Topic 1.31-1.40 - Types of substance Flashcards
Draw a dot and cross diagram for hydrogen
2 H circles overlapping, with one dot and one cross in the overlapping space
Draw a dot and cross diagram for water
A central circle with an O in it that has a circle with a H in it diagonally overlapping with it on either side. In each overlap is a dot and a cross. On the O circle’s perimeter are 4 dots/crosses.
Draw a dot and cross diagram for hydrogen chloride
1 H circle and one Cl circle overlapping with one dot and one cross in the overlapping space and 6 dots/crosses just on the Cl circle’s perimeter
Draw a dot and cross diagram for methane
A circle with a C in it that has a circle with a H in it overlapping on each of its 4 sides. There is a dot and a cross in each overlap.
Draw a dot and cross diagram for oxygen
2 H circles overlapping with 2 dots and 2 crosses in the overlapping space and 4 dots/crosses on the perimeter of each circle
Draw a dot and cross diagram for carbon dioxide
A central circle with an C in it that has a circle with a O in it overlapping with it on either side. In each overlap are 2 dots and 2 crosses. On each O circle’s perimeter are 4 dots/crosses.
Explain the structure of ionic substances
-Ionic compounds are made up of a metal and a non-metal
-Ionic compounds have regular structures (giant ionic lattices) in which there are strong electrostatic forces of attraction in all directions between oppositely charged ions
-They have high melting and boiling points, because a lot of energy is required to break the many strong bonds/strong electrostatic forces between ions
-they often dissolve in water to form an aqueous solution
Explain whether ionic compounds conduct electricity
-When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and carry current
* They do not conduct electricity as solids, because the ions are fixed in place and are not able to move, carrying charge with them
Explain the structure of simple molecular (covalent) substances
-They are made up of nonmetal elements
-Substances that consist of small molecules are usually gases or liquids that have low boiling and melting points
-They have weak intermolecular forces between the molecules. These are broken in boiling or melting, NOT the covalent bonds. Only weak intermolecular forces needing to be overcome results in their low melting/boiling points
* The intermolecular forces increase with the size of the molecules so larger molecules have higher melting and boiling points
Explain whether simple molecular covalent bonds conduct electricity
-Substances that consist of small molecules don’t conduct electricity, because small molecules do not have charged particles or electrons that are free to move so don’t have an overall electric charge. Although, some breakdown in water to form ions which can conduct electricity
Explain whether simple molecular covalent bonds are soluble
Many are insoluble in water, but some are soluble because they can form intermolecular forces with water which are stronger than those between water molecules or their own molecules already (e.g. CO₂ and NH₃)
Explain the structure and properties of giant covalent structures
-They are made up in nonmetal elements
-They are solids with very high melting and boiling points
* All of the atoms in these structures are linked to other atoms by strong covalent bonds which must be overcome to melt or boil these substances
-Some can conduct electricity, whereas others can’t because they have no charged particles that are free to move
Explain the structure of metallic substances
-Metals consist of giant structures of atoms arranged in a regular pattern. they are always made up of just metallic elements
-The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure
-The sharing of delocalised electrons gives rise to strong metallic bonds
The electrons leave the outer shell, resulting in positive metal ions and a sea of delocalised electrons
Explain the properties of metallic substances
-Most metals have high melting and boiling points due to their strong metallic bonding
-They can conduct heat and electricity because of the delocalised electrons in their structures
-Conduction depends on the ability for electrons to move throughout the metal
-The layers of atoms in metals are able to slide over each other, so metals can be bent and shaped (malleable)
-They are insoluble in water, but some can react with it instead
Describe the structure of diamond
Each carbon atom is joined to four others in single covalent bonds. Diamond has a giant covalent structure. This means it includes shared pairs of electrons and strong bonds
Explain the properties of diamond
-In diamond there are no free electrons so it does not conduct electricity.
-Many bonds need to be broken to melt it which needs lots of energy, therefore it has a high melting point.
-It has lots of strong covalent bonds and is therefore a very strong material.
Describe the structure of graphite
Each carbon atom is joined to three others in single covalent bonds. Graphene has a giant covalent structure. This means it includes shared pairs of electrons and strong bonds.
The layers can slide over each other due to a lack of covalent bonds between the layers, but weak intermolecular forces. This means that graphite is soft and slippery.
Explain the properties of graphite
-Many bonds need to be broken to melt it which needs lots of energy, therefore it has a high melting point.
-It has lots of strong covalent bonds and is therefore a very strong material.
-Each carbon atom has one free electron, hence delocalised electrons so it can conduct electricity.
Explain graphite’s uses
-It makes electrodes because it can conduct electricity
-It makes lubricant because it has weak intermolecular forces and no covalent bonds between the layers, therefore it is soft and slippery
Explain diamond’s uses
-It’s used to make cutting tools because its very hard due to its rigid structure
Explain the properties of fullerenes
-The carbon atoms are bonded by strong single covalent bonds with shared pairs of electrons.
-Each carbon atom is joined to three others.
-It has a molecular structure.
-Each carbon atom has one free electron, this is delocalised.
-There is no or little movement of electrons between molecules so fullerene is a poor conductor of electricity. It is termed a semi-conductor. Fullerene only conducts electricity across the surface of the molecule.
Describe the structure of simple polymers
Simple polymers consist of large molecules containing chains of carbon atoms.
They are linked by strong covalent bonds.
Intermolecular forces between polymer molecules are relatively strong so these substances are solid at room temperature.
