What is the difference between a pure substance and a mixture ? Give one example in each case.

Name two solid, two liquid and two gaseous elements at room temperature.

What are the three types in which all the elements are classified ? Name two elements belonging to each group.

Classify the following into metals, non-metals, and metalloids

mercury, diamond, carbon, silicon, copper, helium, magnesium, sodium, boron, germanium.

Name a metal which is soft and a non-metal which is very hard.