Unusual properties of water
Skill 2: Identify the properties of water observed in the lab in real life situations.
Click the image above to watch this Crash Course video on the properties of water.
Click the image above to watch this Crash Course video on the properties of water.
Click the link above or ask for a paper copy of the big picture boxes worksheet. For each property of water on the worksheet, make a drawing of something to remind you of that property. Write a summary of just a few words explaining the 'big picture,' or main idea.
Click the link above or ask for a paper copy of the big picture boxes worksheet. For each property of water on the worksheet, make a drawing of something to remind you of that property. Write a summary of just a few words explaining the 'big picture,' or main idea.
Use the video to the left and the explanations below to help you understand the unique properties of water.
Use the video to the left and the explanations below to help you understand the unique properties of water.
Polar Covalent Molecule
Polar Covalent Molecule
Water is very different from almost any other small molecule. It is a covalent molecule because hydrogen and oxygen share electrons. Water's unusual properties are a direct result of the polar nature of the water molecule. It is polar because the electrons are not shared evenly causing the oxygen end to be negative and the hydrogen end to be positive.
Water is very different from almost any other small molecule. It is a covalent molecule because hydrogen and oxygen share electrons. Water's unusual properties are a direct result of the polar nature of the water molecule. It is polar because the electrons are not shared evenly causing the oxygen end to be negative and the hydrogen end to be positive.
Good Solvent
Good Solvent
Water is the best solvent! It dissolves more different substances than any other solvent known. Many other molecules are polar which attracts them to water which is also polar. This attraction between molecules is similar to the way magnets attract each other. Water attaches to the particles such as salts, sugars, proteins, and hormones and dissolves them. This allows a lot of things to be dissolved in, and carried by, our blood.
Water is the best solvent! It dissolves more different substances than any other solvent known. Many other molecules are polar which attracts them to water which is also polar. This attraction between molecules is similar to the way magnets attract each other. Water attaches to the particles such as salts, sugars, proteins, and hormones and dissolves them. This allows a lot of things to be dissolved in, and carried by, our blood.
Cohesion
Cohesion
Remember that 'co' means share. Cohesion is when two water molecules share a bond, making them stick together. You can see this when a bead of water forms on a surface. You are seeing many water molecules sticking together with cohesion.
Remember that 'co' means share. Cohesion is when two water molecules share a bond, making them stick together. You can see this when a bead of water forms on a surface. You are seeing many water molecules sticking together with cohesion.
Adhesion
Adhesion
To help you remember the difference between cohesion and adhesion, think about adhesion as 'adding' in another substance for water to stick to. You can see this when water sticks to your hair or mirror after a shower.
To help you remember the difference between cohesion and adhesion, think about adhesion as 'adding' in another substance for water to stick to. You can see this when water sticks to your hair or mirror after a shower.
Compare and Contrast
Compare and Contrast
Cohesion = water + water
Cohesion = water + water
Adhesion = water + something else
Adhesion = water + something else
Capillary Action
Capillary Action
A capillary is any tiny tube. If a capillary tube is made of glass or any other substance that is polar, water will spontaneously climb up inside it without having to be pumped in any way. The smaller the tube, the higher the water climbs. The attraction is so great between the water molecules and the molecules of the tube that water will climb in defiance of gravity. This is termed capillary action. This is extremely important for plants because they do not have to expend energy to get water to their highest points.
A capillary is any tiny tube. If a capillary tube is made of glass or any other substance that is polar, water will spontaneously climb up inside it without having to be pumped in any way. The smaller the tube, the higher the water climbs. The attraction is so great between the water molecules and the molecules of the tube that water will climb in defiance of gravity. This is termed capillary action. This is extremely important for plants because they do not have to expend energy to get water to their highest points.
Here's a way to remember capillary action.
Here's a way to remember capillary action.
CA = C + A
CA = C + A
Capillary action = cohesion + adhesion
Capillary action = cohesion + adhesion
High Heat Capacity
High Heat Capacity
Water is able to absorb a lot of heat energy without having its temperature increase much. Because of this, water is said to have high heat capacity. An amount of heat that would raise the temperature of water by 10 degrees will raise the temperature of an equal weight of iron by 94 degrees. This means that an empty frying pan will heat up faster than a pan of water because water absorbs much heat before the temperature rises. Water molecules are held together so strongly by their hydrogen bonds than an amount of heat that will get other molecules moving much faster will not speed up water molecules much at all. This property of water helps to reduce temperature changes in the animal body or plant, and it also minimizes temperature changes close to large bodies of water.
Water is able to absorb a lot of heat energy without having its temperature increase much. Because of this, water is said to have high heat capacity. An amount of heat that would raise the temperature of water by 10 degrees will raise the temperature of an equal weight of iron by 94 degrees. This means that an empty frying pan will heat up faster than a pan of water because water absorbs much heat before the temperature rises. Water molecules are held together so strongly by their hydrogen bonds than an amount of heat that will get other molecules moving much faster will not speed up water molecules much at all. This property of water helps to reduce temperature changes in the animal body or plant, and it also minimizes temperature changes close to large bodies of water.
High Heat of Vaporization and Fusion
High Heat of Vaporization and Fusion
Heat of vaporization is the amount of heat added to evaporate a certain amount of liquid. Water has a very high heat of vaporization, meaning it takes a lot of heat to evaporate just a little water. This keeps lakes and ponds more full during the summer than they would be if water had a lower heat of vaporization. Heat of fusion is the heat that must be removed from water in order to freeze it. Water’s relatively high heat of fusion means that it takes much longer for lakes and streams to freeze in the winter, allowing living things more time to adjust to the change.
Heat of vaporization is the amount of heat added to evaporate a certain amount of liquid. Water has a very high heat of vaporization, meaning it takes a lot of heat to evaporate just a little water. This keeps lakes and ponds more full during the summer than they would be if water had a lower heat of vaporization. Heat of fusion is the heat that must be removed from water in order to freeze it. Water’s relatively high heat of fusion means that it takes much longer for lakes and streams to freeze in the winter, allowing living things more time to adjust to the change.
Expansion on Freezing
Expansion on Freezing
Most things contract when cooled, and water is no exception, up to a point. That point is 3.8 C. When cooled below that temperature, water molecules slow down and spread out. This structure is completed when the water freezes. What is most unusual is that ice takes up more space than the same amount of water, so ice is less dense than water, and it floats. The water below is still at 3.8 C. Since ice is a good insulator, lakes and ponds can freeze over in the winter without freezing all the living things in the water below. If ice didn’t float, lakes would freeze from the bottom up, and many ponds would freeze solid, killing all life in them.
Most things contract when cooled, and water is no exception, up to a point. That point is 3.8 C. When cooled below that temperature, water molecules slow down and spread out. This structure is completed when the water freezes. What is most unusual is that ice takes up more space than the same amount of water, so ice is less dense than water, and it floats. The water below is still at 3.8 C. Since ice is a good insulator, lakes and ponds can freeze over in the winter without freezing all the living things in the water below. If ice didn’t float, lakes would freeze from the bottom up, and many ponds would freeze solid, killing all life in them.
Hydrogen Bonding and Surface Tension
Hydrogen Bonding and Surface Tension
Hydrogen bonds hold water molecules together so tightly that the water’s surface acts like a membrane. The insect known as the water strider is actually able to walk on the surface without breaking through. Hydrogen bonds form because water is polar, with one end of the molecule being negative and the other end positive. Opposites attract like magnets and hold water molecules close together. This is known as a hydrogen bond.
Hydrogen bonds hold water molecules together so tightly that the water’s surface acts like a membrane. The insect known as the water strider is actually able to walk on the surface without breaking through. Hydrogen bonds form because water is polar, with one end of the molecule being negative and the other end positive. Opposites attract like magnets and hold water molecules close together. This is known as a hydrogen bond.
Notice the very specific way that the water molecules align themselves in the diagram above. Explain why they line up this way when forming hydrogen bonds. *Hint - talk about the charges of the oxygen and hydrogen ends of the water molecules. Research this if you need to and then write out your explanation in a few sentences. Be sure to tell me what kind of bond forms between different water molecules.
Notice the very specific way that the water molecules align themselves in the diagram above. Explain why they line up this way when forming hydrogen bonds. *Hint - talk about the charges of the oxygen and hydrogen ends of the water molecules. Research this if you need to and then write out your explanation in a few sentences. Be sure to tell me what kind of bond forms between different water molecules.
Add the link to your Big Picture boxes into your slides. If you completed it on paper, upload screenshots.
Add the link to your Big Picture boxes into your slides. If you completed it on paper, upload screenshots.
After viewing your results, take the time to go back and figure out the correct answers and why your answers may have been wrong. This is where the real learning occurs.
After viewing your results, take the time to go back and figure out the correct answers and why your answers may have been wrong. This is where the real learning occurs.