Question

sep evaluate information graphite is a soft substance used in writing instruments like pencils. carbon nanotubes are the hardest substance known to human. both are made entirely of carbon atoms. explain why each allotrope has such different properties.

revisit
investigative phenomenon
go online to elaborate and evaluate your knowledge of ionic and molecular compounds by completing the class discussion and engineering design activities.

in the cer worksheet, you drafted a scientific argument to explain how materials used on mountaintops are engineered. with a partner, re - evaluate the evidence cited in your arguments.

sep analyze data designing materials requires being able to recognize and categorize properties. on the lab bench, there are three vials labeled a, b, and c. the table summarizes the results of a series of analyses that have been performed on the contents. interpret the data and determine whether each vial contains a molecular, ionic, or covalent network solid.

property	vial a	vial b	vial c
electrical conductivity	moderate	poor	poor
hardness	hard	soft	very hard

Explanation:

Step1: Recall properties of different solids

Ionic solids have high melting - points, moderate electrical conductivity when molten or in solution (moderate conductivity in solid can be due to defects), and are hard. Molecular solids have low melting - points, poor electrical conductivity, and are soft. Covalent network solids have very high melting - points, poor electrical conductivity (except some like graphite), and are very hard.

Step2: Analyze Vial A

Vial A has a high melting - point, moderate electrical conductivity, and is hard. These properties match those of an ionic solid.

Step3: Analyze Vial B

Vial B has a low melting - point, poor electrical conductivity, and is soft. These properties match those of a molecular solid.

Step4: Analyze Vial C

Vial C has a very high melting - point, poor electrical conductivity, and is very hard. These properties match those of a covalent network solid.

Answer:

Vial A contains an ionic solid.
Vial B contains a molecular solid.
Vial C contains a covalent network solid.