Atoms, elements and compounds

Question 1

Distinguishing properties of solids

Answer 1

• Solids have a fixed volume and shape and they have a high density.
• The atoms vibrate in position but can’t change location
• The particles are packed very closely - together in a fixed and regular pattern

Question 2

Distinguishing properties of liquids

Answer 2

• Liquids also have a fixed volume but adopt the shape of the container
• They are generally less dense than solids (an exception is water), but much denser than gases
• The particles move and slide past each other which is why liquids adopt the shape of the container and also why they are able to flow freely

Question 3

Distinguishing properties of gases

Answer 3

• Gases do not have a fixed volume, and, like liquids, take up the shape of the container
  -Gases have a very low density
• Since there is a lot of space between the particles, gases can be compressed into a much smaller volume
• The particles are far apart and move randomly and quickly (around 500 m/s) in all directions
• They collide with each other and with the sides of the container (this is how pressure is created inside a can of gas)

Question 4

Describe the structure of solids in terms of particles, separation arrangement and types of motion

Answer 4

in solids, there are strong forces of attraction between particles which hold them close together and fixed the position to form a very regular lattice arrangement. The particles don’t move from the position so all solid keep a definite shape. The particles vibrate about their positions the hotter the solar becomes the more vibrate (Causing solid expanse slightly when heated)

Question 5

Describe the structure of liquid in terms of particle separation arrangement and types of motion

Answer 5

In liquid there is a weak force of attraction between the particles. They are randomly arranged and free to move past each other but tend to stick closely together. Liquid have a definite volume but don’t keep a definite shape and will flow to fill the bottom of a container. The particles are constantly moving with random motion the hotter the liquid gets the faster the particles move. This causes liquids to expands slightly when heated.

Question 6

Describe the structure of gases in terms of particle separation arrangement and types of motion

Answer 6

In gases the force of attraction between the particles is very weak. They are free to movement are far apart the particles and gases travel in straight lines unless they collide with other particles or the wall of a container. Gases don’t keep a definite shape of volume and will always fill any container. The particles move constantly with random motion the hotter the gas gets the faster they move. gases either expand when heated or the pressure increases.

Question 7

Describe changes of state in terms of melting and boiling

Answer 7

Melting is when a solid changes into a liquid. Requires heat energy which transforms into kinetic energy, allowing the particles to move. Occurs at a specific temperature aka melting point

Boiling is when a liquid changes into a gas. Requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and within the liquid. Occurs at a specific temperature aka boiling point

Question 8

Describe Changes of state in terms of evaporating

Answer 8

Evaporation occurs when a liquid changes into a gas and occurs over a range of temperatures. Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid’s surface at low temperatures, below the b.p. of the liquid
The larger the surface area and the warmer the liquid surface, the more quickly a liquid can evaporate

Question 9

Describe changes of state in terms of condensing

Answer 9

Condensation occurs when a gas changes into a liquid on cooling and it takes place over a range of temperatures
When a gas is cooled its particles lose energy and when they bump into each other they lack the energy to bounce away again, instead they group together to form a liquid

Question 10

Describe changes of state in terms of freezing

Answer 10

Freezing is when a liquid changes into a solid.This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same. Water, for example, freezes and melts at 0 ºC
Requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature

Question 11

Describe And explain diffusion in terms of kinetic particle theory

Answer 11

It is where particles move from an area of high concentration to an area of low concentration. Eventually the concentration of particles is even as the particles are evenly spread throughout the available space. Diffusion happens on its own and no energy input is required
Although, it occurs faster at higher temperatures because the particles have more kinetic energy

Question 12

Describe and explain effect of relative molecular mass on the right of diffusion of gases

Answer 12

At the same temperature, different gases do not diffuse at the same rate.
This is due to the difference in their relative molecular masses
Gases with a lower relative molecular mass are “lighter” which means that they:
Travel faster, Travel further in the same amount of time
The reverse argument is true for gases with a high relative molecular mass, they:
Travel slower and dont travel as far in the same amount of time

Question 13

What is an element?

Answer 13

• A substance made of atoms that can contain the same number of protons and cannot be split into anything simpler

Question 14

What is a compound?

Answer 14

• Pure substance made up of two or more elements chemically combined
• Compounds cannot be separated into the elements by physical means
  e.g CuSO4 (Copper(ll) Sulfate, CO2 (Carbon dioxide) and CaCO3 (Calcium carbonate)

Question 15

What is a mixture?

Answer 15

• A combination of two or more substances (Elements and/or Compounds) They are not chemically Combined
• Can be separated by vocal methods such as filtration or evaporation
  e.g Sand and water, Oil and water, Sulfur powder and iron fillings

Question 16

Define proton number/atomic number

Answer 16

as the number of protons in the nucleus of an atom

Question 17

Define mass number/nucleon number

Answer 17

as the total number of protons and neutrons in the nucleus of an atom

Question 18

State that

Answer 18

• Group 8 noble gases have a full outer shell
• The number of outer shell electrons is equal to the group number in group 1-8
• The number of occupied electron shells is equal to the period number

Question 19

Define isotopes

Answer 19

as different atoms of the same element that have the same number of protons but different numbers of neutrons

Question 20

State that isotopes of the same element

Answer 20

Have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration

Question 21

State that an ionic bond

Answer 21

Is a strong electrostatic attraction between oppositely charged ions

Question 22

Describe the properties of ionic compounds

Answer 22

• High melting and boiling points
• good electrical conductivity with aqueous or molten and poor when solid

Question 23

Describe the gigantic lattice structure of ionic compounds

Answer 23

As a regular arrangement of alternating positive and negative ions

Question 24

Explain in terms of structure and bonding the properties of ionic compounds

Answer 24

Ionic compounds have high melting and boiling points - they have giant structures, strong electrostatic forces of attraction between oppositely charged ions in all directions and the forces need lots of energy to overcome them.

Question 25

Explain in terms of structure and bonding the properties of ionic compounds part two

Answer 25

Ionic compounds are poor conductors in the solid state
The ions are in fixed positions in the lattice, therefore unable to move and carry a charge

Ionic compounds are good conductors of electricity in the molten state or in solution
When the ionic compound is melted or dissolved in water, the ions are able to move and carry a charge

Question 26

State that a covalent bond

Answer 26

Is formed when a pair of electron is shared between two atoms leading to a noble gas electronic configurations

Question 27

Describe in terms of structure and bonding the property of simple molecular compounds

Answer 27

• Low melting and boiling points
• Poor electrical conductivity

Question 28

Describe in terms of structure and bonding the properties of simple molecular compounds

Answer 28

• low melting and boiling points so covalent compounds are usually liquids or gases at room temperature
• poor electrical conductivity

Question 29

Describe the gigantic covalent structures of graphite

Answer 29

Each carbon atom in graphite is bonded to three others forming layers of hexagons, leaving one free electron per carbon atom which becomes delocalised

The covalent bonds within the layers are very strong, but the layers are attracted to each other by weak intermolecular forces

Question 30

Describe the gigantic covalent structures of diamond

Answer 30

each carbon atom bonds with four other carbons, forming a tetrahedron

All the covalent bonds are identical, very strong and there are no intermolecular forces

Question 31

Relate the structures and bonding of graphite to their uses

Answer 31

Graphite as a lubricant: The weak interlayer bonding in graphite allows the layers to slide over each other easily, making it a good lubricant. This property is used in applications like pencil lead, where the layers of graphite can easily slide past each other, leaving a mark on paper

Graphite as an electrode: Graphite is a good conductor of electricity due to the delocalized electrons present in its structure. This property makes it suitable for use as an electrode in batteries and other electrochemical devices

Question 32

Relate the structures and bonding of diamond to their uses

Answer 32

Diamond in cutting tools: The strong covalent bonding in diamond makes it extremely hard and rigid. This property makes it an ideal material for cutting tools, as it can withstand high pressures and temperatures without breaking

Question 34

Describe metallic bonding

Answer 34

As the electrostatic attraction between the positive ions in a gigantic metallic lattice and a ‘sea’ of delocalise electrons

Question 35

Explain in terms of structure and bonding the properties of metal

Answer 35

Most metals have high melting and boiling points
There are strong electrostatic forces of attraction between the positive metal ions and the negative delocalised electrons within the metal lattice structure
These needs lots of energy to be broken

Question 36

Explain in terms of structure and bonding of the properties of metal part 2

Answer 36

Metals are good conductors of heat and electricity .The delocalised electrons are free to move and carry a charge through the whole structure. Most metals are malleable
This means they can be hammered into shape because the atoms are arranged in layers which can slide over each when force is applied