High School Chemistry: Solutions - Electrolytes vs., Nonelectrolytes Conductivity, Salt vs. Sugar Water

1. What This Is (In Plain English)

Electrolytes vs Nonelectrolytes: This is the difference between two types of substances that can dissolve in water, but one type makes the water conduct electricity and the other doesn't.

In real life, this matters because it helps us understand how our bodies work. Electrolytes are essential for our bodies to function properly, especially when it comes to nerve and muscle function. Without electrolytes, our bodies wouldn't be able to send signals to our muscles to move, and we wouldn't be able to think clearly. This is why it's so important to drink electrolyte-rich beverages, like sports drinks, when we're exercising or sweating a lot.

2. Key Ideas & Definitions

• Electrolyte: A substance that breaks down into charged particles (ions) when dissolved in water, allowing the water to conduct electricity.
  • Example: Salt (sodium chloride) is an electrolyte because it breaks down into positively charged sodium ions and negatively charged chloride ions when dissolved in water.
• Nonelectrolyte: A substance that doesn't break down into charged particles when dissolved in water, so the water can't conduct electricity.
  • Example: Sugar (sucrose) is a nonelectrolyte because it doesn't break down into charged particles when dissolved in water.
• Conductivity: The ability of a substance to conduct electricity.
  • Example: A metal wire is a good conductor of electricity because it allows electrons to flow through it easily.
• Ion: A charged particle that forms when an atom gains or loses electrons.
  • Example: A sodium ion is a positively charged particle that forms when a sodium atom loses an electron.
• Solvent: The substance that dissolves the electrolyte or nonelectrolyte.
  • Example: Water is a solvent because it dissolves electrolytes and nonelectrolytes.
• Solute: The substance that dissolves in the solvent.
  • Example: Salt is a solute because it dissolves in water.
• Dissolve: To break down into smaller particles and mix with another substance.
  • Example: Sugar dissolves in water when you stir it.
• Concentration: The amount of solute dissolved in a solvent.
  • Example: A strong solution of sugar in water has a high concentration of sugar.
• Molarity: A measure of concentration that expresses the number of moles of solute per liter of solvent.
  • Example: A 1 M solution of sugar in water has 1 mole of sugar per liter of water.
• Mole: A unit of measurement that represents 6.022 x 10^23 particles (atoms or molecules).
  • Example: 1 mole of sugar molecules is equal to 6.022 x 10^23 sugar molecules.

3. How To Do It (Step-by-Step)

To determine whether a substance is an electrolyte or nonelectrolyte, you can follow these steps:

1. Dissolve the substance in water: Stir the substance into water until it's fully dissolved.
2. Use a conductivity tester: A conductivity tester is a device that measures the ability of a substance to conduct electricity. You can buy one at a science store or online.
3. Check the reading: If the reading on the conductivity tester is high, the substance is an electrolyte. If the reading is low, the substance is a nonelectrolyte.
4. Check the ions: If the substance breaks down into charged particles (ions) when dissolved in water, it's an electrolyte. If it doesn't break down into ions, it's a nonelectrolyte.
5. Check the concentration: If the substance is highly concentrated, it's more likely to be an electrolyte. If it's highly diluted, it's more likely to be a nonelectrolyte.

4. Watch Out! (Common Mistakes)

• Mistake: Thinking that all substances that dissolve in water are electrolytes.
  • Fix: Remember that some substances, like sugar, don't break down into charged particles when dissolved in water, so they're not electrolytes.
• Mistake: Thinking that all substances that conduct electricity are electrolytes.
  • Fix: Remember that some substances, like metals, conduct electricity because of their structure, not because they're electrolytes.
• Mistake: Not checking the concentration of the substance.
  • Fix: Remember that the concentration of the substance can affect whether it's an electrolyte or nonelectrolyte.

5. Practice Problems

Problem 1: Determine whether the following substances are electrolytes or nonelectrolytes:

• Salt (sodium chloride)
• Sugar (sucrose)
• Water
• Lemon juice

Solution:

• Salt (sodium chloride) is an electrolyte because it breaks down into charged particles (ions) when dissolved in water.
• Sugar (sucrose) is a nonelectrolyte because it doesn't break down into charged particles when dissolved in water.
• Water is a solvent, not an electrolyte or nonelectrolyte.
• Lemon juice is an electrolyte because it contains charged particles (ions) like citrate and hydrogen ions.

Takeaway: Remember that electrolytes break down into charged particles when dissolved in water, while nonelectrolytes don't.

Problem 2: Determine the concentration of a solution of sugar in water that contains 2 moles of sugar per liter of water.

Solution:

• The concentration of the solution is 2 M (moles per liter).
• To find the concentration, we can use the formula: concentration = moles of solute / liters of solvent.
• In this case, the moles of solute (sugar) is 2, and the liters of solvent (water) is 1, so the concentration is 2 M.

6. Cram Sheet

• Electrolyte: A substance that breaks down into charged particles (ions) when dissolved in water.
• Nonelectrolyte: A substance that doesn't break down into charged particles when dissolved in water.
• Conductivity: The ability of a substance to conduct electricity.
• Ion: A charged particle that forms when an atom gains or loses electrons.
• Solvent: The substance that dissolves the electrolyte or nonelectrolyte.
• Solute: The substance that dissolves in the solvent.
• Dissolve: To break down into smaller particles and mix with another substance.
• Concentration: The amount of solute dissolved in a solvent.
• Molarity: A measure of concentration that expresses the number of moles of solute per liter of solvent.
• Mole: A unit of measurement that represents 6.022 x 10^23 particles (atoms or molecules).

7. Where to Learn More

• YouTube: Crash Course Chemistry (hosted by Hank Green) has a great video on electrolytes and nonelectrolytes.
• PhET Simulation: The University of Colorado Boulder's PhET Simulation website has a simulation on electrolytes and nonelectrolytes that you can play with.
• School-friendly website: The Science Buddies website has a great article on electrolytes and nonelectrolytes that you can read.