Bulk & Surface Properties of Matter Including Nanoparticles Flashcards

All 12 cards in this deck

What is a nanoparticle?

A particle less than 100 nm in size, made of a few hundred atoms — larger than atoms and molecules but far smaller than everyday particles.

What is 1 nanometre in metres, written in standard form?

$1 \times 10^{-9}$ m

e.g. 100 nm $= 1 \times 10^{-7}$ m

True or false? As the diameter of a nanoparticle decreases, its surface area : volume ratio decreases.

False. As the particle gets smaller the surface area : volume ratio increases.

What are the steps to find the surface area : volume ratio of a cube-shaped nanoparticle?

e.g. a cube of side 10 nm

1. Surface area $= 6 \times$ side $\times$ side $= 6 \times 10 \times 10 = 600$
2. Volume $=$ side$^3 = 10 \times 10 \times 10 = 1000$
3. Write and simplify surface area : volume $= 600 : 1000 = 3 : 5$

Why are nanoparticles of titanium(IV) oxide used in some sunscreens?

They absorb or reflect UV light so prevent sunburn/skin damage, and are so small they cannot be seen on the skin (no white marks).

State a possible risk of using nanoparticulate materials.

Their long-term effects are not known (new technology, no long-term research); they may pass through cell membranes into the body or bloodstream and catalyse changes there.

Why is a catalyst made of nanoparticles better than one made of larger particles?

The nanoparticles have a much larger surface area (large surface area : volume ratio), which increases the rate of reaction.

What is a composite material?

A material made of two or more different materials combined, one reinforcing the other.

e.g. concrete = cement, sand and stone

What are the typical physical properties of glass and clay ceramics?

Hard, stiff and brittle, with high melting points; insulators of heat and electricity; inert (do not corrode or react with water/acids).

What are the typical physical properties of polymers?

Flexible, low density, electrical and thermal insulators, with low melting points; waterproof and generally unreactive.

True or false? Ceramics such as glass are highly flexible and bend easily without breaking.

False. Ceramics have low flexibility — they are brittle and shatter or crack instead of bending.

What are the steps to use a table of property data to choose the best material for a use?

e.g. choosing a material for a container to hold an acid

1. Decide which properties the use needs: inert / does not corrode
2. Compare the data for each material against those properties
3. Pick the best match and justify it: glass, because it is unreactive and does not corrode