Chapter 4: Elements, compounds and mixtures

Question 1

What are atoms?

Answer 1

The smallest particles of an element having the chemical properties of that element. Monoatomic.

Question 2

What are molecules?

Answer 2

Group of 2 or more atoms chemically combined. Can be elements or compounds.

Question 3

What are chemical processes?

Answer 3

A method to change one or more chemicals or chemical compounds.

Eg. oxidation, thermal decomposition, neutralisation, combustion, electrolysis

Question 4

What is an element?

Answer 4

Pure substances that cannot break down into 2 or more simpler substances by chemical processes

Question 5

How do we classify elements?

Answer 5

Metallic and non-metallic properties:

• Physical states at room temperature and pressure
• Appearance (lustrous)
• Melting and boiling points
• Ductility and malleability
• Thermal and electrical conductivity

Question 6

What are compounds?

Answer 6

Pure substances containing 2 or more elements chemically combined in a fixed ratio

Question 7

What is a mixture?

Answer 7

2 or more substances not chemically combined

Question 8

What are some differences between a mixture and compound?

Answer 8

Mixtures:

• Can be separated through physical processes (eg. magnets)
• Chemical properties of mixtures are the same as those of its components
• No energy change/chemical reaction occurs when a mixture is formed
• Can be mixed in an ratio/proportion

Compounds:

• Can only be broken down with chemical processes (eg/ thermal decomposition)
• Physical and chemical properties differ from its elements
• Chemical reaction and energy change occurs
• Always in fixed proportion