Covalent bonds are formed when two atoms are able to <em>share</em> electrons.
Iroinic bonds are form when two atoms are <em> </em> electrons from each other to complete the bond. This results in a pair of ions.
<u>Covalent bonds:</u>
- Have a definite shape.
- Have a low melting point.
- At room temperature they are in a liquid or gas.
- They occur between two non-metals.
<u>Ionic bonds:</u>
- Have no definite shape.
- Have a high melting point.
- At room temperature they are solid.
- They occur between a metal and a nonmetal.
Gathering and preparing for a scarcely adapt winter
Static Electricity - the word static means 'at rest' - this kind of electricity exists when objects separated by an insulator has a build up of opposite charges. Because the attraction between these charges is so strong, they can flow even through great insulators. Ex: lightning, friction
Current Electricity - it makes electronic devices possible. There is a constant flow of charges in this type of electricity. In contrast to static electricity, current electricity is changing, dynamic and always on the move. Ex: starting a car, watching TV, using an electric stove.
Heterospory, highly reduced gametophytes, ovules, pollen, seeds are the five adaptations common to all seed plants that ensure their success in the adaptation to land. Three things: The gametophytes of seed plants are reduced and dependent upon the parent sporophyte which protects them (particularly in the case of the female gametophyte). Pollen is covered with sporopollenin which is resistant to physical factors in the environment. The structure of the seed protects the next generation sporophyte and allows it to remain dormant until conditions are right for germination, development and growth.
