C2.1 Flashcards
Gases, liquids and solids with low melting points consist of what?
Simple molecules
Why do simple molecular substances have low melting and boiling points?
Because the intermolecular forces between molecules are weak
Why do giant covalent structures have high melting and boiling points?
Because there are strong covalent bonds between the atoms
Why is diamond hard?
Because of the large number of strong covalent bonds
What is the difference between the structure of diamond and graphite?
Diamond ~ Each carbon atom forms four covalent bonds with other carbon atoms
Graphite ~ Each carbon atom forms three covalent bonds with other carbon atoms
Why is graphite soft?
~ Because there are weak intermolecular forces between layers
~ so the layers can slide over each other
What is a giant ionic structure?
A regular structure held together by strong forces of attraction between oppositely charged ions
Why do giant ionic structures have high melting and boiling points?
Because large amounts of energy are required to break the strong electrostatic bonds
Why do ionic compounds conduct electricity when molten or in solution?
Because the charged ions are free to move about
What are nanoparticles?
Tiny particles that can combine to form structures called nanostructures
What are nanoparticles sensitive to?
~ Light
~ Heat
~ Magnesium
Nanoparticles possess a high surface area in relation to what?
Their volume
How are nanocomposites made?
By other materials being added to plastics
How are alloys made?
By combining two or more different metals
Why are alloys harder than pure metals?
~ Because they contain different sized atoms
~ This makes it difficult for layers to slide over each other
Graphite is the only non-metal element to do what?
Conduct electricity
What are fullerenes?
Hexagonal rings consisting of different numbers of carbon atoms joined by covalent bonds
What are fullerenes made up of?
Simple molecules
What are some uses of fullerenes?
~ Buckminster fullerenes can be used to deliver drugs into the body, or lubricants, or catalysts
~ Nanotubes can be used for reinforcing materials eg tennis racquets
What are smart materials?
A type of nanostructure designed to have specific properties
What are some examples of smart materials?
~ Lycra
~ Kevlar
~ Gore-Tex
What is Lycra?
~ Stretchy material used in sport clothing
~ Doesn’t get damaged by sweat and detergents
What is Kevlar?
~ Used to make body armour
~ Closely packed molecules and bonds form between adjacent molecules
~ Flexible and strong
What is Gore-tex?
~ Keeps rain out but lets sweat pass through
~ Waterproof
~ Used for outdoor and sports clothing
How big are nanoparticles?
1-100 nanometers
Nanoparticles have a very large what?
Surface area to volume ratio
What can nanoparticles be used for?
~ Catalysts
~ Cosmetics (sun cream, deodrant)
~ Medicine (drug delivery, antiviral and antifungal uses)
~ Construction to make items stronger and lighter
~ Computers
~ Coating (self cleaning windows)
What is a chemical bond?
Transferring or sharing electrons in the outermost shell
What is group 0 in the periodic table?
~ Noble gases
~ Full outer shell
~ Unreactive
What is group 1 in the periodic table?
~ Alkali metals
~ Produce ions with a charge of +1
What is group 7 in the periodic table?
~ The halogens
~ Produce ions called halides with a charge of -1
In ionic bonding, when an atom gets a full outer shell it is said to have reached what?
A noble gas configuration
What makes up the atomic mass?
Protons + neutrons
What does the nucleus of an atom contain?
The protons and neutrons
What do protons have a charge and mass of?
Charge = +1 Mass = 1
What do neutrons have a charge and mass of?
Charge = no charge Mass = 1
What do electrons have a charge and mass of?
Charge = -1 Mass = negligible
What is equal in a stable atom?
The number of protons and electrons because they balance each other out
What are isotopes?
Two atoms of the same element with the same number of protons but a different number of neutrons
What type of bonding occurs in simple molecules?
Covalent bonding
What group of elements do ions have the same electronic structure as?
Noble gases, group 0
What bond do two non metals form?
Covalent bond
What bond does a metal and a non metal form?
Ionic bond
What are metallic bonds?
The attraction between delocalised electrons and positive metal ions
Why do ionic compounds have no overall charge?
Because there are the same number of positively charged ions and negatively charged ions
