Elements & Compounds (SC.P.8.5/8.6/8.8/8.9)

Which of the following best describes how elements are organized in the periodic table?

• By the number of atoms in each element

• By the similarities in their properties

• By the number of compounds they can form

• By their atomic mass

Which of the following is a compound?

• Oxygen

• Water

• Gold

• Helium

How do atoms of different elements combine to form compounds?

• By sharing or transferring electrons

• By changing their atomic number

• By splitting into smaller atoms

• By increasing their atomic mass

Which of the following is a pure substance?

• Saltwater

• Air

• Carbon dioxide

• Soil

Explain why elements in the same group of the periodic table have similar properties.

• They have the same number of protons.

• They have similar electron configurations.

• They have the same atomic mass.

• They have the same number of neutrons.

Compare the properties of acids and bases.

• Acids taste bitter, bases taste sour.

• Acids turn litmus paper blue, bases turn it red.

• Acids have a pH less than 7, bases have a pH greater than 7.

• Acids feel slippery, bases feel rough.

Which of the following is a mixture?

• Pure water

• Table salt

• Air

• Carbon dioxide

Why is it important to recognize that there are a finite number of elements?

• It helps in predicting the formation of new elements.

• It allows us to understand the diversity of compounds.

• It limits the number of possible chemical reactions.

• It simplifies the study of chemistry.

Identify the compound from the following list.

• Hydrogen

• Sodium chloride

• Nitrogen

• Argon

What distinguishes a mixture from a pure substance?

• Mixtures have a fixed composition, pure substances do not.

• Mixtures can be separated by physical means, pure substances cannot.

• Mixtures are always liquids, pure substances are solids.

• Mixtures have a uniform composition, pure substances do not.