Topic 2- States of matter and mixtures

Question 1

What does pure man in chemistry?

Answer 1

-one type of element/compound

Question 2

What is a mixture?

Answer 2

-Multiple chemical components
-Not chemically bonded

Question 3

What is different about a pure vs mixtures melting graph?

Answer 3

• Pure has one temp where all is melted
• Mixture has a range of temps over which it melts

Question 4

How are mixtures separated through simple distillation?

Answer 4

• Heated to form a gas (one element)
• Rises until it is condensed in the condenser
• Collected in a separate vial

Question 5

How are mixtures separated through fractional distillation?

Answer 5

• Same as simple distillation
• Has fractionating column
• Many little glass rods
• High surface area and very cool
  - prevents wrong liquid rising to the condenser
• Cooler at the top due to height (far from heat)

Question 6

What does simple distillation separate?

Answer 6

• Liquid from a solution

Question 7

How can distillation be improved?

Answer 7

• Thermometer to check the temp of the liquid
• Anti-bumping granules
• Water through the bottom of the condenser for control

Question 8

What does fractional simple distillation separate?

Answer 8

Mixture of liquids

Question 9

How are mixtures separated through filtration?

Answer 9

• Liquid (filtrate) seeps through filter paper
• Filter funnel into a beaker
• Leaves solute

Question 10

How are mixtures separated through crystallisation?

Answer 10

• Heated
• Solution evaporated
• Leaves solid

Question 11

How are mixtures separated through Chromatography?

Answer 11

• line drawn in pencil
• dot on the line (ink)
• Chromatography (absorbent) paper in beaker
• Submerge ends with water (not over the line)

-Water (or ethanol)=MOBILE PHASE dissolves the component
-Paper= STATIONARY PHASE

• Different components in thee ink will move up at DIFFERENT RATES (due to attraction to different phases)
• Impure substances will produce more than one spot/ colour

Question 12

How do we calculate the Rf value?

Answer 12

distance travelled by component/ distance travelled by the water

Question 13

How can salt water be made potable through desalinisation?

Answer 13

• it is simple distillation

Question 14

What are the negatives to desalination?

Answer 14

• ## Requires lots of energy

Question 15

What stops water being potable?

Answer 15

• High levels of microbes
• High levels of dissolved salts
• Too high or too low pH (6.5-8.5)

Question 16

How is water made potable (cycle)?

Answer 16

• Rain water collects in reservoirs
• Passed through a metal mesh to get rid of stones and twigs
• Passed through layer of sand and stone to remove smaller substances
• Sterilisation to remove micbrobes, by bubble chlorine gas through it or exposing it to uv light

Question 17

Why must water be pure for science?

Answer 17

So there are not any unknown elements/ compounds interfering with the results.