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Ions and Conductivity (Adorina Moshava)

Ions and Conductivity

Principle investigated:  Can adding ions to water help conduct electricity?

 

 

Student Prior Knowledge:
  -   An ion is an atom or group of atoms that has become electrically charged.

-         An ionic bond is the attraction between 2 oppositely charged ions.

-         Ionic compounds have a crystal shape, high melting point, and electrical conductivity

 

 

Materials:

1)      250 mL beaker

2)      plastic spoon

3)      water

4)      Sodium Chloride (NaCl a.k.a. table salt)

5)      Light bulb and socket

6)      Wires

7)      1.5 Volt batteries

8)      Two Large nails

 

 

Procedure:

1)       Use a wire to connect the positive terminal of a battery to the light bulb and socket.

2)       Connect a wire to the negative terminal of the battery.

3)       Connect a second battery in sequence using wires.

4)       Pour 150 mL of water (hot if possible) into the 250 mL beaker.

5)       Connect the free ends of wires to two large nails and place them into water close to each other (do NOT allow the nails to touch).

6)       Record results

7)       Place one spoonful of sodium chloride (NaCl) into the water.

8)       Stir until dissolved.

9)       Place the nails into water with sodium chloride close to each other (do NOT allow ends of with nails to touch)

10)  Record results.

11)  Repeat steps 7-10.

 

 

Data:

# of Spoonfuls of Sodium Chloride

Conduct Electricity (y/n)

Water + 0

 

Water + 1

 

Water + 2

 

Water + 3

 

Water + 4

 

Water + 5

 

 

Explanation:

·        The pure water does not conduct an electric current. However, the solution of salt water conducts an electric current, so the bulb lights up.

·        The solution that forms when an ionic compound dissolves in water can conduct an electric current because the ions are charged and are able to move freely past one another.

 

Questions:

 

1)    What do you think happens if we replace the salt with sugar? Why?

2)    Explain the property of salt in terms of chemical bond, melting point, and solubility?

3)    Under what conditions are particles of covalent compound and ionic compounds formed?

 

Answers:

1)    Solution of sugar, a covalent compound and water does not conduct an electric current because the molecules of sugar are not charged.

 

2)    Sodium chloride crystals have a regular cubic shape because of the way sodium and chloride ions are arranged in the crystal lattice. Because of strong bonds that hold ions together, ionic compounds have high melting points. Many ionic compounds are highly soluble in water. Water molecules attract each of the ions of an ionic compound and pull the ions away from one another.

 

 

3)     Ionic compounds are formed by strong attractive force of metals with nonmetals. Covalent compounds are formed when two or more atoms share electrons.

 

 

CA- California K-12 Academic Content Standards

Subject : Science

Grade : Grade Eight

Area : Focus on Physical Science

Sub-Strand : Structure of Matter

Concept 3: Each of the more than 100 elements of matter has distinct properties and a distinct atomic structure. ...

Standard b: Students know that compounds are formed by combining two or more different elements and that compounds ...

Standard c: Students know atoms and molecules form solids by building up repeating patterns, such as the crystal ...

Sub-Strand : Periodic Table

Concept 7: The organization of the periodic table is based on the properties of the elements and reflects the ...

Standard c: Students know substances can be classified by their properties, including their melting temperature, ...

 

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