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CHEMISTRY > States of matter and mixtures.1 > Flashcards

States of matter and mixtures.1 Flashcards

1
Q

What’s an element

A

Substance that consists only of atoms with the same atomic number

Same protons in nucleus

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2
Q

What’s a compound

A

Substance that consists of atoms of two or more different elements chemically joined together

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3
Q

What does an element exist as

A

Atoms or molecules

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4
Q

What does pure mean

A

Substance contains only one element or compound

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5
Q

Gas to solid

A

Deposition

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6
Q

Solid to gas

A

Sublimation

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7
Q

What happens during a state change

A

Energy is transferred to or from the particles

The arrangement of particles changes

The movement of particles changes

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8
Q

What type of mixture can be seperated by simple distillation

A

A solvent from a solution

Water from sea water

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9
Q

What’s the function of a condenser in distillation

A

To cool the vapour

To turn it from the gas state to the liquid state

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10
Q

What’s the physical propert allowing substances to be seperated

A

Different boiling points

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11
Q

Describe temperature gradient in a fractionating column

A

Hottest at bottom and coldest at top

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12
Q

What do you use fractional distillation to separate

A

A liquid from a mixture of miscible liquids

(Liquids that mix completely with each other)

Ethanol from water and ethanol

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13
Q

What do you use filtration for

A

To seperate an insoluble substance from a liquid or a solution

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14
Q

Why would you use filtration?

A

To purify a liquid or solution by removing any impurities

Seperate solid you want from liquid it is mixed with

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15
Q

How does filtration work

A

Filter paper has tiny pores
Allows dissolved substances
Doesn’t allow insoluble solid particles going through

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16
Q

What does decanting mean

A

Pouring the liquid away carefully so that the solid stays behind

17
Q

Why do you use crystallisation

A

To produce solid crystals from a solution

18
Q

What happens in crystallisation

A

Solution is heated to remove enough solvent to produce a saturated solution (one that cannot hold any more solute)

Saturation solution is allowed to cool

Crystals form

Crystals seperated from liquid and dried

19
Q

Explain crystallisation

A

Solubility is the mass of solute that dissolved in a given volume of solvent at a given temperature

Crystallisation works because
The solubility of the solute decreases as the saturated solution cools
Crystals from from the excess solute

20
Q

Why’s paper chromatography used

A

To Seperate mixtures of soluble substances

21
Q

Equipment for paper chromatography

A 
Lid to stop evaporation of solvent 
Paper
Drops of different samples
Solvent 
Solvent front 
Different compound 
More soluble compounded
22
Q

Explaining chromatography

A

Two phases:

A stationary phase (substance that does not move)

Mobile phase (substance that moves through the stationary phase - the solvent)

23
Q

What happens during chromatography

A

Each soluble substance in the mixture forms bonds with the two phases
Substances that form stronger attractive forces with the stationary phase stay near the bottom
Substances that form stronger attractive forces with the mobile phase move towards the top

24
Q

Why would you use a chromatogram

A

To distinguish between our and impure substances
Identify a substance by comparing patterns of spots
Identify substances using Rf values

25
Q

How to calculate an Rf value

A

Rf = distance travelled by spot

—

26
Q

Potable water must have

A

Low levels of contaminating substances

Low levels of microbes

27
Q

What is tap water

A

Safe but not pure

Dissolved salts
Dissolved chlorine

28
Q

Main stages in water treatment

A

Sedimentation
Filtration
Chlorination

29
Q

What’s sedimentation

A

Large insoluble particles sink to the bottom of tank

30
Q

What’s filtration

A

Small insoluble particles are removed by filtering through beds of sand

31
Q

What’s chlorination

A

Chlorine gas in bubbled from the water to kill microbes

32
Q

Evaluate distillation of sea water (simple distillation)

A

Used a plentiful raw material
Produces pure water
Kills microbes in sea water
Needs a lot of energy to heat water

33
Q

Describe solids

A

Close together
Regular pattern
Vibrate about fixed positions
Least stored energy

34
Q

Describe liquid

A

Close together
Random
Move around each other

35
Q

Describe gas

A

Far apart
Random
Fast in all directions
Most stored energy

CHEMISTRY (15 decks)

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