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Lesson 7 Properties of Ionic and Molecular Compounds

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Course: Science 10 [5 cr] - AB Ed copy 1
Book: Lesson 7 Properties of Ionic and Molecular Compounds
Printed by: Guest user
Date: Sunday, 7 September 2025, 6:45 PM

Table of contents

Introduction

How can we identify ionic, molecular, acidic, and basic compounds in the lab?



B7.1 Chemist analyzing substance in a test tube
Imagine that law enforcement makes a raid on a known drug den and confiscates a white powder. What is the identity of that white powder? Is it an illicit substance or a common household material? Using properties of compounds can be helpful for identification purposes.

  Targets

By the end of this lesson, you will be able to

  • identify the properties of ionic compounds
  • identify the properties of molecular compounds
  • identify the properties of acidic compounds
  • identify the properties of basic compounds
  • predict the solubility of ionic compounds using the solubility table
  • relate the unique properties of water to its structure

  Watch This

Electrolytes @ YouTube CPDEatUCO 


This video will introduce you to one property that is very important in your study of ionic and molecular compounds: conductivity. This will help get you in the right mindset for this lesson.

  Properties of Ionic and Molecular Compounds

Did you know that it is not water that is responsible for conducting electricity but the substances that are dissolved in it?


B7.2 Hair dryer in a bathtub
Recall that ionic compounds are composed of ions whereas molecular compounds are composed of individual molecules. It is the underlying structures of these compounds that give them their unique characteristics. Using these unique characteristics, you will be able to distinguish between samples of ionic compounds from samples of molecular compounds.

Here is a comparison of some of the key properties of ionic compounds and molecular compounds.

Ionic Molecular
  • solid at room temperature
  • high melting and boiling points
  • hard
  • brittle
  • conduct electricity when liquid or dissolved in water
  • a variety of colours
  • insulators when solid
  • solid, liquid, or gas at room temperature
  • relatively low melting and boiling points
  • softer
  • more flexible
  • do not conduct electricity when liquid or dissolved in water
  • mostly colourless or white
  • more flammable

  Digging Deeper

© Wikimedia Commons
B7.6 Neuron

Electrolytes are essential in the human body.  One process that they are required for is to help the transmittance of nerve signals.

The characteristic properties of ionic compounds are a result of the strong, rigid, directional bonds formed between cations and anions in the crystal lattice structure and the ability of the ions to separate into individual species when the substance melts or is dissolved in water.

  Watch This

Properties of Ionic Substances @ YouTube FuseSchool – Global Education  


Watch this video to see how ionic properties are related to the crystal lattice structure.

 

  Properties of Ionic and Molecular Compounds Continued


Let’s look more closely at why ionic compounds conduct electricity when they are melted or dissolved in water and why molecular compounds do not.

B7.3 Solution not conducting because there are just neutral water molecules
B7.4 Solution conducting because of free floating ions
B7.5 Solution not conducting because there are just neutral water molecules and other neutral molecules present
Water does not conduct because it does not contain charged particles. Ionic compounds dissociate (break apart into ions) when they dissolve in water. These charged particles (ions) provide a pathway to conduct electricity. Molecular compounds do not create ions in solution because the atoms of the molecules stay bonded together. When molecular compounds dissolve, they created neutral molecules, so there is no pathway for electricity to flow.

  Watch This

Molten Salt (NaCl) Conducts Electricity @ YouTube BerkeleyChemDemos 


Watch this video to see how conductivity is affected when table salt (sodium chloride) melts.

  Virtual Lab

Conductivity/Solubility of Solids/Solutions @ YouTube BerkeleyChemDemos


Please watch this video. Conductivity is tested for several solids. Then the conductivity is tested again when the substance is put in water. 


Click the procedure tab to continue.

  1. Make a copy of the data table in your notebook.
  2. Based on the chemical formula of each substance, identify the type of substance.
  3. Click on the play icon to open the virtual lab video.
  4. Pause the video to record your observations as each substance is tested.
  5. Click on the analysis tab to complete the analysis questions.

Substance Type of Substance
 Conductivity As
a Solid
 Conductivity When
Put In Water
H2O
Al
C12H22O11
NaCl
SiO2
[CH2]n
C2H6O
Cu
CaCl2
CuSO4



    Substance Type of Substance
    		 Conductivity As
    a Solid
    		 Conductivity When
    Put In Water
    H2O
    		 molecular no
    Al metal yes no
    C12H22O11 molecular no no
    NaCl ionic no yes
    SiO2 molecular no no
    [CH2]n molecular no no
    C2H6O molecular no no
    Cu metal yes no
    CaCl2 ionic no yes
    CuSO4 ionic no yes

  1. What type of substance conducts electricity as a solid?

  2. What type of substance conducts electricity as a solution?

    ionic compounds
  3. What type of substance does not conduct electricity as a solid no a solution?

    molecular compounds


  Read This

Please read pages 51 to 55 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the properties of ionic compounds. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions

Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. Based on the properties for each of the substances listed, identify if it would be ionic or molecular.

    1. This substance melts at 800 °C, has a pink colour, and is a hard crystal.

    2. This substance is a liquid at room temperature and is flammable.

      molecular
    3. This substance is an easily crushed white solid that melts at 48 °C.

      molecular
Use the following diagrams to answer the next question.

A B
B7.7 Solution that lights up a light bulb
B7.8 Solution that does not light up a light bulb

  1. Identify the results—A or B—that would be expected if each of the following solutions was tested.

    Solution Result
    LiF(aq)
    C6H12O6
    NH4Cl(aq)

    Solution Result Explanation
    LiF(aq) A Li is a metal and F is a non-metal, so this is an ionic compound that will produce a conducting solution.
    C6H12O6 B C, H, and O are all non-metals, so this is a molecular compound that will produce a solution that does not conduct electricity.
    NH4Cl(aq) A NH4 is a polyatomic cation and Cl is a non-metal, so this is an ionic compound that will produce a conducting solution.

  Solubility of Ionic Compounds

Barium ions are toxic, yet are taken internally by patients to provide contrast for x-ray diagnosis of gastrointestinal problems. How is that possible?


B7.9 X-ray with barium contrast
Some ionic compounds are very soluble, which means they will dissolve in water to form aqueous solutions. These substances will be identified with the state written as “(aq).” Other ionic compounds are only slightly soluble, which means that relatively few ions will dissolve in water. These compound states are written as “(s).” Doctors use barium sulfate (BaSO4(s)) to provide the contrast for X-rays. Barium sulfate is only slightly soluble, and thus barium ions (the toxic part) remain bound in the compound and are not absorbed into the body.

Please note that the solubility table in your textbook is outdated. Only use the solubility table in your data booklet to answer questions in this course.
B7.10 Solubility table

  Digging Deeper

© Wikimedia Commons
B7.10 Precipitate in a test tube

Understanding the solubility table will help you predict precipitates that will be formed during a chemical reaction.




Follow these steps to determine the solubility of an ionic compound:

  1. Identify if the cation is from group 1 or is the ammonium ion. If it is either, the compound will most likely be very soluble, (aq).
  2. If the compound does not contain a group 1 or ammonium cation, locate the anion across the top of the solubility table.
  3. Locate the cation in the column below the anion.
  4. If the cation is in the first row, the substance will be very soluble and form an aqueous solution, (aq).
  5. If the cation is in the second row, the substance will be slightly soluble and will be identified as having a solid state, (s).

Examples

Determine the solubility and the state for each of the following ionic compounds when they are placed in a beaker of water. Each example has a video to go with it. To play the video, click on the play icon next to the example.

Identify the cation. If it is from group 1 or is the ammonium ion, then the compound will most likely be very soluble and will be (aq).

Ba is not in group 1.
If the cation is not from group 1 nor is it the ammonium ion, then locate the anion across the top.

Locate the cation in the column below the anion. If it is in the first row, the substance will be very soluble, (aq); if it is in the second row, the substance will be slightly soluble, (s).

Record the answer.

slightly soluble
BaSO4(s)

Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/in06sfv4t4
 

Identify the cation. If it is from group 1 or is the ammonium ion, then the compound will most likely be very soluble and will be (aq).

Li is in group 1.
Record the answer.

very soluble
Li2CO3(aq)

Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/klor3z6cao
 

Identify the cation. If it is from group 1 or is the ammonium ion, then the compound will most likely be very soluble and will be (aq).

Fe is not in group 1.
If the cation is not from group 1 nor is it the ammonium ion, then locate the anion across the top.

Locate the cation in the column below the anion. If it is in the first row, the substance will be very soluble, (aq); if it is in the second row, the substance will be slightly soluble, (s).

Record the answer.

very soluble
FeF3(aq)

Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/in06sfv4t4
 

Identify the cation. If it is from group 1 or is the ammonium ion, then the compound will most likely be very soluble and will be (aq).

Fe is not in group 1.
If the cation is not from group 1 nor is it the ammonium ion, then locate the anion across the top.

Locate the cation in the column below the anion. If it is in the first row, the substance will be very soluble, (aq); if it is in the second row the substance will be slightly soluble, (s).

Record the answer.

very soluble
Fe2(SO4)3(aq)

Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/4x0aeej9ig
 
Identify the cation. If it is from group 1 or is the ammonium ion, then the compound will most likely be very soluble and will be (aq).

Ca is not in group 1.
If the cation is not from group 1 nor is it the ammonium ion, then locate the anion across the top.

Locate the cation in the column below the anion. If it is in the first row, the substance will be very soluble, (aq); if it is in the second row, the substance will be slightly soluble, (s).

Record the answer.

slightly soluble
Ca(OH)2(s)

Watch this video to see a teacher work through this example.  https://adlc.wistia.com/medias/jw7lqmxh8h
 

  Read This

Please read pages 57 and 58 in your Science 10 textbook. Please note that the solubility table in your textbook is outdated. Only use the solubility table in your data booklet to answer questions in this course. Make sure you take notes on your readings to study from later. You should focus on using a solubility table to determine whether an ionic compound will be slightly soluble or very soluble. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions

Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. Identify if the following ionic compounds will be very soluble or slightly soluble in water.

    Substance Solubility
    AgCl
    KMnO4
    Cu3(PO4)2
    CO(IO3)2

    Substance Solubility
    AgCl slightly
    KMnO4 very
    Cu3(PO4)2 slightly
    CO(IO3)2 very

  2. Identify the state (s or aq) for each of the following substances when they are placed in water.


    Substance State
    K2Cr2O7
    CrBr3
    Al2(SO3)3
    ZN(IO3)2

    Substance State
    K2Cr2O7
    		 (aq)
    CrBr3 (aq)
    Al2(SO3)3 (s)
    ZN(IO3)2 (s)



  Special Properties of Water

Did you know that water is called the universal solvent?


B7.12 Various solutions
Water is a very special compound with a unique set of properties. The properties result from the bonding and structure of the water molecule. The term “universal solvent” means that water has the ability to dissolve many different types of substances.


© Wikimedia Commons
B7.13 Water molecule

  Did You Know?


B7.17 Spring turnover in a lake

Did you know that water is its most dense at 4 °C. This important property accounts for the fall and spring turnover in lakes that keeps lakes from becoming stagnant or freezing solid. As surface water reaches 4 °C, it becomes denser and sinks.

© Wikimedia Commons
B7.14 Water molecule with charges
Water is a molecular compound and has covalent bonds in which electrons are shared between the oxygen atom and the hydrogen atoms. These electrons are not shared equally; the oxygen has a stronger pull on the electrons and holds them closer to its nucleus.

Since the electrons are closer to the oxygen, the oxygen will be slightly negative (because electrons are negative) and the hydrogen atoms will be slightly positive.

This uneven sharing results in water being a polar molecule. These charges result in attraction between water molecules. Forces of attraction between molecules are called intermolecular forces. Specifically, for water, these are called hydrogen bonds. The polar ends of water will also cause attraction to other charged particles.


© Wikimedia Commons
B7.15 several water molecules attracted to each other


In addition to water’s ability to dissolve both ionic and other polar molecules, there are several other properties that are a result of water’s polar structure.

The electrostatic attraction (attraction between positive and negative charges) between water molecules is strong, so it takes a lot of energy to move the water molecules apart (which is what melting and boiling essentially is).
When water molecules bond together to form ice, they form in a hexagonal pattern (so that there is a maximum number of positive and negative interactions between water molecules). This creates a six-sided solid structure in which water molecules are farther apart than in the liquid form, causing water to be less dense as a solid.


© Wikimedia Commons
B7.16 Ice crystals forming


Increasing temperature means that particles move more. It takes a lot of energy to raise the temperature of water because of the strong attraction between molecules holding them in place.
Water molecules are strongly attracted to each other (aides in the transport of water in plants).
Water molecules are strongly attracted to other particles (aides in the transport of minerals in plants).
The attraction between water molecules at the surface of a liquid causes them to stick together and create a “film” on the surface that allows insects to walk on water.

  Watch This

Why Does Ice Float in Water @ YouTube TED-Ed  


Watch this video that will go over some unique properties of water.


  Read This

Please read pages 60 and 61 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the structure and properties of water. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions

Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. What is a polar molecule? Provide an example.

    A polar molecule is a neutral molecule that has partial charges on atoms due to uneven electron sharing. Water is a polar molecule.


    B7. 18 Polar water molecule


  2. Using your own words, explain why water has high melting and boiling points.

    Because water molecules are polar, they form strong attractions between neighbouring molecules. It takes a lot of energy to break these forces of attraction and move the molecules farther apart.


    B7.19 Attraction between two water molecules





  Properties of Acids and Bases

Did you know that citrus fruits taste sour because of their acidic content?


B7.20 Girl eating a lemon
You already learned how to recognize that a substance is an acid or a base by analyzing its chemical formula. In acid formulas, “H” is written first (e.g., HCl and H2SO4) or ends with “COOH” (e.g., CH3COOH). In bases, the formula is a metal bonded to hydroxide (e.g., NaOH and LiOH). In addition to recognizing formulas as acidic or basic, you also need to be able to distinguish between acids, bases, and neutral compounds by observing their properties.

Here is a table that compares the properties of acids to bases.

Properties of Acids
 Properties of Bases
  • taste sour
  • is corrosive
  • turn blue litmus red
  • pH below 7
  • conduct electricity
  • react with active metals to produce hydrogen gas
  • taste bitter
  • feel slippery
  • turn red litmus blue
  • pH above 7
  • conduct electricity

Note: Even though taste is a characteristic property of acids and bases, this should not be used as an analysis technique in laboratory settings! The same goes for touching a solution to determine if it is slippery.

  Did You Know?


© Wikimedia Commons
B7.21 Detergent pod

Manufactures put certain chemicals with bitter tastes (bases) into items that they do not want people to ingest? One such additive is denatonium benzoate. This substance is a base and is classified as one of the bitterest substances in the world. It is added to rat poison, antifreeze, and even detergent pods in the hopes that if a human accidently ingests one of these toxic substances, they will immediately spit it out. https://letstalkscience.ca/Explore/ArticleId/6171/dont-eat-laundry-pods.aspx

Learn More

  Virtual Lab

Mystery Powder Analysis @ Explore Learning
Please work through this lab to identify unknown substances as acidic, basic, or neutral based on their properties.

Please click on the procedure tab to continue. 

Please note: if you scroll down while in the Gizmo you will see a list of questions. You DO NOT need to complete these questions. You are able to complete them for extra practice if you would like.

  1. Click on the play icon to open the virtual lab. The virtual lab can also be accessed by going to the Online Resources for Print Students section in your online course.
  2. In your notebook, create a data table similar to the one found below. 
  3. Set “Select a sample” to “Unknown”:  .
  4. Drag sample 1 to “Place tube here.”
  5. Click “Test” at the bottom of “Litmus test.”
  6. Record the results.
  7. Click “Reset.”
  8. Repeat steps 4 to 7 for unknown samples 2 and 5.
  9. Click on the analysis tab to complete the analysis questions.

Sample
 Litmus Test Results
Red Litmus
 Blue Litmus
1
2
5

    Sample
    		 Litmus Test Results
    Red Litmus
    		 Blue Litmus
    1 red blue
    2 blue blue
    5 red red

  1. Classify each unknown as acidic, basic, or neutral.

    Sample 1—neutral
    Sample 2—basic
    Sample 5—acidic
Remember that acids turn blue litmus red, bases turn red litmus blue, and neutral substances do not affect litmus paper.

  1. Identify which sample would most likely contain the following substances: HOOCCOOH, LiOH, KNO3.

    Sample 1—KNO3
    Sample 2—LiOH
    Sample 5—HOOCCOOH

  Read This

Please read pages 62 to 68 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on identifying substances as acidic, basic, or neutral based on their properties. Remember, if you have any questions or you do not understand something, ask your teacher!

  Practice Questions

Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.

  1. Based on the following observations, classify each substance as acidic, basic, or neutral.

    Observed Properties
    		 Classification
    conducts electricity and tastes sour
    conducts electricity and has a pH of 10
    produces bubbles when mixed with magnesium metal and turns blue litmus red
    causes red litmus to stay red and has a pH of 7
    feels slippery and tastes bitter

    Observed Properties
    		 Classification
    conducts electricity and tastes sour acidic
    conducts electricity and has a pH of 10 basic
    produces bubbles when mixed with magnesium metal and turns blue litmus red acidic
    causes red litmus to stay red and has a pH of 7 neutral
    feels slippery and tastes bitter basic


  Lesson 7 Conclusion

Did you know that the RCMP only has three forensic labs in all of Canada and one is located in Edmonton?


B7.22 Vial of unknown powder
Understanding simple tests to help determine the identity of an unknown substance is crucial in forensic investigations.

In this lesson, you learned how to identify ionic, molecular, acidic, and basic compounds based on their properties. You also learned how to predict the solubility of ionic compounds. As well, you studied the special properties of water that are related to its bonding.

  Problem Solving Activity

Mystery Solution Analysis
In this activity, you are going to take the information you have learned about the properties of ionic, molecular, acidic, and basic compounds and use it to identify four unlabelled containers. Each beaker contains a clear solution. Using litmus paper and a conductivity apparatus, determine which beaker contains each of the following substances: calcium bromide, methanol, hydrofluoric acid, and potassium hydroxide.

Click on the data tab to continue.
Unknown
Conductivity Results
Litmus Results
1
2
3
4

Click on the analysis tab to answer the analysis questions.
  1. Write the chemical formula for each of the compounds.

    calcium bromide—CaBr2
    methanol—CH3OH
    hydrofluoric acid—HF
    potassium hydroxide—KOH
  2. Based on the chemical formula, classify each of the compounds as being ionic neutral, molecular neutral, acidic, or basic.

    calcium bromide—ionic neutral
    methanol—molecular neutral
    hydrofluoric acid—acidic
    potassium hydroxide—basic
  3. Based on the data and the classifications in question 2, match each chemical compound with its correct unknown sample.

    calcium bromide—3
    methanol—2
    hydrofluoric acid—1
    potassium hydroxide—4




2.4 Assignment

Unit B Assignment Lessons 5-8

It is now time to complete the Lesson 7 portion of 2.4 Assignment. This assignment has two parts.

  1. Part 1 Written Portion: Select the preferred document type from the options below. Download and save the assignment on your desktop (or documents folder).

    PDF Document       
  2. Open and print this saved document.
  3. Record your responses in the appropriate textboxes.
  4. When you have completed the assignment, scan it and save it on your desktop (or documents folder).
  5. Once you have completed the written portion of your assignment, click on the button below to go to the submission page.

    Written Portion Submission Page
  6. Part 2 Online Portion: It is now time to complete the Lesson 5 questions of the online portion of this assignment. Click on the button below to go to the online questions of this assignment.

    Online Questions

This assignment is worth ___% of your final grade.