Which Freezes Faster? Water or Sugar Water?

Introduction: (Initial Observation)

In winters salt is used to prevent icing and freezing water on the side walks and streets. Salt can melt ice and can prevent or delay freezing of water. Is it possible that sugar also has some similar properties? Is it possible that sugar can also melt ice or prevent icing. To find out the answer, we will perform some experiments and see which one freezes faster? water or sugar water?

Information Gathering:

Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about freezing time and freezing temperature. Keep track of where you got your information from.

Following are samples of information that you may find:

All the materials on earth are in one of the three states – solid, liquid, or gas.
The “state” of the matter refers to the group of matter with the same properties. In other words, you group the objects together according to their properties.

A solid has a certain size and shape.

A liquid doesn’t have a definite shape, but have size or volume. It takes the shape of its container. Liquids can flow, be poured, and spilled.

A gas is matter that has no shape or size of its own. Gases are all around you. You can feel gas when the wind blows. The wind is moving air. Air is many gases mixed together.

The state of a matter depends on the temperature. In very low temperatures all materials become solid. In very high temperatures all materials become gas. We often think of the state of a matter at room temperature. So if we say water is a liquid, we simply mean that water is a liquid at room temperature.

When the temperature decreases, maters may change their state from gas to liquid or from liquid to solid.

Changing the state of a matter from liquid to solid is called freezing. Pure water freezes at 0º Celsius (32º Fahrenheit). This temperature is also known as freezing point of water. 

Freezing Point Depression in Solutions

The freezing point of pure water is 0°C, but that melting point can be depressed by the adding of a solvent such as a salt. The use of ordinary salt (sodium chloride) on icy roads in the winter helps to melt the ice from the roads by lowering the melting point of the ice. A solution typically has a measurably lower melting point than the pure solvent.

Source…

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this experiment is to see which one freezes faster, water or sugar water?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

In this project you are studying the effect of sugar concentration on freezing point or freezing temperature of water. You may measure the freezing time instead of the freezing temperature with similar results. In other words the solutions that freeze faster (less time) have a higher freezing point. (Note that -2ºC is higher than -5ºC).

Independent variable also known as manipulated variable is the sugar concentration (percent of sugar in water or relative concentration of none, low and high).

Dependent variable is the freezing temperature or freezing time of the solution.

Controlled variables (constants) are all experiment procedures and other factors that may affect the freezing time such as:

1. Containers used for freezing experiments (size and material)
2. Amount of liquid (sugar solution) in each container
3. Freezer (Freezing temperature)

Hypothesis:

Based on your gathered information, make an educated guess about which one freezes faster? Water or sugar water?

A sample Hypothesis:

I believe, by adding sugar to the water, we will slow down freezing. My hypothesis is based on my previous observations that salt can melt ice and snow and prevents forming ice on the sidewalks in winters. I think sugar will have a similar affect.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Introduction:

Perform an experiment to test which one freezes faster, water or sugar water.

Procedure:

Put a bowl on the counter and measure exactly one-quarter cup of water and pour the water into into a plastic cup. Fill up 6 cups in this way. All pouring and measuring should be done over the bowl to catch any excess waters.

It does not matter if you do your experiment with one quarter cup or more. What matters is that all cups must have the same amount of water.

Mark two cups as “water”. Add one teaspoon sugar each to two other cups and mark them as ” Low Sugar”. Add two teaspoon sugar each to the last two cups and mark them as “High sugar”. Stir the sugar until it is fully dissolved in water.

To do this experiment precisely you need to make sure that all your test samples (water and water sugar), are at the same temperature. To do this, place them into the refrigerator for a long period of time before continuing this experiment. Also, at this time set the freezer to the desired temperature and do not change it until the experiment is done. I recommend to turn it as high as possible.

Then, place all 6 cups in your freezer equidistant from the freezer cooling radiators. Check every five minutes until you notice that they are starting to freeze. Now, check every minute. Once fully frozen, remove from freezer and record time immediately so you don’t forget it. Record the results in a table like this:

Note: This experiment is modified so it can be performed at home without any need to additional materials. What sugar really does is not delay in freezing. Instead sugar will drop the freezing point (freezing temperature). Pure water freezes at 0º Celsius, but when you add sugar to that, it will freeze at lower temperatures such as -5º C or -8ºC. Original version of this experiment required students to have a thermometer and measure the temperature when the solution starts to freeze. In this case what you record is not the time, it is the temperature.

The experiment in its current format is based on an assumption that it will take more time for a solution to drop its temperature to 0ºC than dropping it to -5ºC.

This method often works well for young students who don’t have access to laboratory thermometers.

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Materials and Equipment:

1 Large Bowl

1 1/8 Measuring Cup

1 ¼ Measuring Cup

1 Gallon of Water

6 Identical Containers such as plastic cups

Supply of Sugar

1 Freezer

1 Refrigerator

Cleaning Tools (Towel, Soap, etc.)

Results of Experiment (Observation):

Measuring- All of the test samples will be a quarter of a cup. They will all be placed in identical containers and will be placed equidistant from the cooling source inside the freezer. The time the waters take to freeze will be measured in minutes.

Data- The times that it took for all samples to start freezing and freeze completely is in this table.

Since we used two samples for each test we need to calculate the average of the results of each two identical sample. We write the average in a table like this and use that to draw a graph.

All of the freezing times were higher after adding sugar. In this experiment the amount of sugar was my independent variable. The dependent variable in my experiment was the freezing time. The sugar increased the freezing time. The graph below shows visually the time difference. (This graph is just a model and is not made based on real data. You need to do your own experiment and come up with real data)

Calculations:

In order to calculate the averages, we add two results and divide it by two. For example if one of the low sugar water samples froze in 27 minutes and the other froze in 29 minutes, add them up it becomes 56, then divide it by two the final result is 28.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

This is a sample conclusion:

From this experiment I conclude that sugar does indeed slow down the freezing process. All the data in the above table and graphs show this. By studying the freezing times I have determined that my predictions about the effect of sugar in freezing of water must be correct and my hypothesis is supported from all the data and observations. Although most of my predictions were only inferences, I still believe them to be correct because they are supported by the data.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

Visit your local library and find books related to water, water chemistry, general chemistry and chemical physics. Look for chapters that discuss the freezing point of water. List such books in your bibliography. Also list any electronic or online references that you may have used.

Following is a sample:

Salt and the freezing point of water

Water Science for Schools

Water Chemistry

Water Chemistry

y Vernon L. Snoeyink, David Jenkins (Hardcover – April 3, 1980)

Water Chemistry

by Mark M Benjamin (Hardcover – March 15, 2001)

Question: what would make you want to know which one freezes faster?

Answer: Water expands when it freezes and its expansion can crack the tanks, pipes and other containers of water. By adding some chemicals to water we can prevent, slow down or delay the freezing at certain low temperatures and prevent such damages. Chemicals like salt and sugar act as anti-freeze. By knowing which anti-freeze is better, we can ensure that we are lowering the risk of such damages.