Introduction: (Initial Observation)
Suppose you will be having a party soon and you need to make some ice cubes for the drinks. To make the ice you fill up an ice tray with water and place it in the freezer. In the cold temperature of the freezer, water will freeze and become ice in a few minutes or a few hours. The time that it takes for water to freeze (or become ice) may depend on many different factors.
For example the temperature of the freezer, the size of the freezer, the way that you stack material in the freezer and many other factors may affect the speed of freezing water. In this project we want to see if the temperature of water used to make ice affects the time it takes for water to freeze. Is it better if we fill up our ice trays with cold water or warm water?
Find out about different states of water (Solid, liquid, gas) and how water will transform from one state to the other. Read books, magazines or ask professionals who might know in order to learn about the conditions and factors that affect freezing of water. Keep track of where you got your information from.
While gathering information about the conditions that makes water freeze, you may also find out that normally colder water freezes faster, however in certain conditions warm or hot water may freeze faster. The following links have information about special conditions that may result in hot water to freeze faster.
Before you start the experiment you need to find out:
- the temperature at which water freezes and boils
- the temperature of the freezer
- the room temperature
- the procedures and materials.
You may also do some experiments as background research.
You may use the book Science with water to help you identify the different temperatures at which water boils and freezes.
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 question is:
Does the temperature of water affect the time it takes for water to freeze?
The purpose of this project is to see how temperature of water affects the time that it takes to freeze.
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.
Independent variable also known as manipulated variable for this project is the water temperature before starting the freezing experiment.
Dependent variable is the time that it takes for water to freeze.
We control all other variables and keep them constant. Controlled variables are:
- The amount of water for each sample or each experiment.
- The initial temperature of freezer.
- The position of the sample in the freezer.
- The type and size of water containers or cups.
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
These are a sample hypothesis. You may come up with your own hypothesis or select any of the following.
Sample Hypothesis 1:
The initial temperature of water has no effect on the time that it takes to freeze.
Sample Hypothesis 2:
I hypothesize that it will take more time for warmer water to freeze.
Sample Hypothesis 3:
My hypothesis is that it will take more time for colder water to freeze.
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.”
Before you start your experiment do some initial tests to see at what temperature does water freeze? Since you may not be using pure water and since drinking water contains some salt and minerals, the freezing temperature of your water sample may be slightly different from what you have seen in books.
Also measure the temperature of your freezer, the temperature of your tap water and do an initial test to see how long it takes for a sample of tap water to freeze. If freezing takes much more than one hour, you will need to adjust the freezer to a colder temperature.
For this experiment we freeze five identical samples of water with different initial temperatures and record the time that it takes for water to freeze. We use plastic cups or any similar plastic container for freezing water. You can place all five samples in the refrigerator at the same time or do it one at a time so you will repeat the test 5 times.
- Set the freezer to its coldest temperature and leave it closed for at least 30 minutes so it will be at its lowest temperature.
- Get 5 identical plastic cups and mark them for water level in all five cups. Place the marks inside the cups, exactly 2 inches from the bottom of each cup. The purpose of this marking is to make sure that all samples contain the same amount of water. So if you know any other way, you can skip marking. For example, you may use a measuring cup to transfer water to the test cups.
- Prepare water with different temperatures as described here:
Very cold water Place some water in the refrigerator for about 2 hours so it gets very cold. Cold water Open the tap water for about a minute until it gets to cold water. Room temperature water Place some water in a metal container in normal room temperature for about 2 hours until it gets to the room temperature. warm water Warm water can be obtained from hot water tap or you may use a heater or microwave to warm up water. If the water is hot, mix it with some cold water to make warm water. hot water Hot water can be obtained from hot water tap or can be made using a heater or microwave.
You need about one cup of each sample water.
- Label your cups for different water temperatures. You may use masking tape as labels because it can easily be removed, or you may write on the cups using a water proof marker.
- Fill up the cups with the water up to the level already marked or using a measuring cup. Fill up each cup with the water matching the label.
- If you have a thermometer, measure and record the temperature of each water sample and record the results.
- Place all five cups in the freezer equidistance from the walls of the freezer and Close the freezer door.
- Every five minutes open the freezer and check the conditions of all water samples by inserting a plastic rod into each cup. You may use the handle of a plastic spoon to do that. If you see that some water samples are frozen, you may continue your observation every 3 or 2 minutes. Record the time and results of your every observation. If you have a thermometer you may also record the temperatures of water samples on each observation.
- Depending on how cold your freezer is you may need to repeat your experiment and adjust the inspection intervals until you get the best results. For example if in your first observation you notice that 3 of the samples are frozen, you will not know which one is frozen first. So you will need to repeat your experiment but this time make observations every 2 minutes instead of every 5 minutes.
Note: Do not leave the freezer door open for an extended period of time.
Materials and Equipment:
This is only a sample. You will make your own material and equipment list.
- 5 identical plastic cups or similar containers
- Candy Thermometer (to measure temperature of water)
- Watch, clock or timer (to measure time it takes for water to freeze)
- Measuring cup (to measure the amount of water to put in the container)
- Microwave (to heat water)
- Freezer (to freeze water)
- Plastic rod or spoon to feel if the water is frozen or not
Results of Experiment (Observation):
Record the results of your experiments in a table like this:
|Water Temperature||Initial temperature||Condition of samples after 5 minutes||Condition of samples after 10 minutes||Condition of samples after 15 minutes|
|Very cold water||5ºC – 41ºF|
|Cold water||15ºC – 59ºF|
|Room temp. water||25ºC – 77ºF|
|Warm water||40ºC – 104ºF|
|Hot water||65ºC – 149ºF|
Please note that the above table is just an example and your results table may need many more columns. For example, if it takes one hour for all samples to freeze, you have done 12 observations so your table will have a total of 14 columns. However, you can then simplify your tables and just show the amount of time it took for each sample to freeze.
The following table shows the time at which the water in the three bottles froze on the top:
|Temperature of Water||Time ice forms on top||Time taken to freeze|
|Very cold||25 minutes||35 minutes|
|hot||1 hour 15 minutes||1 hour 29 minutes|
You may need to do some calculations to convert minutes to hours. If you do any calculations also write them in your reports.
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.
The results of my experiment showed that temperature of water has an effect on the time it takes to freeze. My experiment proved my hypothesis – the higher the temperature of the water, the longer the time it takes for water to freeze – and showed that my hypothesis was correct.
Related Questions & Answers:
Additional optional information that you may include in your report can have the following titles:
How did I come up with my project idea?
What did I learn from my experiment?
How close were my hypothesis and conclusion?
Did I learn anything new from my project?
Yes. I learned a lot of things in doing this experiment. They are:
- I learned how to be specific with my work
- I learned how to make a table
- I learned how to make a graph
- I learned to take pride in my work
- I learned to make a bar graph
- I learned to take my time.
- I learned how to use a thermometer.
- I learned how to read a thermometer.
- I learned to revise my work.
- I learned how to spell new words.
- I think the scientific method is hard.
What was the most interesting part of my project?
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.
List of References