Blank #1: Polyatomic
Blank #2: 2 (see explanation)
Blank #3: 1 (see explanation)
<h3>Explanation</h3>
Both the ammonium ion 
and the sulfate ion 
contain more than one atom in each ion. The two species are thus <em>polyatomic</em>. The chloride ion 
, for example, is <em>monoatomic</em>.
Superscripts above formulae of the ions indicate their charge. Each ammonium ion carries a positive one (+1) charge. Each sulfate ion carries a charge of negative two (-2).
Ammonium sulfate is an ionic compound. A sample of this compound contain myriads of ammonium ions and sulfate ions. The ions are packed in three-dimensional lattices. Thus unlike water, ammonium sulfate does not exist as molecules in nature.
Assuming that the second and third blanks refers to a formula unit, rather than a molecule, of ammonium sulfate. The empirical formula of ammonium sulfate gives the minimum whole-number ratio between the two ions in a sample.
Charges shall balance between the two ions. Ammonium ions are of charge +1. Sulfate ions are of charge -2. The sample shall thus contain two ammonium ions for every one sulfate ion.
The empirical formula of ammonium sulfate is therefore 
.
There are thus two ammonium ions and one sulfate ion in each formula unit of ammonium sulfate.
Answer:
A chemical change
Explanation:
The marshmallow turning brown and bubbling implies that a chemical change has taken place.
For chemical changes to occur, we observe any of the following:
- a new kind of matter is formed.
- it is always accompanied by energy changes
- the process is not easily reversible
- it involves a change in mass
- requires considerable amount of energy.
ii. Two signs that shows a chemical change has taken place is that:
- bubbles are being formed as it is roasted and it implies that new substances have been formed.
- also, significant amount of heat energy is supplied for the roasting.
Answer:
Car B has a greater momentum than car A
Explanation:
Given data:
Mass of car A = 1200 Kg
speed of car A = 22 km/hr
Mass of car B = 1200 Kg
speed of car B = 25 Km/hr
Solution:
For car A:
p = mv
p = 1200 Kg × 22 km/hr
p = 26400 kg.km/hr
For car B:
p = mv
p = 1200 Kg × 25 km/hr
p = 30,000 kg.km/hr
Answer : When the nuclear reaction produces too many neutrons.
Explanation : In a nuclear fission reactor where the reaction is controlled by regulating the number of neutrons produced by the chain reaction. Production of too many neutrons may cause an accelerated uncontrolled chain reaction which may cause enormous heat to be generated in a very short period of time inside the reactor which may result into an explosion.
For, this purpose control rods, made of neutron absorbing species, like cadmium, are placed in the nuclear reactors to control the excess number of neutrons at any point of reaction when required.
