Name: Neel Hingorani
Class: ISP3B
Date: 21st March 2023
Title: An experiment to find out the effect of impurities (salt solution: 0ml, 2ml, 4ml, 6ml and
8ml) on the melting point of ice, as determined by calculating the time taken (mins) for the
ice to melt at room temperature (°C) - case study of pink salt.
Background:
Melting point is the temperature at which a substance changes from a solid to a liquid state. A
compound’s melting point is determined by the force of attraction between molecules and
symmetry. The higher the intermolecular forces between molecules, the higher will be the
melting point. Melting points are usually affected by many factors, such as impurities.
Impurities refer to a chemical substance inside a confined chemical phase which differs from
the chemical composition of that phase. In this investigation we intend to find out the effect
of impurities (salt solution: 0ml, 2ml, 4ml, 6ml and 8ml) on the melting point of ice. This is
determined by calculating the time taken for the ice to completely turn into a liquid or melt.
To perform this investigation or experiment, we needed a substance to add to the water (ice)
to make it more impure, in this case we used a solution of pink salt (contains: iron, zinc, and
calcium etc.....). Salt is a chemical compound consisting of an ionic assembly of positively
charged cations and negatively charged anions. To test this out, we had put pink salt into
water using a spatula, once it had evenly distributed in the water to form a solution, we then
put a certain amount of that solution into a relative quantity of water using a syringe so that it
adds up to 10ml and froze it, Once it has been solidified, we put it out in room temperature
for it to melt, throughout the melting process, time is taken into consideration and the
investigation is repeated to avoid possible false results.
1
Aim: To find out the effect of impurities (salt solution: 0ml, 2ml, 4ml, 6ml and 8ml) on the
melting point of ice, as determined by calculating the time taken (mins) for the ice to melt at
room temperature (°C).
Research question: What is the effect of impurities (salt solution: 0ml, 2ml, 4ml, 6ml and
8ml) on the melting point of ice, as determined by calculating the time taken (mins) for the
ice to melt at room temperature?
Hypothesis: I predict that ice cubes with higher impurity (salt solution) will have a higher
melting point (as determined by a longer time taken for the ice cube to melt in mins), this is
because, as the ice cubes become more impure (salt solution) there will be more particles at a
given volume, making the ice cube to absorb more thermal energy for it to turn into liquid,
therefore taking a longer time to completely melt.
Requirements:
 Water
 Pink salt (powdered form)
 Refrigerator (LG)
 Ice box
 Spatula
 Phone stopwatch (Samsung Galaxy A51)
 Syringe
Tables of variables:
Types of variables
Independent variable
Method of justification
 The quantity of impurity used (salt
solution: 2ml, 4ml, 6ml and 8ml)
2
Justification
These are variables
that constantly
changes in the
experiment to find its
effect on another
variable, in this case it
is the quantity of salt
solution used that we
change each trial.
Dependent variable
 The time taken for the ice cube to
melt in mins (the melting point)
These are variables
that hugely rely on the
independent variable,
meaning as the
quantity of impurity is
changed, it also has
effects on the melting
point (time taken to
melt/mins).
Constant variable
 The temperature of the place.
These are variables
 The amount of water (10 ml).
that are kept the same
 The type of stopwatch used.
throughout the
 The type of salt used to make the
investigation inorder
solution.
to avoid false and
 The type of water used.
inaccurate results, in
 The type of refrigerator used to
this case:
solidify the water.
 The Shape of the ice cube / cm2
3
-
The amount of
water was the
 The position (Surface area) of the ice
same, since
cube
different
quantities of
water, will
take uneven
time to melt.
-
The position
of the ice cube
was the same,
so as to avoid
one cube from
being exposed
to more heat.
-
The type of
salt and water
was the same
as not all
waters and
salts have the
same chemical
component.
-
The shape of
the ice is kept
the same to
avoid any
4
changes in the
lattice
structure.
Etc.….
Set up / design:
Spatula
Water
Salt
Stopwatch (Samsung
galaxy A51)
Syringe
5
Procedure:
1. Firstly, you will have to make a salt solution, by putting pink salt using a spatula into
water and mixing it till the salt is evenly distributed, so you can use it as your
impurity.
2. Once its evenly spread, put different quantities of your impurity using a syringe (salt
solution: 0ml, 2ml, 4ml, 6m and 8ml) into the relative amount of water so the total
solution adds up to 10ml.
3. Thirdly, put it in an ice box and let it freeze for at least an hour.
4. Once you take it out, immediately start the stopwatch till the ice melts completely.
5. Repeat each solution at least two times.
Results and table:
 Calculation: To calculate the average time taken for the ice to melt / mins, we used
the method below. (N.B: This applies to all the quantities of impurities in ml / salt
solution).
To show this we used the result for 2ml of salt solution (impurity):
1st Trial = 50.38 mins
2nd trial = 55.28 mins
Average = (1st Trial + 2nd Trial) ÷ 2 = (50.38+55.28) ÷ 2 = 105.66 ÷ 2 = 52.83 minutes
6
 Data collection:
The quantity of impurity in a 10ml ice cube
The melting point (time taken /
(salt solution / ml)
mins)
1st Trial
2nd Trial
Average
0
53.61
52.34
52.98
2
50.38
55.28
52.83
4
44.58
48.38
46.48
6
42.52
49.15
45.84
8
39.24
39.48
39.36
 Graph: The line graph is the best option because the data above is only discrete or
only involves numbers in both the x and y axis.
The melting point (time taken / mins)
A graph that shows the melting point of ice cubes (time taken to
melt / mins) against the quantity of impurity (Salt solution) in a
10ml ice cube /ml
56
52,98
52,83
51
46,48
45,84
46
39,36
41
36
0
2
4
6
The quantity of impurity in a 10ml ice cube (salt solution / ml)
7
8
Discussion:
According to the results, it shows a decreasing trend. The reason for this depression of the
melting point of ice (less time taken to melt / mins) occurs due to the existence of the solid
state of a substance. Many of the solids, such as ice, form crystalline ions or molecular
repeating lattices. This lattice is kept together by intermolecular forces which create a strong,
stable structure. The presence or introduction of impurities therefore weakens the lattice,
rendering it less stable. The compound then melts at a lower temperature, making it melt
quicker.
Conclusion:
According to our results and facts, the hypothesis made was wrong. Instead, as the impurity
(salt solution: 0ml, 2ml, 4ml,6ml and 8ml) of ice cubes increase, the melting point (time
taken to melt / mins) of ice cubes decreases, which can be seen from our results: between 0ml
to 2ml of impurity (salt solution), the melting point (time taken to melt / mins) slowly
decreases from 52.98 minutes to 52.83 minutes. Between 2ml to 4ml of impurity (salt
solution), the melting point (time taken to melt / mins) decreases very quickly from 52.83
minutes to 46.48 minutes. Between 4ml to 6ml of impurity (salt solution), the melting point
(time taken / mins) decreases very slowly from 46.48 minutes to 45.84 minutes and finally
between 6ml to 8ml of impurity (salt solution) drastically decreases from 45.84 minutes to
39.36 minutes. This negative trend is explained by using ideas of lattice structures. Ice which
has a lattice structure gets interrupted by other impurities making the intermolecular forces
weaker and weaker depending on the quantity of impurity used (salt solution: 0ml, 2ml, 4ml,
6ml and 8ml).
Evaluation:
 Risks:
8
 Safety risks:

Someone can accidentally drink the salt solution, thinking its water, which
can affect one’s health.

The salt solution can enter your eyes if your hand touches your eyes and
the salt solution at the same moment, which can make you have eye issues.

Once the ice is melted, some water could leak out / spill onto the floor,
which can make someone slip easily.

If a person is close to salt, he/she can accidentally sniff in salt due to wind
pushing the salt, this can make the person cough, have breathing issues and
nausea.

Once the ice cubes melt, some of the liquid could either spill or leak onto
the floor, if the liquid is next to any electronic device or a source of
electricity, it can conduct electricity and can shock or make objects catch
on fire as its impure, meaning it contains ions which can facilitate
electricity conduction.

The salt solution can pour on someone’s skin and can cause either skin
rashes or allergies.
 Environmental risks:

While throwing the salt solution, it can enter a lake or pond, which can
pollute the water.

The salt solution can kill sea creatures and other animals if dumped in a
sea or a pond.

If you throw the salt solution into the soil, it can make concentrate and
intoxicate the soil, killing many micro-organisms like decomposers and
even small plants.
9
 Safety precautions:

I labelled the containers, so that people don’t accidentally drink them.

I wore masks and googles, to avoid the salt from accidentally entering my
nose and eyes through wind.

I wore gloves and lab jackets, to prevent the salt solution from affecting or
causing irritation.

I made sure electronic devices were kept as far as possible from the set up.

I cleaned the spilled water and salt solution after the experiment.
 Sources of error:

The positions of each ice cube weren’t the same, as more heat was
absorbed than the other since more surface area was exposed.

The methodology that we used to measure the quantity of impurity was
quiet inaccurate.

At the first trial, the containers weren’t labelled, this created confusion.

The syringe wasn’t cleaned after each trial.

I didn’t start the timer immediately when the ice cubes were taken out of
the freezer.

I kept touching the ice while it was cooling to make sure if its already
liquid or not.
 Limitation:

There might be a possibility that rain might have occurred at random
during the experiment, causing a change in the temperature of the place.

Since ice and water are transparent, it was quiet hard to know when the ice
completely melted.

Reaction time of the person start / stop the ice cubes.
10
 Improvements:

By placing the ice cubes at the same position.

By not continuously touching the ice cube.

Using a scale balance to measure the impurity instead of a solution.

By washing every equipment after each trial

Labelling each container to avoid confusion.
 Weaknesses:

Time wasn’t properly managed.

The experiment took too long.

No equipment was given, so there was a financial burden.
 Strengths:

A preliminary experiment was done.

There was enough time.

Most of the safety precautions were taken into consideration.
 Suggestions of new methods:

We could firstly freeze the ice and put a thermometer in place, we add some
amounts of impurities and wait till it reaches your ideal temperature and
calculate the time taken for it to reach that ideal temperature.
Citation (ApA 7):
 Wikipedia contributors. (2023, March 17). ‘Salt (chemistry)’. Wikipedia. Online:
https://en.wikipedia.org/wiki/Salt_(chemistry) . Retrieved March 22, 2023.
 ‘What are the effects of impurities on the melting point and boiling point?’
Do impurities increase. . . (n.d.). Study.com. Online:
https://homework.study.com/explanation/what-are-the-effects-of11
impurities-on-the-melting-point-and-boiling-point-do-impurities-increaseor-decrease-melting-and-boiling-point-why.html . Retrieved March 22, 2023.
 Abdin, A. Y., Yeboah, P., & Jacob, C. (2020). ‘Chemical Impurities: An
Epistemological Riddle with Serious Side Effects. International Journal of
Environmental Research and Public Health, 17(3), 1030’.
https://doi.org/10.3390/ijerph17031030. Retrieved March 22, 2023.
 State the effect of presence of impurity on the melting point of ice. Give one use of
it. (n.d.-d). Online: https://www.vedantu.com/question-answer/state-the-effect-ofpresence-of-impurity-on-the-class-10-physics-cbse-5f1776cdb5f5457bc4319703 .
Retrieved March 22, 2023.
12