GRADE 8 SCIENCE
IONIC AND COVALENT COMPOUNDS LAB INVESTIGATION
Background
We know that atoms bond to each other. Scientists have found that there are only three types of
bonds: ionic bonds, covalent bonds, and metallic bonds. If atoms have an ionic bond, the solid
they make is called an ionic compound. If atoms have a covalent bond, the solid they make is
called a covalent compound.
B Research Question
What are the physical properties of ionic compounds and covalent compounds?
C Variables
Experiment
1
Independent Variable
Dependent Variable
Smell
2
Melting point
3
Microscopic structure
4
Hardness
Ionic and covalent
solid
5
Solubility
6
Electrical conductivity
7
Flame test
Constant Variables
Distance from the substance, same
amount, turn of the AC
Same heat, turn of the AC, distance
between the heat and the solid
Same magnification, same microscope,
same amount of the solid
Same amount of the solid, same power to
crush the solid, same spatulas to crush
the solid
Same amount of water, same amount of
solid, same time putting the solid in the
water
Same equipment, same amount of
electricity, same amount of solid
Same heat, turn of the AC, distance
between the heat and the solid
D Hypothesis
If a solid has strong bonds between its atoms, then
 The smell will be weak because a strong bonded solid is not easy to spread its smell comparing
to weak bonds like gases.
 The melting point will be high because strong bonded solid needs higher temperature to break
up into smaller pieces.
 The microscopic structure will be complicated because a strong bonded compound must have a
huge amount of atoms bonded together in a high density.
 The hardness will be strong because if the structure is strong enough, it should be very hard.
 The solubility will be low because strong bonded solid is not easy to break up and dissolve into
water compared to liquid and gases.
 The electrical conductivity will be low because I find water and salt that are weakly bonded goes
pretty well with electricity unlike diamond.
E Equipment and Materials
You will need all of this equipment at one point in the investigation. Collect only the equipment you
need for each new experiment.


Lab coat (to wear throughout the practical investigation)
Safety glasses (to wear when appropriate - you choose when and your teacher will check!)
 Sodium carbonate (ionic compound)
 Naphthalene (covalent compound)
 Pen for labeling glass containers
 2 spatulas
 1 watch glass
 2 test tubes and test tube holder
 2 test tube tongs
 Spirit burner or Bunsen burner
 Stopwatch
 2 microscope slides
F Method and G Diagram
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1 microscope
4 test tubes
Water
2 small glass beakers
1 lamp
1 ammeter
1 battery or power supply pack
3 electrical cables
2 carbon electrodes
2 flame-test-sticks
Experiment 1: Smell
1. Use a spatula to place a sample of each solid on a watch glass.
2. Observe and record your observations.
Experiment 2: Melting Point
1. Put 2 spatulas of each solid in a test tube (use two separate test tubes).
2. Heat each test tube for the same amount of time until one of the solids melts.
3. Continue heating them for three more minutes.
4. Observe and record your observations.
Experiment 3: Microscopic Structure
1. Place a sample of each solid on a microscope slide.
2. View the solid under the microscope
3. Observe and record your observations.
Experiment 4: Hardness
1. Attempt to crush some of each solid on the watch glass using the spatula.
2. Observe and record your observations.
Experiment 5: Mixing with other Liquids
1. Put 2 cm of water (an ionic liquid) into 2 different test tubes.
2. Add a spatula-tip of each solid to separate test tubes (use one test tube for each solid).
3. Observe and record your observations.
4. Put 2 cm of 2-propanol (a covalent liquid) into 2 different test tubes.
5. Add a spatula-tip of each solid to separate test tubes (use one test tube for each solid).
6. Observe and record your observations.
Experiment 6: Electrical Conductivity
1. Construct an electrical conductivity tester similar to the diagram (use a power supply instead of
a battery and add an ammeter in series with the lamp)
2. Half-fill 2 beakers with water
3. Stir a spatula tip full of each solid into separate beakers (use one beaker for each solid).
4. Observe and record your observations.
Experiment 7: Flame Test (Just for Fun! – Not really to do with ionic and covalent solids)
1. Put a small amount of each solid on the flame-test-stick and hold each solid in a flame.
2. Observe and record your observations.
H Observations
Experiment/Substance
Smell
Substance A
Strong odor
Substance B
No smell
Melting point
Very low
Very high
Microscopic structure
Big and separated
Small and almost no
space with others, has
flat surface
Hardness
Easy to crush
Easy to crush
Mixing with other
liquids
With water: Does not
dissolve
With 2-praponal:
Dissolve quickly
With water: Dissolve
quickly
With 2-praponal:
Slightly dissolve
Electrical conductivity
Does not conduct at all
Slightly conductible,
0.2mA
Reaction with fire
Turns into black smoke
Disappears slowly,
nothing happens
Hypothesis
Stronger bonds doesn’t
have strong odor.
Substance B is
considered to be a
strong bond.
Stronger bonds have
higher melting point.
Substance B is
considered to be a
strong bond.
Stronger bonds are
more complicated, and
have less space
between each other.
Substance B is
considered to be a
strong bond.
Stronger bonds are
harder. Both of them
are easy to crush.
Stronger bonds dissolve
slowly in water.
Substance A does not
dissolve at all.
Substance A will be
considered as a strong
bond.
Stronger bonds do not
conduct electricity.
They are both not good
conductors.
--
J Conclusion
Ionic compounds have physical properties such as conductible, hard to crush, high melting
point, high density and dissolvable in water but not with nonpolar liquids, like 2-propanol.
(http://chemistry.about.com/od/moleculescompounds/a/Ionic-Compound-Properties.htm) Covalent
compounds often have the exact opposite physical properties of ionic compounds. As we can see from
the result, Substance A should be a covalent compound and Substance B should be an Ionic
compound. Ionic compounds are usually considered as strong bonds.
My hypothesis was mostly correct, but the dissolubility. I found that ionic compounds dissolve in
polar liquids (liquids that have positive and negative charges) like water, better than nonpolar liquids.
(http://answers.yahoo.com/question/index?qid=20080129135618AANHf0L) This happens because
ionic compounds are attracted to each other with different charges, and we can only separate them by
putting liquids that also have charges to pull them out.
Ionic compounds usually have strong bonds because they are attracted to each other’s charge.
Breaking a strong bond needs a lot of energy, thus ionic compounds have higher melting points. Ionic
compounds are strong and hard to break down into gas form, so we can’t smell much from them.
When Ionic compounds are dissolved, the ions would have space to move and it will often be
conductible. Covalent compounds have all opposite properties and their reasons from Ionic
compounds, as the observation has shown.
L Real Life Application
We often use sodium chloride to preserve food, and it is also an important ingredient that we need to
keep some amount in our body. Calcium chloride is chalk we use for black boards. Water is what all
living creatures need. Diamond is the hardest compound from all, and it is one of the most expensive
jewelries.
M Works Cited
"Isopropyl Alcohol." Wikipedia. Wikimedia Foundation, 02 May 2013. Web. 07 Feb. 2013.
Planeswalker, Mishra. "Common Examples of Ionic Bonds and Bonding." Helium. Helium, 22 Dec. 2009.
Web. 07 Feb. 2013.
"Why Is Water a Polar Molecule?" About.com Chemistry. N.p., n.d. Web. 13 Feb. 2013.
"Ionic Compound Properties." About.com Chemistry. N.p., n.d. Web. 13 Feb. 2013.
"Why Are Ionic Compounds Soluble in Water Whereas Metals and Covalent Compounds Are Insoluble in
Water?" Yahoo! Answers. Yahoo!, n.d. Web. 13 Feb. 2013.
Criterion B: Communication in Science
Student’s Teacher’s
Opinion Decision
SWA MYP Descriptor

0


1–2



3–4



5–6

The student does not reach a
standard described by any of the
descriptors given below.
The student uses a limited range of
scientific language correctly.
The student communicates scientific
information with limited
effectiveness
When appropriate to the task, the
student makes little attempt to
document sources of information.
The student uses some scientific
language correctly.
The student communicates scientific
information with some
effectiveness.
When appropriate to the task, the
student partially documents
sources of information.
The student uses sufficient scientific
language correctly.
The student communicates scientific
information effectively.
When appropriate to the task the
student documents the sources of
information correctly.
Student Self-Assessment
 My work does not match requirements below.
 I used some scientific language.
 For most sections of the lab report I followed
most of the requirements listed on the task
sheet.
 I give some info for some of my sources.
 I used only scientific language.
 For each section of the lab report I followed
most of the requirements listed on the task
sheet.
 Source information is missing making it hard for
the reader to trace my sources
 I used clear, concise, scientific language.
 For each section of the lab report I followed
completely the requirements listed on the task
sheet.
 I correctly cite my sources of information in text
and with a Works Cited list.
Criterion E: Processing Data
Student’s Teacher’s
Opinion Decision
0
SWA MYP Descriptor

The student does not reach a standard
described by any of the descriptors given
below.

My work does not match the
requirements below.

The student collects some data and
attempts to record it in a suitable format.
The student organizes and presents
data using simple numerical or visual
forms.
The student attempts to identify a trend,
pattern or relationship in the data.
The student attempts to draw a conclusion
but this is not consistent with the
interpretation of the data.
The student collects sufficient relevant
data and records it in a suitable format.
The student organizes, transforms and
presents data in numerical and/or visual
forms with some errors or omissions.
The student interprets the data stating a
trend, pattern or relationship in the data.
The student draws a conclusion
consistent with the interpretation of the
data.
The student collects sufficient relevant
data and records it in a suitable format.
The student organizes, transforms and
presents data in numerical and/or visual
forms logically and correctly.
The student correctly interprets the data
stating a trend, pattern or relationship in
the data.
The student draws a clear conclusion
consistent with the correct
interpretation of the data and explains
it using scientific reasoning.

Some of my data is relevant and my
table is partly correct

I tried to make a conclusion.

My data is relevant and recorded in a
suitable way.
I try to organize and process the data.
My conclusion matches the observations.

1–2




3–4




5–6
Student Self-Assessment




 My data is relevant and my presentation
is logical and clear.
 I correctly interpret the data.
 In my conclusion I comment on the
reliability of my data through comparing
my results to what would be expected
from published data.
 I give a scientific explanation of my
conclusion.
Criterion F: Attitudes in Science
Student’s Teacher’s
Opinion Decision
0
1–2
3–4
5–6
SWA MYP Descriptor
 The student does not reach a standard
described by any of the descriptors given
below.
 The student requires some guidance to
work safely and some assistance when
using material and equipment.
 The student requires some guidance to
work responsibly with regard to the living
and non-living environment.
 When working as part of a group, the
student needs frequent reminders to
cooperate with others.
 The student requires little guidance to
work safely and little assistance when
using material and equipment.
 The student works responsibly with
regards to the living and non-living
environment.
 When working as part of a group, the
student cooperates with others on
most occasions.
 The student requires no guidance to
work safely and use materials and
equipment competently.
 The student works responsibly with
regards to the living and non-living
environment.
 When working as part of a group, the
student cooperates with others.
Student Self-Assessment









My work does not reach a standard
described by any of the descriptors
given below.
During the experiment I did not know
what to do.
I forgot safety routines such as wearing
goggles, standing up, etc.
During the experiment I asked
questions even though the answer to
the question was provided in writing
and orally beforehand.
I forgot safety routines such as wearing
goggles, standing up, etc.
I did not ask questions that had already
been answered in writing.
I knew what I was doing in the lab
I included safety precautions in my
report and followed all safety routines
responsibly during the experiment.
I worked well with classmates.