Gr 8 Natural Sciences Ch 2.1: Pure substances

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Questions and Answers

What is true about the properties of elements in a compound?

  • The properties are the same as the individual elements
  • The properties are different from the individual elements (correct)
  • The properties are only slightly different from the individual elements
  • The properties are similar to the individual elements, but with a slight change

Which type of molecule is composed of different kinds of atoms?

  • O2 (oxygen)
  • N2 (nitrogen)
  • H2O (water) (correct)
  • CO (carbon monoxide)

What holds atoms together in a molecule?

  • Gravitational forces
  • Chemical bonds (correct)
  • Electromagnetic forces
  • Nuclear forces

What is represented by a chemical formula?

<p>The types and numbers of atoms in a molecule (B)</p>
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What occurs in a decomposition reaction?

<p>A single compound breaks down into two or more simpler substances (C)</p>
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What is the result of the decomposition of water?

<p>Hydrogen gas and oxygen gas (D)</p>
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What is the chemical equation for the decomposition of water?

<p>2H2O → 2H2 + O2 (B)</p>
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What occurs in a chemical reaction?

<p>The breaking of chemical bonds and the formation of new chemical bonds (D)</p>
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What is a pure substance?

<p>A material made of only one kind of matter (C)</p>
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What is a compound?

<p>A substance made up of two or more different kinds of atoms chemically bonded together (D)</p>
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What is the difference between an element and a compound?

<p>An element is made up of one kind of atom, while a compound is made up of two or more different kinds of atoms (A)</p>
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What is the chemical formula for water?

<p>H2O (D)</p>
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What is the chemical formula for carbon dioxide?

<p>CO2 (D)</p>
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What is an example of an element?

<p>Copper (Cu) (D)</p>
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What is an example of a compound?

<p>Water (H2O) (A)</p>
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What is the term for the force that holds atoms together in a molecule?

<p>Chemical Bond (A)</p>
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What is the primary reason for the difference in properties between a compound and its constituent elements?

<p>The formation of chemical bonds (A)</p>
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What is the result of the breaking of chemical bonds in a chemical reaction?

<p>The formation of simpler substances (D)</p>
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What is the purpose of a chemical formula?

<p>To indicate the types and numbers of atoms in a molecule (A)</p>
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What is the difference between molecules composed of same kind of atoms and those composed of different kinds of atoms?

<p>Their properties (D)</p>
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What is the role of protons and electrons in the formation of chemical bonds?

<p>They attract each other (B)</p>
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What is the result of the formation of new chemical bonds in a chemical reaction?

<p>The formation of new substances (D)</p>
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What is the characteristic of a molecule composed of oxygen and hydrogen atoms?

<p>It is a liquid at room temperature (A)</p>
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What is the role of a chemical equation in a chemical reaction?

<p>It represents the chemical reaction (B)</p>
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What is a characteristic of elements?

<p>They exist as individual atoms or molecules made up of the same type of atoms (A)</p>
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Which of the following is an example of a pure substance?

<p>Copper (C)</p>
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What is the main difference between elements and compounds?

<p>Elements consist of only one kind of atom, while compounds consist of two or more kinds of atoms (B)</p>
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What is the term for a group of two or more atoms bonded together?

<p>Molecule (B)</p>
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Which of the following substances consists of only one kind of atom?

<p>Copper (C)</p>
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What is a characteristic of compounds?

<p>They have a fixed ratio of atoms (D)</p>
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What is the fixed ratio of atoms in a compound?

<p>Fixed (C)</p>
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What is true about the atoms in a molecule of oxygen?

<p>They are chemically bonded (D)</p>
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What is the primary reason for the difference in properties between a compound and its constituent elements?

<p>The formation of new chemical bonds (D)</p>
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Which of the following statements is true about molecules?

<p>Molecules can be composed of same kind of atoms or different kinds of atoms (B)</p>
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What is the role of chemical formulae in chemistry?

<p>To represent the types and numbers of atoms in a molecule (A)</p>
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What is the result of the breaking of chemical bonds in a chemical reaction?

<p>The decomposition of the reactant (A)</p>
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What is the purpose of a chemical equation?

<p>To represent the chemical reaction (C)</p>
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What is the result of the formation of new chemical bonds in a chemical reaction?

<p>The formation of new substances (C)</p>
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What is the characteristic of a molecule composed of oxygen and hydrogen atoms?

<p>It is a compound (B)</p>
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What is the role of protons and electrons in the formation of chemical bonds?

<p>Protons attract electrons (D)</p>
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What is unique about the properties of an element?

<p>They are fixed and distinct from those of its compounds. (B)</p>
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Why do elements exist as individual atoms or molecules?

<p>Because they are made up of only one kind of atom. (A)</p>
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What is the relationship between the atoms in a compound?

<p>They are chemically bonded in a fixed ratio. (C)</p>
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What is the main difference between the molecules of oxygen and carbon dioxide?

<p>The type of atoms in each molecule. (D)</p>
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What is a characteristic of the atoms in a molecule of a compound?

<p>They are of different kinds. (D)</p>
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What is a result of the chemical bonds between atoms in a molecule?

<p>A change in the properties of the individual atoms. (C)</p>
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What is the purpose of a chemical formula in a compound?

<p>To represent the ratio of atoms in a molecule. (D)</p>
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What is the difference between an element and a compound in terms of their chemical bonds?

<p>Elements have chemical bonds between same kind of atoms, while compounds have chemical bonds between different kinds of atoms. (D)</p>
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What is the primary characteristic of an element?

<p>It consists of only one kind of atom. (D)</p>
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What is the main difference between an element and a compound?

<p>The type of atoms that make them up. (A)</p>
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What is the role of chemical bonds in a molecule?

<p>They hold the atoms together in a molecule. (C)</p>
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What is the fixed ratio of atoms in a compound?

<p>Fixed and dependent on the type of atoms. (C)</p>
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What is the result of the decomposition of a compound?

<p>A simpler substance is formed. (D)</p>
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What is the characteristic of molecules composed of the same kind of atoms?

<p>They are elements. (D)</p>
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What is the importance of understanding the difference between elements and compounds?

<p>It is essential for studying chemistry. (B)</p>
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What is the main difference between the properties of a compound and its constituent elements?

<p>The compound's properties are different from the individual elements. (D)</p>
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Which of the following molecules is composed of only two atoms?

<p>O2 (A)</p>
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What is the primary role of chemical bonds in a molecule?

<p>To hold atoms together. (D)</p>
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What is the result of the decomposition of H2O?

<p>2H2 + O2 (A)</p>
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What is the purpose of a chemical formula?

<p>To indicate the type and number of atoms in a molecule. (B)</p>
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What occurs during the formation of new chemical bonds in a chemical reaction?

<p>Atoms are rearranged to form new substances. (A)</p>
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What is the role of protons and electrons in the formation of chemical bonds?

<p>The attraction between protons and electrons forms bonds. (D)</p>
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What is a characteristic of a molecule composed of different kinds of atoms?

<p>It is always a compound. (B)</p>
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