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In chemistry, pH is a measure of the acidity or basicity of an aqueous solution.[1] Pure water is said to be neutral, with a pH close to 7.0 at 25 °C (77 °F). Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline. pH measurements are important in medicine, Biology, chemistry, agriculture, forestry, food science, environmental science, oceanography, civil engineering and many other applications.
In a solution pH approximates but is not equal to p[H], the negative logarithm (base 10) of the molar concentration of dissolved hydronium ions (H3O+); a low pH indicates a high concentration of hydronium ions, while a high pH indicates a low concentration. This negative of the logarithm matches the number of places behind the decimal point, so, for example, 0.1 molar hydrochloric acid should be near pH 1 and 0.0001 molar HCl should be near pH 4 (the base 10 logarithms of 0.1 and 0.0001 being −1, and −4, respectively). Pure (de-ionized) water is neutral, and can be considered either a very weak acid or a very weak base, giving it a pH of 7 (at 25 °C (77 °F)), or 0.0000001 M H+.[2] The pH has no upper or lower limit and can be lower than 0 or higher than 14,[3] although with water, it is limited by the acidity and basicity of water. For an aqueous solution to have a higher pH, a base must be dissolved in it, which binds away many of these rare hydrogen ions. Hydrogen ions in water can be written simply as H+ or as hydronium (H3O+) or higher species (e.g., H9O4+) to account for solvation, but all describe the same entity. Most of the Earth's freshwater bodies surface are slightly acidic due to the abundance and absorption of carbon dioxide;[4] in fact, for millennia in the past, most fresh water bodies have had a slightly acidic pH.
However, pH is not precisely p[H], but takes into account an activity factor. This represents the tendency of hydrogen ions to interact with other components of the solution, which affects among other things the electrical potential read using a pH meter. As a result, pH can be affected by the ionic strength of a solution---for example, the pH of a 0.05 M potassium hydrogen phthalate solution can vary by as much as 0.5 pH units as a function of added potassium chloride, even though the added salt is neither acidic nor basic.[5]
Hydrogen ion activity coefficients cannot be measured directly by any thermodynamically sound method, so they are based on theoretical calculations. Therefore, the pH scale is defined in practice as traceable to a set of standard solutions whose pH is established by international agreement.[6] Primary pH standard values are determined by the Harned cell, a hydrogen gas electrode, using the Bates--Guggenheim Convention.
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Are gases more dense than liquid?
In general, gases are less dense than liquids because gas molecules are more spread out and have higher kinetic energy compared to liquid molecules, which are more closely packed. This results in gases having lower density than liquids. However, there are exceptions, such as some liquid metals that have lower density compared to certain gases at normal conditions.
How is density of matter affected by the state of matter?
The density of matter can vary depending on the state of matter. In general, solids are more dense than liquids, and liquids are more dense than gases. This is because the particles are more closely packed together in solids compared to liquids and gases, leading to higher density.
Why do some things flaot while others sink?
Some things float or sink based on their density. Objects that are less dense than the liquid they are placed in will float, while those that are more dense will sink. Additionally, the shape and size of an object can also affect whether it floats or sinks.
How do liquids form layers?
Liquids form layers based on their densities, with denser liquids sinking to the bottom and less dense liquids floating on top. This is known as liquid stratification, and it occurs due to differences in the masses of the liquid components. The layers typically do not mix due to differences in their physical properties such as density, viscosity, and solubility.
Why do some liquids travel faster than others?
The speed at which a liquid travels is influenced by its viscosity - the resistance to flow. Liquids with lower viscosity flow more easily and thus typically travel faster than liquids with higher viscosity. Other factors such as temperature and pressure can also affect the speed at which liquids travel.
Are solids Less dense than liquids?
Not necessarily. The density of a substance depends on its mass and volume, so it can vary for both solids and liquids. In general, solids are denser than liquids because the particles in solids are typically more closely packed together.
Why do some liquids sink in liquids?
The more-dense liquid will sink because it's more dense and this is the lowest-energy state. If both are polar or both are nonpolar, some mixing will occur, but the effect can still be seen.
Are liquids dense?
Some liquids are denser than others. In general, everyday experience, most liquids are denser than gases, but not as dense as solids. There are some exceptions to this rule.
Why does some matter sink and others float?
I am not sure, but matter that is less dense usually gets pushed up, specially liquids.
What is some liquids flow more easily than others?
water
Why do some liquids burn while others do not?
The chimicals in some liquids burn others do not.
Why do some liquids sinks in liquids?
Some liquids sink in other liquids due to differences in density. When a liquid is denser than the liquid it is placed in, it will sink because of gravity. This is similar to how some objects sink or float in water based on their density compared to the water.
Which is the best conductor of sound a gas a liquid or a solid?
Solids and liquids are better conductors. You can't say which of the two because some solids are more dense than some liquids and vice versa.
Are liquids quite dense and have alot of particles in a small volume?
Yes, liquids are relatively dense compared to gases because they have more particles packed closely together in a given volume. This high particle density allows liquids to take the shape of their container, but they still have some degree of fluidity.
What causes some objects to be more dense than others?
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Why do some liquids freeze faster than others?
Because some liquids have less kinetic energy.
Are gases more dense than liquid?
In general, gases are less dense than liquids because gas molecules are more spread out and have higher kinetic energy compared to liquid molecules, which are more closely packed. This results in gases having lower density than liquids. However, there are exceptions, such as some liquid metals that have lower density compared to certain gases at normal conditions.
