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Flashcards in MIXTURES AND SEPARATION Deck (40)
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1

How can matter be classified?

Matter can be classified into pure substances and mixtures.

2

What is a pure substance?

A pure substance is composed of a single type of material only.

3

What are 3 general characteristics of a pure substance?

1. Its composition is fixed and constant.


2. Its properties are fixed and constant, for example, its melting point, boiling point and density.

3. The component parts cannot be separated by any physical process.

4

How can a pure substance be distinguished from an impure one?

To find out if a substance is pure, its melting point or boiling point can be measured. If any impurities are present they will usually lower its melting point and raise its boiling point.


Example
The boiling point of water = 100
The boiling point of sodium chloride = 108.7

5

What is an element?

Elements are the simplest form of matter.


An element is a pure substance that cannot be broken down into simpler substances by using any ordinary physical or chemical process.

Each element is composed of atoms of one kind only, example silver (Ag). A few elements are made up of molecules, e.g. nitrogen (N2) is made up of nitrogen molecules, each molecule being composed of two nitrogen atoms.

6

What is an atom?

There are three different types of particles that make up matter: atoms, molecules, ions.


An atom is the smallest (indivisible) particle of an element that can exist by itself and still have the same chemical properties as the element.

7

What is a molecule?

Molecules are groups of two or more atoms bonded together and which can exist on their own.


Molecules may be made up of atoms of the same kind (H2) or of atoms of different kinds (CO2).

Molecules of elements are made up of the same kinds of atoms whereas molecules of compounds are made up of different kinds of atoms.

8

What is an ion?

Ions are electrically charged particles. Ions may be formed from a single atom (the potassium ion, K+ or may be formed from groups of two or more atoms bonded together (the nitrate ion NO3-).

9

What is a mixture?

A mixture consists of two or more substances (elements and or compounds) which are physically combined together in variable proportions. Each component retains its own individual properties and is not chemically bonded to any other component of the mixture.


Homogenous Mixture
Heterogenous Mixture

10

What are 3 general characteristics of a mixture?

1. Its composition can vary.

2. Its properties are variable because its component parts keep their individual properties.

3. Its component parts can be separated by physical means.

11

How can a metal be described based on the following properties?

1. melting and boiling points
2. state of room temperature
3. appearance of the solid
4. bend-ability of the solid
5. density
6. electrical and thermal conductivity

1. usually high
2. solid (except mercury)
3. shiny
4. malleable (can be hammered into different shapes) and ductile (can be drawn out into wires)
5. usually high
6. good

12

How can a non-metal be described based on the following properties?
1. melting and boiling points
2. state of room temperature
3. appearance of the solid
4. bend-ability of the solid
5. density
6. electrical and thermal conductivity

1. usually low
2. can be solid, liquid or gas
3. dull
4. brittle
5. usually low
6. poor (except graphite)

13

atomic symbol?

Each element can be represented by an atomic symbol. The atomic symbol represents one atom of the element.

14

What are atomic symbols of the following metals?


aluminium
barium
beryllium
calcium
chromium
cobalt
copper
gold
iron
lead
lithium
magnesium
manganese
mercury
nickel
potassium
silver
sodium
tin
zinc

Al
Ba
Be
Ca
Cr
Co
Cu
Au
Fe
Pb
Li
Mg
Mn
Hg
Ni
K
Ag
Na
Sn
Zn

15

What are atomic symbols of the following non-metals?

argon
boron
bromine
carbon
chlorine
fluorine
helium
hydrogen
iodine
krypton
neon
nitrogen
oxygen
phosphorus
silicon
sulfur

Ar
B
Br
C
CI
F
He
H
I
Kr
Ne
N
O
P
Si
S

16

What is a compound?

A compound is a pure substance that is formed from two or more different types of elements which are chemically bonded together in fixed proportions and in a way that their properties (chemical and physical) have changed.

17

What is an example of a compound?

sodium + chlorine - - - sodium chloride
(element) (element) (compound)


The proportions, by mass, of sodium and chlorine in any pure sample of sodium chloride are always the same and the elements cannot be separated by physical means because they are chemically bonded together. The properties of sodium chloride are different from those of both sodium and chlorine.

Compounds can be represented by chemical formulae.

a metal and a non-metal
a metal and a radical
a non-metal and a non-metal

18

What is a homogenous mixture?

A homogenous mixture is a uniform mixture; it has the same composition and properties throughout the mixture. It is not possible to distinguish the component parts from each other. All solutions are homogeneous mixtures.

19

What is a heterogenous mixture?

A heterogeneous mixture is a non-uniform mixture; it is possible to distinguish the component parts from each other, though not always with the naked eye. Heterogeneous mixtures include suspensions and colloids.

20

What is a solution?

A solution is a homogeneous mixture of two/more substances; one substance is usually a liquid.

21

What is a saturated solution?

A saturated solution is a solution in which the solvent cannot dissolve any more solute at a particular temperature, in the presence of undissolved solute.

22

What are examples of solutions based on the following combinations?


1. solid + liquid
2. liquid + liquid
3. gas + liquid
4. solid + solid
5. gas + gas

1. solid + liquid = sea water (sodium chloride dissolved in water)


2. liquid + liquid = white vinegar (ethanoic acid dissolved in water)

3. gas + liquid = soda water (carbon dioxide dissolved in water)

4. solid + solid = bronze (tin dissolved in copper)

5. gas + gas = air (oxygen, carbon dioxide, noble gases and water vapour dissolved in nitrogen)

23

How can a solution be described based on the following properties?

size of dispersal
visibility of particles
sedimentation
passage of light
appearance

Size of dispersal — extremely small.


Visibility of particles — not visible, even with a microscope.

Sedimentation — components do not separate if left undisturbed.

Passage of light — light usually passes through.

Appearance — usually transparent due to light passing through.

24

What is a colloid?

A colloid is a heterogeneous mixture in which minute particles of one substance are dispersed in another substance, which is usually a liquid. The dispersed particles are larger than those of a solution, but smaller than those of a suspension.

25

What are examples of colloids based on the following combinations?


1. solid + liquid
2. liquid + liquid
3. gas + liquid
4. solid + solid
5. gas + gas

1. solid particles dispersed in a liquid = gel (gelatin, jelly)

2. liquid droplets dispersed in a liquid = emulsion (mayonnaise, milk, hand cream)

3. gas bubbles dispersed in a liquid = foam (whipped cream, shaving cream)

4. solid particles dispersed in a gas = solid aerosol (smoke)

5. liquid droplets dispersed in a gas = liquid aerosol (fog, aerosol sprays, clouds)

26

How can a colloid be described based on the following properties?

size of dispersal
visibility of particles
sedimentation
passage of light
appearance

Size of dispersal — larger than those in a solution but smaller than those in a suspension.


Visibility of particles — not visible, even with a microscope.

Sedimentation — dispersed particles do not settle if left undisturbed.

Passage of light — most will scatter light.

Appearance — translucent due to the scattering of light, or may be opaque.

27

What is a suspension?

A suspension is a heterogeneous mixture in which minute, visible particles of one substance are dispersed in another substance, which is usually a liquid.

28

What are examples of colloids based on the following combinations?

1. solid particles in a liquid
2. liquid droplets in a liquid
3. solid particles in a gas

1. Solid particles in a liquid - mud in water and powdered chalk in water

2. Liquid droplets in a liquid - oil shaken in water

3. Solid particles in a gas - dust in the air

29

How can a suspension be described based on the following properties?
size of dispersal
visibility of particles
sedimentation
passage of light
appearance

Size of dispersal — Larger than those in a colloid


Visibility of particles — visible to the naked eye

Sedimentation — dispersed particles settle if left undisturbed

Appearance — opaque due to light not being able to pass through

30

What is solubility?

Solubility is the mass of solute that will saturate 100g of solvent at a specified temperature. The solubility of a solid solute in water increases as the temperature increases.


A solubility curve is drawn by plotting solubility against temperature.