Unit Two - Biochemistry - Properties of Water Flashcards
What is water’s molecular structure?
H20
What type of bonds do hydrogen and oxygen form in water?
Covalent bonds
What are covalent bonds?
Chemical bond - e- shared between two atoms
What are the charges of water?
Oxygen - partially negative charge
Hydrogen - partially positive charge.
Why is hydrogen and oxygen charges so different?
Oxygen attracts SO much more electrons than hydrogen
Is water polar or nonpolar? Why? (4)
- Polar
- Uneven distribution of e-
- Creates different charges between the atoms of the molecule
- Enables water’s unique properties.
What are hydrogen bonds?
Attraction between two polar molecules
(Due to Polarity)
This enables cohesion, adhesion, surface tension and capillary action.
Are hydrogen bonds weak or strong and why?
Hydrogen bonds are weak because they are making and breaking at a fraction of a second. However, numerous hydrogen bonds exist at once, so there is a lot of attraction overall.
Why is water’s high specific heat important to living things? (2)
- Water keeps environment at constant temp.
- Endotherms can resist environmental changes in temperature because of water in the blood.
WHY does water have a high specific heat? (2)
- Water forms H - bonds
- Takes hi E to break bonds & heat H20
What is cohesion?
Water molecules stick to each other.
H - Bonds form
How does surface tension form? (3)
- At water’s surface
- There’s less adjacent water molecules for bonding
- Hydrogen bonds are reinforces with between molecules.
What is adhesion?
Water sticks to other polar objects
How does capillary action occur? (Adhesion, Cohesion, Surface Tension, 4)
- Adhesion - Water molecules adhere to the polar substance
- Cohesion - Pulls other water molecules up with it
- Surface Tension - Maintain meniscus, creating a pressure difference that pull more molecules up the tube
This causes the water to rise in the tube, even against gravity
Definition of Surface Tension (2)
- Thin & invisible skin at surface
- Minimizes SA
HOW does surface tension connect to the xylem?
When water sticks together and to a surface, it creates surface tension
Like adding water to the penny, you can only add so much and the water will break over the side.That can be measured with the drops on the penny and other scientific ways. Water always has surface tension, h bonding, cohesion, adhesion, polarity
How does water relate to the xylem? (Cohesion, Adhesion, Surface Tension)
- Cohesion - Keeps water molecules sticking together, forming a continuous column
- Adhesion - Helps water molecules stick to the walls of the xylem vessels, aiding their upward journey
- Surface tension - maintains stability of the water column, preventing air bubbles from breaking it apart.
- Negative pressure created by transpiration pulls more water up from the roots
What is the analogy that helps explain negative pressure?
Think of it like sucking on a straw. When you create a lower pressure inside the straw by sucking, the liquid is pulled up from the glass to fill the space. Similarly, transpiration creates a pulling effect that draws water up through the xylem vessels in plants.
Why is ice less dense? (3)
- Molecule movement decreases
- Hydrogen bonds stabilize
- Holds molecules farther apart
