Available Answers

1. 1.

   Multiple choice questions:

   1. No new substances are formed in a/an __________ change.
      1. atomic
      2. molecular
      3. chemical
      4. physical
   2. Which of the following happens in a chemical change?
      1. Products give rise to reactants.
      2. Reactants give rise to produces.
      3. The number of atoms decreases.
      4. New atoms are formed.
   3. A reactant breaks down to form two or more simpler products in a _________ reaction.
      1. combination
      2. decomposition
      3. rusting
      4. displacement
   4. X and Y are numbers that will balance the following question: XMg + O₂ → YMgO
      What are the values of X and Y?
      1. X:2, Y:1
      2. X:1, Y:1
      3. X:2, Y:2
      4. X:2, Y:3
   5. In the reaction CuSO₄ + Fe → FeSO₄ + Cu, the reactants are ___________.
      1. iron and copper
      2. iron sulphate and copper
      3. copper sulphate and iron
      4. copper sulphate and iron silphate
   6. Which of the following does not happen when copper sulphate solution reacts with iron?
      1. Copper is deposited on the iron.
      2. The solution turns brown.
      3. The solution turns green.
      4. A displacement reaction takes place.
2. 2.

   Fill in the blanks.

   1. Chemical reactions result in the formation of new __________ or the breaking of old ______________.
   2. The number of ___________ remains the same at the end of a chemical reaction.
   3. A chemical change or reaction can be represented by a chemical ______________.
   4. An equation in which the number of atoms of each kind is equal on both sides of the arrow is called a ______________ equation.
   5. The two conditions that are necessary for iron to rust are the presence of _____________ and _______________.
3. 3.

   Match the words in column A with those is column B.

   Column A	Column B
   i. Reactants	a. Formed in a reaction
   ii. Products	b. Layer of iron oxide
   iii. Rust	c. Layer of zinc
   iv. Galvanisation	d. Start a reaction

    

4. 4.

   Say whether the following statements are true or false. Correct the false statements.

   1. The number of atoms of different kinds does not change during a chemical reaction.
   2. A chemical equation can be used to represent a physical change.
   3. To balance an equation, we should change the formulae of molecules.
   4. An element cannot undergo a decomposition reaction.
   5. A combination reaction can happen only between two elements.
5. 5.

   How are new substances formed during a chemical change?

6. 6.

   Define chemical bond.