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Kamis, 09 Agustus 2012

EYEO FESTIFAL 2012 RECAP

A

eyeo festival 2012 recap

2012 August 3
by Chuck
In June I was fortunate enough to attend the quickly sold out eyeo festival. This was the second year of the event, and given the apparent success of the first I was excited to attend. It’s held in Minneapolis and this year the main venue was the Walker Art Center, but other evening events were held at different venues each night. Minneapolis seems like a great town, and the Walker was a good choice of venue for the main events during the day.

As others who have written about the conference have mentioned, it is difficult to pin such a broad event down to a single blog post. I can’t help but think back to the conferences years ago that revolved around the Flash design and development community and how they were attempting to speak to many audiences at once. eyeo is certainly more focused toward a design slant but features enough for anyone interested in the area no matter their title. Here, I think there is a sense of a burgeoning scene around designers and data visualization coming together that allows for a broad spectrum of practice and theory to mix comfortably.
The increasing quantity and complexity of information generated means methods of helping people consume the data will continue to evolve. As Drew Breunig shares in his “Frontiers through the Ages” list, Data is the next frontier.

Speakers

I wanted to talk about a few speakers in this post. Over time, the organizers are adding talks to their vimeo channel so you will likely be able to see more than I discuss here. However, the talks below resonated with me because of how we work at DesignMap and their relationships to the type of deliverables we create and how we create them.

Amanda Cox

Amanda Cox is a Graphics Editor for The New York Times, has spoken several times at various conferences and won many awards for her work in data visualization.
Amanda shared an historical view at her department beginnings along with a truly massive selection of graphics the team has created over the past 20 years. What she showed was a hefty sample of the 100,000 graphics created in the department organized in a huge scrolling page. What was interesting was to see and hear about the influences each graphic has had on later, similar problems the team has tried to solve. To see previous work recombined in more effective ways, cross-pollinating, was only possible by looking at all of the work. Certain graphics couldn’t happen without previous graphics.

A few snippets of her talk:

Can we tell you something more by throwing something away?
Bar charts don’t respect what’s unique about the data. It’s the lowest level of conversation. Not exposing the underlying content in a new more useful way.
The best kind of journalism is not mad-lib journalism. Same thing goes for graphics. You can make fine graphics, but you’ll never make great graphics.

Stefanie Posavec

Stefanie is known for her visual analysis of the novel On The Road by Jack Kerouac and this project is what she shared at the conference. She spent 3 weeks documenting the novel in various ways, the end result was 4 poster that visually represent aspects of the novel. By visualizing the book in this way, Stefanie is able to call out the key themes of the novel and when they appear in the narrative. What resonated most for me was the fact that her work of analysis was done by hand, something that we value here at DesignMap highly. By putting her nose in the source material so thoroughly, she left with an intimate understanding of that material and was able to craft something that would undoubtedly have moved the author with her insights.
Details from Stefanie Posavec's poster series dissecting Jack Kerouac's On The Road.
Stefanie manually collected the data used for her poster series by marking up a copy of the novel.

Nicholas Felton

Interior page from Felton's 2010/2011 Biannual Report
Covers for some of Felton's Annual Reports
I wasn’t sure how much I’d take away from Nicholas’ talk. Seeing as how his Annual Report work is something I own copies of and read through several times, I expected it might not be as eye-opening as other sessions. But it was interesting to hear him discuss his process for design in more detail. How he deals with the same blank-page anxiety we all do and especially how he starts working with something, anything, to keep moving in a direction until he knows the right direction.
I did however leave the talk wanting to understand a bit more about the relationship between the data he records and how it influences his end result. On his blog, he describes the purpose of the 2010/2011 report with a Philip K. Dick quote:
“a person’s authentic nature is a series of shifting, variegated planes that establish themselves as he relates to different people; it is created by and appears within the framework of his interpersonal relationships.”
The Feltron 2010/2011 Biennial Report explores this notion by overlapping facets of Nicholas’ behavior to visualize how his personality varies based on location and company.
He discussed many of the steps to ending up with the finished piece, but one detail that I enjoyed was his use of triangles to form what are essentially bar charts in the 2010/2011 Biennial Report. A detail like this exposes underlying thinking which isn’t always obvious by viewing the end result.
Felton explored a more effective way to display data sets with extreme upper and lower limits. A triangle-shaped "bar" allows the viewer insight into the relative height when it falls off of the printed page.
Felton chose 2 colors for the main themes of the report. 2010 was represented by cyan while 2011 was magenta.

Natalie Miebach

Natalie’s work is probably the hardest to qualify as having specific parallels or direct use for inspiration in our day-to-day work here at DesignMap. However, I found the work very interesting because it was taking data visualization in a different direction. Manifesting data in 3 dimensions or the form of music scores (including performances of the scores) were moving away from a reliance on written language to communicate these complex patterns of data. She focuses on translating data into a tactile experience in the form of woven sculptures and musical scores. By using 3 dimensions in her woven sculptures, she’s able to relay the relationships between data in a way that’s difficult to do in printed form, or even in interactive ways.
Visualization of "The Perfect Storm" using wind data to create a sculpture made from reed and wood.
It felt as though, given enough time, and enough samples with like data sets and scales, that one could learn this new language.
Some of these sculptures reminded me of an exhibit I saw in Peru years ago. The exhibit contained several examples of quipu, recording devices made from knotted strings meant to track numeric values such as crop yields and other bookkeeping needs for the Andean people of South America.

These quipu translate data into a tactile form in the same way Natalie does in her sculptures. Of course, the data density of the quipu is much smaller, but the notion is the same. To me, this example means the work Natalie does isn’t as far out as it might seem at first glance.

Would attend again

To wrap up, there were so many interesting talks about a big variety of data and visualization techniques that I didn’t cover here, so definitely check out the videos. I hope to attend again next year and would recommend it for others interested in the field.
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DESIGNING FOR AN IRREGULAR DATA SET

JB

Designing for an Irregular Data Set

2012 May 15
by Youna Yang

At DesignMap we pay careful consideration to all different levels of problems. An interesting and reoccurring problem I’ve come across lately is designing within a limited space while accommodating different types of restrictions. This particular example is around viewing and editing countries within a modal. The modal is triggered from a world map widget within a dashboard that provides an overview of selected countries. Here are some constraints, desires, and context around the problem:
Constraints
  • Number of regions and countries are in flux so scalability is crucial (started with 77 countries with 7 regions; ended with 163 countries with 5 regions)
  • Range in number of countries per region (One region has 2 countries while another has 45)
  • Cannot alter how regions are broken up and which countries fall under a region
  • Search is not in scope
Desires
  • Scannability
  • Digestibility
  • Sensible modal size

Context
  • For the general use case, the smart default is with all regions and countries selected
  • Each modal option has a “Select/Deselect All” checkbox for cases when the user only wants to select a few countries in different regions (i.e. if the user wants to select just the US from the Americas and the UK from Europe, a Select/Deselect All option prevents a user from having to individually deselect 161 countries)
  • Checkboxes left of each region provides quick regional select and deselection for the same reason, on a smaller scale
  • To the right of each region is a count of selected and total countries in parentheses indicating the current state
Here are six different options with some pros and cons that were considered in designing around these restrictions:

1. Wrapping list


This wrapping list in a modal is utilitarian and not usable.
Pros
  • All countries are visible at one glance
  • No extra selection needed to view regional data
Cons
  • Difficult to scan; category headers are mixed in with listed sub content
  • No hierarchy
  • Increases cognitive load

2. Horizontally Navigated Tabs


This option breaks up the regions into more digestible sections. The main downside is that it doesn’t scale well horizontally. Pushing tabs onto subsequent rows takes up vertical space and hiding tabs become an issue. While more digestible than the wrapping list modal, design of this layout still does not fit the content well.
Pros
  • Breaks up the regions into more digestible sections
Cons
  • Limited horizontal space for tabs; five tabs can be seen here
  • Countries are hidden due to regional separation into tabs
  • Space is poorly used for the region with the fewest countries (Imagine two countries in a tab)
  • Tabbed interface creates repeating sub headers (We now need to create another Africa sub-header for the regional Select/Deselection)

3. Vertically Navigated Tabs


Traditionally, vertically navigated tabs take up a significant amount of real estate; however in this case because the region with the most countries fit within the given space, it is not a concern. For this case, the vertical tabs work better than the horizontal tabs, however the cons still outweigh the pros.
Pros
  • Flexibility of adding tabs is easier than horizontal tabs
  • Easy vertical scanning of regions
Cons
  • Space is not used well for the region with the fewest countries (again the tab with only two)
  • Countries are hidden due to regional separation into tabs
  • Won’t scale well horizontally if number of countries per region increases
  • Tabbed interface creates repeating sub headers

4. Scrolling with containers


A scrolling list with containers separating regions would work if regions did not get hidden.
Pros
  • Scales well
  • Works well with small number of items (two countries within a region)
Cons
  • Content below the fold may get lost unless users scroll all the way to the bottom.
  • Regions are not scannable
  • Countries or regions may be missed if scrolled quickly
  • Cognitive load for scrolling and finding desired content (User has to move to the scroll bar, click, move and down)

5. Separated Columns


Separating the regions and countries into columns is another option, however the number of countries per region is not small enough to fit vertically.
Pros
  • Headers are horizontally scannable at the top
  • Most of the countries are visible before scrolling
  • No hidden regions or need to click into separate regions
Cons
  • Countries towards the bottom of the alphabet are hidden
  • Still need to scroll to view the rest of the countries
  • Does not handle range in number of countries well (i.e. Region with two countries)
  • Layout forces the content to feel too tight in this modal

6. Accordion Menu


In an accordion menu, one panel preferably the most important one, is open all the times. Ideally the most important one will be open if there is any hierarchy. This pattern is especially a great fit since there are just two levels of information here.
Pros
  • All regions visible at all times
  • Regions are vertically scannable
  • Auto-sizing accommodates a wide range of countries (Both 2 countries and 45 countries work well)
  • Larger height of an accordion provides larger click area and affords a larger header
Con
  • All countries not viewable at once
Although the accordion option does not allow the user to view all countries at once, all the pros outweigh the single con. This solution scales well, is scannable, easily digestible, and auto-sizes according to the content. The characteristic of elegantly compacting categories in a small space makes great use of an accordion menu for this example.
Even if it’s just contemplated in our head it’s valuable to explore variations of a design not only to derive at the best solution, but also to comprehend the rationale behind it. That way when we are presented with similar cases in the future we have a stronger intuition about the best approach.
Here are some links for additional information on accordion menus:
http://ui-patterns.com/patterns/AccordionMenu
http://www.welie.com/patterns/showPattern.php?patternID=accordion
http://developer.yahoo.com/ypatterns/navigation/accordion.html
All options are wireframed for discussion purposes.
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The Difference Between a Light Switch and a Toggle in UX.

The Difference Between a Light Switch and a Toggle in UX.

2011 October 14

by Jason
Here at DesignMap we go to lengths in determining the best controls for our clients. Often in the course of explaining our choices, we uncover important distinctions, that we feel adds to the growing field of UX. One of those instances came up recently regarding the use of a light switch vs a toggle. Here is how we see the differences.

Light Switch
Light Switch is a sliding button which displays its current state, clicking the button will switch states. A Light Switch should be used as a gate, in scenarios where simple binary functions are necessary. For example turning on a set of features or search criteria. In the diagram below the grey line represent information flow with the Light Switch acting as a gate: either the information flows or it is stopped.

Toggle
Toggle, a button which only allows for one item to be selected at a time, turn off unselected items as a selection is made. The Toggle should be used as a pivot where both items in the Toggle are options – for example, filtering a grid by one of the options in the Toggle. In the diagram below the information flow is diverted to either option of the Toggle.

Best Practices
Light Switches generally should have very short items names, “On” and “Off”, “Yes” and “No”, etc. Additionally, to the user, the name that is not selected should be able to be inferred from the selected name. For example, most people would know that if they see “Yes” the opposite would be “No”, even though they cannot see the word No in the Light Switch.
Toggles need to show all options to the user as the non-selected options cannot always be inferred by the selected option
Furthermore, Toggles could have more than two options, so showing all options at a glance is imperative.
Incorrect Usage
In the case of Toggle switches, “On” and “Off” do not work well. The reason behind this assertion is, that it requires users to read two labels in order to know the current state of the switch. Additionally there is no color difference between the two options, which would also help with the determining the state of the Toggle.

Both Light Switches and Toggles have places in modern web applications. Hopefully the above descriptions will help clarify which scenarios those controls are better suited.
What do you think? Do you use Light Switches in your interaction design? Let us know in the comments.
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UX Magazine Gamification Article

2011 May 24
by Audrey Crane
UX Magazine logo Super-excited to have the opportunity to contribute to UX Magazine.
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Stories, Maps and Products

2011 May 14
by Neil McKay
Story Mapping
Product opportunities come in many forms, and there’s just as many ways to define an opportunity and translate it into something tangible.
To create a great product, Product Managers, Developers, and Designers (among others) need to both understand the larger context, and develop an intimate knowledge of every detail.
Recently we’ve been using a pattern called ‘Story Mapping’ (coined by Jeff Patton) to help us do both. Originally developed to bridge the apparently irreconcilable practices of user centered design and agile development, the benefits of Story Mapping apply even when the organization is not using an Agile methodology.

The (my) case for story mapping

Story mapping gives us a tool to decide what’s in scope and what’s not.  Ideas are easy, and making a great product is as much about making tough calls on which features don’t make the cut as it is about interaction design. Story Mapping can help you balance what your user needs and what you can deliver on time.
This is a low cost, fast and transparent process. It’s great for exposing and managing complexity that otherwise may have only been found when the developer or designer are actually building the product.
The act of writing a ‘story’ requires us to empathize with our user. A product that anticipates the desires, fears and aspirations of a user will almost certainly exceed expectations.

Getting Started

The Story Mapping process needs inputs, something to frame the activity. We need to know where this story starts, where it goes, and where it ends.
These goals are usually found in business requirement documents. As the name implies though, story mapping, like a good story works best with actors and motives. In the user experience world we create Personas to consolidate user research into a set of archetypes representing the spectrum of your audience.
Before getting started we choose one of our Personas to be our headline actor. With our feet firmly in our persona’s shoes we start telling stories of how Jane (no longer just a ‘user’) would get this job done, and very importantly: why Jane does this.
We’ve been trying to keep this process simple, light weight and maybe even fun. This way the team can see the benefits of the process as they’re working on it.
Get started with lots of post-it notes, lots of wall space, and a cross discipline team. Keep your team small, I’d suggest 3 at most. People who’ve been involved in your research, listening to potential users, are your best bet for informed contributions.
Product managers, subject matter experts, client support staff and designers are also likely candidates for your team, and don’t hesitate to work with developers, even potential users themselves. You can always bring other people to your completed map later to review and test the stories.

Telling stories with your team

See Jane’s user experience

Epics

Begin with high level chunks, describe Jane’s work flow from end-to-end.  Use a post-it for each step.  Keep the steps broad enough that reading through the steps end to end will be about the length of a sentence. This is often called the ‘Epics’ level.
An over simplified example:
[Read incoming emails] [Manage emails] [Respond to emails] [Create and Send new emails]
Reading through your 'Epics' should describe the tool in the length of a sentence.
Jane wants to read, manage and respond to incoming email and also create and send new emails.
Think of these as buckets of functionality to cover the user’s needs, and, of course, to address all your business requirements.
Keep reviewing and adjusting these as you build the map.

Activities

For each of those high level steps do the same again, but now with a bit more detail.
Note what the user’s goal is, what they want, and why.
“Jane wants to prioritize emails from multiple accounts to balance two jobs and feel in control.”
We call this level of story ‘activities’.
Activities
Jeff Patton describes Activities as groups of related tasks that can be achieved in one sitting.

Tasks

Think more granular as you write the next level of stories: what are the individual decisions or actions that Jane wants to make?
These ‘Tasks’ get us into the details of each Activity, and expose all the complexity of activities that previously we wrote off as simple, or not a big deal.
Position them horizontally in sequence so you can read from one to the next: Jane ‘browses’, [and then] ‘selects’ [and then] ‘marks email as high priority’.
Tasks
Read 'or' between tasks down the column, 'and then' between columns.
Of corse in any workflow there maybe several options at any one point.  To accommodate this we stack stories vertically  – so we can read down a column of stories with ‘or’ in between: Jane ‘browses all emails’ [or] ‘searches by keyword’.
It’s important to give this step it’s due. Tasks are the building blocks of your map. The key benefits of story mapping are gained by validating the Activities and Epics above with cohesive, comprehensive and highly detailed tasks.
You may find the need to revise the Activities and Epics as you expose the details.

Feature Prioritization

Triage for user satisfaction
Take all those vertically stacked ‘or’ tasks and prioritize them. Reposition the tasks that are most crucial to Jane and move them to the top of each column. These are the tasks that are necessary for Jane to complete her goals. In my very simple example above, it’s critical to be able to select an email, selecting multiple emails is not.
The items at the top must allow the Jane to move horizontally through the stories and achieve the most important goals – this is your minimum viable product.

Scoping

This step makes Story Mapping ‘agile’ and time-line friendly
Your team can now slice through the map horizontally to select which tasks will be addressed per release. Here you can evaluate effort estimates, demand or necessity of a feature and of course your time line. If your organization is using agile you can fill your backlog and sprints in this step.
Prioritization and Scoping
'Search can wait, but we're able to do multiple select now...'

So…

I think this is a great tool to shine a light into all the corners of your product. A wall covered with post-it notes makes product plans tangible and physical, everyone can see literally how big it is.
Stand back to see the big picture, step forward to understand every little piece.
Be prepared for your map to get HUGE, and for folks to baulk at putting the effort into something made of post-it notes. If that happens, I’d point out the alternative: some individual has to sit down and type out a document that details every little bit of the product. Then many people have to sit down read, and respond to that document. Revise and repeat. Personally, I’d prefer to hash it all out in a team with pens and paper.
You can rally your team around the story map, where everyone can discuss, understand and contribute to the entire undertaking, and celebrate each milestone reached.
P.S. Obviously story mapping is best in-person, but reality means we work remotely sometimes. I’m still struggling to find a good online tool to do this process with remote teams. There’s a growing list of tools, from simple and literal post-it note apps like Listhings, through to agile project solutions like Silver Stories, and ScrumDesk, none of which I endorse due to either being under powered or overly complex

LAJU REAKSI KIMIA


LAJU REAKSI

Laju / Kecepatan reaksi adalah banyaknya mol/liter suatu zat yang dapat berubah menjadi zat lain dalam setiap satuan waktu.

Untuk reaksi: aA + bB
®   mM + nN
maka kecepatan reaksinya adalah:


1 (dA)
1 d(B)
1 d(M)
1 d(N)
V = -
------- = -
------- = +
-------- = +
----------

a dt
b dt
m dt
n dt
dimana:
- 1/a . d(A) /dt
= rA
= kecepatan reaksi zat A = pengurangan konsentrasi zat A per satuan wakru.
- 1/b . d(B) /dt
= rB
= kecepatan reaksi zat B = pengurangan konsentrasi zat B per satuan waktu.
- 1/m . d(M) /dt
= rM
= kecepatan reaksi zat M = penambahan konsentrasi zat M per satuan waktu.
- 1/n . d(N) /dt
= rN
= kecepatan reaksi zat N = penambahan konsentrasi zat N per satuan waktu.
Pada umumnya kecepatan reaksi akan besar bila konsentrasi pereaksi cukup besar. Dengan berkurangnya konsentrasi pereaksi sebagai akibat reaksi, maka akan berkurang pula kecepatannya.
Secara umum kecepatan reaksi dapat dirumuskan sebagai berikut:

V = k(A) x (B) y

dimana:

V = kecepatan reaksi
k = tetapan laju reaksi
x = orde reaksi terhadap zat A
y = orde reaksi terhadap zat B
(x + y) adalah orde reaksi keseluruhan
(A) dan (B) adalah konsentrasi zat pereaksi.



Orde reaksi adalah banyaknya faktor konsentrasi zat reaktan yang mempengaruhi kecepatan reaksi.
Penentuan orde reaksi tidak dapat diturunkan dari persamaan reaksi tetapi hanya dapat ditentukan berdasarkan percobaan.

Suatu reaksi yang diturunkan secara eksperimen dinyatakan dengan rumus kecepatan reaksi :
v = k (A) (B) 2

persamaan tersebut mengandung pengertian reaksi orde 1 terhadap zat A dan merupakan reaksi orde 2 terhadap zat B. Secara keselurahan reaksi tersebut adalah reaksi orde 3.

Contoh soal:
Dari reaksi 2NO(g) + Br2(g) ®   2NOBr(g)
dibuat percobaan dan diperoleh data sebagai berikut:
No.
(NO) mol/l
(Br2) mol/l
Kecepatan Reaksi
mol / 1 / detik
1.
0.1
0.1
12
2.
0.1
0.2
24
3.
0.1
0.3
36
4.
0.2
0.1
48
5.
0.3
0.1
108
Pertanyaan:
a. Tentukan orde reaksinya !
b. Tentukan harga k (tetapan laju reaksi) !

Jawab:
a.
Pertama-tama kita misalkan rumus kecepatan reaksinya adalah V = k(NO)x(Br2)y : jadi kita harus mencari nilai x den y.
Untuk menentukan nilai x maka kita ambil data dimana konsentrasi terhadap Br2 tidak berubah, yaitu data (1) dan (4).
Dari data ini terlihat konsentrasi NO naik 2 kali sedangkan kecepatan reaksinya naik 4 kali maka :

2x = 4 ®   x = 2 (reaksi orde 2 terhadap NO)

Untuk menentukan nilai y maka kita ambil data dimana konsentrasi terhadap NO tidak berubah yaitu data (1) dan (2). Dari data ini terlihat konsentrasi Br2 naik 2 kali, sedangkan kecepatan reaksinya naik 2 kali, maka :

2y = 2 ®   y = 1 (reaksi orde 1 terhadap Br2)

Jadi rumus kecepatan reaksinya : V = k(NO)2(Br2) (reaksi orde 3)

b.
Untuk menentukan nilai k cukup kita ambil salah satu data percobaan saja misalnya data (1), maka:
V = k(NO)2(Br2)
12 = k(0.1)2(0.1)

k = 12 x 103 mol-212det-1

Teori tumbukan didasarkan atas teori kinetik gas yang mengamati tentang bagaimana suatu reaksi kimia dapat terjadi. Menurut teori tersebut kecepatan reaksi antara dua jenis molekul A dan B sama dengan jumiah tumbukan yang terjadi per satuan waktu antara kedua jenis molekul tersebut. Jumlah tumbukan yang terjadi persatuan waktu sebanding dengan konsentrasi A dan konsentrasi B. Jadi makin besar konsentrasi A dan konsentrasi B akan semakin besar pula jumlah tumbukan yang terjadi.

TEORI TUMBUKAN INI TERNYATA MEMILIKI BEBERAPA KELEMAHAN, ANTARA LAIN :
-
tidak semua tumbukan menghasilkan reaksi sebab ada energi tertentu yang harus dilewati (disebut energi aktivasi = energi pengaktifan) untak dapat menghasilkan reaksi. Reaksi hanya akan terjadi bila energi tumbukannya lebih besar atau sama dengan energi pengaktifan (Ea).

-
molekul yang lebih rumit struktur ruangnya menghasilkan tumbukan yang tidak sama jumlahnya dibandingkan dengan molekul yang sederhana struktur ruangnya.
Teori tumbukan di atas diperbaiki oleh tcori keadaan transisi atau teori laju reaksi absolut. Dalam teori ini diandaikan bahwa ada suatu keadaan yang harus dilewati oleh molekul-molekul yang bereaksi dalam tujuannya menuju ke keadaan akhir (produk). Keadaan tersebut dinamakan keadaan transisi. Mekanisme reaksi keadaan transisi dapat ditulis sebagai berikut:
A + B ®   T* --> C + D
dimana:

- A dan B adalah molekul-molekul pereaksi
- T* adalah molekul dalam keadaan transisi
- C dan D adalah molekul-molekul hasil reaksi







SECARA DIAGRAM KEADAAN TRANSISI INI DAPAT DINYATAKAN SESUAI KURVA BERIKUT


Dari diagram terlibat bahwa energi pengaktifan (Ea) merupakan energi keadaan awal sampai dengan energi keadaan transisi. Hal tersebut berarti bahwa molekul-molekul pereaksi harus memiliki energi paling sedikit sebesar energi pengaktifan (Ea) agar dapat mencapai keadaan transisi (T*) dan kemudian menjadi hasil reaksi (C + D).
Catatan :
energi pengaktifan (= energi aktivasi) adalah jumlah energi minimum yang dibutuhkan oleh molekul-molekul pereaksi agar dapat melangsungkan reaksi.

Dalam suatu reaksi kimia berlangsungnya suatu reaksi dari keadaan semula (awal) sampai keadaan akhir diperkirakan melalui beberapa tahap reaksi.
Contoh: 4 HBr(g) + O2(g) ®  2 H2O(g) + 2 Br2(g)
Dari persamaan reaksi di atas terlihat bahwa tiap 1 molekul O2 bereaksi dengan 4 molekul HBr. Suatu reaksi baru dapat berlangsung apabila ada tumbukan yang berhasil antara molekul-molekul yang bereaksi. Tumbukan sekaligus antara 4 molekul HBr dengan 1 molekul O2 kecil sekali kemungkinannya untuk berhasil. Tumbukan yang mungkin berhasil adalah tumbukan antara 2 molekul yaitu 1 molekul HBr dengan 1 molekul O2. Hal ini berarti reaksi di atas harus berlangsung dalam beberapa tahap dan diperkirakan tahap-tahapnya adalah :
Tahap 1:
HBr + O2
®   HOOBr
(lambat)
Tahap 2:
HBr + HOOBr
®   2HOBr
(cepat)
Tahap 3:
(HBr + HOBr
®   H2O + Br2) x 2
(cepat)

------------------------------------------------------ +


4 HBr + O2
--> 2H2O + 2 Br2

Dari contoh di atas ternyata secara eksperimen kecepatan berlangsungnya reaksi tersebut ditentukan oleh kecepatan reaksi pembentukan HOOBr yaitu reaksi yang berlangsungnya paling lambat.
Rangkaian tahap-tahap reaksi dalam suatu reaksi disebut "mekanisme reaksi" dan kecepatan berlangsungnya reaksi keselurahan ditentukan oleh reaksi yang paling lambat dalam mekanisme reaksi. Oleh karena itu, tahap ini disebut tahap penentu kecepatan reaksi.


Beberapa faktor yang mempengaruhi kecepatan reaksi antara lain konsentrasi, sifat zat yang bereaksi, suhu dan katalisator.
A. KONSENTRASI
Dari berbagai percobaan menunjukkan bahwa makin besar konsentrasi zat-zat yang bereaksi makin cepat reaksinya berlangsung. Makin besar konsentrasi makin banyak zat-zat yang bereaksi sehingga makinbesar kemungkinan terjadinya tumbukan dengan demikian makin besar pula kemungkinan terjadinya reaksi.

B. SIFAT ZAT YANG BEREAKSI
Sifat mudah sukarnya suatu zat bereaksi akan menentukan kecepatan berlangsungnya reaksi.
Secara umum dinyatakan bahwa:
-
Reaksi antara senyawa ion umumnya berlangsung cepat.
Hal ini disebabkan oleh adanya gaya tarik menarik antara ion-ion yang muatannya berlawanan.

Contoh: Ca2+(aq) + CO32+(aq) ®  CaCO3(s)
Reaksi ini berlangsung dengan cepat.


-
Reaksi antara senyawa kovalen umumnya berlangsung lambat.
Hal ini disebabkan karena untuk berlangsungnya reaksi tersebut dibutuhkan energi untuk memutuskan ikatan-ikatan kovalen yang terdapat dalam molekul zat yang bereaksi.

Contoh: CH4(g) + Cl2(g)
®   CH3Cl(g) + HCl(g)
Reaksi ini berjalan lambat reaksinya dapat dipercepat apabila diberi energi misalnya cahaya matahari.


C. SUHU
Pada umumnya reaksi akan berlangsung lebih cepat bila suhu dinaikkan. Dengan menaikkan suhu maka energi kinetik molekul-molekul zat yang bereaksi akan bertambah sehingga akan lebih banyak molekul yang memiliki energi sama atau lebih besar dari Ea. Dengan demikian lebih banyak molekul yang dapat mencapai keadaan transisi atau dengan kata lain kecepatan reaksi menjadi lebih besar. Secara matematis hubungan antara nilai tetapan laju reaksi (k) terhadap suhu dinyatakan oleh formulasi ARRHENIUS:
k = A . e-E/RT
dimana:

k : tetapan laju reaksi
A : tetapan Arrhenius yang harganya khas untuk setiap reaksi
E : energi pengaktifan
R : tetapan gas universal = 0.0821.atm/moloK = 8.314 joule/moloK
T : suhu reaksi (oK)


D. KATALISATOR
Katalisator adalah zat yang ditambahkan ke dalam suatu reaksi dengan maksud memperbesar kecepatan reaksi. Katalis terkadang ikut terlibat dalam reaksi tetapi tidak mengalami perubahan kimiawi yang permanen, dengan kata lain pada akhir reaksi katalis akan dijumpai kembali dalam bentuk dan jumlah yang sama seperti sebelum reaksi.
Fungsi katalis adalah memperbesar kecepatan reaksinya (mempercepat reaksi) dengan jalan memperkecil energi pengaktifan suatu reaksi dan dibentuknya tahap-tahap reaksi yang baru. Dengan menurunnya energi pengaktifan maka pada suhu yang sama reaksi dapat berlangsung lebih cepat.


Reaksi yang dapat berlangsung dalam dua arah disebut reaksi dapat balik. Apabila dalam suatu reaksi kimia, kecepatan reaksi ke kanan sama dengan kecepatan reaksi ke kiri maka, reaksi dikatakan dalam keadaan setimbang. Secara umum reaksi kesetimbangan dapat dinyatakan sebagai:
A  +  B  ®   C  +  D



ADA DUA MACAM SISTEM KESETIMBANGAN, YAITU :
1.
Kesetimbangan dalam sistem homogen
a.
Kesetimbangan dalam sistem gas-gas
Contoh: 2SO2(g) + O2(g) 
«   2SO3(g)
b.
Kesetimbangan dalam sistem larutan-larutan
Contoh: NH4OH(aq) 
«   NH4+(aq) + OH- (aq)
2.
Kesetimbangan dalam sistem heterogen
a.
Kesetimbangan dalam sistem padat gas
Contoh: CaCO3(s) 
«   CaO(s) + CO2(g)
b.
Kesetimbangan sistem padat larutan
Contoh: BaSO4(s) 
«   Ba2+(aq) + SO42- (aq)
c.
Kesetimbangan dalam sistem larutan padat gas
Contoh: Ca(HCO3)2(aq)  
«   CaCO3(s) + H2O(l) + CO2(g)



Hukum Guldberg dan Wange:
Dalam keadaan kesetimbangan pada suhu tetap, maka hasil kali konsentrasi zat-zat hasil reaksi dibagi dengan hasil kali konsentrasi pereaksi yang sisa dimana masing-masing konsentrasi itu dipangkatkan dengan koefisien reaksinya adalah tetap.
Pernyataan tersebut juga dikenal sebagai hukum kesetimbangan.
Untuk reaksi kesetimbangan: a A + b B 
«   c C + d D maka:
Kc = (C)c x (D)d / (A)a x (B)b

Kc adalah konstanta kesetimbangan yang harganya tetap selama suhu tetap.

BEBERAPA HAL YANG HARUS DIPERHATIKAN
-
Jika zat-zat terdapat dalam kesetimbangan berbentuk padat dan gas yang dimasukkan dalam, persamaan kesetimbangan hanya zat-zat yang berbentuk gas saja sebab konsentrasi zat padat adalah tetap den nilainya telah terhitung dalam harga Kc itu.
Contoh: C(s) + CO2(g)  «   2CO(g)
Kc = (CO)2 / (CO2)
-
Jika kesetimbangan antara zat padat dan larutan yang dimasukkan dalam perhitungan Kc hanya konsentrasi zat-zat yang larut saja.
Contoh: Zn(s) + Cu2+(aq)  «   Zn2+(aq) + Cu(s)
Kc = (Zn2+) / (CO2+)
-
Untuk kesetimbangan antara zat-zat dalam larutan jika pelarutnya tergolong salah satu reaktan atau hasil reaksinya maka konsentrasi dari pelarut itu tidak dimasukkan dalam perhitungan Kc.
Contoh: CH3COO-(aq) + H2O(l)  «   CH3COOH(aq) + OH-(aq)
Kc = (CH3COOH) x (OH-) / (CH3COO-)


Contoh soal:
1. Satu mol AB direaksikan dengan satu mol CD menurut persamaan reaksi:
AB(g) + CD(g)  «   AD(g) + BC(g)
Setelah kesetimbangan tercapai ternyata 3/4 mol senyawa CD berubah menjadi AD dan BC. Kalau volume ruangan 1 liter, tentukan tetapan kesetimbangan untuk reaksi ini !
Jawab:
Perhatikan reaksi kesetimbangan di atas jika ternyata CD berubah (bereaksi) sebanyak 3/4 mol maka AB yang bereaksi juga 3/4 mol (karena koefsiennya sama).
Dalam keadaan kesetimbangan:

(AD) = (BC) = 3/4 mol/l
(AB) sisa = (CD) sisa = 1 - 3/4 = 1/4 n mol/l

Kc = [(AD) x (BC)]/[(AB) x (CD)] = [(3/4) x (3/4)]/[(1/4) x (1/4)] = 9
2. Jika tetapan kesetimbangan untuk reaksi:
A(g) + 2B(g)  «   4C(g)
sama dengan 0.25, maka berapakah besarnya tetapan kesetimbangan bagi reaksi:
2C(g) 
«   1/2A(g) + B(g)
Jawab:
- Untuk reaksi pertama: K1 = (C)4/[(A) x (B)2] = 0.25
- Untuk reaksi kedua : K2 = [(A)1/2 x (B)]/(C)2
- Hubungan antara K1 dan K2 dapat dinyatakan sebagai:
   K1 = 1 / (K2)2 ®   K2 = 2



Azas Le Chatelier menyatakan: Bila pada sistem kesetimbangan diadakan aksi, maka sistem akan mengadakan reaksi sedemikian rupa sehingga pengaruh aksi itu menjadi sekecil-kecilnya.
Perubahan dari keadaan kesetimbangan semula ke keadaan kesetimbangan yang baru akibat adanya aksi atau pengaruh dari luar itu dikenal dengan pergeseran kesetimbangan.
Bagi reaksi: 
A  +  B   «    C  +  D


KEMUNGKINAN TERJADINYA PERGESERAN
1. 
Dari kiri ke kanan, berarti A bereaksi dengan B memhentuk C dan D, sehingga jumlah mol A dan Bherkurang, sedangkan C dan D bertambah.
2.
Dari kanan ke kiri, berarti C dan D bereaksi membentuk A dan B. sehingga jumlah mol C dan Dherkurang, sedangkan A dan B bertambah.

FAKTOR-FAKTOR YANG DAPAT MENGGESER LETAK KESETIMBANGAN ADALAH :
a. Perubahan konsentrasi salah satu zat
b. Perubahan volume atau tekanan
c. Perubahan suhu

A. PERUBAHAN KONSENTRASI SALAH SATU ZAT
Apabila dalam sistem kesetimbangan homogen, konsentrasi salah satu zat diperbesar, maka kesetimbangan akan bergeser ke arah yang berlawanan dari zat tersebut. Sebaliknya, jika konsentrasi salah satu zat diperkecil, maka kesetimbangan akan bergeser ke pihak zat tersebut.
Contoh: 2SO2(g) + O2(g)  «   2SO3(g)
- Bila pada sistem kesetimbangan ini ditambahkan gas SO2, maka kesetimbangan akan bergeser ke kanan.
- Bila pada sistem kesetimbangan ini dikurangi gas O2, maka kesetimbangan akan bergeser ke kiri.




B. PERUBAHAN VOLUME ATAU TEKANAN
Jika dalam suatu sistem kesetimbangan dilakukan aksi yang menyebabkan perubahan volume (bersamaan dengan perubahan tekanan), maka dalam sistem akan mengadakan berupa pergeseran kesetimbangan.
Jika tekanan diperbesar = volume diperkecil, kesetimbangan akan bergeser ke arah jumlah Koefisien Reaksi Kecil.
Jika tekanan diperkecil = volume diperbesar, kesetimbangan akan bergeser ke arah jumlah Koefisien reaksi besar.
Pada sistem kesetimbangan dimana jumlah koefisien reaksi sebelah kiri = jumlah koefisien sebelah kanan, maka perubahan tekanan/volume tidak menggeser letak kesetimbangan.



Contoh: 
N2(g) + 3H2(g)  «   2NH3(g)

Koefisien reaksi di kanan = 2
Koefisien reaksi di kiri = 4

-
Bila pada sistem kesetimbangan tekanan diperbesar (= volume diperkecil), maka kesetimbangan akan
bergeser ke kanan.
-
Bila pada sistem kesetimbangan tekanan diperkecil (= volume diperbesar), maka kesetimbangan akan
bergeser ke kiri.

C. PERUBAHAN SUHU

Menurut Van't Hoff:

-
Bila pada sistem kesetimbangan subu dinaikkan, maka kesetimbangan reaksi akan bergeser ke arah yang membutuhkan kalor (ke arah reaksi endoterm).
Bila pada sistem kesetimbangan suhu diturunkan, maka kesetimbangan reaksi akan bergeser ke arah yang membebaskan kalor (ke arah reaksi eksoterm).
Contoh:
2NO(g) + O2(g) «  2NO2(g) ; DH = -216 kJ
-
Jika suhu dinaikkan, maka kesetimbangan akan bergeser ke kiri.
-
Jika suhu diturunkan, maka kesetimbangan akan bergeser ke kanan.

PENGARUH KATALISATOR TERHADAP KESETIMBANGAN
Fungsi katalisator dalam reaksi kesetimbangan adalah mempercepat tercapainya kesetimbangan dan tidak merubah letak kesetimbangan (harga tetapan kesetimbangan Kc tetap), hal ini disebabkan katalisator mempercepat reaksi ke kanan dan ke kiri sama besar.

HUBUNGAN ANTARA HARGA Kc DENGAN Kp

Untuk reaksi umum:

a A(g) + b B(g) 
«   c C(g) + d D(g)

Harga tetapan kesetimbangan:

Kc = [(C)c . (D)d] / [(A)a . (B)b]
Kp = (PCc x PDd) / (PAa x PBb)
dimana: PA, PB, PC dan PD merupakan tekanan parsial masing-masing gas A, B. C dan D.

Secara matematis, hubungan antara Kc dan Kp dapat diturunkan sebagai:

Kp = Kc (RT) Dn
dimana Dn adalah selisih (jumlah koefisien gas kanan) dan (jumlah koefisien gas kiri).
Contoh:
Jika diketahui reaksi kesetimbangan:
CO2(g) + C(s)  «   2CO(g)

Pada suhu 300o C, harga Kp= 16. Hitunglah tekanan parsial CO2, jika tekanan total dalaun ruang 5 atm!

Jawab:
Misalkan tekanan parsial gas CO = x atm, maka tekanan parsial gas CO2 = (5 - x) atm.
Kp = (PCO)2 / PCO2 = x2 / (5 - x) = 16  ®   x = 4
Jadi tekanan parsial gas CO2 = (5 - 4) = 1 atm
Disosiasi adalah penguraian suatu zat menjadi beberapa zat lain yang lebih sederhana.
Derajat disosiasi adalah perbandingan antara jumlah mol yang terurai dengan jumlah mol mula-mula.
Contoh:
2NH3(g)  «   N2(g) + 3H2(g)
besarnya nilai derajat disosiasi (a):
a = mol NH3 yang terurai / mol NH3 mula-mula

Harga derajat disosiasi terletak antara 0 dan 1, jika:

a = 0 berarti tidak terjadi penguraian
a = 1 berarti terjadi penguraian sempurna
0 <
a < 1 berarti disosiasi pada reaksi setimbang (disosiasi sebagian).
Contoh:
Dalam reaksi disosiasi N2O4 berdasarkan persamaan

      N2O4(g)
«   2NO2(g)

banyaknya mol N2O4 dan NO2 pada keadaan setimbang adalah sama.

Pada keadaan ini berapakah harga derajat disosiasinya ?
Jawab:
Misalkan mol N2O4 mula-mula = a mol
mol N2O4 yang terurai = a
a mol ®  mol N2O4 sisa = a (1 - a) mol
mol NO2 yang terbentuk = 2 x mol N2O4 yang terurai = 2 a
a mol
Pada keadaan setimbang:
mol N2O4 sisa = mol NO2 yang terbentuk
a(1 - a) = 2a a ®  1 - a = 2 a ®  a = 1/3




BY : RULY PERMATA I / 22
( ELEVEN SCIENCE 2 )
PENGOLAHAN AIR KOTOR UNTUK AIR MINUM
Air yang digunakan harus memenuhi syarat dari segi kualitas maupun kuantitasnya. Secara kualitas, air harus tersedia pada kondisi yang memenuhi syarat kesehatan. Kualitas air dapat ditinjau dari segi fisika , kimia dan biologi. Kualitas air yang baik ini tidak selamanya tersedia dialam. Dengan adanya perkembangan industri dan pemukiman dapat mengancam kelestarian air bersih. Sehingga diperlukan upaya perbaikan secara sederhana maupun modern

Persyaratan Air Minum / air bersih
1. persyaratan fisik

jernih atau tidak keruh

tidak berwarna

rasanya tawar

tidak berbau

temperaturnya normal

tidak mengandung padatan

2. persyaratan kimia

pH netral

tidak mengandung kimia beracun

tidak mengandung garam atau ion-ion logam

kesadahan rendah

Tidak mengandung bahan organik

3. persyaratan mikrobiologis

Tidak mengandung bakteri pathogen
















Pengertian Dan Prinsip Pengolahan Air
proses pengolahan air minum merupakan proses perubahan sifat fisik, kimia dan biologi air baku agar memenuhi syarat untuk digunakan sebagai air minum. Tujuan dan kegiatan pengolahan air minum adalah :
menurunkan kekeruhan

mengurangi bau, rasa, dan warna

mematikan mikroorganisme

mengurangi kadar bahan-bahan yang terlarut dalam air

menurunkan kesadahan

memperbaiki pH


prinsip dasar pengolahan air:

Besifat tepat guna dan sesuai dengan kondisi, lingkungan fisik, maupun sosial
budaya setempat

Pengoperasiannya mudah dan sederhana

Bahan-bahan yang digunakan berharga murah

Bahan-bahan yang digunakan teersedia dilokasi dan mudah diperoleh

Efektif, memiliki daya pembersihvyangsar untuk memurnikan air.

Pembuatan Penjernihan Air Dengan Cara Penyaringan

Bahan :

Arang

Kran air

Tawas

Kaporit

Pasir

Ijuk

Kerikil


Alat :

Drum/Bak Pengendap dan Drum/Bak Penyaring
Tahapan penjernihan air kotor adalah pengendapan dan penyaringan. Media
penyaringnya adalah :
o
Pasir - digunkan untuk menyaring padatan. Ukuran pasir yang dipakai
biasanya 0,2-0,8 mm. Jika sudah jernuh, pasir harus dibersihkan.
o
Arang Batok - terbuat dari tempurung kelapa/kayu yang dibakar hingga jadi arang. Berguna untuk mengurangi warna dan bau. Ukurannya berdiameter 0.1 mm atau berbentuk bubuk. Jika air yang disaring sudah tidak jernih lagi, arang
batok harus dicuci atau diganti.
oKapur, Tawas, Dan Kaporit - disebut penggumpal koagulan yang membantu zat
kimia pencemar menjadi endapan. Selanjutnya air disaring lagi dengan media
lain.
oPenyaring lain-yang mudah didapat adalah Ijuk dan Kerikil. Logikanya batu
ukuran besar menyaring kotoran yang besar, begitu seterusya hingga ke ukuran
yang paling kecil.
Langkah-langkah:
1. Air kotor masuk ke Bak Pengendap, kemudian masukkan 1 grtaw as/10 liter air, 1 grkapur/10 liter air dan 2.5 gr kaporit/10 liter air. Aduk air dalam Bak secara perlahan dan satu arah. Pengadukan ini sebaiknya dilakukan pada malam hari sehingga pada pagi hari pengendapan berlangsung dengan sempurna. Buka keran pada Bak Pengendap secara perlahan agar endapan tidak terbawa pada Bak Penyaringan.
2. Pada Bak Penyaringan, susun media penyaringan sebagai berikut:
-Kerik il setinggi 5 cm pada dasar bak kemudian,
- Arang Batok setinggi 10 cm kemudian
-Iju k setinggi 10 cm dan
- Pasir Halus berdiameter 0,25 - 0,1 mm setinggi 20 cm.
Air yang megalir dari Bak Pengendapan akan dijernihkan lagi melalui proses
penyaringan sehingga diharapkan air bersih akan keluar pada saat keran dibuka.
Jika air yang keluar pada bak ke dua sudah tidak jernih lagi, medai penyaring
perlu dicuci atau diganti yang baru. Penggunaan drum sebagai bak Pengendapan
dan Bak Penyaring dapat diganti dengan pemakaian Gentong.








MY PHOTO

MY PHOTO
HOW CUTE ... :P