How to speed up chemical reactions (and get a date) - Aaron Sams

2,215,731 views ・ 2012-06-18

TED-Ed


Please double-click on the English subtitles below to play the video.

00:14
Meet our chemist, Harriet.
0
14013
1531
00:15
She has a chemical reaction that needs to occur more quickly.
1
15568
3358
00:18
A chemist has some processes at her disposal
2
18950
2081
00:21
that can help her speed up her reaction,
3
21055
1944
00:23
and she knows of five ways.
4
23023
1650
00:24
And to remember them,
5
24697
1151
00:25
she thinks back to her days as a high school student,
6
25872
2531
00:28
and the day she got a date for the dance.
7
28427
1979
00:31
Harriet was in high school, studying between classes.
8
31369
2501
00:33
She had lost track of time and was going to be late to class.
9
33894
2895
00:36
Unbeknownst to her,
10
36813
1157
00:37
Harold, who was just around the corner, was running late, too.
11
37994
2927
00:40
They both sprinted to class
12
40945
1476
00:42
and, as it happened, sprinted directly into one another.
13
42445
3175
00:45
Now, this was no small collision.
14
45644
1779
00:47
They ran squarely into one another in such a way
15
47447
2261
00:49
that he knocked the books right out of her hand.
16
49732
2265
00:52
"I'm sorry," he said. "Let me help you with your books."
17
52021
2697
00:54
He kindly helped her re-collect her belongings,
18
54742
2215
00:56
and politely offered to walk her to class.
19
56981
2023
00:59
And you'll never guess who went together to the dance later that year.
20
59028
3389
01:02
Yup, those two.
21
62441
1319
01:04
So as we can see from this example,
22
64459
1684
01:06
the key to getting a date for the dance is to collide with someone
23
66167
3118
01:09
and knock the books out of their hands.
24
69309
1869
01:11
Now, you're probably already aware
25
71202
1626
01:12
that not all collisions lead to dates for the dance,
26
72852
2433
01:15
thankfully.
27
75309
1160
01:16
The collisions must have two important characteristics:
28
76493
2577
01:19
One, correct orientation that allows books to be knocked from one's hands;
29
79094
3689
01:22
and two, enough energy to knock the books out.
30
82807
2178
01:25
Shortly after this incident,
31
85009
1386
01:26
Harriet decided to tell me, her chemistry teacher, all about it.
32
86419
3032
01:29
I noticed some interesting parallels
33
89475
1741
01:31
between her story and chemical reaction rates,
34
91240
2161
01:33
which happened to be what she was studying in the hallway
35
93425
2695
01:36
the day of the collision.
36
96144
1198
01:37
Together, we decided to set out on two missions.
37
97366
2533
01:39
Harriet wanted to help all chemistry students and chemists
38
99923
2737
01:42
remember how to speed up the rate of chemical reactions
39
102684
2666
01:45
and I, being the nice guy that I am,
40
105374
1731
01:47
decided to make it my mission to help create educational environments
41
107129
3270
01:50
in which more book-dropping collisions can take place
42
110423
2492
01:52
to increase future chemists' chances of getting a date for the dance.
43
112939
3719
01:56
In order to facilitate this improved dance-date-getting process,
44
116682
3294
02:00
I propose five changes to all schools
45
120000
1976
02:02
that parallel Harriet's five ways to increase chemical reaction rates.
46
122000
3851
02:06
First, I propose that we shrink the size of the hallways.
47
126454
2889
02:09
This will make it more difficult to safely navigate the hallways
48
129367
3015
02:12
and will cause more collisions than in larger hallways.
49
132406
2608
02:15
And by increasing the number of collisions,
50
135038
2008
02:17
we increase the likelihood
51
137070
1246
02:18
that some of those collisions will have the correct alignment
52
138340
2889
02:21
and enough energy to create a date to the dance.
53
141253
2513
02:23
Now, chemically speaking,
54
143790
1200
02:25
this is equivalent to lowering the volume of a reaction vessel
55
145014
2919
02:27
or a reaction mixture.
56
147957
1289
02:29
In doing so, the individual particles are closer together,
57
149270
3147
02:32
and more collisions will occur.
58
152441
1635
02:34
More collisions means a greater likelihood
59
154100
2086
02:36
that collisions with the appropriate energy and configuration will happen.
60
156210
4204
02:40
Second, I propose increasing the overall population of the school.
61
160438
3960
02:44
More students equals more collisions.
62
164422
2161
02:47
By increasing the number of particles available for collision,
63
167513
2951
02:50
we create an environment where more collisions can take place.
64
170488
2960
02:53
Third, we must reduce the time allowed between classes --
65
173472
2714
02:56
heck, let's just cut it in half.
66
176210
1541
02:57
In doing so, students will need to move more quickly
67
177775
2445
03:00
to get from one class to the next.
68
180244
1635
03:01
This increase in velocity will help make sure
69
181903
2129
03:04
collisions have the appropriate amount of energy necessary
70
184056
2730
03:06
to ensure book-dropping.
71
186810
1499
03:08
This is analogous to increasing the temperature of the reaction mixture.
72
188333
3440
03:11
Higher temperature means particles are moving faster.
73
191797
2531
03:14
Faster-moving particles means more energy,
74
194352
2167
03:16
and a greater likelihood of the reaction-causing collision.
75
196543
2985
03:19
Fourth, students must stop traveling in packs.
76
199980
3484
03:23
By traveling in packs, the students on the outside of the pack
77
203488
2941
03:26
insulate those in the middle from undergoing any collisions.
78
206453
2943
03:29
By splitting up, each student has more area exposed
79
209420
2798
03:32
that is available for a collision from a passing student.
80
212242
2706
03:34
When particles travel in packs, the surface area is very small,
81
214972
3192
03:38
and only the outside particles can collide.
82
218188
2351
03:40
However, by breaking up the clumps into individual particles,
83
220563
3040
03:43
the total surface area is increased,
84
223627
2184
03:45
and each particle has an exposed surface that can react.
85
225835
2935
03:49
Fifth and finally, we hire a matchmaker.
86
229975
2699
03:52
Is this colliding and book-dropping too violent?
87
232698
2275
03:54
Is there an easier way to get a date that requires less initial energy?
88
234997
3484
03:58
Then a matchmaker will help with this.
89
238505
2080
04:00
The matchmaker makes it easier for a couple to get together,
90
240609
2880
04:03
by coordinating the match.
91
243513
1722
04:06
Our matchmaker is like a catalyst.
92
246136
1889
04:08
Chemical catalysts function by lowering the activation energy --
93
248049
3403
04:11
in other words, by lowering the energy required to start a reaction.
94
251476
3213
04:14
They do this by bringing two particles together
95
254713
2198
04:16
and orienting them correctly in space so that the two can meet
96
256935
3449
04:20
at the correct configuration and allow a reaction to take place.
97
260408
3865
04:24
So, to sum up: if a future chemist wants a date for the dance,
98
264297
3039
04:27
he must collide with another person
99
267360
1879
04:29
and knock the books out of their hands.
100
269263
2216
04:31
And if a chemist wants to make a chemical reaction occur,
101
271503
2724
04:34
the particles must collide in the correct orientation
102
274251
2508
04:36
with an appropriate amount of energy.
103
276783
1793
04:38
And both of these processes can be accelerated,
104
278600
2254
04:40
using the five methods I've described.
105
280878
1912
About this website

This site will introduce you to YouTube videos that are useful for learning English. You will see English lessons taught by top-notch teachers from around the world. Double-click on the English subtitles displayed on each video page to play the video from there. The subtitles scroll in sync with the video playback. If you have any comments or requests, please contact us using this contact form.

https://forms.gle/WvT1wiN1qDtmnspy7