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CC7F
GCSE Combined Science Chemistry
Question | Answer |
---|---|
What is a molecule? | A particle made from two or more atoms bonded together by covalent bonds. |
What is the name of the structure of a substance if it is made up of small molecules? | Simple Molecular |
Describe the structure and bonding of molecular substances? | Atoms in a molecule are held together by strong covalent bonds. Neighbouring molecules are held close by weak intermolecular forces. |
Why are the melting point of simple molecular substances low? | Melting them only needs a little energy to break weak intermolecular forces. |
Why don’t simple molecular substances conduct electricity? | Their structure does not contain any charged particles that are free to move. |
Name three examples of simple molecular substances | Any three from Hydrogen, oxygen, chlorine, water, carbon dioxide, methane |
Describe the structure of a substance which is giant molecular | An infinite structure made up of a repeating pattern of atoms covalently bonded together. |
Why are the melting point of giant molecular substances high? | It requires the breaking of many strong covalent bonds. |
Why don’t giant molecular substances conduct electricity? | Do not conduct (except graphite) because there are no electrons free to move. |
What is a polymer? | A large molecule made of a small unit repeated many times. |
What is a monomer? | A small molecule that can be joined together many times to form a polymer |
What is an allotrope of an element? | A different structural form of an element made of the same atoms just bonded together differently. |
Name the four allotropes of carbon | Graphite, diamond, graphene and fullerenes |
Why is graphite a good lubricant? | The layers of carbon atoms can slide over each other |
Why is graphite a good conductor of electricity? | There are delocalised electrons between the layers of carbon atoms. |
Why is diamond so hard? | Every carbon atom is bonded to four other carbon atoms in a repeating pattern. |
Why can’t diamond conduct electricity? | There are no delocalised electrons in diamond? |
Describe the structure of graphene | A single layer of carbon atoms in a honeycomb pattern. |
Describe the structure of Buckminster fullerene | A ball shaped molecule of 60 carbon atoms. |
Describe the structure of metals | A lattice of positive metals ions surrounded by a cloud of delocalised electrons. |
Why can metals all conduct electricity? | The delocalised electrons are free to move. |
What does malleable mean? | When a substance dents when it is hit instead of shattering. |
Why are metals malleable | The layers of metal ions can easily slide over each other when hit. |
Why do metals have high melting points | Melting metals requires breaking the strong force of attraction between the lattice of metal ions and the cloud of delocalised electrons. |
List the properties of ionic compounds | High melting point, often soluble in water, solid does not conduct electricity, liquid/solution does. |
List the properties of simple molecular substances | Low melting point, does not conduct electricity, sometimes soluble in water. |
List the properties of giant molecular substances | High melting point, does not conduct electricity (except graphite), insoluble in water. |
List the properties of metals | High melting point, does conduct electricity, insoluble in water |
List three problems of bonding models. | Dot and cross diagrams make electrons seem different, they are not |
What is the name given to the structure of diamond, graphite and silicon dioxide? | Giant covalent |
How many bonds does each carbon have in diamond? | 4 |
Explain why diamond has a high melting point | Giant structure, Strong covalent bonds between the atoms, requires a lot of energy to break |
Explain why most giant covalent substances do not conduct electricity (3 marks) | There are no electrons/ions/charged particles that are free to move |
Explain why graphite conducts electricity | Has delocalised electrons between the layers that can move through the graphite |
Explain why graphite can act as a lubricant | Weak forces between layers which are free to slide over each other |
What is a fullerene? | Substance made of carbon atoms arranged in a cage |
What type of substance are methane and water? | Simple molecular (or simple molecules) |
What is a molecule? | A group of atoms chemically bonded together |
Describe the structure of simple covalent molecules | Strong covalent bonds between atoms, weak forces holding the molecules together |
What are intermolecular forces? | Weak forces between molecules which hold them together |
Explain why methane has a low melting point | It is a simple molecular substance with weak forces between the molecules (which are easy to break) |
What is a polymer? | Millions of small molecules joined together in a chain to form a large molecule |
Explain why metals can conduct electricity | Delocalised electrons are free to carry charge |
Explain why pure metals are soft | Layers of metal ions are free to slide over each other |
What are the limitations of dot and cross diagrams. | It does not show the shape of the molecule or the size of the atoms. |
If a compound name ends in -ate what does this show? | It is a molecule made of the other elements in the name and oxygen. |
What are the limitations of a ball and stick model | It does not show the electrons involved in the bonds. It does not show the 3d shape |
What elements are in sodium sulfate? | Sodium, sulfur and oxygen |