Structure Of Molecules Flashcards
Giant covalent structures have many atoms joined together by covalent bonds to form?
A giant lattice
Giant covalent lattices have …. Melting and boiling points
High
Why does graphite conduct heat and electricity well?
Because it has free electrons.
Why do simple molecular substances not conduct electricity?
Because they don’t have free electrons or an overall electric charge.
Why do simple molecular substances have low melting and boiling points?
Because they have weak intermolecular forces.
Why do substances with giant covalent structures have high melting points?
Because a lot of strong covalent bonds must be broken.
Why does graphite have layers that can slide over each other?
Because there are no covalent bonds between them.
What is a thermos offending polymer?
They soften when heated and can be shaped when hot. The shape will harden when cooled, but it can be reheated and reshaped.
What is a thermosetting polymer?
Once moulded, they don’t soften when heated and can’t be reshaped.
Metals are malleable. What does this mean?
They can be bent and shaped because they consist of layers of atoms. These layers can slide over each other when the metal is bent, hammered or pressed.
What is a metallic bond?
Metals form giant structures, in which electrons in the outer shells of the metal atoms are free to move. The metallic bond is the force of attraction between these free electrons and metal ions.
Why are metallic bonds strong?
So metals can maintain a regular structure and usually have high melting and boiling points.
Why are metals good conductors of electricity and heat?
Because the free electrons can move throughout the metal.
What is an alloy?
A mixture of 2 or more elements, where at least one element is a metal
Why are alloys harder than the pure metal?
Because alloys contain atoms of different sizes, so the arrangement of the atom is distorted. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.
