Questions

The main goals of psychology are four. They are::

1. To describe,

2. To explain,

3. To predict (and)

4. To control the behavior and mental processes of others.

Inhaling of oxygen and releasing of carbon dioxide to make our living is the process called as respiration. We know that, air is a mixture several gases like 78% of nitrogen, 21% of oxygen and several other gases with watervapour.

Hence, Oxygen is essential for respiration process.

When heated any substance, the molecules move apart from each other. Alike in the air the molecules move apart from each other. We know that the warm air is lighter than the cool air. Since after heating air gets warmer, it floats up and the cool air comes down to occupy the warm air place.

They are teeth. 

Gregarious is spelt correctly which means sociable.

Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can fill up their outer electron shell and gain stability.

Examples of compounds with covalent bonds ::

HCl, CO2, O2,... 

An ionic bond is formed between two molecules when transfer of valency electrons take place between them.