Pure Substances and Mixtures

What is a pure substance in chemistry?

• A substance with added preservatives

• A single substance made of only one type of particle

• A mixture of different elements

• A combination of compounds and elements

Which of the following is an example of a pure substance?

• Sea water

• Air

• Helium gas

• Orange juice

What does the term 'impure' mean in chemistry?

• A single compound with no impurities

• A substance with a fixed boiling point

• A substance made from only one element

• A mixture of elements or compounds not chemically bonded

Why does adding salt to water change its boiling point?

• Salt raises the boiling point

• Salt lowers the boiling point

• Salt has no effect on boiling point

• Salt makes the water pure

What is the boiling point of pure water?

• 90°C

• 120°C

• 100°C

• 110°C

Which of the following is NOT a pure substance?

• Distilled water

• Mountain stream water

• Carbon dioxide

• Sodium chloride

What is a compound?

• A mixture of different gases

• A pure substance made from two or more elements chemically bonded

• A substance with impurities

• A single element

How can you test if a substance is pure?

• By checking its color

• By tasting it

• By measuring its melting or boiling point

• By smelling it

What is the melting point of pure water?

• 0°C

• 10°C

• 20°C

• 30°C

Which of the following statements is true about air?

• Air is made of only oxygen

• Air is a compound

• Air is a mixture of gases

• Air is a pure substance