CHEMISTRY MIDDLE SCHOOL

What is the optimal level of fluoride in water?

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Answer 1
Answer:

Answer:

The agency's recommended ratio of fluoride to water, newly calibrated at 0.7 parts per million, results from years of scientifically rigorous analysis of the amount of fluoride people receive from all sources.

Related Questions

Why did the United States government set aside land for the first national parks?A. They wanted to settle the west as quickly as possible. B. They worried people would destroy the animals and land. C. They worried Native Americans wouldn’t have anywhere to go. D. They wanted to make sure all citizens would get a piece of land.
What is a living compound that contains hydrogen?
What is one of the by products of using a cooling system?
Calculate the heat required for the following two processes, and compare the results.a. A 100.0 g sample of solid ethanol melts at its melting point. Hfus = 4.94 kJ/molb. A 100.0 g sample of liquid ethanol vaporizes at its boiling point. Hvap = 38.6 kJ/mol
Based on their electronegativities, you would expect ____ elements to pull on electrons more strongly than ______ elements.

Which sentence best describes the process of convection? A. A rock melts when magma touches it. B. Water vapor in the air forms liquid water. C. Cool air sinks, which forces warm air to rise. D. Sunlight travels through space. Can i please get help!

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convection is when cool air sinks and warm air rises. i am not 100% sure though

the mass of a 125 cm3 piece of material is 82.75 g. determine the density of this material . please explain

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you would do 82.75 divided by 125 cm3 and get 0.6620 g/cm3 because to find density you mist divide mass and volume and grams is always mass and cm3 or mL is always volume. hope i helped!

Helium does not usually react with other substances. Does this mean that helium has no chemical properties? Please explain.

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The electron "shell" (or orbitals) for helium is full with two electrons. It, like hydrogen, follows the duet rule. This means that it is "happy" and not very reactive once it has two elections in its shell. For helium, it is inert (doesn't react, no chemical properties) if it keeps the electrons in its shell. If, however, one were to remove an electron (ionize it) the atom would be helium, as it has 2 protons, but would react with elements that have 1 valence electron in order to get the full shell. This is VERY uncommon simply because it takes a great amount of energy to remove the electron the process is not very useful. The answer to your question is essentially, no like other noble gases, helium does not have chemical properties.

Final answer:

Though helium doesn't usually react with other substances due to its full electron shell, it doesn't mean it lacks chemical properties. Properties like atomic number, atomic mass, density, and reactivity are its chemical properties.

Explanation:

The statement that helium does not usually react with other substances  is correct. This is due to helium being a noble gas with a complete set of electrons in its outer shell, making it stable and unlikely to participate in chemical reactions. However, this does not mean it has no chemical properties. Properties such as atomic number, atomic mass, density, and the inability to react or bond with other elements are indeed chemical properties.

Learn more about Helium here:

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Can “happy, full” elements like He, and Xenon bond with other atoms? Explain what this is like.

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No because they have their complete octet. They are completely filled and don't need to bond with any other atoms. The full atoms that are happy are the noble gases.

What are noble gases ?

Noble gases have electron shells with full valence. Valence electrons are the atom's outermost electrons and are typically the only electrons involved in chemical bonding.

Noble gases are elements that have completely filled their valence shells, completing their octets. Helium, Neon, Argon, Krypton, Xenon, and Radon are examples of noble gases.

Thus, the elements like He, and Xenon can not form bond with other atoms because they have completely filled orbital so, they are not loosing or gaining any electron from other atoms, that's why they are called “happy, full” elements.

To learn more about the noble gases, follow the link;

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No because they have their full octet. They are full and don't need to bond with any other atoms. The full atoms that are happy are the noble gases.

---- If you need anymore chemistry help ask me....because im very good at chemistry.

3. Mr. Hill has 27 students in his classand Mr. Chang has 24 students in his
class. Both classes will be divided into
equal sized teams within their own
classes. What is the greatest number of
students that can be on team so that all
the teams are an equal number?​

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Answer: the answer for mr hills class is 13 and the answer for mr chang is 12

Explanation: The thing that i did was just divide the numbers by 2 and the number is how many teams can be formed at once in both classes

Just dived both numbers by two

List five physical properties?

Answers

Some examples of physical properties are:

color (intensive)

density (intensive)

volume (extensive)

mass (extensive)

boiling point (intensive): the temperature at which a substance boils.

melting point (intensive): the temperature at which a substance melts.
Physical Properties are used to describe how something is. Examples include:

1. Color
2. Shape
3. Size
4. Density
5. Melting/ Boiling point
6. Ordor

Physical changes: occur when matter changes form but not composition (Ex: ice is still H2O). Examples of physical change are:

1. Phase Change (Boiling, melting, freezing, etc.)
2. Size and/ or shape change
3. Dissolving
4. No Color Change (Except dyes)
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