Answer:
The number of electrons, in turn, determines the chemical properties of the atom. Protons contribute to the mass of an atom and provide the positive charge to the nucleus. The number of protons also determines the identity of the element
<span>These are five questions and five answers.
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</span><span>1. A substance that can be separated into two or more substances only by a chemical change is a.</span><span /><span />
<span>Answer: compound
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<span>Explanation:
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<span>i) solution is a homogenous mixture and it can be separated by physical media. For example, a brine: you can evaporate the water from the salt by heating the solution (brine)
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<span>ii) elements cannot be separated into two or more substances except by nuclear reactions.
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<span>iii) mixtures: heterogenous and homogenous mixtures can be separated by physical treatments.
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<span>iv) compounds are substaces composed of different elements bonded chemically; only chemical reactions break the chemical bonds or create new chemical bonds leading a compound to form other substances.
2. Which of the following materials is a substance?
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<span>Answer: silver
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<span>Explanation:
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</span><span>Substances have a definite composition that can only be modified by chemical reactions.
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</span><span>Elements and compounds are substances.
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</span><span>Silver is an element, such as sodium, gold, oxygen. You can find the list of the 118 known elements in a periodic table.
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</span><span>Mixtures, either homogenous or heterogeneous, can be separated by physical mechanisms and so they are not substances: air, gasoline, and stainless steel are mixtures because they have not a unique chemical formula but are formed by other compounds or elements in different proportions, i.e. with not a unique chemical formula.</span><span /><span>
3.The first figure in a properly written chemical symbol always is _____.
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<span>Answer: capitalized
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<span>Explanation:
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</span><span>This is a rule to write the symbols of the elements. For example, Na (sodium), Br (bromine), I (iodine), O (oxygen), Ne (neon).</span><span /><span>
4. Which of the following represents a compound?
Answer: H2O
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</span><span>Explanation:
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</span><span>That is the only chemical formula. The other representations are not valid chemical formulas. A chemical cormula can oly contain chemical symbols and subscript numbers, to represent the kind of atoms (elements) and how many of each (the subscrip).</span><span /><span>
5. What do chemical symbols and formulas represent, respectively?
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<span>Answer: elements and compounds
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<span>Justification:
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<span>1) The symbols are used to represnt elements, such as Na (sodium), Li (lithium), Be (berylium)
2) Chemical formulas represent compunds. For example: CO is carbon monoxide, CO2 is carbon dioxide, H2CO3 is carbonic acid, Na2CO3 is sodium carbonate.
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<span>Each compound has a unique chemical formula.
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Answer:
All solutions are mixtures because it is two or more substances mixed together.
Explanation:
When is a mixture considered a solution.
B, C and E. In radioactive decay unstable atoms stabilize by releasing energy.