Evaporation

Introduction: (Initial Observation)

Evaporation of water is changing water from it’s liquid form to gas form. Water vapors also known as moisture and cloud will remain in the air until they get in contact with a cold surface or a cold air. Then they will condense and become liquid water again. It is important for us to be able to control the rate of evaporation (or the speed of evaporation).

For example if we wash something, we may want them to dry fast. But on the other hand if we have a flower pot, we may not want it to dry fast. In this project we will study the factors that affect the rate of evaporation.

Information Gathering:

Find out about the evaporation process. Read books, magazines or ask professionals who might know in order to learn about factors that may slow down or speed up the evaporation of water. Keep track of where you got your information from.

Following are some basic important information:

We are surrounded by water, and use it every day — to drink, to cook with, to flush our toilets and wash our dishes. 70 percent of the earth’s surface is water. That’s a lot of water, isn’t it!

Another cool thing about water is that it recycles itself. Most of the water on the earth today has been around for millions of years. It continually evaporates (changes from liquid to gas) and condenses (changes from gas to liquid). In other words, the rain falling from the sky has fallen millions of times before and will fall millions of times again.

We usually think of water in its liquid state–the water that flows from our taps and rivers, makes up our lakes and oceans. But water comes in two other forms: solid, like ice and snow; and as a gas.

The temperature of the water determines its physical state. At 32° Fahrenheit (0° Celsius) and below, water freezes into its solid form (ice). Above 32° F, water remains a liquid.

In its liquid form, water continually evaporates. Tiny, invisible droplets break off from the liquid mass and float into the air. The warmer the temperature of the water, the faster the droplets break off and the more quickly the water evaporates. That’s why rain puddles dry up faster on hot days.

When the water temperature reaches 212° F, water boils. In boiling water, the invisible droplets break off so quickly that they form bubbles in the water that rise to the top and release the vapor (the invisible droplets) into the air.

Have you ever seen mist sitting over a lake or field, or steam rising from a hot bath and wondered why it was there? Well, when water vapor hits cooler air, the invisible droplets start clinging together until they become big enough for our eyes to see, but they remain small enough to float in the air. The mist hovering over a lake or field is very much like a cloud in the sky.
Clouds are gatherings of water droplets that have evaporated from the earth. As temperatures cool, more and more droplets gather combine until they are too heavy to keep floating in the cloud. Then they fall from the sky and we have rain. If the air temperature is lower than 32° F, the droplets will keep condensing until they turn into snow.

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 project is to find out what factors affect the rate of evaporation.

More specific questions are:

How does temperature affect the evaporation of water?

How does wind affect the evaporation of water?

Identify Variables:

When you think you know what variables may affect the rate of evaporation, 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.

Variables that may affect the rate of evaporation and we will study them in this project are:

• • Temperature
  • Wind
  • Surface area

If you can think of any other variable that may affect the rate of evaporation, add them to the above list and design experiments for them.

For a specific question such as “How does temperature affect the evaporation of water?” this is how you may define variables.

Independent variable (also known as manipulated variable) is the temperature.

Dependent variable (also known as responding variable) is the rate of evaporation or the percent of water evaporated in each hour.

Controlled variables are light and wind.

Hypothesis:

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.

My hypothesis is that temperature, wind and surface area are very effective in the evaporation of water.

For a specific question such as “How does temperature affect the evaporation of water?” this is how you may propose a hypothesis.

Water evaporates faster (at a higher rate) if the temperature is warmer.

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.”

Experiment 1:

The purpose of this experiment is to see how does the temperature affect the evaporation of water.

Procedure:

Fill up 4 identical cups with water, all at the same level. Label the cups with control, cold, warm and hot.

Place the cup labeled control somewhere safe at room temperature.

Place the cup labeled cold in a refrigerator.

Place the cup labeled warm in a warm place (Over a heat radiator, or some other warm place with the help of your parents)

Place the cup labeled hot in a hot place.

One good example of hot and warm place can be under a desk lamp. You may even replace the bulb with a heat lamp sold in hardware stores. Place the hot cup directly under the center of the lamp, where it gets the most heat. Place the warm cup a little away, so it will get heat, but not as much.

Inspect the level of water in all cups each day and record the results in a table like this:

Experiment 2:

The purpose of this experiment is to see how does the wind affect the evaporation of water.

Procedure:

Fill up 4 identical cups with water, all at the same level. Label the cups with control (no wind), low wind, medium wind and high wind.

Place the control cup somewhere in the room with no wind, but all other conditions such as temperature and light must be the same. Place the 3 other cups in front of an electric fan in a way that high wind cup is closest to the fan and low wind cup is the farthest from the fan. obviously medium wind will be in between.

observe the cups every day and record the water level in a table like the following. However if the evaporation is very fast, either you need to make hourly observation and recording or you need to place the cups in a higher distance from the fan to slow the evaporation.

Experiment 3:

The purpose of this experiment is to see the effect of surface area on the evaporation of water.

Procedure:

Place same amount of water in four different containers in a way that each container will have a larger surface area than the other. For example you may use a bottle, a cup, a soup bowel and a plate

To make sure all the containers will have the same amount of water, use a measuring cup or any other controlled method.

Keep all containers next to each other somewhere in the room. Make daily observation and record the water levels until the plate dries up. Record the results in a table like this. 

Materials and Equipment:

List of material can be extracted from the experiment design. You may replace material and modify the design based on what is available to you.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. For example in the first experiment the only variable that we modified was the temperature. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results. In the first experiment, each cup was used for a different experimental run.

You can use completed table as results. That is acceptable for lower grades. Higher grades may also need to create other tables that instead of the water level, shows the percentage of evaporation. So for each sample, you will need to calculate what percentage of water evaporated each day. 

For the first experiment for example you may make a table like this.

Calculations:

To calculate the percentage of evaporation, you divide the decrease in water level by the initial water level. For example if the initial water level was 100 millimeters and it dropped down to 96 millimeters after one day, it shows that 4 millimeters of water is evaporated. Divide 4 by 100 and it becomes 4%. That is the evaporation rate for that day.

Also if you have the evaporation rate for 5 days, you can divide it by 5 to calculate the evaporation rate (per day).

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.

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:

List your references here.