Bio Test #3 Flashcards
How are compounds formed?
Atoms interact with each other forming compounds
Compound
Made of 2 or more elements in specific proportions
Ex: H2O & H2CO3
What are compounds held together by?
When atoms form compounds they are held together by atomic bonds
What are 2 types of bonds?
Covalent & ionic
Covalent
Electrons are shared
Ionic
Transfer electrons (from one atom to another)
Why do atoms form bonds?
Atoms form bonds according to how electrons are arranged in their orbitals
Noble gases
Atoms are chemically stable when orbitals of its highest level are filled with maximum number of electrons
Molecule
The simplest part of a substance that retains all the properties of that substance
In an ionic bond, what is done when both elements have unfilled outer orbitals?
They transfer electrons making them both more stable and both gain a charge that keeps them together
Hydrogen Bond
Force of attraction between partially positive charge of one molecule and the partially (or full) negative charge of another molecule
What does partially positive or negative mean?
Electrons turn so they are not always positive or negative
Polar Molecules
Molecules with uneven distribution of charges
How are hydrogen bonds compared to covalent & ionic?
Hydrogen bonds are not as strong as ionic or covalent bonds, they break more easily
How many hydrogen bonds can form from each H2O molecule?
4
How does a water molecule behave like an electromagnet?
Having the positive end attract a negative ion or negative end of another polar molecule and vice versa
Why does a water molecule behave like an electromagnet?
Because of its polarity
What are properties water exhibit because if its electromagnetism?
Transparency, adhesion, cohesion, solvent, thermal, transport medium, & medium for metabolic reaction
Transparency
Light can pass through ware
Adhesion
Because of water polarity, water molecules can interact with molecules of other substances. This attraction makes capillary action possible
Capillary Action
Property of water to pull itself up through a small opening against the force of gravity. Important in plants to get water from the soil to the leaves
Cohesion
Because of hydrogen bonds water molecules interact with other water molecules- creating surface tension which allows some animals to use it as a habitat (example: mosquito larvae, spiders can walk on it, “Jesus Lizard”
Solvent Properties
Because of water polarity, water can break bonds between other substances (dissolve substance)
Is water a universal solvent?
Water is a very strong solvent, but it is not a universal solven because if it were, we could not drink it, swim it, hold it in ourselves, store it in a bottle, etc. however water can break bonds between many substances such as: salt & glucose
Thermal properties
Heat capacity, boiling & freezing point, cooling effect of evaporation
Heat capacity
Water has a large amount of energy & is needed to raise water temperature of 1 degree Celsius. This is due to water polarity because a lot of energy is needed to break hydrogen bonds between water molecules. As hydrogen bonds break molecules move faster & this generates heat. Allowing water to be stable & use blood to move heat around the body
Boiling & freezing point
Water having a high boiling point allows for water to change from liquid to gas by breaking all hydrogen bonds. When water freezes it becomes less dense because as molecules slow down, they form hydrogen bonds & spread apart. However the ice that forms at the surface of a lake/ river, creates an insulation layer that allows the water underneath not to freeze
Cooling effect of evaporation
Water can evaporate at temperatures lower than boiling temp. In order for some water molecules to evaporate from the surface, hydrogen bonds need to be broken. The energy used to break the bond is taken from the water itself. Evaporation allows water to cool because When water loses energy it’s temp goes down
Why is water a good transport medium?
Because of water solvent properties and how dense water is
Transport medium
Because of its density water can support mass of large & small organisms which live and move in it. Also currents in water help carry nutrients, spores, & organisms from one place to the next. Water is also used in cells & organisms to transport all kinds of nutrients & molecules from one place to the next (ex: water is an important part of digestion, blood, & both vascular tissues
Medium for metabolic reactions
Water is the medium in which most reactions take place & is capable of breaking bonds between compounds & once those compounds are free, they can react with other compounds. Water is not the only medium for reactions, but in most living organisms it is where most metabolic reactions occur
