Litmus Paper and the Litmus Test

Litmus Paper and the Litmus Test You can make paper test strips to determine the pH of an aqueous solution by treating filter paper with any of the common pH indicators. One of the first indicators used for this purpose was litmus. Litmus paper is paper that has been treated with a specific indicator- a mixture of 10-15 natural dyes obtained from lichens (mainly Roccella tinctoria) that turns red in response to acidic conditions (pH 7). When the pH is neutral (pH 7) then the dye is purple. History The first known use of litmus was around 1300 CE by Spanish alchemist Arnaldus de Villa Nova. The blue dye has been extracted from lichens since the 16th century. The word litmus comes from the old Norse word for to dye or color. While all litmus paper acts as pH paper, the opposite is not true. Its incorrect to refer to all pH paper as litmus paper. Fast Facts: Litmus Paper Litmus paper is a type of pH paper made by treating paper with natural dyes from lichens.The litmus test is performed by placing a small drop of sample onto the colored paper.Usually, litmus paper is either red or blue. Red paper turns blue when the pH is alkaline, while blue paper turns red when the pH turns acidic.While litmus paper is most often used to test the pH of liquids, it can be used to test gases if the paper is dampened with distilled water before exposure to the gas. Litmus Test To perform the test, place a drop of liquid sample on a small strip of paper or dip a piece of litmus paper in a small specimen of the sample. Ideally, you dont dip litmus paper in an entire container of a chemical; the dye could contaminate a potentially valuable sample. The litmus test is a quick method of determining whether a liquid or gaseous solution is acidic or basic (alkaline.) The test can be performed using litmus paper or an aqueous solution containing litmus dye. Initially, litmus paper is either red or blue. The blue paper changes to red, indicating acidity somewhere between the pH range of 4.5 to 8.3. (Note, however, that 8.3 is alkaline.)  Red litmus paper can indicate alkalinity with a change to blue. In general, litmus paper is red below a pH of 4.5 and blue above a pH of 8.3. If the paper turns purple, this indicates the pH is near neutral. Red paper that does not change color indicates the sample is an acid. Blue paper that does not change color indicates the sample is a base. Remember, acids and bases refer only to aqueous (water-based) solutions, so pH paper wont change color in non-aqueous liquids, such as vegetable oil. Litmus paper may be dampened with distilled water to give a color change for a gaseous sample. Gases change the color of the entire litmus strip since the whole surface is exposed. Neutral gases, such as oxygen and nitrogen, do not change the color of the pH paper. Litmus paper that has changed from red to blue can be reused as blue litmus paper. Paper that has changed from blue to red can be reused as red litmus paper. Limitations The litmus test is quick and simple, but it suffers a few limitations. First, its not an accurate indicator of pH. It does not yield a numerical pH value. Instead, it roughly indicates whether a sample is an acid or a base. Second, the paper can change colors for other reasons besides an acid-base reaction. For example, blue litmus paper turns white in chlorine gas. This color change is due to bleaching of the dye from hypochlorite ions, not acidity/basicity. Alternatives to Litmus Paper Litmus paper is handy as a general acid-base indicator, but you can get much more specific results if you use an indicator that has a more narrow test range or that offers a wider color range. Red cabbage juice, for example, changes color in response to pH all the way from red (pH 2) through blue at neutral pH to greenish-yellow at pH 12, plus you are more likely to find cabbage at the local grocery store than lichen. The dyes orcein  and azolitmin yield results comparable to those of litmus paper.

Strategies for How to Improve English Listening Skills

Strategies for How to Improve English Listening Skills As a new English speaker, your language skills are progressing well grammar is now familiar, your  reading comprehension is no problem, and you are communicating quite fluently   but listening is still posing a problem. First of all, remember that you are not alone. Listening comprehension is probably the most difficult task for almost all learners of English as a foreign language. The most important thing is to listen, and that means as often as possible. The next step is to find listening resources. This is where the Internet really comes in handy (idiom to be useful) as a tool for English students. A few  suggestions for interesting listening selections are  CBC Podcasts,  Ã‚  All Things Considered (on NPR), and  the BBC. Listening Strategies Once you have begun to listen on a regular basis, you might still be frustrated  by your limited understanding. Here are a few courses of action you can take: Accept the fact that you are not going to understand everything.Stay relaxed when you do not understand even if you continue to have trouble understanding for a while.Do not translate into your native language.Listen for the gist (or general idea) of the conversation. Dont concentrate on detail until you have understood the main idea(s). First, translating creates a barrier between the listener and the speaker. Second, most people repeat themselves constantly. By remaining calm, you can usually understand what the speaker had said. Translating Creates a Barrier Between Yourself and the Person Who Is Speaking While you are listening to another person speaking a foreign language (English in this case), the temptation is to immediately translate into your native language. This temptation becomes much stronger when you hear a word you dont understand. This is only natural as we want to understand everything that is said. However, when you translate into your native language, you are taking the focus  of your attention away from the speaker and concentrating on the translation process taking place in your brain. This would be fine if you could put the speaker on hold. In real life, however, the person continues talking while you translate. This situation obviously leads to less not more understanding. Translation leads to a mental block in your brain, which sometimes doesnt allow you to understand anything at all. Most People Repeat Themselves Think for a moment about your friends, family, and colleagues. When they speak in your native tongue, do they repeat themselves? If they are like most people, they probably do. That means that whenever you listen to someone speaking, it is very likely that they will repeat the information, giving you a second, third or even fourth chance to understand what has been said. By remaining calm, allowing yourself to not understand, and not translating while listening, your brain is free to concentrate on the most important thing: understanding English in English. Probably the greatest advantage of using the Internet to improve your listening skills is that you can choose what you would like to listen to and how many and times you would like to listen to it. By listening to something you enjoy, you are also likely to know a lot more of the vocabulary required. Use Key Words Use keywords or key phrases to help you understand the general ideas. If you understand New York, business trip, last year you can assume that the person is speaking about a business trip to New York last year. This may seem obvious to you, but remember that understanding the main idea will help you to understand the detail as the person continues to speak. Listen for Context Lets imagine that your English speaking friend says, I bought this great tuner  at JRs. It was really cheap and now I can finally listen to National Public Radio broadcasts. You dont understand what a tuner  is, and if you focus on the word tuner  you might become frustrated. If you think in context, you probably will begin to understand. For example; bought is the past of buy, listen is no problem and radio is obvious. Now you understand: He bought something the  tuner to listen to the radio. A tuner must be a kind of radio. This is a simple example but it demonstrates what you need to focus on: Not the word that you dont understand, but the words you do understand. Listening often is the most important way to improve your listening skills. Enjoy the listening possibilities offered by the Internet and remember to relax.