1.) A compound is a substance that originates from two or more separate elements. It shares some similarities with a mixture.
2.) A compound has quite different properties from which it was formed. It also cannot be separated easily. Compounds are formed by chemical reactions.
3.) A pure substance has a constant composition and has consistent properties. It can be a compound or an element, but its composition is constant.
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There is 12 inches in 1 foot.
Divide 16 with 12 to get feet
16/12 = ~1.33 (rounded)
1.33 is your answer
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Why was 1990 an important year regarding air quality? Check all that apply.
2.Cost-effective ways to reduce pollution were emphasized.
4.Modifications and improvements were made to the Clean Air Act.
i just took the test this is 100% correct
Answer: Physical change
Explanation: Condensation is the phase change of a gas to the liquid state. There is no formation of new products so it does not undergoes chemical change. Any phase change is considered a physical change.
<h3>Answer:</h3>
Option-D, "their elements have very similar properties and exhibit a clear trend" is the correct answer.
<h3>Explanation:</h3>
In periodic table the elements are arranged in tabular form with respect to their atomic masses, atomic numbers, electronic configurations and chemical properties. It is called periodic because the properties of elements repeats periodically.
Furthermore, the rows from left to right also called Periods basically shows the metallic and non metallic characters of elements. \those on the left are metals and those at the rights are non metals.
The columns from top to bottom are called as Groups. Groups contain elements of same chemical properties.
<h3>Example:</h3>
Group I elements are called as <em>Alkali Metals</em>. They all have one valence electron and hence, loose one electron to form the corresponding cation. i.e.
M → M⁺¹ + 1 e⁻
Group VII elements are called <em>Halogens</em>, they all are non metals and tend to gain one electron to form the corresponding halide ion. i.e.
X + 1 e⁻ → X⁻¹
