What Is The pH Scale | Acids, Bases & Alkalis | Chemistry | FuseSchool
Summary
TLDRThis educational video explores the pH scale and the use of indicators to determine the acidity or alkalinity of substances. It explains how litmus paper, either red or blue, changes color in response to acids or alkalis, but cannot quantify the pH level. The video then introduces the universal indicator, a mixture of dyes that can indicate the pH value of a solution across the full 0 to 14 scale. It also touches on the use of a pH meter for more precise measurements. Examples of various substances' pH levels, such as stomach acid, milk, and seawater, are provided to illustrate the concept.
Takeaways
- 🔬 The pH scale is a measure of how acidic or alkaline a substance is, ranging from 0 (extremely acidic) to 14 (extremely alkaline), with 7 being neutral.
- 🌈 Indicators are substances that change color in the presence of acids or alkalis, helping to identify their properties.
- 🍂 Litmus paper, derived from lichens, is a simple indicator that turns red in acids and blue in alkalis.
- 📄 Red litmus paper changes color to blue in alkaline conditions, while blue litmus paper changes to red in acidic conditions.
- 🚫 Litmus paper cannot provide the degree of acidity or alkalinity; it only indicates the presence of an acid or alkali.
- 🌈 Universal indicator is a more complex mixture that can show the pH value of a solution through various color changes.
- 🔍 The pH scale is used to measure the exact level of acidity or alkalinity, with substances like stomach acid being very acidic (pH 2) and bleach being very alkaline (pH 13).
- 🌊 Examples of substances with specific pH levels include acid rain (around 5.5), milk (neutral at 7), and seawater (slightly alkaline).
- 🔬 Universal indicator is called 'universal' because it can indicate the entire pH spectrum, unlike some other indicators with limited color changes.
- 📊 For even more precise pH measurements, a pH meter can be used, providing readings accurate to two decimal places.
Q & A
What is an indicator and how does it help in determining the acidity or alkalinity of a substance?
-An indicator is a substance that changes color in the presence of acids or alkalis, helping to identify whether a substance is acidic, neutral, or alkaline.
What are the two forms in which litmus paper is available, and what is its source?
-Litmus paper is available in two forms: liquid and paper, with the paper form being easier and more reliable. It is sourced from lichens, which have been used for centuries to dye cloth.
How does red litmus paper react to alkaline conditions, and what color does it change to?
-Red litmus paper changes color from red to blue under alkaline conditions.
What is the color change of blue litmus paper under acidic conditions?
-Blue litmus paper changes color from blue to red under acidic conditions.
What is the pH scale and what does it measure?
-The pH scale is a scale from 0 to 14 that measures the acidity or alkalinity of a solution, with 0 being extremely acidic, 7 neutral, and 14 extremely alkaline.
What is a universal indicator and how does it differ from litmus paper?
-A universal indicator is a mixture of different indicators or dyes that can show many color changes, indicating the pH value of a solution. It differs from litmus paper in that it provides a more detailed indication of where on the pH scale a solution lies.
What is the pH of stomach acid, and how does it compare to the pH of acid rain?
-Stomach acid has a pH of about 2, which is stronger than acid rain, which has a pH of about 5.5.
Why is a universal indicator called 'universal'?
-A universal indicator is called 'universal' because it can indicate the entire pH spectrum, providing a detailed view of a solution's acidity or alkalinity.
How can one get more accurate pH measurements than what is provided by a universal indicator?
-One can use a pH meter for more accurate measurements, which can provide readings to two decimal places of the pH scale.
What is the pH range for acids, neutral substances, and alkalis according to the script?
-Acids are from 0 to 6, neutral is 7, and alkalis are from 8 to 14 on the pH scale.
What is the pH of milk, and how does it relate to the concept of neutrality?
-Milk has a pH of 7, which is considered neutral, neither acidic nor alkaline.
Outlines
🔬 Understanding pH Scale and Indicators
This video segment introduces viewers to the pH scale, which is a measure of how acidic or alkaline a substance is. It explains that indicators, like litmus paper, can be used to determine if a substance is acidic or alkaline. Litmus paper is red in acids and blue in alkalis, and it is made from lichens, which have been used for centuries to dye cloth. The segment also mentions that while litmus paper can indicate the presence of an acid or alkali, it does not provide information about the degree of acidity or alkalinity. To measure this, one can use the pH scale or a universal indicator. The pH scale ranges from 0 (extremely acidic) to 14 (extremely alkaline), with 7 being neutral. Examples given include stomach acid at pH 2, milk at pH 7, and bleach at pH 13. The video also touches on the use of a universal indicator, which can show the pH value of a solution through various color changes, and the use of a pH meter for more precise measurements.
Mindmap
Keywords
💡pH scale
💡Indicators
💡Litmus paper
💡Acidic
💡Alkaline
💡Neutral
💡Universal indicator
💡Acid rain
💡Seawater
💡pH meter
💡Stomach acid
Highlights
The pH scale and indicators are discussed to determine if a substance is acidic, neutral, or alkaline.
Indicators show different colors in acidic or alkaline conditions.
Litmus paper is a simple indicator made from lichens, used to determine if a substance is acidic or alkaline.
Litmus paper comes in red and blue forms, with red indicating alkalis and blue indicating acids.
Red litmus paper turns blue in alkaline conditions and remains red in acidic conditions.
Blue litmus paper turns red in acidic conditions and remains blue in alkaline conditions.
Litmus paper cannot indicate the degree of acidity or alkalinity.
The pH scale ranges from 0 to 14, with 0 being extremely acidic, 7 neutral, and 14 extremely alkaline.
Universal indicator is a mixture that shows the pH value of a solution through various color changes.
Universal indicator can be used as a liquid or on paper.
Stomach acid has a pH of about 2, indicating it is a strong acid.
Acid rain has a pH of about 5.5.
Milk is neutral with a pH of 7.
Seawater is slightly alkaline.
Soapy water and bleach are examples of strong alkaline substances.
A pH meter provides more accurate pH readings to 0.01.
Indicators can tell us if a substance is acidic or alkaline and the degree of acidity or alkalinity.
Acids range from 0 to 6 on the pH scale, neutral is 7, and alkalis are from 8 to 14.
Transcripts
In this video we are going to have a look at the pH scale and some other simple
indicators of acids and alkalis. In other videos we have seen what makes something
acidic, neutral or alkaline. We can tell if something is acidic, alkaline or neutral
by using an indicator. Indicators are substances that show different colours
when they are in acidic or alkaline conditions. Litmus paper is a simple
indicator that tells us whether something is acid or alkali. Litmus is
red in acids and blue in alkalis. Litmus paper is made from lichens
which have been used to die cloth for hundreds of years. It can be used as a
liquid or paper. The paper is easier and more reliable. It comes as red litmus
paper and blue litmus paper. Red litmus paper changes colour from red to blue
under alkaline conditions but no change under acidic conditions.
Blue litmus paper changes colour from blue to red under acidic conditions but no change under alkaline conditions.
So just remember that red litmus paper changes
colour for alkalis and blue litmus paper changes colour for acids. However litmus
paper only tells us whether something is acid or alkali, but it does not tell us
HOW acidic or alkaline a substance is. For this, we have the pH scale and a
universal indicator. Universal indicator is a mixture of different indicators or
dyes which has many different colour changes and so shows us the pH value of
the solution. Again it can be used as a liquid or paper. The pH scale runs from 0 to 14.
With 0 being extremely acidic, 7 being neutral and 14 being extremely alkaline.
Stomach acid is a strong acid with pH of about 2. Acid rain has a pH
of about 5.5. Milk is neutral with a pH of 7. Seawater is slightly alkaline.
Soapy water is a strong alkaline and bleach is a really strong alkaline with a
pH of 13. Universal indicator is
so called due to it's ability to indicate the entire pH spectrum. There are other
indicators that can be used that have other colour changes, but these two are
the ones you need to know. We can also get even more accurate measurements of
pH using a pH meter which will give us readings to 0.01 of the pH. So from this
lesson you should now know that indicators can tell us whether something is acidic or
alkaline, and HOW acidic or alkaline it is. Red litmus paper changes colour for
alkalis and blue litmus paper changes colour for acids. And universal indicator can
give us more detail indicating where on the 0 to 14 pH scale a solution is.
Acids are from 0 to 6, neutral is 7 and alkalis are 8 to 14.
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