C1h - Paints and pigments

Question 1

Describe paint

Answer 1

a colloid where the particles are mixed and dispersed with particles of a liquid but are not dissolved

Question 2

Explain why the components of a colloid will not separate

Answer 2

The particles are dispersed evenly throughout the mixture and are sufficiently small so as not to settle at the bottom

Question 3

Describe how most paints dry(2)

Answer 3

Paint is applied as a thin layer

as the solvent evaporates, the paint dries and the other ingredients join to form a tough, coloured layer on the painted
surface

Question 4

Describe how oil paints dry(2)

Answer 4

solvent evaporates

the oil is oxidised by atmospheric oxygen, turns solid, forming a tough surface layer on the painted surface

Question 5

Describe emulsion paints

Answer 5

water based paints that dry when the solvent evaporates

Question 6

How can more colour changes be achieved from thermochromic pigments

Answer 6

thermochromic pigments can be mixed with acrylic paints to give even more colour changes

(e.g. blue thermochromic pigment which turns colourless when hot is added to yellow acrylic paint, the paint will appear green when cool and yellow when hot)

Question 7

How do phosphorescent pigments glow in the dark? (2)

Answer 7

they absorb natural or artificial light and store the energy

then release it as light over period of time until no energy left

Question 8

Why are phosphorescent pigments a better alternative to radioactive substances? (2)

Answer 8

safer

does not cause cancer via radiation - radioactive substances can damage cells