Acids, Bases, and pH

Summary

In this educational video, Mr. Andersen delves into the concept of acids, bases, and pH, crucial for understanding biological processes. He explains that pH measures the concentration of hydrogen ions, with 7 being neutral, below 7 acidic, and above 7 basic. Using water as a starting point, he illustrates how hydrogen bonding leads to the formation of hydronium ions, affecting pH. The video further discusses the impact of pH on proteins, such as myoglobin in muscles, and the environmental implications, including acid rain and ocean acidification, emphasizing the importance of pH stability for life and ecosystems.

Takeaways

• 😀 pH measures the concentration of hydrogen or hydronium ions in a solution, indicating whether it's an acid or base.
• 😀 Water has a neutral pH of 7, with acids having a lower pH and bases a higher pH than 7.
• 😀 Proteins like myoglobin in muscles function best within a specific pH range (5-7), and deviations can cause denaturation.
• 😀 Water molecules are polar, forming hydrogen bonds between molecules, which is crucial for water's properties like cohesion.
• 😀 Hydronium ions (H3O+) form when a hydrogen atom detaches and attaches to another water molecule, influencing pH levels.
• 😀 pH is calculated as the negative logarithm of the hydrogen ion concentration, making it a log scale for acidity and basicity.
• 😀 Hydrochloric acid (HCl) dissociates in water, increasing H+ concentration, lowering pH, making the solution more acidic.
• 😀 Sodium hydroxide (NaOH) acts as a base, reducing hydrogen ion concentration by forming water, raising the pH.
• 😀 The oceans' pH has been decreasing due to carbon dioxide combining with water, leading to ocean acidification.
• 😀 Even a small change in pH can have significant biological impacts, including coral reef damage and mass extinctions tied to acidification.

Q & A

What does pH measure?

pH measures the concentration of hydrogen ions or hydronium ions in a solution.

Why is pH important in biology?

pH is important in biology because it affects the activity of proteins like myoglobin, which is found in muscles and is most active at a pH of 6. Extreme pH levels can cause proteins to denature, affecting the functioning of muscles and other biological processes.

What is the significance of the pH of water being 7?

A pH of 7 for water indicates neutrality, meaning the concentration of hydrogen ions is balanced and rare, occurring at a rate of about 1 in 10,000,000.

What is a polar molecule and how does it relate to water?

A polar molecule is one where electrons are unevenly distributed, resulting in partial positive and negative charges. Water is a polar molecule because oxygen pulls electrons towards itself, creating a partial negative charge, while hydrogen has a partial positive charge.

What is a hydrogen bond and how does it occur in water?

A hydrogen bond is a type of dipole-dipole attraction between a partially positive hydrogen atom in one water molecule and a partially negative oxygen atom in another. This results in water molecules aligning in a way that allows them to be attracted to each other, contributing to properties like cohesion.

What is hydronium and how is it formed?

Hydronium is formed when a hydrogen atom from one water molecule becomes detached and attaches to another water molecule, resulting in H3O+ with a positive charge. This leaves behind a hydroxide ion (OH-).

How is the pH scale related to acids and bases?

The pH scale is used to measure how acidic or basic a substance is. A pH of 7 is neutral, values below 7 indicate acidity (with lower numbers being more acidic), and values above 7 indicate basicity (with higher numbers being more basic).

What happens to the pH when hydrochloric acid is added to water?

When hydrochloric acid is added to water, it dissociates into hydrogen ions and chloride ions, increasing the concentration of H+ ions and thus lowering the pH, making the solution more acidic.

How does sodium hydroxide affect the pH of water?

Sodium hydroxide, when added to water, dissociates into sodium ions and hydroxide ions. The hydroxide ions react with hydrogen ions in the water to form more water molecules, reducing the concentration of H+ ions and thus raising the pH, making the solution more basic.

What is the relationship between pH and the environment?

Changes in pH can have significant environmental impacts. For example, acid rain and the acidification of oceans due to increased carbon dioxide levels can alter the pH, affecting marine life and ecosystems.

Why is it important to understand the pH scale in the context of environmental issues?

Understanding the pH scale is crucial for assessing environmental issues like ocean acidification because even small changes in pH can have large effects on the concentration of hydrogen ions, which in turn can impact marine life and ecosystems.

Outlines

00:00

🌡 Understanding pH and Its Importance

This paragraph introduces the concept of pH, explaining that it measures the concentration of hydrogen ions in a solution. It emphasizes the importance of pH stability for biological processes, using the example of myoglobin, a protein in muscles that denatures outside its optimal pH range. The paragraph also delves into the molecular structure of water, highlighting its polarity and the formation of hydrogen bonds, which are crucial for understanding how pH affects the behavior of substances in water. The concept of hydronium ions (H3O+) is introduced as a product of water autoionization, and their role in determining pH is explained. The pH scale is briefly touched upon, with a focus on how pH values relate to the acidity or basicity of a solution.

05:02

🔍 Deep Dive into Acids, Bases, and pH Calculation

This paragraph expands on the酸碱性质 of substances and how they affect pH levels. It explains that acids, such as hydrochloric acid found in stomachs, increase the concentration of hydrogen ions (H+) in a solution, resulting in a lower pH value. The process of how bases, like sodium hydroxide, reduce the hydrogen ion concentration by forming water is described, leading to a higher pH. The paragraph also clarifies common misconceptions about how changes in hydrogen ion concentration affect pH values, cautioning that an increase in hydrogen ions lowers pH, contrary to what some might initially assume. The discussion concludes with real-world implications, such as acid rain and ocean acidification, emphasizing the environmental significance of pH changes and their logarithmic scale's sensitivity to small numerical shifts.

Keywords

💡pH

pH is a scale used to specify the acidity or basicity of a solution. It is a measure of the hydrogen ion concentration in a solution, which determines its acidity or alkalinity. In the video, pH is central to understanding how acids and bases affect biological systems, with the example of myoglobin, a protein in muscles, being most active at a pH of 6. The video explains that pH is calculated as the negative logarithm of the hydrogen ion concentration, and how changes in pH can impact the functionality of proteins and the health of ecosystems, such as the acidification of oceans.

💡Acids

Acids are substances that donate hydrogen ions (protons) when dissolved in water. In the context of the video, acids are discussed as substances that lower the pH of a solution. An example given is hydrochloric acid, which is found in the human stomach and has a pH of around 2. The video explains how acids increase the concentration of hydrogen ions, thus decreasing the pH value.

💡Bases

Bases are substances that accept hydrogen ions (protons) or donate hydroxide ions when dissolved in water. The video describes bases as substances that raise the pH of a solution. An example used is sodium hydroxide, which when added to water, reacts with hydrogen ions to form water molecules, thus reducing the concentration of hydrogen ions and increasing the pH value.

💡Hydrogen Ion

A hydrogen ion, often represented as H+, is the fundamental unit of acidity. It is a proton without its electron. In the video, the hydrogen ion is discussed as the key player in determining the pH of a solution. The video explains that the pH scale is essentially a measure of the concentration of hydrogen ions in a solution.

💡Hydronium Ion

The hydronium ion, represented as H3O+, is a form of hydrated hydrogen ion. It forms when a hydrogen ion (H+) is solvated by water. In the video, the concept of hydronium is introduced to explain the formation of this ion when a hydrogen atom detaches from one water molecule and attaches to another, leaving behind a hydroxide ion.

💡Hydroxide Ion

The hydroxide ion, represented as OH-, is a form of the hydroxide when it is an ion. It is formed when a hydrogen ion is removed from a water molecule. In the video, the hydroxide ion is discussed in the context of how bases react with water to form hydroxide ions, which then react with hydrogen ions to form more water, thus affecting the pH.

💡Polar Molecule

A polar molecule is a molecule that has an uneven distribution of electron charge, leading to areas of partial positive and partial negative charge. In the video, water is described as a polar molecule due to the electronegativity of oxygen, which pulls electrons towards itself, creating a partial negative charge, while hydrogen ends up with a partial positive charge.

💡Hydrogen Bond

A hydrogen bond is a type of dipole-dipole interaction that occurs between a hydrogen atom covalently bonded to a highly electronegative atom (like oxygen) and another electronegative atom. In the video, hydrogen bonding is discussed as a key property of water molecules, where the partially positive hydrogen of one water molecule is attracted to the partially negative oxygen of another, contributing to water's cohesion.

💡Neutral pH

A neutral pH is a pH value of 7, indicating that a solution is neither acidic nor basic. In the video, the concept of neutral pH is introduced to explain the balance point on the pH scale, where the concentration of hydrogen ions is equal to that of hydroxide ions, as in pure water.

💡Acid Rain

Acid rain is rain that has a pH less than 7, caused by atmospheric pollution by sulfur dioxide and nitrogen oxides. In the video, acid rain is mentioned as an example of how changes in pH can have significant environmental impacts, affecting ecosystems and the chemistry of bodies of water.

💡Ocean Acidification

Ocean acidification is the ongoing decrease in the pH of the Earth's oceans, caused by the uptake of carbon dioxide from the atmosphere, which reacts with seawater to form carbonic acid. In the video, ocean acidification is discussed as a critical environmental issue, where the increase in carbon dioxide levels leads to a decrease in pH, impacting marine life and ecosystems.

Highlights

pH measures the acidity or basicity of a solution.

Water has a pH of 7, which is neutral.

Acids have a pH lower than 7, while bases have a pH higher than 7.

pH levels are crucial for the proper functioning of proteins, such as myoglobin in muscles.

Water molecules are polar, leading to the formation of hydrogen bonds.

Hydronium (H3O+) and hydroxide (OH-) ions are formed when water molecules ionize.

pH is defined as the negative log of the hydrogen ion concentration.

Distilled water's rare ionization results in a pH of 7.

Adding hydrochloric acid to water increases the hydrogen ion concentration, lowering the pH.

Sodium hydroxide (a base) reacts with water to consume hydrogen ions, increasing the pH.

The pH scale is logarithmic, meaning small changes in pH represent large changes in hydrogen ion concentration.

Acid rain and ocean acidification are environmental issues related to changes in pH.

The increase in atmospheric CO2 leads to the formation of carbonic acid in the oceans, decreasing their pH.

A decrease of 0.1 on the pH scale indicates a significant increase in hydrogen ions in the oceans.

Changes in ocean pH can impact marine life, including coral reefs.

Historically, mass extinctions have been correlated with the acidification of oceans.

Transcripts

Hi. It's Mr. Andersen and in this video I'm going to talk about Acids,

Bases and pH. If you ask people what pH measures, they'll usually say if something is an acid

or a base. And they might know that water has a pH of 7. That acids are generally lower

than that and bases higher than 7. But that's where a lot of people's understanding ends.

And so I kind of want to explain to you what pH is and how it's determined. But before

that I want to tell you why it's important. And I'm a biology teacher. And so everything

kind of goes back to life. And so this is a protein. It's called myoglobin. It's found

in your muscles. And it's going to be most active at a pH of 6. It's going to work at

a pH of 5 all the way up to 7. But if we start to move our pH too low or too high, that protein

is going to denature. And our muscles aren't going to work. And so it's important that

the pH levels remain relatively constant and they're not changing that much. But what is

pH? Well we've got to start by talking about water. And so this is a water molecule. Remember

we're going to have hydrogen here. Two hydrogen atoms. And then one oxygen atom. Now one thing

that you need to understand is that this is a polar molecule. And what that means is there's

a covalent bond between the hydrogen and the oxygen. Between this hydrogen and oxygen as

well. And oxygen is really greedy when it comes to electrons. It's going to pull the

electrons towards it. And so this is a sharing of electron between these atoms. But it's

a polar covalent bond. And what that means is since oxygen is pulling the electrons towards

it, it's going to have partial negative charge on this side of the oxygen. And the hydrogens

are going to have a positive charge on the other side. And so if we were to add another

molecule of water, these are not going to arrange this way. In fact what we'll have

is they'll be arranged like that. And so the hydrogen atom of one water molecule is going

to be attracted to the oxygen of another. And that bond is called a hydrogen bond. A

lot of students think that hydrogen bond is in here, but no, that's covalent. But the

hydrogen bond is going to be between the positive hydrogen, partially positive. And the negative

oxygen. And that's why if we have one water molecule and the hydrogens are like positive

and the oxygens are negative. And we have another one, they're going to line up like

this. And as I pull one water molecule, the other one is going to go along with it. And

that's why we have cohesion. And it explains a lot about water. But some weird thing happens

with water. Sometimes that attraction is so great that this hydrogen atom will actually

become detached from the water and it will be come attached on to this other water molecule.

That would be like me pulling this pinky off and attaching it over on to this other water

molecule. Leaving me just with this. And so what is that called? This is called hydronium.

Hydronium is going to be H3O and it's going to have a positive charge. What are we left

with over here? This is a hydroxide ion. And so what is pH a measure of? Well the p stands,

we think, for the power of hydrogen. In other words the amount of hydrogen. But it could

also be the amount of hydronium or the amount of just free hydrogen ion inside the water.

And so if we look at the power of that, or almost the percentage of that, that's going

to be what pH measures. And in regular water, distilled water, they amount of this occurring

is really, really rare. In other words it's a 1 in 10,000,000 chance that we're going

to have hydronium. And this is really a molar concentration. So to give you a sense of the

scale, let's say this hydronium ion right here is represented with this little cube.

And so what I'm going to do is pull back. And let's say this is one cube and 10 and

100 and 1000 and eventually what we get, if we scale that, you really can't see that cube

anymore. But this would represent 10 million cubes. And so the chances of that one hydronium

forming are going to be really really low. But even though the probability of hydronium

forming is low, it actually occurs in water and it has huge impacts on things that are

found within that water itself. And so that 1 in 10,000,000, I want you to think about

that for just a second, and let's kind of add a little bit of the equation of pH. And

so some kids get scared by the equation. It's not that scary. So pH or the power of hydrogen

is equal to the negative log of the hydrogen ion concentration. It's also the same as the

hydronium. That's that H3O plus. Those are essentially the same thing. So it's the negative

log of that. And so it's the negative log, think of this, as 1 in 10,000,000. And this

would actually be a molar concentration. But we're keeping it conceptual right now. And

so if we take the negative log of that, let's write 1 in 10,000,000 in scientific notation.

And so it's the negative log of one times 10 to the negative 7th. So this is going to

be a really small number here, and this is where the math gets really easy. If you were

to put this in your calculator, if we take the negative log of one times 10 to the negative

7, what do we get? 7. And so the pH is going to be 7. And this gives us a number that we

can actually deal with. And so what does it mean if the pH is 7? It means that the concentration

of this hydrogen ion is going to be really, really small. And if we ever vary that, then

we're going to be varying the pH. And so pH of 7 is neutral. But if we ever have a value

greater than 7, it's going to be a base. And if it's ever lower than that then it's going

to be an acid. And so let's start by dealing with the acids. What's an acid that almost

everybody is familiar with? That's hydrochloric acid. You'd find that in your stomach. And

so if we add hydrochloric acid to water, it's going to disassociate. It's going to breakdown

into hydrogen ions and chloride ions. And so you can see here that we're increasing

the amount of this H+. And so what is that going to do to that concentration? Now instead

of being 1 in 10,000,000, it might be as often or as common as 1 in 100. And so if we were

to right that as scientific notation. It's the negative log of 1 times 10 to the negative

2. So we would have a pH of 2. And so depending on the concentration of hydrochloric acid,

we could have a pH of 2 or 1 or 3. It depends on how much hydrochloric acid is in there.

Now let's look at a base. And so a base for example, this would be sodium hydroxide. Or

lye. What's going to happen to that when we add it to water? It's going to break apart

into sodium ions. And hydroxide ions. Now that doesn't help us. Remember, because pH

stands for the power of hydrogen ion. But what do you think is going to happen to that

hydrogen ion that happens to be in the water? Now we've got a hydrogen ion and we have a

hydroxide ion. And those are quickly going to combine to form water. And as it does that

it's going to gobble up that hydrogen ion. What's that going to do the amount of hydrogen

ion in the water or hydronium ion for that matter? It's going to make it even more rare.

And so now we have the PH equal to the negative log of 1 times 10 to the negative 12 for example.

And so what's that going to be? That's going to give us a pH of 12. And so what does pH

measure? It just measures the amount of hydrogen ions. Or hydronium ions. And bases and acids

are going to have different amounts of that. We measure that using a pH scale. And so distilled

water is going to have a pH of 7. If we have anything higher than that, that's going to

be a base. Anything lower than that, that's going to be an acid. But when you're taking

a test, it can be somewhat confusing. And so let's say we increase the amount of hydrogen

ions in a solution. So we're going to have more of them. What's that going to do to the

pH? It's actually going to lower it. And vice versa on bases. And so watch out for that

when you're taking a test. Why is this important? Well acid rain is one example of that. Or

the acidification of our oceans is another example. And so this is looking at the pH

in the oceans over the last couple hundred years. And what we see is that our oceans

are becoming more acidic. How does that work? You're combining carbon dioxide with the water.

And as we increase the amount of carbon dioxide in the atmosphere, that water and the carbon

dioxide are combining to make carbonic acid in the oceans. And that's increasing the acidity

of our oceans. And so we could hear, see here, the pH is decreasing. So we've seen a decrease

of around negative 0.1 on the pH scale over the last couple hundred years. And you might

think, well that's not that big of deal. But remember this is a log scale. So by decreasing

it by a small amount in the pH, we're going to increase it quite a bit in the hydrogen

ion. And that's going to effect anything living in the oceans. It could effect coral reefs.

And every time we have a massive extinction on our planet, it seems to be correlated with

the acidification of our oceans. And so that's pH. Pretty simple. And I hope that was helpful.