Question

the properties of water lab
lab objectives:

• describe how life happens in water.
• illustrate water as a polar molecule.
• model properties of polar and nonpolar molecules.
• explain how water interacts with the cell membrane.

materials:

• 3 - d molecular designs water kits (one per 2 students)
• student lab packet (1 per student)
• optional: phospholipid paper models

pre - lab questions:

1. how much water is in the human body?
2. what is the molecular formula for water?
3. where is water found in the body?
4. fats and oils are also called lipids. what happens when you pour vegetable oil into water?
5. what happens when you shake water and oil together (like in salad dressing) in a closed container and then let it sit? explain what you observe.

the polar nature of water student lab packet

Explanation:

1. The percentage of water in the human body varies by age and other factors, but on average it's about 60 - 70% for adults, not 90%.
2. The molecular formula for water is $H_2O$.
3. Water is found in cells (intracellular fluid), in the spaces between cells (extracellular interstitial fluid), in blood plasma, etc.
4. Vegetable oil (lipid) is non - polar and less dense than water, so it floats on top due to immiscibility.
5. When water and oil are shaken in a closed container, they form a temporary emulsion. When left to sit, the oil and water separate again because non - polar oil molecules do not mix with polar water molecules.

Answer:

1. On average, about 60 - 70% of the human body is water for adults.
2. $H_2O$
3. In cells, interstitial spaces, blood plasma etc.
4. The oil floats on top as it is non - polar and less dense.
5. A temporary emulsion forms when shaken, then they separate again when left to sit due to the non - mixing of polar water and non - polar oil.