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Form 1 Chemistry Simple Classification of Substances Questions and Answers
Classify the following processes as either chemical or physical.
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1.
The curve below represents the variation of temperature with time when pure and impure samples of a solid were heated separately Which curve shows the variation in temperature for the pure solid? Explain.
2.
In an experiment to separate a mixture of two organic liquids, liquid M (b.p #56^0C#) and liquid N (b.p #118^0C#), a student set up the apparatus shown below. (a) Identify two mistakes in the set up. (b) What method would the student use to test the purity of the distillates obtained?
3.
The diagram below represents a paper chromatogram for three brands of juices suspected to contain banned food colorings The result showed the presence of banned food colorings in L and M only. On the same diagram: (a) Circle the spots which show the banned food colorings (b) Show the solvent front
4.
The diagram below shows the relationships between the physical state of matter. Study it and answer the questions that follow. (a) Name the process R,V,W and U (b) Name one substance which can undergo the process represented by S and T
5.
State and explain the change in mass that occurs when the following substances are separately heated in open crucibles. (a) Copper metal (b) Copper (II) nitrate
6.
The set-up below represents the apparatus that may be used to separate a mixture of two miscible liquids C and D whose boiling points are #80^0C# and #110^0C#. (a) Name B (b) What is the purpose of the thermometer? (c) Which liquid was collected in the test tube?
7.
A piece of chromatography paper was spotted with coloured inks obtained from pens labelled 1 to 6. The diagram below shows the spots after chromatogram was developed. (a) Which two pens contained the same pigment? (b) Which pen contained only one pigment? (c) According to the chromatogram, which pigments are present in the ink of pen number 6?
8.
(a) The diagram below spots of pure substance A, B and C on a chromatography paper. Spot D is that of a mixture. After development, A,B and C were found to have moved 8 cm, 3 cm and 6cm respectively. D was separated into two spots which had moved 6 cm and 8 cm. (i) On the diagram I. Label the baseline II. Show the positions of all the spots after development. (ii) Identify the substances present
9.
Study the properties of substances V1 to V4 in the table below and answer the questions that follow. (a) Which of the substance are liquids at #24^0#C? (b) Describe how a mixture containing V2 and V4 can be separated
10.
The graph below shows a curve obtained when water at #20^0C# was heated for 15 minutes. (a) What happens to the water molecules between points W and X? (b) In which part of the curve does change of state occur? (c) Explain why the temperature does not rise between points X and Y.
11.
Samples of urine from three participants F, G and H at an international sports meeting were spotted onto a chromatography paper alongside two from illegal drugs A1 and A2. A chromatogram was run using methanol. The figure below shows the chromatograms. (a) Identify the athlete who had used an illegal drug (b) Which drug is more soluble in methanol?
12.
The graph below is a cooling curve of a substance from gaseous state to solid state. Give the name of the: (a) Process taking place between #t_0# to #t_1#. (b) Energy change that occurs between# t_3# to #t_4#
13.
Classify the following processes as either chemical or physical.
14.
Hydrated cobalt (II) chloride exists as a pink crystals and anhydrous cobalt (II) chloride is a blue powder. Describe a laboratory experiment that can be used to show that the action of heat on hydrated cobalt (II) chloride is a reversible action.
15.
A mixture contains ammonium chloride, copper (II) oxide and sodium chloride. Describe how each of the substances can be obtained from the mixture.
16.
A sample of water in a beaker was found to boil at #101.5^0C# at 1 atmospheric pressure. Assuming that the thermometer was not faulty, explain this observation.
17.
Describe an experimental procedure that can be used to extract oil from nut seeds
18.
The chromatogram below was obtained from a contaminated food sample p. Contaminants Q, R, S and T are suspected to be in p. Use it to answer the following questions. (a) Identify the contaminant in mixture p? (b) Which is the most soluble contaminant in p?
19.
Draw a set up that can be used to separate mixture of sand and iodine
20.
The set up below was used to separate a mixture of methanol and propanol. Study it and answer the questions that follow. (a) State the function of X (b) Which liquid will collect first in the beaker? Give a reason.
21.
When solid A was heated strongly, it gave off water and a solid residue. When water was added to the solid residue, the original solid A was formed. (a) What name is given to the process described (b) Give one example of solid A
22.
Describe how samples of lead (II) sulphate, ammonium chloride and sodium chloride can be obtained from a mixture of the three.
23.
The graph below is a cooling curve for water. Study it and answer the questions that follow. (a) Explain what happens to the molecules of water in the region BC in terms of kinetic theory. (b) In what state is the water in the region DE?
24.
Iron (III) oxide was found to be contaminated with copper (II) sulphate. Describe how a pure sample of iron (III) oxide can be obtained.
25.
Explain how a student can establish whether a liquid sample extracted from a plant is pure.
26.
An experiment was carried out to determine the presence of substances P,Q, R and S in mixture T. the results obtained are shown below. (a) Name the method of separation illustrated in the figure above. (b) Select (i) One substance which contains a component not present in T (ii) A substance which is least soluble in the solvent used
27.
The graph in figure 4 was obtained when a certain substance was heated and its temperature recorded at regular intervals. (a) State the purity of the substance (b) Explain the answer in (a)
28.
Against each mixture write down suitable methods of separation. (a) Colored extracts of grass dissolved in ethanol. (b) Kerosene from Crude oil. (c) Paraffin from water. (d) Iron filings from Sulphur powder. e).Ammonium chloride from Sodium chloride. (f) Seawater, to obtain salt.
29.
Why is fractional distillation suitable for separating crude oil constituents?
30.
Monica a form one student decides to separate powdered calcium carbonate from powdered calcium chloride by shaking the mixture with water and then filtering. Would this procedure succeed? Explain your answer.
31.
What does distillation mean and what is its importance in chemistry?
32.
What do you understand by a saturated solution?
33.
What do impurities do to both Boiling points and melting points of substances?
34.
State how chromatography is applied in real life situation.
35.
The diagram shows the results of an experiment to separate and identify the colors present in two colored mixtures, A and B. Substances C, D, E and F are single colors. (a) Name this method of separation. (b) Why should a pencil be used instead of a pen to draw the origin line?
36.
A mixture of ethanol and water can be separated by fractional distillation. The apparatus below can be used to carry out such a separation in the laboratory. (a) Name each piece of apparatus. A B C (b) What is the purpose of D?
37.
What does Kinetic theory of matter state?
38.
Describe an experiment to show matter is particulate.
39.
How do you identify pure substances in chemistry?
40.
Using Kinetic theory of matter explain condensation process.
41.
Consider the solubility of substance X, Y and Z in different solvents in the table below. Describe how you would obtain a sample of Y from the mixture.
42.
Study the diagram below and answer the questions that follow a).What observation is made when the iodine is heated? b).Name the process which iodine undergoes when heated c).Give two other substances which undergoes the process named in b above
43.
The chromatogram below shows constituents of a flower extract A using an organic solvent. Study it and answer questions which follow a).Name two possible organic solvents which can be used for the process. b).Name two properties of the red pigment which makes it to move furthest distance. c).State one
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