Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chemistry > C7-Energy Changes > Flashcards

C7-Energy Changes Flashcards

(53 cards)

Start Studying
1
Q

What are Exothermic reactions ?

A

Exothermic reactions transfer energy from the reacting molecules to the surroundings . Thereforre , the temperature of the surroudings increases (hotter ) .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Examples of Exothermic rections .

A

Combustion and certain oxidation and neutralisation reactions .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How do scientists represent energy changes that take place in a reaction ?

A

By drawing an energy profile diagram .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What does star one show for exothermic reaction profile ?

A

Products have less energy that reactants , as energy is being transferred from the reaction to the surroudnings ..

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do we figure out the energy released to the surroudings in an exothermic reaction profile ?

A

The difference between the energy of the reactans and the enrgy of the products tells us the energy released to the surroudnigs .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Label the energy change on the exothermic diagram .

A

.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Wat are tewo uses of exothermic reactions .

A
  • Hand warmers

- Self-heating cans example food and drink .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are endothermic reactions ?

A

They tae in energy fromt heir surroundings . Thereofore the temperature of the surroundigns decreases (gets colder )
an example i thermal decompostion .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does star one show for enndothermic reaction profile ?

A

Products have got more energy than reactants . As enegry is being taken in from the surroudnigns .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How do we figure out the energy release taken in from the surroudings in an endothermic reaction profile ?

A

-The difference in energy between the reactants and products , tells us the amount of energy taken in by the reaction .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Similarirites in both endo and oexothermic reactions ?

A

-In both cases eergy rises to a peak . This is the activaiton energy . WHICH ARE THE PEAKS OF THE CURVES , LABEL IT ON ENERGY PROFILE .
-The minimum amount of energy that paricles must have in order to react is called he activation eenrgy .
FROM THE PEAK TO THE CURVE CHECK HE SHEET AND LABEL ON PROFILES .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the RQP for invesigating temp chage ?

A
  • Investigating the temperature change in an exothermic reaction .
  • This is a reaction between hydrochloric acid and the alkali sodium hydroxid e.
  • We are going to add incresing volumes of sodium hydroxide solution to hydrochloric acid . In each experiment , will measure the maximum temperature reached .
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the independant variable ?

A

Volume of sodium hydroixide solution .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the dependant variable

A

The maximum temperature reached .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the control variable ?

A

VOLUME OF HYDROCHLORIC ACID AND CONCENTRATION OF BOTH SODIUM HYDROIXDE SOLUTION AND HCL .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Stage one for RQP for investigation temp change ?

A

Use a measuring cylinder to measure 30cmcubed of dilute hydrochloric acid .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Stage two for RQP for investigation temp change ?

A

Transefr acid into a polystyrene cup .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Stage three for RQP for investigation temp change ?

A

Stand the polstyrene cup inside a beaker , this stops the cup from falling over .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Stage four for RQP for investigation temp change ?

A

Next we use a thermometer to measure the temperture of the acid and we record this in a table .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Stage five for RQP for investigation temp change ?

A

Now we use a measuring cyclinder to meassure 5cm cubed of sodium hydroxide solution and we transfer this to the polystrene cup .

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Stage six for RQP for investigation temp change ?

A

Fit a plastic lid to the cup and plce thermometer through the hole in the lid .
-The bulb of the thermometre must be in the solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Stage seven for RQP for investigation temp change ?

Study These Flashcards
A

Use the thermometer to gently stir the solutoin .
-Because this reaction is exothermic , it releases energy . This means that the temperature of the solution will increase.

23
Q

Stage eight for RQP for investigation temp change ?

Study These Flashcards
A

Now we look carefully , at the temperature rise , on the thermoemeter .
-When the reading on the thermomeer sops chaning , we record the highest temperature reached .

24
Q

Stage Nine for RQP for investigation temp change ?

Study These Flashcards
A

Rinse out the polstyrene cup . Repea the whole experiemnt using 10cm cubed of sodium hydroxide solution .
-Carry out the experiment severla more times , each tie increading the volume of sodium hydroxide solution b 5cm cubed until we reach a maximum of 40 cm cubed of sodium hydroixde solution

25
Stage ten for RQP for investigation temp change ?
Repeat the experiemnt one more time , so e have wo ses of results . Use this to calcualte a mena caue , for maximum temperature reached for each volume of sodium hydroxide soluon .
26
Check the graph for the RQP , what does star one show ?
-As we increase the volume of sodium hydroxide solution , the maximum temperature reaced increases . BECUASE - as we add more particles of sodium hydroxide ,t hey react iwth hydrochloric acid . -This is an EXOTHERMIC reaction , so more enrgy is releaseed and the maximum temperature reached increases .
27
Check the graph for the RQP , what does star twos hwo ?
At a certian volume of sodium hydroxide solution , the maximum temperature reached starts to decrease . - At this point we are adding so much sodium hdroxide ,that there is not enough hydrochloric acid . Meaning some of the sodium hydroxide is unable to react . - Because of this ,t he amoutn of energy released by the reaciton has reached a maximum .
28
Why does the temperature actually decerase from start two ont he RQP graph ?
- In each experiemnt , we are adding a greater volume of solution . - So energy relesed is now spread out into a greater volme . - Because of this ,when we dd large volumes of sodium hydroixde solution , the maximum temperature reached decreases .
29
EXAM QESTION - , why are we using a polystyrene cup ith a lid ?
- As we are measuring the temperature in the ecperiment . This means , we want to reduce any heat loss . - Polystyrene is a good thermal inslator , reducing heatloss htrough the sides and the botto , and the lid reduces heat loss into the air .
30
What can we do if we ake two different metals and place them into an electrolyte ?
-We can produce electricity .
31
What is an electrolyte ?
-AN electrolyte is a solution that can doduct electricty , e.g a solution of an ionic compound .
32
Look at the setup on the page , | what is the setup for a cell ?
- a strip of copper nad magnesium is palced inside an electrolyte soluton . - If you connect the two metals with a voltmetre , you cn see a potetntial difference and an electric current will flow through the wire . - A chemical reaction is taking place on the surface of the two metals , and these reactions are producing electircity , this setupp is called a CELL . - Cells can be used to generate electricity .
33
Facts about a cell
- A cell can only produce electicity for a certian period of time . - Eventually the chemicals in the cell runout and the reaction stops . - Cells only produce electicity if we use metals with different reactivities .
34
Reactivity and votage ?
- The bigger the difference in reactivity in metals , the larger potential difference produced by the cell . - THe electrolyte also affects the potential difference .e
35
A battery
-A battery cotins two or mroe cells connected ins eries , to produce a greater voltage
36
Alkaline batteries ?
- In alkaline batteries at some point , the reactants in the batteries run out and no more electricity is produced . - There is now way we can reverse these reactions so these are NON - RECHARGEABLE BATTERIES.
37
Rechargeable batteries ?
- Rechargeable batteries can be rechrged . | - As we can reverse the chemical reactions when we apply an electric current .
38
What happens in a fuel cell ?
- We react a fuel (hydrogen) with either pure oxygen or air . - Inside the fuel cell ,a chemical reaction reaction takes place , producing an electric current , the only waste prodcut is water .
39
Draw the diagram .
:)
40
What happens at the negative electrode of the reaction ?
-The hydrogen molecule spilts into hydrogen ions and electrons . -These electrons pass through the wire and that is the electric current . See the equation on the page and learn .
41
What happens at the positive electrode of the reaction ?
- Oxygen molecules combine with electrons and hydrogen ions produced at the negative electrode . - See equation on the page and learn .
42
TO CONCLUDE , what happens at the hydrogen fuel cell ?
-In a hydrogen fuel cells , hydrogen is combined with oxygen (Hydrogen is oxidiised .) The overal equaion is (check book too ) Nh2+O2--->2H20 (Hydrogen is being oxidised )
43
What is one advantage of hydrogen fuel cells ?
Hydorgen fuel cells will produce electricity for AS LONG AS YOU PROVIDE HYDROGEN .
44
What is another advanatage of hydrogen fuel cells ?
Hydrogen fuels cellsdo not get less efficent the logner they are run .
45
What is the last advantage of hydorgen fuel cells ?
Hydrogen fuel cells can be a source of drinkable water e.g on a spacecraft .
46
What is one disadvantage of a hydrogen fuel cell ?
Hydrogen fuel cells runon hydrogen which is an explosive gas and it is very difficult to store safely .
47
What is another disadvanatge of hydrogen fuel cells ?
-Hydrogen fuel cells produce a realtively low potential diffeence , or voltage so several are needed together
48
What is one advantage of rechargeable batteries ?
-No dangerous fuels are required with rechargeable batteries . (Some types of rechargeable batteries can catch fire if not manufactured correctly )
49
What is another advantage of rechargeable batteries
Rechargeable batteries can produce a greaer potential difference than a hydrogen fuel cell .
50
What is one disadvantage of rechargeable batteries ?
-Rechargeable batteries run out , and need to be recharged .
51
What is another disadvantage of rechargeable batteries ?
-Rechargeable batteries can store less electricity the more charginc ycles they go through and eventually need replacing so are not that efficent .
52
yay fuel cells
-dont produce ppllutants whereas fossil fuels do . petrolc omesfrom fosilf uels - combustion of that porduces co2 atmosphere . -fossil fuels re a finite supply , whereas getting hydorgen from water wont run out .
53
hydorgen fuel cells noo
Hydrogen is a gas and requires a much larger storage volume compared to fossil fuels like petrol. no efficent wya to produce hdyorgen , actually still genrared from burnign fosisl fuels . electrolysis for h ydrogen fuel cells is expensive .,

Chemistry (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions