Question

CHECK POINT 2
1. Separate the following pure substances as elements and compounds:
Diamond, oxygen, sodium chloride, graphite, distilled water
2. Classify the following as compounds and mixtures:
Air, sugar, tap water, brass, copper sulphate, gasoline
3. Classify the following as homogeneous and heterogeneous mixtures:
(i) sodium chloride in water
(ii) glucose in water
(iii) sand and water
(iv) air
4. Justify that water is a compound but not a mixture of hydrogen and oxygen.​

Answer 1

Answer:

1. Graphite is an element. Diamond is carbon. Oxygen (O), nonmetallic chemical element of Group 16 (VIa, or the oxygen group) of the periodic table.

2. Sugar, Air, and water are mixtures. Brass and copper are elements.

3.  NaCl + H₂O = Homogeneous mixture  C₆H₁₂O₆ + H₂O = Homogeneous mixture  c. SiO₂ + H₂O = Heterogeneous mixture  d. Air = Homogeneous mixture.

4. (i) The two elements hydrogen (H) and oxygen (O) are combined chemically to form water (H2O) which boils at a fixed temperature. (ii) The properties of water are altogether different from the constituting elements. For example, molecular hydrogen (H2) is combustible and molecular oxygen (O2) supports cumbustion.

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Explanation: