Is it always possible to identify something as an element, compound, pure substance or mixture just by looking at it? explain using examples from the tables. (table attached)

The chart shows the bid provided by four contractors to complete a job. which contractor is the most cost-effective?

Suppose you wanted to make 100 grams of water. what is the molar mass of water (h2o)?

Some liquids can be distilled, but only at temperatures that are so high that it is impractical, or so high the compound decomposes. explain why distillation such compounds at significantly less than atmospheric pressure (some degree of vacuum) would solve this problem.