Sec 3 Pure Chem ECM Quiz

Identify the following as an element, compound or mixture.

• element

• compound

• mixture

• not sure

Answer explanation

The different atoms in each molecule are chemically combined together to form a molecules and hence each molecule is a compound. Since all the molecules are identical in the diagram, the diagram thus represent a compound.

Identify the following as an element, compound or mixture.

• element

• compound

• mixture

• not sure

Answer explanation

Notice that the atoms exist as individual single atoms, not combined to any other atoms. Thus each atom here represent an atom from the same element since the atoms are identical.

Identify the following as an element, compound or mixture.

• element

• compound

• mixture

• not sure

Answer explanation

The different atoms in each molecule are chemically combined together to form a molecules and hence each molecule is a compound. Since all the molecules are identical in the diagram, the diagram thus represent a compound.

Identify the following as an element, compound or mixture.

• element

• compound

• mixture

• not sure

Answer explanation

Here the diagram shows two different substances mixed together.

There are two different substances, one substance that consist of molecules of compound and another consist of molecules of an element.

Thus the diagram shows a mixture of one compound and one element.

Identify the following as an element, compound or mixture.

• element

• compound

• mixture

• not sure

Answer explanation

The molecules consists of identical atoms chemically combined together. Thus each molecule represent a molecule of an element. Thus the particle diagram shows an element.

Identify the following as an element, compound or mixture.

• element

• compound

• mixture

• not sure

Answer explanation

Here the diagram shows two different substances mixed together.

One substance consist of molecules of an element and another substance consist of an element made up of only one single atom.

Thus the diagram shows a mixture of two elements.

What substances can br represented by the particle diagram shown?

• oxygen gas & nitrogen gas

• helium gas & argon gas

• oxygen gas & water

• oxygen gas & helium gas

Answer explanation

Group 18 elements are monatomic, which means that they exist as single atoms.

Generally, most gases are diatomic, which means that they exist as a molecule containing two identical atoms chemically combined together.

A compound can be separated into its constituent elements using ..................... methods.

Answer explanation

A compound chemical bonds between the atoms and hence only chemical methods can break these bonds to separate the atoms in the compound. Examples of chemical methods are use of electricity (electrolysis), heating (thermal decomposition) etc.

A mixture can be separated into its constituent elements using ..................... methods.

Answer explanation

Physical methods such as the various separation techniques which you have learnt before, such as crystallization, filtration, chromatography etc are used to separate the components in a mixture.

Determine if each of the following is an element, compound or mixture.

Ammonia gas

• element

• compound

• mixture

• not sure

Answer explanation

Ammonia gas has a chemical formula of NH₃ and hence is a compound since it has atoms bonded in a fixed ratio in one molecule of ammonia.