Section b Summary: 25-34 p. 52

25. Qualitative tests tell us if there are particles present in the sample, while quantitative tests let us know how much of a substance is present.

26.A confirming test is a laboratory test giving a positive result if a particular chemical species is present.

27.

a.    A reference solution is used to compare a sample to, to see if it its result is positive.

b.    A blank, on the other hand, is used as a comparison to see if the sample does not have ion.

28. No, the student has to see if there is any precipitate, because the iron ion may not have a change in color in that sample of groundwater.

29.

a.    I would first let it sit, because if it were a solution then the suspended particles would separate from the substance. The Tyndall effect would also be helpful to see if the particles are large enough to reflect the light. A filtering process could be used as well, to see if there is any change in the substance after it has been filtered. Also, if the substance seems pure, an electrical conductivity test may be performed to see if there are any particles that conduct electricity present in the substance. Lastly. These confirming tests may be used to see if there are ions that have mixed into the substance.

b.    Letting the substance sit would tell us if it is a suspension, since suspended particles do not remain mixed for long. The Tyndall effect could let us know if it was a colloid or suspension, or a solution since larger particles reflect the light. Filtering tells us if it is a suspension, since the large particles would not remain in the filtrate, but we would not know if it was a colloid because not all colloid particles can be filtered out. An electrical conductivity test tells us if it is a solution, or pure water, since distilled water contains no salt, which conducts electricity. Finally the confirming tests just tells us if it a solution with particles, or a pure sample with either no ions or just a small amount of them.

30.Failing to follow the “shake before using” instructions in a medicine bottle could result in an ineffective dose of medicine, or consuming substances that are harmful if swallowed alone.

31.It is useful so scientists all over the world can interact and share experiences, without the confusion, of which element is which.

32. See picture.

33. No, it is not, because certain gases such as Nitrogen, Oxygen, and Carbon Dioxide with always dissolve into water. This means whenever water comes in contact with open air, the gases can combine and dissolve within the water.

34.Water is liquid at room temperature, is very rare except for on earth, and has a freezing pint of 0 degrees centigrade. Hydrogen and Oxygen are both gases at room temperature, and while oxygen is not abundant outside of earth, hydrogen is. Also the freezing points of oxygen and hydrogen are -222.65 degrees centigrade and -258.975 degrees centigrade, respectively.