Evaporation Rate of Water
Category: Chemistry—Physical Changes
Project Idea by: Ben and Hank Osborne
Matter is anything that has mass (an amount of material) and volume (an amount of occupied space). The three common forms of matter on Earth, called the states of matter, are solid, liquid, and gas. A solid has a definite shape and volume; a liquid has a definite volume but no definite shape; a gas has no definite volume or shape.
Substances commonly exist in one of the three states, but they can be in any one of the three states depending on temperature. For example, water is commonly a liquid, but when cooled it forms a solid called ice. When liquid water is heated, it forms a gas.
The state of matter doesn't change the kind of particles of which a substance is made. Instead, the states of matter differ in how close their particles are as well as how tightly bonded the particles are. For example, each particle of liquid, gas, or solid water is made of one atom of oxygen combined with two atoms of hydrogen. Water particles in the gas state are far apart. Liquid water particles are closer together, and some are bonded to one another. Solid water particles, called ice, are close together and are the most tightly bonded.
When water changes from one state to another, there is a gain or loss of energy. States of matter in order from least to most energy are solid, liquid, gas. To change to a higher energy state, such as when water changes from ice (solid) to liquid or from a liquid to a gas, heat must be added. The process of changing from a solid to a liquid is called melting. The process of changing from a liquid to a gas is called vaporizing.
If vaporization happens at the surface of a liquid, the process is called evaporation. The gaseous state of a substance at a temperature at which that substance is usually in a solid or liquid state is called a vapor. When water evaporates, vapor is formed. Evaporation rate is the amount of liquid that evaporates in a certain amount of time. A project question might be, "What effect does surface area have on the evaporation rate of water?"
Clues for Your Investigation
Design a way to measure evaporation rate such as marking volume measurements on four or more containers with different-sized openings. For example, place a piece of tape down the side of each container. Then pour in a measured amount of water, such as 10 mL, and mark the water level on the tape. Continue adding the same amount of water in each container and marking its surface level on the tape until you have the amount of water in each container you need for your experiment. Place the containers next to each other. You can use the markings on the containers to measure the water lost to evaporation after a determined amount of time, such as one day. You may wish to mark the tape each day for one week.
Independent Variable: Surface area of a liquid
Dependent Variable: Evaporation rate
Controlled Variables: Temperature, amount of water at the beginning of the test, measuring period, method of measuring evaporation rate
Control: Container with the medium-sized opening
Other Questions to Explore
- How does temperature affect the rate of evaporation?
- What effect, if any, does the temperature of water have on the freezing rate?
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