the reactant.
ShouG A:
1. Endothermic: it shows that the energy is the product greater than the energy in the reactant, we can conclude from this that it absorbs energy.

Thank you dear ( 5 points Afnan- Noor-Aya-Laian-Jawaher-Nawal ) Afnan Dawood

2020-09-22 17:46:14 UTC

If 3.00 g of aluminum foil, placed in an oven and heated from 20°C to 662.0°C, absorbs 1728 J of heat, what is the specific heat of aluminum?
A. 0.131 J/g*°C
B. 0.870 J/g*°C
C. 0.897 J/g*°C
D. 2.61 J/g*°C
E. 0.261 J/g*°C

Answers:
Maryam Hasan: C
Noor.A: using the equation c = q/m*t we will get 0.8971 J/g*°C
Aya Khalil: c
Laian: C
Najla: C
jawaher: C
Nawal=c
Ghazlan=C
yara:c
Asma O: C
Maitha : C
maryem yaser : C
Fm: C
ShouG.A: C

Excellent answer for the question (5 points) Nawal & Noor Anwar Nawal hisham

2020-09-22 18:48:34 UTC

when a 58.8g piece of hot alloy is placed in 125g of cold water in ac calorimeter, the temperature of the alloy decreased by 106.1C while the temperature of the water increased by 10.5C .why is the specific heat of the alloy?

Answers:
Noor.A : c alloy = qwater * mwater * T / m alloy * T = (4.184)(125)(10.5) / ( 58.8)(106.1) = 0.88023 J/g * C
Aya Khalil: cw m T =caloy m T
c=(4.184*10.5*12.5)/(58.8*106.1)=0.88J/gC
Najla:
cw* m* T =c alloy* m* T
c = (4.184*10.5*12.5)/(58.8*106.1)=
0.88J/g*C
Asma O: cw m T = caloy m T
c=(4.184x10.5x12.5)/(58.8x106.1)
c=0.88J/gc
Maitha Fadhel : cw m T = c alloy x T
C= (4.184x10.5x12.5)/(58.8x106.1)
=0.88J/g*c
Laian: c×m×T = c alloy×m×T
c= 0.8802 J/gc

jawaher:
cxmxT= c alloyxmxT
c= 0.8802 J/gc
ShouG A: c (alloy) = q( H2O) * m (H2O) * T / m (alloy) * T = 0.88023 J/g * C

Thank you Noor & Aya the first equation for 2 mol of SO3 & S THE 2ND for 1 mol Noor Anwar (5 points for Noor & Aya)

noooranwar2016 — 2020-09-22 19:03:26 UTC

.compare the equations, how they are different and why?

2S + 3O_2 ---> 2SO_3 delta H =-792KJ
S + 3/2 O_2 ---> SO_3 delta H = -396 KJ

Answers:
Aya Khalil :
the first equation is is the double of the second equation
equation1= 2(equation 2)
therefore the energy released(because it is exothermic reaction) is doubled too -396*2=-792
Najla:
The 1 equation double of the second equation
equation1 = 2(equation2 )
therefore the energy released is doubled as well= -396 * 2= - 792
(negative for exothermic)
Maitha :
equation one is doubled of the second equation
Therefore equation one equals 2 times equation 2
Energy released = energy released x 2
Equals =-792
Laian:
the first equation is double the second one, so equation 1 = 2×equation 2. for this, the energy will be doubled.
-396×2= -792 | exothermic

ShouG.A: Thermochemical Equations are usually written and balanced for one mole of product.
The first quation is double of the second equation

Thank you (5 points for Aya- Noor Anwar) Aya Khalil Ali

2020-09-22 19:12:56 UTC

how much heat is liberated when 5kg of coal is burned if the coal is96.2% carbon by mass and the other materials inthe coal do not react? delta H comb of carbon is -394 kJ /mol

Answers:
Noor.A: First we need the mass of carbon : mcoal * % = (5)(96.2%)*(1000g/1kg ) = 4810 g
find mol : 4810 g * 1/12 g = 400.83 mol
mol * H = 400.83 mol* -394 kJ /mol = -157927 KJ
Najla:
mass of caol*% = 5(96.2%)*(1000g/kg) = 4810g
which is the mass of carbon.
mol*heat = 400.83mol(-394kj)/mol = -157927kj
Maitha:
mcoal * % = (5)(96.2%)*(1000g/1kg ) = 4810 g

find mol : 4810 g * 1/12 g = 400.83 mol

mol * H = 400.83 mol* -394 kJ /mol = -157927 KJ

Thank you Laian (5 points) Laian Ali

2020-09-22 20:27:25 UTC

is the reaction shown in the given figure endothermic or exothermic? justify your answer.

Answers:
Aya: delta enthalpy is positive and H of reactant is less than H products so its end thermic
jawaher :it is endothermic, because the heat absorbed and the value of delta H is positive.
Najla:
endothermic, because the upward arrow shows that heat absorbed from the surrounding to the process (system).
Rawan: endothermic because the arrow upward and that shows that the heat absorbed from the sourrounding in the process.

GHAZLAN :for this figure the reaction is endothermic process,because H product> H reactants ,positive value is obtained.
Maitha Fadhel : this reaction is endothermic because as shown ( the arrow refers to heat absorption )
NoorA: Endothermic since the energy is going from reactant to product as it will have a positive value for Hrxn

Thank you Jawaher (5 points) jawaher alhosani

2020-09-23 06:19:45 UTC

one calorie equals 4.184 joules
A)true
b)false

The conversion of a gas to a liquid involves the........
A)released of heat
B)absorb heat
C)molar enthalpy of vaporization

Answers:
Najla: A, A
Asma O: A,A
Ghazlan:a,a
Yara:A,A
Rawan : True - released of heat
Maryam Hasan: True, release of heat
Maitha Fadhel : true , release of heat
Maryem yaser : AA
Laian: Q1= A, Q2 = A
Aya :A A
Noor.A: True, A
ShouG.A: A, A

Thank you ( 5 points Badria-Jawaher -Nawal ) badreia

2020-09-23 06:34:46 UTC

If a reaction releases more energy when new bonds are made than the amount of energy absorbed to break bonds in the reactants, which statement is true?
a. It is endothermic
b.It is exothermic
c.It is very slow

Answers:
jawaher: B
Nawal:B
Najla: B
Ghazlan=b
Rawan :B
Asma O: B
yara:B
Maryam Hasan: B
Maitha Fadhel : B
Maryem Yaser b
Laian: B
Aya :B
Noor.A: B
ShouG.A: B

Q : Water is sprayed on oranges during a frosty night.If an average of 11.8 g of water freezes on each orange,how much heat is released?

dulaimimuna — 2020-09-23 14:06:27 UTC

Anaswer:
Ghazlan=q = mass H2O x heat fusion, heat of fusion of water is 79.8 cal/g, or 334 J/g.
((11.8 g)(334 J/g) = 3.94 kJ.) relesed
Najla:
11.8gH2O*(1mol H2O/ 18.015gH2O) (-6.01kj/1mol H2O) = -3.94 Kj (negative for exothermic)
mass of H2O = 2(1.008)+1(15.999)= 18.015g
Asma O: q=mass H2O * heat fusion
heat fusion of water = 334J/g
(11.8g)(334J/g)=3.94KJ = release
Maryem yaser : apprioximatly 4KJ
Laian: 3.94 KJ
Aya :
11.8g(1 mol/18.0146 g )=0.655mol
0.655mol(-6.01/1mol)=-3.94 KJ
Noor.A: finding the mol of 11.8 g of water, then multiply it by the specific heat of Water(solid) = 3.94KJ released
ShouG.A: 11.8g *(1mol/18.015g)= 0.65 mol
0.65 mol * (6.01 ) = 3.94 KJ is releases

Maitha:11.8g *(1mol/18.015g)= 0.65 mol

0.65 mol * (6.01 ) = 3.94 KJ is releases

Q: to vaporize 2.00 g of ammonia, 656 calories are required. how many kilojoules are required to vaporize the same mass of ammonia? (Ghazlan omar )

ghazoly15 — 2020-09-23 14:25:31 UTC

Answer:
Najla :
656cal(4.184j/1cal)(1kj/1000j)=2.74kj
you need 2.74 kilojoules to vaporize it.
Maryam Hasan: 656x4.184/1000= 2.74kj
yara:656x(4.184/1cal)
(1kj/1000j)=2.7kj
Asma O:
(656cal)(4.184j/1cal(1Kj/1000j)=2.74Kj
Maitha Fadhel :656x4.184/1000j=2.74kj
jawaher:
656cal(4.184j/1cal)
= (1kj/1000j)
=2.74kj
Rawan: 656cal (4.184J / 1 cal ) =2744.7 ( 1KJ /1000J) = 2.744 KJ
Laian: (656)(4.184/1cal) = 2.7KJ
Aya :
656cal(4.184j/1cal)(1kj/1000j)=2.74kj
2.74 kilojoules is required for vaporization process
Noor.A: 656 cal * 4.184 = 2.774 J *1/1000 = 2.74KJ
ShouG.A: convert to J = 2.774J
2.774 J convert to KJ = 2.74 KJ

Maitha:convert to J = 2.774J

2.774 J convert to KJ = 2.74 KJ

2020-09-23 14:51:54 UTC

Maitha Fadhel
If a 49 g sample of water releases 1621j of heat energy and cools from 34 C what is the final temperature of the water?
Answers:
Najla:
Tf-34c = 1621j /(4.184j/g*c)(49g)
Tf = 41.90c

GHAZLAN : q=m*c*T
1621J/4.184J/g*C *49g=Tf-34C
Tf= appro

yara: q=mxcxT
Tf-34c=1621/(4.184/gxc)(49)
Tf=41.9c

Asma O : q=m*c*T
= (1621j)/(4.184j/g*c)/(49g)
=41.90c
Alanood; Tf= 42C
Aya:
T f-34c=1621/(4.184/gxc)*(49)
T f=41.9c
Noor.A:
Tf = q/ c*m + Ti = 41.9 oC
ShouG.A: Tf = q/ (c*m) + Ti = 1621J / (4.184KJ/g*C * 49g ) + 34 oC = 41.9 oC
Laian: Tf = 42 C

Najla Naseraldeen

2020-09-23 14:58:46 UTC

Ethanol is being used as an additive to gasoline. The combustion of 1 mol of ethanol releases 1367 kJ of energy. How many Calories are released?
A) 325.2Cal
B) 326.7Cal
c) 385.4Cal
D)374.1C
answers:
jawaher: B
GHAZLAN:B
Asma O : B
Maitha : B
Yara:B
Afnan D: B
Laian: B
Shahad :B
Aya :B
Noor.A: B
ShouG.A: B
Maitha:b

Najla Naseraldeen

2020-09-23 15:08:08 UTC

Which of the following statements is true concerning a chemical reaction?
A) Endothermic reactions have lower activation energies than exothermic reactions.
B)A catalyst reduces the enthalpy change for the reaction.
c)Exothermic reactions are always spontaneous.
D)The ΔHvalue for the forward reaction is negative the ΔH

value of the reverse reaction.

Answers:
GHAZLAN : A(more energy is required to break bonds in reactants in an endo reaction)
Asma O:A
jawaher: A
Rawan: C
Yara:A
Maryem Yaser : endothermic reaction has greater activation energy. (B)
Laian: B
Aya :B
Noor.A: B
ShouG.A: B
Maitha:b

jawaher alhosani

2020-09-23 15:10:35 UTC

If a sample of water was heated by burning 1.5 g of ethanol, and the water absorbed 3000 joules, what is the energy density of the fuel in joules per gram?
A) 4500 J/g
B) 2000 J/g
C) 2300 J/g
D) 3001.5 J/g

answers:
GHAZLAN :B
Najla: B
Asma O : B
Laian: B
Maryem Yaser : B
Shahad :B
Aya :B
Afnan D: B
Noor.A: B
ShouG.A: B
Maitha: b

jawaher alhosani

2020-09-23 15:10:43 UTC

What is always true about the enthalpy change for an endothermic reaction?
A)It is positive
B)it is negative
C) it is zero
D)all the above are true

Answers:
Najla: A
Asma O:A
yara:A
Maitha: A
maryem yasser a
GHAZLAN:A
Rawan: positive (A)
Laian: A
Shouq AB :A
Shahad:A
Aya :A
Afnan D: A
Noor.A: A
ShouG.A: A

jawaher alhosani

2020-09-23 15:15:41 UTC

jawaher alhosani

2020-09-23 15:15:49 UTC

What is always true about the enthalpy change for an endothermic reaction?
A)It is positive
B)it is negative
C) it is zero
D)all the above are true

Answers:
Najla: A
Asma O:A
yara:A
Maitha: A
maryem yasser a
GHAZLAN:A
Laian: A
Fm:A
Aya :A
Afnan D: A
Noor A: A
ShouG A: A
jawaher alhosani
If a sample of water was heated by burning 1.5 g of ethanol, and the water absorbed 3000 joules, what is the energy density of the fuel in joules per gram?
A) 4500 J/g
B) 2000 J/g
C) 2300 J/g
D) 3001.5 J/g

answers:
GHAZLAN:B
Najla: B
Rawan : B
Maryem Yaser : B
Laian: B
Asma O : B
Fm: B
Aya :B
Afnan D: B
Noor.A: B
Maitha:b
ShouG A: B
Yara:B
jawaher alhosani
What is always true about the enthalpy change for an endothermic reaction?
A)It is positive
B)it is negative
C) it is zero
D)all the above are true

Answers:
Najla: A
Asma O:A
yara:A
Maitha: A
maryem yasser a
GHAZLAN:A
Rawan : A
Laian : A
Fm: A
Aya: A
Afnan D: A
Noor.A: A
ShouG A: A
jawaher alhosani
If a sample of water was heated by burning 1.5 g of ethanol, and the water absorbed 3000 joules, what is the energy density of the fuel in joules per gram?
A) 4500 J/g
B) 2000 J/g
C) 2300 J/g
D) 3001.5 J/g

answers:
GHAZLAN :b
maryem yaser " b
Laian: B
Fm: B
Aya :B
Afnan D: B
Noor.A: B
ShouG A: B
Maitha:b
yara:B

GHAZLAN omar

ghazoly15 — 2020-09-23 15:21:41 UTC

Which of the following statements is true?
A. In an endothermic reaction, the energy of the products is the same as the energy of the reactants.

B. In an endothermic reaction, the energy of the products is less than the energy of the reactants.

C. In an exothermic reaction, the energy of the products is the same as the energy of the reactants.

D. In an exothermic reaction, the energy of the products is less than the energy of the reactants.

Answer:
Rawan: D
Najla : D
Maryem yaser : D HprodLaian : D
Asma O: D
Shahad :D
Aya :D
Afnan D: D
Noor.A: D
ShouG.A: D
Maitha:D
NoorM: d

Maryem Yaser 12A

2020-09-23 15:35:32 UTC

How do farmers use heat of fusion to protect fruits ?
use pg 93.

Answers:
Najla:
the farmers often spray the trees with water. When the temperature drops, this water freezes and releases heat to its environment, some of which is the still-ripening fruit.
Laian: When the temperature decreases, water freezes, and releases heat to its environment, some of which is the still-ripening fruit. This heat is enough to protect the fruit inside from freezing. So, paradoxically, causing ice to form on the fruit protects it from freezing.

Noor.A: If the temp. reaches to a freezing point, the farmers tend to overflow their fields with water. This technique is used to prevent frost damage. Once the water freezes it releases energy that warms the surroundings.

Maitha: as the temperature reaches its freezing point when the farmer sprays water. Once the water freezes (energy is released which result in warmer surrounding)

Maryem Yaser 12A

2020-09-23 15:40:58 UTC

what does the zero subscript in standard enthalpy reactions symbols tells you ?
a) all reactants at standard conditions
b) all products at standard conditions
c) zero energy is released or absorbed in the reaction
d ) a and b

ANSWERS :
Najla: D
Laian: D
yara:D
Asma O : D
Afnan D: D
Shouq AB : D
jawaher: D
FM: D
Aya K.: D
NAWAL=D
Noor.A: D
ShouG A: D

YARA MOHAMMAD 12A

2020-09-23 15:46:08 UTC

write the sign of Hsystem for each of the following changes in physical state.
a.C2H5OH(s) ---> C2H50H(L)
b.H2O(g)--->H2O(L)
C.CH3OH(l)--->CH3OH(g)
d.NH3(L)--->NH3(s)

ANSWERS:
Maryem yaser : + - + -
Najla: positive(endo) , negative(Exo), positive(endo), negative(Exo)
Laian: a=positve. b=negative, c=positve, d=negative
Asma O : positive, negative, positive, negattive
jawaher: (positive , negative, positive, negative )
FM: positive/negative/positive/negative
Aya :
+ ,- ,+,-
Afnan D:
(positive, negative, positive, negative)
Noor.A: positive - negative - positive - negative
ShouG A: a. positive b. negative c. positive d. negative
Alanood; + - + -

Maryem Yaser12A

2020-09-23 15:46:15 UTC

which of the following is NOT an example of endothermic reaction ?
1.cooking an egg
2.Respiration
3.dissolving salt in water
4.photosynthesis

ANSWERS :
Najla: 2
yara:2
Laian: 2
Asma O : 2
Afnan D: 2
jawaher : 2
FM: 2
Shahad :2
Aya k.:2
Noor.A: 2
ShouG A: 2
Maitha:2

Maryem Yaser 12A

2020-09-23 16:05:36 UTC

why is a measured amount of water essential in a calorimeter ? (choose 2 answers )
a) to cool the metal down
b) to reach balance in a reaction
c) to absorb energy released from the reacting system
d) to provide energy absorbed by the system

ANSWERS :
Najla: C
Laian: C
Afnan D: C
jawaher: C
Shahad:c
Asma O : c
Aya: c
Fm: c
yara:C
badreia: B, C
Noor A: C
ShouG.A: C
Maitha:c
Rawan: A-C

Najla Naseraldeen

2020-09-23 16:07:04 UTC

use the information in the figure to calculate how much heat is required to vaporize 4.33mol of water at 100.0c.
Answer:
maryem yaser : 40.7kj
Laian: 40.70 KJ
jawaher: 40.70KJ
Asma o :40.70kj
Aya:40.7
Noor.A: 40.7 KJ
ShouG.A: 40.7 KJ
Maitha: 40.7kj
NoorM: 40.7 KJ

Laian Ali

2020-09-23 16:11:09 UTC

Why is a foam of cup used i a student calorimeter rather than atypical glass beaker?

Answers:
Najla: The foam cup acts as an insulator. This means that less, if any, heat can escape. This will allow the calorimeter to be more precise.
Maryem yaser : foam cup will be an insulator which means heat will be contained properly. Thus the calomtier will be more précised rather than a glass beaker that will let the heat escape.
Aya : foam cup is used because it is an insulator so less amount of energy will escape and therefore the reaction will be more efficient because it occurs inside an isolated system.
Noor.A:
because it can be an insulator in result while using it energy will be less likely to escape.
ShouG.A:
Foam cups act as insulator this will help the energy to stay inside and not escape.
Maitha: because the foam cup acts as an insulator which heat ( energy ) remains inside

yara mohammad

2020-09-23 16:16:49 UTC

why is a stirrer important in a bomb calorimter?

ANSWERS:
Najla:
for an even distribution of heat coming from the combustion reaction to the liquid (water) and so that the measured temperature of the liquid represents its final temperature.'
Maryem yaser : to easure uniform temperature.
Laian: A stirrer is used in a calorimeter to ensure precise mixing of the contents of the calorimeter. This will help correct measurement of temperature, and thus the associated heat exchange estimated will have less error
Aya k.: It ensure accurate measure of the temperature and even mixing of the content.
Noor.A:
ensure proper mixing of the contents of the calorimeter and it will help in correct measurement of temperature
ShouG A: stirrer mix the contents properly, in addition it help with in correct measurement of temperature.
Maitha: ensure the accuracy of the measurements even during mixing of component

Najla Naseraldeen

2020-09-23 16:25:46 UTC

A 248-g piece of copper initially at 314 °C is dropped into 390 mL of water initially at 22.6 °C. Assuming that all heat transfer occurs between the copper and the water, calculate the final temperature.
A) 35.6c
B)38.8c
C)10.0c
D)31.2c

Answers:'
Maryem yaser : to find t final use q=cxmx(Tf-22.6C) , after substituting , divide both side to get Tf , which equals 38.8C (b).
Laian: B
jawaher : B
Asma O : B
Aya:B
Sada: B
Alanood; B
Noor.A: B
ShouG A: D
Maitha:D

Maryem Yaser 12A

2020-09-23 16:46:44 UTC

Calculate ΔH for the following reaction:

CH_{4 (g)} + O₂ (g) ⇌ CO_{2 (g)} + H₂O (l)
Compound ΔH

CH₄ (g) -74.8 kJ/mol

H₂O (l) -285.8 kJ/mol

CO₂(g) -393.5 kJ/mol
a)604.5 kJ/mol

b)-604.5 kJ/mol

c)889.7 kJ/mol

d)-890.3 kJ/mol

e)not enough information
ANSWERS :
Najla: B
Laian: B
jawaher: B
FM: B
Shahad :B
Asma o : B
Aya khalil :b
NAWAL=B
Yara:B
Alanood; B
Noor.A: B
ShouG.A: B
Maitha: b

Najla Naseraldeen

2020-09-23 16:58:00 UTC

Under 1 atm pressure CO2(s) sublimes at –78 °C. Is the transformation of CO2(s) to CO2(g) a spontaneous process at –100 °C and 1 atm pressure?
Answers:
Sada: No, the reverse process is spontaneous at this temperature.

Noor.A: No '
ShouG.A: No
Maitha: no
asma O: no
Laian: No
NoorM: no
Aya :No

SHOUQ ABDULKAREEM

2020-09-23 17:13:46 UTC

One similarity and one difference between endohermic and exothermic :)

Answer:
Laian:
difference: endothermic absorbs energy while exothermic releases energy
similarity: the energy comes in form of heat in exo and endo
Najla:
"Thermic" refers to heat, just as in the word "thermometer." "Exo" means "outside" and "endo" means "inside." Thus, an endothermic reaction pulls heat into an object or area, while an exothermic reaction expels heat.
Aya Khalil:
exothermic and endo thermic are both forms of transferring heat and chemical potential energy between system and surrounding .
exothermic release heat to surrounding from the system
endothermic is absorbing heat to surrounding from the system

Noor.A: Exothermic and Endothermic both refer to heat. Exothermic is the process of releasing heat, while endothermic is the process of absorbing heat.

ShouG A:
Similarity : Both have the word (thermic) which refer to heat
Difference: Exo - release heat
Endo - absorb heat

Maitha: endothermic + exothermic = the forms of heat transfer however exothermic releases heat ( energy) from the system to the surroundings and exothermic release heat to surroundings from the system .

Laian Ali

2020-09-23 17:20:31 UTC

why delta H for an exothermic reaction always has a negative value?
Answers:
Najla:
In an exothermic reaction, energy is released because the total energy of the products is less than the total energy of the reactants.

jawaher : because when energy is released the total energy of the products become less than the total energy of the reactants.
Aya :
the chemical potential energy of the reactant is greater than the chemical potential energy of the products so delta H= H product-H reactant will be negative

Noor.A:
Exothermic always releases energy so the product is less than the reactant ;
Hproduct -H reactant = - Hrxn
ShouG A:
The process of exothermic always end up releasing energy this result in a negative value for H

Maitha:negative value if H result from the process of exothermic that releases energy

Rawan : because it release energy , and exothermic reactions are reactions that lose heat , and the products is less that reactions

Najla Naseraldeen

2020-09-23 17:47:13 UTC

The negative of heat of vaporization is?
a) Heat of Condensation
b) Heat of fusion
c) Heat of solidification
d) Heat of sublimation
Answers:
Aya : A
jawaher: A
Nawal=D
Afnan D: A
Yara:A
badreia:A
Noor.A: A
ShouG.A: A
Maitha:A
Asma O:A
Rawan :A
Laian: A

Najla Naseraldeen

2020-09-23 17:50:00 UTC

Which statement is not correct?
A)Solidification refers to a change of phase.
B)Above its critical temperature, it is no longer possible to liquefy a gas.
C) Fusion is the reverse process of liquefaction.
D)Fusion and melting both refer to the same process.
Answers:
Aya :B
jawaher: B
Yara:A
badreia:B
NoorA: B
ShouG.A: B
Maitha: B
Asma O:B
Laian: B

Shahad adel

2020-09-23 17:50:54 UTC

Is water evaporating exothermic?
Yes or no explain

answers
Aya : no it's an endothermic reaction because heat is absorbed from the surrounding to the system.
Najla: NO, Evaporation is endothermic because water molecules must absorb heat from the surroundings to increase their kinetic energy.
jawaher : no, because when molecules give up heat energy, it is called endothermic
Noor.A: No, because the water absorbs heat from the surrounding.
yara: no because its endothermic reaction ,the water molecules absorb heat from the surrounding to the system
ShouG.A: Since we know that in an endothermic reaction, the process end up absorbing heat from the surrounding so the answer is No.
Maitha Fadhel : no because its endothermic reaction ,the water molecules absorb heat from the surrounding to the system
Rawan : No ,Because when water is melting it absorb energy from the surrounding to the system
Laian: No, heat is absorbed from the surrounding to the systems which means its endothermic.

Fatima

2020-09-23 18:05:37 UTC

What factors determine the amount of chemical potential energy that an object has?

answer choices:

A-Mass of molecules and the position of chemical bonds

B-Speed and mass of the molecules

C-The type of molecules present and their ability to catch fire

D-Temperature of the molecules and position of the chemical bonds

Answer:
Najla: A
Aya A
jawaher A
Afnan D: A
YARA:A
badreia: A
Noor.A: A
ShouG A: A
Maitha: A
Asma O:A
Rawan:A
Alanood; A
Laian: A
Nawal=A

Which of these is not a source of chemical energy?

answer choices:

A-Spaghetti

B-The Sun

C-Battery

D-Petroleum

Answer:

Najla: B
Aya :B
jawaher: B
Afnan D: B
YARA:B
badreia: B
Alanood; B
Noor.A: B
ShouG A: B
Maitha:b
Asma O: B
Laian: B
nawal=B

What type of energy can chemical transform into?

answer choices:
A-Heat

B-Light

C-Electrical

D-All of the above

Answer:
Najla: D
Aya :D
jawaher: D
Afnan D: D
YARA:D
Alanood; D
badreia: D
Noor.A: D
ShouG A: D
Maitha:D
Asma O: D
Laian: D

What is energy?

answer choices

A-The ability to cause a change

B-A force

C-Electricity

D-The ability to transform work
Answer:
Najla: A
Aya :A
jawaher: A
Afnan D: A
YARA:A
badreia:A
Alanood; A
Noor.A: A

ShouG A: A
Maitha:A
Asma O: A
Laian: A

Fatima

2020-09-23 18:11:49 UTC

A battery converts what type of energy to another?

answer choices:

A-sound to kinetic

B-light to heat

C-mechanical to electrical

D-chemical to electrical

Answer:
Najla: D
Aya :D
Alanood; D
jawaher: D
NAWAL=D
Afnan D: D
Yara:D
Sada: D
badreia: D
NoorA: d
ShouG.A: D
Maitha: d
Asma O: D
Rawan:d
Salama: D - cahmical to electrical
Laian: D
Shoug Anwar: D

Fatima

2020-09-23 18:16:21 UTC

What type of energy is in this picture?

answer choices:

A-Kinetic

B-Potential

C-Chemical

D-Sound
Answer:
Najla: B
Aya:B
Alanood; B
jawaher: B
Nawal:B
Afnan D: B
Yara:B
badreia: B
Noor.A: B
ShouG.A: B
Maitha : b
Asma O: B
Rawan : B
Laian: B - potential

Aya Khalil

2020-09-23 18:28:39 UTC

How much energy (J) is required to heat 12.5 g of ice at –10.0 oC to water at 0.0 oC?
Answers:
Najla:
q = 12.5 g (2.03 J/g *C)(0.0 - -10.0 C) = 253.75j
nawal=
254J
yara: 12.5 x 2.03 x(0-10)=253.7j
Noor.A: q =c*m*t = 253.7 J
ShouG.A: q =c*m*t = (12.5)(2.03)(0-10) = 253.7 J
Maitha Fadhel :q =c*m*t = (12.5)(2.03)(0-10) = 253.7 J
Laian: it will equal to 253.7 J
NAWAL=235.7J Q=C*M* delta T

Aya Khalil

2020-09-23 18:29:20 UTC

Najla:
1- 52.8g
2- 45.6c
3-76.6c
Laian: 53 g - 45.7 C - 76.6 C

Aya Khalil

2020-09-23 18:31:47 UTC

240. g of water (initially at 20.0oC) are mixed with an unknown mass of iron initially at 500.0oC (CFe = 0.4495 J/goC). When thermal equilibrium is reached, the mixture has a temperature of 42.0oC. Find the mass of the iron.

Answers:
Najla:
-q = q
m*c(iron)*T= -m*c(water)*T
m=-(240g)(4.184j/g*c)(42-20)/(0.4495j/g*c)(42-500)
m=107g (iron)
Noor.A:
m = m*cH2O * t / cIRON * t = 107.3 g
ShouG.A: m iron = m*c*t (water)/c*t (iron) = 107.3 g
Maitha :m iron = m*c*t (water)/c*t (iron) = 107.3 g
Laian: m=107.3 g

Aya Khalil

2020-09-23 18:32:22 UTC

If 59.0 g of water at 13.0 oC are mixed with 87.0 g of water at 72.0 oC, find the final temperature of the system.

Answers:
Najla:
-lose heat = gain heat
-(m)*c*T = m*c*T
-(59g)(4.184j/g*c)(Tf-13)=(87g)(4.184j/c*g)(Tf-72)
Tf = 48.2c

Noor.A: using the equation : (mass) (c) (DT)] = (mass) (c) (DT) = Tf = 48.2oC

yara: m x c x T= m x c x t
59 x 4.184 x (Tf-13)=87 x
4.184 x (Tf-72)
Tf=48.2c
ShouG.A: m*c*T = m*c*T= Tf = 48.2oC
Maitha Fadhel :m*c*T = m*c*T= Tf = 48.2oC
Laian: Tf = 48.20 C

Aya Khalil

2020-09-23 18:33:06 UTC

A 97.0 g sample of gold at 785oC is dropped into 323 g of water, which has an initial temperature of 15.0oC. If gold has a specific heat of 0.129 J/goC, what is the final temperature of the mixture? Assume that the gold experiences no change in state of matter.

Answers:
Najla:
-q(Au) =q(water)
-(m)*c*T =m*c*T
-(0.129j/c*g)(97g)(Tf-785c)=(4.184j/c*g)(323g)(Tf-15)
Tf =22.1c
Noor.A: using the equation : (mass) (c) (DT)] = (mass) (c) (DT) = Tf = 22.05oC
ShouG.A: m *c*DT = m *c*DT= Tf =22.1 oC
Maitha Fadhel : m *c*DT = m *c*DT= Tf =22.1 oC
Laian: Tf = 22.10 C

nawal hisham

2020-09-23 18:40:04 UTC

The molar enthalpy of fusion of methanol is 3.22 kJ/

mol. What does this mean?

Answers:
Najla:
it requires 3.22KJ to react with one mole of solid methanol and cause it to melt (turn liquid).
Noor.A: It means that is needs this amount of heat for each mol in the Methanol to make it melt.
ShouG.A: Amount of heat needed per 1 mol of Methanol to make it melt is 3.22 KJ/mol
Maitha Fadhel: to make it melts an amount of heat per mil is required to such process . In this case it requires 3.22kj/ mol to melt
Laian: it means that the heat needed / 1mol of methanol to make it melt will be = to 3.22kJ/mol
Aya :3.22kJ is required to react with one mole of solid methanol and cause it to melt (turn liquid).

nawal hisham

2020-09-23 18:40:27 UTC

A sample of ammonia (∆H solid=5.66 kJ/mol)

liberates 5.66 kJ of heat as it solidifies at its melting

point. What is the mass of the sample?

Noor.A: 1 mol* 14.007+3×1.0079 g = 17.0307 g
ShouG.A: 17.0307 g
Maitha: 17.0307 g
Laian: 17.0307 g
ALANOOD; 17.03 g
NoorM: 17.03 g
Aya: 17.03
Najla: 17.03g

nawal hisham

2020-09-23 18:42:44 UTC

Metallurgy

A 25.0-g bolt made of an alloy absorbed

250 J of heat as its temperature changed from 25.0°C

to 78.0°C. What is the specific heat of the alloy?
Answers:
sada: 0.189 J/g⁰C
Noor.A: c = q / m*delta T = 1.886J/ g * C
ShouG.A: c= q / (m* T) = 1.889J/ g*oC
Maitha Fadhel :c= q / (m* T) = 1.889J/ g*oC
Rawan: q=c m T-> 250= c(25)(78-25) = 0.189J/gC
Laian: = 0.189 J/gC
NoorM: c = 0.189 J/gC
Aya Khalil: c=0.189 J/gC

nawal hisham

2020-09-23 18:44:01 UTC

Give two examples of chemical systems and define

the universe in terms of those examples.

Answers:
Sada: Universe = System + Surroundings
In this reaction, the System gains heat, and the
Surroundings lose heat. The Universe remains constant
Noor.A: heat pack : heat flows from the system which is the pack to the surrounding which is hands. The universe is the pack + hands.
cold pack: heat flows from the hands (surrounding) to the pack(system)
Universe is the pack + hands.
Maitha Fadhel: universe consist of system and surrounding
So the system gains energy as the surrounding loses energy
However the universe remains consist
Rawan : cup(system) and coffee(surrounding)-> the cup will be warm ---beaker(system)and wet wood(surrounding)--> the beaker will freeze in the wood.
Laian:
photosynthesis:
system: plant | surrounding: everything outside the plant.
reaction in a beaker:
system: beaker and its contents | surrounding: everything outside the beaker
Najla:
universe consist of system and surrounding. the system gains energy as the surrounding loses energy, moreover the universe remains constant.

nawal hisham

2020-09-23 18:44:56 UTC

For a given compound, what does the standard

enthalpy of formation describe?

Answers:
Najla: The standard enthalpy of formation, or standard heat of formation, of a compound is the change in enthalpy that accompanies the formation of one mole of the compound from its elements in their standard states.
Noor.A: Is defined as the change in enthalpy that accompanies the formation of one mole of the compound in its standard state from its elements in their standard state.
ShouG.A: the change in enthalpy that accompanies the formation of one mole of the compound in its standard state from its elements in their standard state.
Maitha Fadhel : Is defined as the change in enthalpy that accompanies the formation of one mole of the compound in its standard state from its elements in their standard state
Rawan : refer that pg 99 , that is the change in enthalpy that accompanies the formation of 1 mole of the compound in its standard state from its elements in their standard states.
Laian: The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.

Aya:
The standard enthalpy of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.

jawaher alhosani

2020-09-23 18:47:05 UTC

what is the symbol for the enthalpy of reaction
A)∆H
B)H
C)∆Hrxn
D)Hrxn

answers:
Najla: A
Aya:A
Alanood; A
Fm: A
Afnan D: A
Yara:A
badreia: A
Noor.A: A
ShouG.A: A
Maitha:A
Asma O: A
Rawan: A
Salama: C - delta(Hrxn)
Laian: A
NoorM: a
Nawal=A

Afnan Dawood

2020-09-24 05:53:04 UTC

20 g of water. specific heat of water is 4.18 J/g�°C. temperature changes from 25° C to 20° C, how much heat energy (Q) moves from the water to the surroundings?

A. 418 J
B. 209 J
C. 83 J
D. 4.18 J

Answers:
Noor.A: A
ShouG A: A
Najla: A
Maitha:A
Rawan :A
Alanood; A
Laian: A
Aya A
The specific heat of aluminum is 0.21 cal/g°C. How much heat(Q) is released when a 10 g piece of aluminum foil is taken out of the oven and cools from 100° to 50°?
A. 105 J
B. 10.5J
C.1.05 J

Answers:
Noor.A: A
ShouG A: A
Najla: A
Maitha:a
Rawan :A
Laian: A
Aya:a
Alanood; A

The unit Joules is for____
A. Temperature
B. Heat energy
C. Specific heat

Answers:
Noor.A: B
ShouG A: B
Najla: B
Maitha:b
Rawan: A
Alanood; B
Laian: B
Aya:A
∆H value in an endothermic reaction is a positive number.
A. True
B. False

Answers:
Noor.A: A
ShouG A: A
Najla: A
Maitha:A
Asma O:A
Rawan : A
Laian: A
Alanood; A
Aya :A

As a reaction is taken place, the student notices that the temperature has dropped. This indicates that the system has increased in energy. What type of process is this?
A. Endothermic
B. Exothermic

Answers:
Noor.A: A
ShouG A: A
Najla: A
Maitha:A
Asma O: A
Alanood; A
Rawan:A
Laian: A
Aya :A

sada sultan ali

2020-09-24 06:18:31 UTC

What is the sign for delta H for an exothermic reaction?

Answers:
Najla: Negative
Afnan D: Negative
badreia: negative
Noor.A: negative
yara: negative
ShouG.A: Negative
Maitha: negative
Alanood; negative
Asma O: negative
Afnan Ibrahem: negative x
Rawan : negative
Salama: Negative value of delta H
Laian: negative sign
NoorM: negative
Aya: negative
nawal=negative

sada sultan ali

2020-09-24 06:21:07 UTC

State whether this is exothermic or endothermic:
A block of solid ethanol melting?
Answers:
Najla: endothermic
Afnan D: Endothermic
badreia: endothermic
NoorA: Endo
ALANOOD; endothermic
yara: endothermic
Maitha: endothermic
ShouG.A: Endothermic
Asma O: endothermic
Rawan : Endothermic
Salama : Endothermic
Laian: Endothermic reaction
NoorM: endothermic
Aya: endothermic

sada sultan ali

2020-09-24 06:27:14 UTC

Convert 0.5720 kcal into joules:

Answers:
Najla:
0.5720Kcal (4.184j/1cal) = 2.393kj
2.393kj(1000/1k)= 2393.24j
Noor.A:
0.5720 kcal * 1000 / 1 = 572 cal
572 cal * 4.184 / 1 cal = 2393J
Maitha : 0.5720 kcal * 1000 / 1 = 572 cal

572 cal * 4.184 / 1 cal = 2393J

yara: 0.5720 Kcal x 4.184/1cal= 2.393kj
2.393kj x (1000/1k)= 2393.24j
ShouG A:
0.5720 kcal * (1000 / 1) = 572 cal
572 cal * (4.184 / 1 cal) = 2393J
Rawan:
0.5720Kcal (4.184/1cak)=2.39KJ
2.39KJ (1000/1K) = 2393.2 J
Salama: 0.5720kcal x (1000cal/1Calorie) =572cal
572cal x (4.184J/1cal)=2393.25J
Laian: 0.572Kcal×(1000/1) = 572cal
572cal×(4.184÷ 1) = 2393.2J
Aya:
0.5720 kcal * 1000 / 1 = 572 cal
572 cal * 4.184 / 1 cal = 2393.2J

sada sultan ali

2020-09-24 06:36:37 UTC

Endothermic or Exothermic:
Water vapor condensing?
Answer:
badreia: exothermic
Alanood; Exothermic
Najla: Exothermic
Afnan D: Exothermic
Noor.A: Exothermic
yara: Exothermic
Maitha: exothermic
ShouG A: Exothermic
Asma O: exothermic
Afnan ibrahem: exothermic
Rawan: Exothermic
Salama: Exothermic
Laian: Exothermic reaction
Aya K.: exothermic reaction
Nawal=exothermic

Salama Mahmoud

2020-09-26 12:43:58 UTC

Calculate the specific heat in J/(g x C) of an unknown substance if a 2.50g sample releases 12.0cal as its temperature changes from 25.0C to 20.0C.
Answers:
NoorM: 0.96 Cal / gC
Laian: 0.96 Cal/gC
Noor.A: 0.96 Cal/ g*C
ShouG.A: 0.96 Cal/ g*C
Sada: 0.96 Cal/gC
Aya K.: 0.96 Cal/ g*C
nawal=0.96Cal\gc
Najla : 0.96Cal/g*c

Noor Mohamed

2020-09-26 13:28:13 UTC

Categorize whether condensation, solidification, vaporization and fusion as ENDOTHERMIC or EXOTHERMIC processes.
ANSWERS:
Salama: Condensation - exothermic
Solidification - exothermic
Vaporization - endothermic
Laian:
exothermic:
- condensation, solidification
endothermic:
-vaporization
Noor.A: Cond: Exo, Solid: Exo, Vap: Endo
ShouG.A: Condensation and Solidification is Exothermic process, while vaporization is Endothermic process.
Aya :
condensation - exothermic
Solidification - exothermic
Vaporization - endothermic
Najla:
1-Condensation - exothermic
2-Solidification - exothermic
3-Vaporization - endothermic

Noor Mohamed

2020-09-26 13:33:39 UTC

What is a calorimeter and how does it work?

ANSWERS:
Salama: A calorimeter is a device used to measure the amount of heat involved in a chemical and physical reactions. it simply works by measuring the change in temp.
Laian: calorimeter a device used to measure the amount of heat involved in a chemical or physical process. in a calorimeter , the heat produced by the reaction is absorbed by the solution, which increases its temperature
Noor.A: A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity.
ShouG.A: Calorimeter is a device used to measure the amount of heat involved in a chemical or physical process. Works by capturing all the energy released (or absorbed).
Aya :
its an insulated devise that is used to measure the amount of heat released or absorbed by the system. it works by measuring delta enthalpy of the reaction.
Najla:
A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Multiplying the temperature change by the mass and specific heat capacities of the substances gives a value for the energy given off or absorbed during the reaction.
NAWAL:
a calorimeter is a device measure the amount of heat absorb or released in a chemical reaction or physical change and it work by measuring the initial heat of water then add a specific mass of substance and measure it initial temperature then we add the substance calorimeter then finally we see the final temperature so we can measure the change in enthalpy.

Noor Mohamed

2020-09-26 13:39:12 UTC

Write a thermochemical equation for the combustion of methane.
ANSWERS:
Laian: CH₄ + 2 O₂ → CO₂ + 2 H₂O (ΔH = −891 kJ/mol
Noor.A: CH_4 + 2O_2 --> CO_2+ 2H_2O Hrxn = -891 kJ/mol
ShouG.A:CH_4(g) + 2O_2(g) --> CO_2(g) + 2H_2O(g) DHrxn = -891 kJ/mol
Aya :
H₄ + 2 O₂ → CO₂ + 2 H₂O ΔH = −891 kJ/mol
Najla:
CH4 +2O2 = CO2 + 2H2O
Delta H = -891kj/mol

Noor Mohamed

2020-09-26 13:43:05 UTC

What is the meaning of a combustion reaction?
ANSWERS:
Laian: is the scientific word for burning
Noor.A: scientific word for burning. In a combustion reaction a substance reacts with oxygen from the air and transfers energy to the surroundings as light and heat.
ShouG.A: scientific word for burning. In a combustion reaction a substance reacts with oxygen from the air and transfers energy to the surroundings as light and heat.
Aya:
reaction that includes burning process (it react with oxygen)
Najla:
Combustion is the scientific word for burning. In a combustion reaction a substance reacts with oxygen from the air and transfers energy to the surroundings as light and heat. The products of a combustion reaction are called oxides.

Laian Ali

2020-09-26 13:50:11 UTC

explain how energy changes from one form to another in an exothermic and endothermic reactions.

Answers:
NoorM: when a solid ice cube melts to liquid water, it releases heat, which makes the reaction (fusion) exothermic.
Noor.A: Turning solid to liquid releases heat (Exo)
Turning Gas to Liquid absorbs heat (Endo)
ShouG.A: From Solid to liquid to gas, energy is being released so the change in enthalpy is going to be (-). From gas to liquid to solid, energy is being absorbed so the change in enthalpy is going to be (+).
Aya :
in exothermic reaction heat is released in particular forms such as thermal energy
in endothermic heat is absorbed in particular forms
Najla:
The difference between the energy of the reactants and the energy of the products is called the enthalpy change (∆H) of the reaction. For an exothermic reaction, the enthalpy change is always negative. In an endothermic reaction, the products are at a higher energy than the reactants.

Laian Ali

2020-09-26 13:50:56 UTC

state the law of conservation of energy:

Answers:
Salama: Energy cannot be created or destroyed, but it can change from one form to another.
NoorM: Energy can be converted from one form to another, but it is neither created nor destroyed.
Noor.A: law of conservation of energy states that energy cannot be destroyed nor created, it can only convert from one form to another.
ShouG.A: energy can only be convert from one form to another, but it can't be destroyed nor created.
Aya:
energy can be transformed from 1 form to another but it can't be created or destroyed
Najla:
In physics and chemistry, the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be conserved over time. For instance, chemical energy is converted to kinetic energy when a stick of dynamite explodes.

Laian Ali

2020-09-26 13:53:13 UTC

explain how perspiration can help cool your body

Answers:
NoorM: perspiration helps releasing moisture onto your skin and when it evaporates it removes some heat, making your body cooler.
ShouG.A: The sweat leaves your skin through tiny holes called pores. When the sweat hits the air, the air makes it evaporate (this means it turns from a liquid to a vapor). As the sweat evaporates off your skin, you cool down.
NoorA: Sweating helps to cool the body. It allows the water to evaporate from the skin which results in loss of body heat. Hence, it removes excess heat from the body. Also, it makes the skin wet. Due to this, the skin feels cooler.
Aya :
perspiration helps releasing moisture to your skin and when it evaporates heat is removed , making your body cooler.
Najla:
Sweat helps cool you down by releasing moisture onto your skin. . First, it makes your skin feel cooler when it's wet. And when it evaporates it removes some heat. But sweat will only evaporate in an environment where there isn't much water in the air.

Laian Ali

2020-09-26 13:54:44 UTC

compare and contrast temperature and heat

Answers:
NoorM: Heat is a form of energy that can be transferred from one object to another or even created at the expense of the loss of other forms of energy. Temperature is a measure of the warmth or coldness of an object or substance with reference to some standard value. Heat is the total energy of the motion of the molecules inside the object or particle, whereas Temperature is merely a measure of this energy. The relationship could be, the more heated an object is there higher the temperature the object will have.
ShouG.A: The core difference is that heat deals with thermal energy, whereas temperature is more concerned with molecular kinetic energy. Heat is the transfer of thermal energy, whereas temperature is a property the object exhibits.
Noor.A: Temperature is more concerned with molecular kinetic energy. Temperature describes the average kinetic energy of molecules. Heat deals with thermal energy. Thermal energy can be otherwise understood as the total microscopic kinetic and potential energy of a system.
Aya :
The core difference is that heat deals with thermal energy, whereas temperature is more concerned with molecular kinetic energy. Heat is the transfer of thermal energy, whereas temperature is a property the object exhibits.
Najla:
The core difference is that heat deals with thermal energy, whereas temperature is more concerned with molecular kinetic energy. Heat is the transfer of thermal energy, whereas temperature is a property the object exhibits.

Laian Ali

2020-09-26 13:55:45 UTC

The symbol for specific heat is ______
A. c
B. m
C. Q
D. t

Answers:
Alanood: A
MAITHA;A

NoorM: A
Sada: A
Noor.A: A
ShouG.A: A
badreia:A
yara:A
Aya :A
NAWAL=A
Rawan: A
Najla: A

Noor Mohamed

2020-09-26 14:02:31 UTC

What does Hess's law state?

ANSWERS:
Laian: it states that if you can add 2 or more thermochemical equations to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is the enthalpy change for the final reaction

Noor.A: Hess's Law states that if you can add two or more thermochemical equations to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is the enthalpy change for the final reaction.
ShouG.A: states that if you can add two or more thermochemical equations to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is the enthalpy change for the final reaction.
Aya :
it states that if you can add two or more thermochemical equations to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is the enthalpy change for the final reaction.
Najla:
it states that if you can add two or more thermochemical equations to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is the enthalpy change for the final reaction.

Laian Ali

2020-09-26 14:09:43 UTC

what do we mean by Enthalpy ( heat of reaction ) ?

Answer:
Sada: its the change in the enthalpy of a chemical reaction that occurs at a constant pressure
ShouG.A: The heat content of a system at a constant pressure.
NoorA: The heat content of a system at a constant pressure.
Rawan: Where the heat are constant of the system at at a constant pressure.

Alanood Fahad;
heat content of a system at a constant pressure.
Aya :
The heat content of a system at a constant pressure.
Najla:
The enthalpy of reaction is defined as the internal energy of the reaction system, plus the product of pressure and volume.

Laian Ali

2020-09-26 14:10:26 UTC

If 200 grams of water is to be heated from 24.0° C to 100.0° C to make a cup of tea, what is the mass and what is the change in temperature?

A. m=200g
∆t= 66
B. m=200g
∆t=124
C. m=200g
∆t=76
D. m=200
∆t=100

Answer:
ShouG.A: C
Noor.A: C
Alanood; C
Aya K.: C
Rawan :C
nawal=c
Najla: C

Sada sultan ali

2020-09-26 17:50:58 UTC

What is enthalpy of combustion? How does it differ from the enthalpy of reaction?

Answers:

ShouG.A: The enthalpy of combustion of a substance is defined as the heat energy given out when one mole of a substance burns completely in oxygen. Combustion is always an exothermic process. Because of this, enthalpy change of combustion must always be positive; on the other hand, enthalpy change of formation can be either positive or negative.
NoorA: The enthalpy of combustion of a substance is defined as the heat energy given out when one mole of a substance burns completely in oxygen.

enthalpy of reaction can be negative or positive, while enthalpy of combustion is always negative because it is exothermic.

Aya:
it is the heat energy given out when one mole of a substance burns completely in oxygen.

enthalpy of combustion is always negative because it is exothermic reaction .

however enthalpy of reaction could be negative or positive.

Najla:
Combustion is always an exothermic process. Because of this, enthalpy change of combustion must always be positive; on the other hand, enthalpy change of formation can be either positive or negative, since a reaction to form 1 mole of a substance can be either exothermic or endothermic.

Sada sultan ali

2020-09-26 17:52:45 UTC

What is the molar enthalpy of fusion?

Answers:

ShouG.A: Molar enthalpy of fusion is the amount of energy needed to change one mole of a substance from the solid phase to the liquid phase at constant temperature and pressure.
NoorA: It is the amount of energy needed to change one mole of a substance from the solid phase to the liquid phase at constant temperature and pressure

Alanood; moral enthalpy is the amount of energy needed to change one mole of a substance from the solid phase to the liquid phase at constant temperature and pressure.
Aya:
The amount of energy required to change one mole of a specific substance from solid to liquid

shoug Anwar

2020-09-27 06:41:29 UTC

Define physical change and give an example
Answers:

Noor A: when a substance changes its form, but its not chemical make up, eg: melting ice
Aya : its when a substance change from 1 physical state to another by a chemical reaction
ex: dissolving salt'
Najla:
Physical changes are changes affecting the form of a chemical substance

Al Anood

2020-09-27 08:36:13 UTC

how does energy changes from a form to another? in endothermic and exothermic?

Answers;
Alanood; endothermic changes from a for to another by absorbing energy during the reaction.
exothermic changes from a form to another by releasing energy during the reaction
Aya :
in exothermic reaction heat is released to the surrounding
in endothermic reaction heat is absorbed from the surrounding
yara:
exothermic is the reaction that released heat from system to the surrounding
endothermic is the reaction that absorbed heat from surrounding to the system
Najla:
An exothermic reaction is one that releases energy in the form of heat or light. In other reactions, the energy that must be absorbed to break the bonds in the reactants, is more than the energy that is released when the new bonds in the products are formed. This type of reaction is known as an endothermic reaction.
nawal=
in exothermic reaction the energy change to heat and it get released but in endothermic reaction energy absorb so the chemical potential energy increase >

Hess's law

dulaimimuna — 2020-09-27 17:42:00 UTC

Dear students: Solve the following problem by tomorrow

Rawan Khaled Alkatheeri 12A

2020-11-15 10:16:16 UTC

https://quizizz.com/join/quiz/5f50ee3b64bba6001b6e6268/start?studentShare=true