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Chemistry > The chemical Earth > Flashcards

The chemical Earth Flashcards

1
Q

What are compounds?

A

Pure substances that are composed of two or more elements chemically bonded together. They are composed of a fixed number of atoms of each component. Can be decomposed into their components or simpler compounds

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2
Q

What are mixtures?

A

Have various particle types and compositions. They are a mix of different elements or compounds which are not chemically bonded together

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3
Q

What are homogenous and heterogenous mixtures?

A

Homogenous mixtures have uniform composition. Their individual components cannot be easily distinguished

Heterogenous mixtures do not have uniform composition. Their invidious components can be easily distinguished due to visible boundaries

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4
Q

What are pure substances?

A

Substances that have fixed properties and composition. They cannot be decomposed by physical separation techniques

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5
Q

What are impure substances?

A

They are mixtures. They have variable composition and properties. They can be separated via physical separation techniques

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6
Q

What are the the four major spheres of the earth?

A

The lithosphere
The atmosphere
The hydrosphere
The biosphere

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7
Q

What’s the lithosphere and give examples of different substances that are found in this sphere?

A

Consists of the crust and the upper mantle

Main elements that are found include oxygen, silicon and aluminium

Many minerals are also found including quarts, calcite and orthoclase feldspar

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8
Q

What are elements?

A

Simplest pure substance that consists of only one atom, cannot be decomposed or broken down

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9
Q

What is the biosphere and what are its major substances?

A

All living things, occurs in all spheres

Elements include oxygen, carbon and hydrogen

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10
Q

What is the atmosphere? Give examples of elements

A

Air, is a mixture of different molecules and gases

Major gases are nitrogen, oxygen and argon

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11
Q

What is the hydrosphere? Give examples

A

Liquid part of the earth

Hydrogen and oxygen are most abundant

Contain many dissolved minerals

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12
Q

What is sieving used for?

A

To separate solids of different particle sizes

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13
Q

What is filtration used for?

A

To separate substances of different particle sizes(usually liquid and solid)

Passes through filter paper and what is left is called the filtrate

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14
Q

What is centrifuging used for?

A

Spins mixture so more dense particles sink to the bottom

Difference in density

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15
Q

What is magnetic separation?

A

Uses a magnet to separate magnetic and non magnetic components

Used to separate iron mineral grains from rock

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16
Q

What is sedimentation and decanting?

A

Where heavier particles sink to the bottom of a liquid. Removal of the liquid portion is called decanting. Solid stuff can then be collected

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17
Q

What is froth flotation?

A

Air is blown through a mixture after adding substances called ‘collectors’, collection of froth yields particles, uses tendency to adhere to bubbles

18
Q

What is evaporation used for?

A

To separate a solute from a solvent. Difference in boiling points

Eg salt water

19
Q

What is distillation?

A

The separation of liquids based on large difference in boiling points

20
Q

What does miscible and Immiscible mean?

A

Miscible refers to two liquids that can dissolve into one another

Immiscible refers to when a significant proportion does not form a solution

21
Q

What is fractional distillation used for?

A

Used to separate liquids or gases that have close boiling points

Used to separate crude oil

22
Q

What is gravimetric analysis?

A

Involves separating the components of a mixture and accurately determining their masses

Percentage composition can then be calculated

23
Q

When would gravimetric analysis be used in industry?

A

Percentage by weight of ingredients in food

Extent of heavy pollution in river water and human food

Purity and composition of alloys in building construction

24
Q

What are some examples of physical properties?

A 
Density
Boiling point 
Melting point 
Electrical conductivity 
Appearance 
Thermal conductivity
25
Q

What are some uses of metals based on their physical properties ?

A

Electrical wiring
Jewellery (gold silver)
Construction

26
Q

What are some used for semi metals?

A

Transistors in computer chips

27
Q

What are atoms?

A

The smallest particles of an element that can take part in a chemical reaction

28
Q

What are ions?

A

Charged atoms that are formed when an atom gains are loses an electron

29
Q

What are atoms made of?

A

Protons, neutrons and electrons

30
Q

What are isotopes ?

A

Elements that have different number of neutrons

31
Q

What is an ionic substance?

A

A substance that consists of a metal and non metal

32
Q

What is a covalent substance ?

A

A substance that consists of non metals

33
Q

What is a metallic substance?

A

A substance that consists of metal cations

34
Q

What is decomposition?

A

When a compound or molecule decomposes to form its individual components

35
Q

What is synthesise?

A

A type of reaction in which two or more reactants react to form one product

36
Q

outline the steps in the seperation of argon from air

A
  1. compression
    air is cooled crygenically and compressed

2.rapid expansion
air cools and liquifies

3.fractional distillation
argon seperates from the other gases (except for oxygen) when the temperature exceeds -186C

oxygen is removed by its reaction with hydrogen forming water, argon doesnt react and is inert

after removing the water using a molecular sieve dryer, the argon is re-cooled

37
Q

what are the properties of argon that enable it to be extracted in this way?

A

its inert

it has a different boiling point then all the other gases in air (but close to oxygen)

38
Q

in what sphere does this seperation involve?

A

the atmosphere

39
Q

what are the uses for argon?

A
  • inert atmosphere when manipulating metals

- blue-green discharge lamps (‘neon’ signs)

40
Q

what are the waste managment issues associated with the extraction of argon from air?

A

heat must dissipate slowly into the environment to limit thermal pollution

41
Q

what is the difference between the boiling of water and the electrolysis of water?

A

the boiling on water is a physical change, where the inter-molecular forces between each water molecule is weakened and broken, enabling these molecules to be in rapid motion, hence it becomes a gas

electrolysis however is a chemical change, where two new compounds or elements are created from breaking the intramolecular bonds between the hydrogen and oxygen atoms in the molecule. this process requires a lot more energy than to boil water, hence electrical energy

Chemistry (5 decks)

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