PNM

Question 1

What is the Brownian motion

Answer 1

The random movement of particles suspended in a liquid or gas

Question 2

What does the kinetic theory of matter state

Answer 2

All matter is made up of numerous tiny particles which are in continuous random motion

Question 3

Why do liquids have fixed volume but not gases

Answer 3

Particles in gases move freely and randomly at high speeds to occupy any empty space. On the other hand, particles in solids can only vibrate about fixed positions while particles in liquids slide past one another freely and change positions. Thus, solid and liquids have a fixed volume

Question 4

Why are gases compressed more easily compared to solids and liquids

Answer 4

Particles in gases are spaced furthest apart compared to solids and liquids

Question 5

Why do solids have fixed shape but not liquids and gases

Answer 5

Particles in solids can only vibrate about fixed positions. On the other hand, particles in liquids slide past one another freely and change positions while particles in gases move freely and randomly at high speeds to occupy any empty space

Question 6

Why do objects expand

Answer 6

When the object is heated, its particles gain energy and vibrate more vigorously about their fixed positions. Thus, the distances between particles increase. This causes the volume of the object to increase and thus, expands

Question 7

Why do objects contract

Answer 7

When the object is cooled, its particles lose energy and vibrate less vigorously about their fixed positions. Thus, the distances between particles decrease. This causes the volume of the object to decrease and thus, contacts

Question 8

State the problems caused by expansion

Answer 8

Too much expansion on v. hot days can cause roads or pavements to crack, or tile to pop out
Railway tracks can warp due to expansion
If boiling water poured into a thick glass, glass likely to crack due to uneven expansion

Question 9

What are the uses of expansion and contraction

Answer 9

A red, hot rivet is put into position. Then hammered then allowed to cool. Contraction on cooling helps to pull two plates together
Bimetallic strip to keep temp. cold/hot (consists of 2 diff metals riveted together that expand at different rates when heated)

Question 10

What are the factors affecting rate of evaporation

Answer 10

Temperature, exposed surface area, motion of air, nature of liquid, humidity of surrounding air, pressure