module 2 Flashcards

Question

What are properties of simple molecular structures and covalent bonds?

Answer 1

Usually gas or liquid at room temperature, as molecule gets bigger strength of intermolecular force increase, so more energy needed to break them, melting and boiling points increase. Molecular compounds don't conduct electricity. because aren't charged; so no free electrons or ions.

Answer 2

lots of small units linked together to form long molecule that has repeating sections. Joined together by covalent bonds.

Answer 3

can draw shortest repeating section in brackets and put a small n on the bottom right to show it repeats. To find molecular formula write down molecular formula of repeated section an put 'n' outside bracket. e.g. poly(ethene)=(C2H4).

Answer 4

Larger than intermolecular forces than simple covalent molecules, more energy needed to brake them. Most polymers are solid at room temperature. Intermolecular forces still weaker than ionic or covalent bonds so generally have lower boiling points than ionic or giant molecular compounds.

Answer 5

Bonded by strong covalent bonds, high melting and boiling points so lots of energy needed to brake covalent bonds between atoms. Don't contain charged particles-don't conduct electricity-not even when molten (few exceptions e.g. graphite).

Answer 6

giant covalent structure, each carbon atom forms 4 strong covalent bonds making diamond really hard and needs lots of energy to break-high melting point, in a very rigid giant covalent structure. Doesn't conduct electricity because has no free electrons or ions.

Answer 7

Each carbon atom forms 3 covalent bonds to create layers of carbon hexagons. Each carbon atom also has one delocalised electron. No covalent bonds between layers-held together weakly-free to move over each other. Makes graphite soft and slippery making graphite the ideal lubricating material. High melting point-covalent bonds need lots of energy to break. Only 3 of 4 electrons in outer shell shared-1 delocalised electron-conducts electricity and thermal energy.

Answer 8

Sometimes called silica, this is what sand is made of. Each grain of sand is one giant structure of silicon and oxygen

Answer 9

sheet of carbon joined in hexagons. Sheet 1 atom thick-2 dimensional compound. Network of covalent bonds makes it very strong, incredibly light-can be added to composite materials to improve strength without adding much weight. Contains delocalised electrons so can conduct electricity through whole structure. Means has potential to be used in electronics.

Answer 10

molecules of carbon shaped like closed tube or hollow balls. Mainly made of carbon atoms arranged in hexagons but also contain pentagons or heptagons.

Answer 11

can be used to 'cage' other molecules. Fullerene structure forms around another atom or molecule, then trapped inside. Could deliver drug into body. Has high surface area, could help make great industrial catalysts-individual catalyst molecule could be attached. Also make great lubricant.

Answer 12

What fullerenes come from-tiny carbon cylinders. Ratio between length and diameter of nanotubes is high, can conduct electricity and thermal energy (heat). Have high tensile strength (don't break when they're stretched)

Answer 13

Technology that uses small particles such as nanotubes is called nanotechnology. Nanotubes can be used in electronics or to strengthen materials without adding much weight such as tennis racket frames.

Answer 14

metals are giant structure. Electrons in outer shell of metal atoms are delocalised. Strong forces of electrostatic attraction between positive metal ions and shared negative electrons.

Answer 15

forces of attraction hold atoms together in regular structure and are known as metallic bonding. Metallic bonding is very strong.

Answer 16

Delocalised electrons in metallic bonds which produce all the properties of metals.

Answer 17

electrostatic forces between metal atoms and delocalised sea of electrons are very strong (revision guide). So needs lots of energy to be broken. Most compounds with metallic bonds have very high melting and boiling points, so generally solid at room temperature.

Answer 18

Delocalised electrons carry electrical current and thermal (heat) energy through whole structure, so metals are good conductors of electricity and heat.

Answer 19

Layer of atoms in metal can slide over each other, making metal malleable-means they can be bent or hammered or rolled into flat sheets.

Answer 20

pure metals are often soft, so are mixed with other metals to make them harder, most of metals we use everyday are alloys-mixture of 2 or more metals or metal and other element. Alloy is harder and more useful than pure metals.

Answer 21

When new element is mixed with pure metal, new metal atoms will distort layers of metal atoms, making it more difficult for them to slide over each other. Makes alloys harder than pure metals.

Answer 22

temperature depends on how strong the forces of attraction are between particle and material.

Answer 23

material, temperature, pressure.

Answer 24

strong forces of attraction between particles, which holds them closer together in fixed positions to form a very regular lattice arrangement. Particles don't move from their positions, so all keep a definite shape and volume and don't flow. Particle vibrate about their positions-hotter the solid becomes, more they vibrate (causing solids to expand slightly when heated.)

Answer 25

Weak forces of attraction between particles. Random arranged and free to move past each other, tend to stick closely together. Have definite volume but don't keep definite shape and flow to fill bottom of container.

Answer 26

Very weak forces of attraction, free to move and far apart. Particles in gases travel in straight lines. Gases don't keep definite shape or volume, will always fit container. Particles move constantly with random motion. Hotter gas gets faster move. Gases either expand when heated or their pressure increases.

Answer 27

particles aren't solid or inelastic and aren't spheres-they're atoms, ions or molecules. Also model doesn't show forces between particles so there's no way of knowing how strong they are.

Answer 28

Dissolved in water (see revision guide to see state symbols).

Answer 29

When solid is heated its particles gain more energy

Answer 30

Makes particles vibrate more, which weakens forces that hold the solid together.

Answer 31

At certain temperature, called melting pint particles have enough energy to break free from their positions. Called melting and solids turns into liquid

Answer 32

When liquid is heated again, particles get even more energy

Answer 33

Energy makes particles move faster, weakens and brakes bonds holding liquid together

Answer 34

At certain temperature called boiling point, particles have enough energy to break bonds. This is boiling (or evaporating) liquid becomes gas

Answer 35

As gas cools, particles no longer have enough energy to overcome forces of attraction between them.

Answer 36

Bonds form between particles

Answer 37

At boiling point, so many bonds have formed between gas particles that gas becomes liquid. Called condensing.

Answer 38

When liquid cools, particles have less energy, so move around less

Answer 39

There's not enough energy to overcome attraction between particles, so more bonds form between them.

Answer 40

At melting point, so many bonds have formed between particles that they're held in place. Liquid becomes solid, called freezing.

Answer 41

the strength of forces between particles are, stronger forces=more energy needed to brake them=higher melting and boiling points.

Answer 42

(PM10[small 10]) and 10,000 nm (1*10-5m). Also called dust.

Answer 43

(PM2,5[small 2.5]) has diameter 100nm (1*10-7m) and 2,500nm (2.5*10-6m)

Answer 44

has diameter between 1nm (1*10-9m) and 100nm (1*10-7m). Particles contain only a few hundred atoms.

Answer 45

Nanoscience.

Answer 46

surface area to volume ratio=surface area/volume.

Answer 47

Surface area increases in relation to their volume. Causes their surface area to volume ratio to increase.

Answer 48

have high surface area to volume ratio, means surface area is very large compared to volume.

Answer 49

Can cause properties of material to be different depending on whether it's a nanoparticle or a bulk. E.g. you'll often need less of a material that's made up of nanoparticles to work as an effective catalyst compared to a material; made of 'normal' size particles (containing billions of atoms rather than a few hundred)

Answer 50

high surface area to volume ratio-new catalysts. Nonomedicine-tiny particles are absorbed more easily by body than most particles. Can deliver drugs to cells where needed. Some nanoparticles conduct electricity-used in tiny electric circuits for computer chips, silver nanoparticles have antibacterial properties-added to polymer fibers that are often used in surgical masks and wound dressing and can also be added to deodorants. Nanoparticles also being used in cosmetics. E.g. used to improve moisturisers without making them really oily

Answer 51

Way affect body not fully understood-important to test new products thoroughly to minimise risks. Some worried that products containing nanoparticles been available before effects on human health been investigated properly, we don't know long-term impacts on health. Some believe products containing nanoscale products should be labelled, so customers can choose whether or not to use them.

Answer 52

Idea: Being tested on sun creams as been shown to be better than materials in traditional sun creams at protecting skin from harmful UV rays, also gives better skin coverage than traditional sun creams. Limitations: Not yet clear whether nanoparticles can get into your body and whether they can damage cells. Also possible when they are washed away, might damage environment.

module 2 Flashcards

(76 cards)