States of matter and mixtures.1 Flashcards Preview

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Flashcards in States of matter and mixtures.1 Deck (35):
1

What’s an element

Substance that consists only of atoms with the same atomic number

Same protons in nucleus

2

What’s a compound

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

3

What does an element exist as

Atoms or molecules

4

What does pure mean

Substance contains only one element or compound

5

Gas to solid

Deposition

6

Solid to gas

Sublimation

7

What happens during a state change

Energy is transferred to or from the particles

The arrangement of particles changes

The movement of particles changes

8

What type of mixture can be seperated by simple distillation

A solvent from a solution

Water from sea water

9

What’s the function of a condenser in distillation

To cool the vapour
To turn it from the gas state to the liquid state

10

What’s the physical propert allowing substances to be seperated

Different boiling points

11

Describe temperature gradient in a fractionating column

Hottest at bottom and coldest at top

12

What do you use fractional distillation to separate

A liquid from a mixture of miscible liquids

(Liquids that mix completely with each other)

Ethanol from water and ethanol

13

What do you use filtration for

To seperate an insoluble substance from a liquid or a solution

14

Why would you use filtration?

To purify a liquid or solution by removing any impurities

Seperate solid you want from liquid it is mixed with

15

How does filtration work

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

16

What does decanting mean

Pouring the liquid away carefully so that the solid stays behind

17

Why do you use crystallisation

To produce solid crystals from a solution

18

What happens in crystallisation

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

Explain crystallisation

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

Why’s paper chromatography used

To Seperate mixtures of soluble substances

21

Equipment for paper chromatography

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

22

Explaining chromatography

Two phases:

A stationary phase (substance that does not move)

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

23

What happens during chromatography

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

Why would you use a chromatogram

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

25

How to calculate an Rf value

Rf = distance travelled by spot

26

Potable water must have

Low levels of contaminating substances
Low levels of microbes

27

What is tap water

Safe but not pure

Dissolved salts
Dissolved chlorine

28

Main stages in water treatment

Sedimentation
Filtration
Chlorination

29

What’s sedimentation

Large insoluble particles sink to the bottom of tank

30

What’s filtration

Small insoluble particles are removed by filtering through beds of sand

31

What’s chlorination

Chlorine gas in bubbled from the water to kill microbes

32

Evaluate distillation of sea water (simple distillation)

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

33

Describe solids

Close together
Regular pattern
Vibrate about fixed positions
Least stored energy

34

Describe liquid

Close together
Random
Move around each other

35

Describe gas

Far apart
Random
Fast in all directions
Most stored energy