Answer : Broadly solids are divided into three categories;
i) Crystalline solids have a regular definite structure, in which the particles pack in a repeating pattern from one edge of the solid to the other.
ii) Amorphous solids have a random structure, with little unorganized pattern long-range order.
iii) Polycrystalline solids are those where an aggregate which consists of a large number of small crystals or grains in which the structure is regular, but the crystals or grains are found to be arranged in a random fashion.
Also solids can be divided into 3 more categories according to their bonds;
i) Covalent solids, like diamond, which forms crystals that can be viewed as a single giant molecule made up of an almost endless number of covalent bonds.
ii) Ionic solids are basically salts, such as NaCl, in which the molecules are held together by the strong force of attraction between ions of opposite charge.
iii) Metallic solids are found in metals which have the force of attraction between atoms of metals, such as copper and aluminum, or alloys, such as brass and bronze, are metallic bonds.
Answer:
D
Explanation:
Gamma radiation penetrates the cell wall of prokaryotic organisms such as bacteria and can inhibit their metabolic functions as well as destroy their DNA.
Debunking the other answers:
A is incorrect as Gamma radiation is used in the treatment of cancer via radiotherapy.
B is incorrect as Gamma rays are too small and would just penetrate any smoke particles.
C is incorrect because Gamma rays are used to disinfect food products to prevent food borne illness. Irradiation is safe to use on food and does not make it radioactive.
Thus, D is correct.
Answer : The masses of calcium chloride and water used were, 352.6 g and 487.0 g.
Explanation :
As we are given that 42.0 % calcium chloride by mass that means 42.0 grams of calcium chloride present in 100 grams of solution.
In the solution or mixture, 42.0 % calcium chloride and 58.0 % (100-42.0=58.0) water.
Now we have to determine the mass of calcium chloride for 839.6 grams of solution.
As, 100 grams of solution contains 42.0 grams of calcium chloride
So, 839.6 grams of solution contains 
grams of calcium chloride
Thus, the mass of calcium chloride used is, 352.6 grams.
Now we have to determine the mass of water.
Mass of water = Mass of solution - Mass of calcium chloride
Mass of water = 839.6 g - 352.6 g
Mass of water = 487.0 g
Thus, the mass of water used is, 487.0 grams.
