Topic 8

Question 1

What do we know about the melting and bioling points of pure substances ?

Answer 1

They will melt and boil at a specific temperature
e.g pure water boils at exactly 100

Question 2

What do we know about the melting and boiling points of impure substances ?

Answer 2

They melt and boil across a range of temps
e.g impure water may boil between100-105 degrees

Question 3

What is a formulation? Give an example

Answer 3

A mixture that has been designed for a specific use
E.g. paints, fuel, cleaning products

Question 4

What is the stationary phase in chromatography?

Answer 4

The paper

Question 5

What is the mobile phase in chromatography

Answer 5

The solvent

Question 6

What would the result of chromatography to a pure substance be?

Answer 6

Only 1 dot on the piece of paper

Question 7

What would the result of chromatography to a impure substance be?

Answer 7

Multiple dots on the paper

Question 8

Explain the steps to chromatography.

Answer 8

• use a pencil to draw a line at the bottom of the paper
• dot dye/ink along the pencil line
• lower the paper into the solvent
• the solvent should be below the line
• wait until the solvent reaches the top of the paper into

Question 10

How can you use chromatography to identify a substance?

Answer 10

Find its rf value

Question 11

What is the test for hydrogen?

Answer 11

Squeaky pop
- hold a burning splint at the end of a test tube containing hydrogen
- if hydrogen is present you will hear a squeaky pop sound

Question 12

What is the test for oxygen?

Answer 12

• hold a glowing splint at the end of a test tube containing oxygen
• if oxygen is present the splint will relight

Question 13

What is the test for carbon dioxide

Answer 13

• bubble carbon dioxide through lime water
• this will cause the lime water to turn milky

Question 14

What is the test for chlorine?

Answer 14

• place damp litmus paper at the end of a test tube containing chlorine
• the litmus paper will be bleached and turn white