Bulk & Surface Properties Flashcards

All 12 cards in this deck

What size range of structures does nanoscience refer to?

$1$–$100$ nm, of the order of a few hundred atoms.

What range of diameters do fine particles (PM2.5) have?

Between $100$ nm and $2500$ nm, i.e. $1\times10^{-7}$ m to $2.5\times10^{-6}$ m.

What range of diameters do coarse particles (PM10) have, and what are they often called?

Between $1\times10^{-5}$ m and $2.5\times10^{-6}$ m; they are often referred to as dust.

What are the steps to express a particle size given in nanometres as a size in metres in standard form?

e.g. a particle of diameter $40$ nm

1. Recall $1$ nm $= 1\times10^{-9}$ m
2. Multiply: $40\times10^{-9}$ m
3. Write in standard form: $4\times10^{-8}$ m

How do the dimensions of nanoparticles compare with the typical size of atoms and molecules?

Nanoparticles ($1$–$100$ nm) are only a few hundred atoms in size; a single atom is about $0.1$ nm across.

What are the steps to calculate the surface area to volume ratio of a cube?

e.g. a cube of side $2$ cm

1. Surface area $= 6 \times$ side$^2 = 6\times2\times2 = 24\ \mathrm{cm^2}$
2. Volume $=$ side$^3 = 2\times2\times2 = 8\ \mathrm{cm^3}$
3. Ratio $= 24 : 8 = 3 : 1$

True or false? As the side of a cube decreases by a factor of 10, its surface area to volume ratio also decreases by a factor of 10.

False. The surface area to volume ratio increases by a factor of 10.

Why may nanoparticles have different properties from the same material in bulk?

Because they have a very high surface area to volume ratio.

True or false? Larger quantities of a nanoparticulate material are needed to be effective than of the same material with normal particle sizes.

False. Smaller quantities of the nanoparticulate material are needed to be effective.

Give the main applications of nanoparticles.

Medicine, electronics, cosmetics and sun creams, deodorants, and catalysts.

Give one advantage of using nanoparticles instead of fine particles of the same material in a coating or cream.

Less material is needed for the same effect (a thinner coating), because of the higher surface area to volume ratio.

What possible risks are associated with the use of nanoparticles?

Their effects on health are not fully known — they may be absorbed into the body or enter cells, and long-term effects have not been tested.