Answer:
It's the oesophagus.
Explanation:
The worm digestive system consists of the pharynx, the esophagus, the crop, the intestine and the gizzard. The oesophagus is not mentioned. Thus, it's not part of the worm digestive system.
Answer:
Five
Explanation:
All group 15 elements have five valence electrons, but they vary in their reactivity.
Answer:
This means that the metal is more properly viewed as an array of positive ions surrounded by a “sea of mobile valence electrons.” Electrons which are capable of moving freely throughout the empty orbitals of the metallic crystal are called delocalized electrons (Figure below).
The factors that affect the rate of a reaction are:
- <em>nature of the reactant</em> - when reactants with different chemical composition are exposed to same conditions they would react differently. For instance, when an acid or base is added on litmus paper, blue litmus paper turns red in presence of acid while red litmus paper turns blue when base is added.
- <em>surface area</em>- a compound with small pieces spread over a large area will react faster than a big lump of a compound occupying a small area.
- <em>temperature of reaction</em>- reactants would react faster at high temperatures. this is because they have higher kinetic energy to collide with each other. Hence a plate of food on the table spoils faster than a plate of food in the fridge.
- <em>concentration</em>- an increase in concentration leads to more molecules available to collide and form products. An example, when you add more of indicator in a solution, the color becomes more clear since more particles react to give more color.
- <em>presence of a catalyst</em>- a catalyst lowers the activation energy, which means less energy is required to shift reaction in forward direction. In the presence of iron (Fe) a catalyst, nitrogen N₂ and hydrogen H₂ react to produce NH₃
A drop of iquid mercury is D. <span> a pure substance and an element. This is because mercury is an element which exists as liquid in the normal or standard conditions. It is a metal that is toxic to all environments. It is pure because it is composed only of one kind of substance.</span>
