2.2) Thermal expansion

Question 1

what is thermal expansion

Answer 1

When a material is heated, particles have more kinetic energy so move more, resulting in more space between molecules

Question 2

Order of expansion in states of matter

Answer 2

expansion in gases> liquids> solids
because gases have the largest intermolecular spaces and least intermolecular forces

Question 3

How to fit gear and axle by expansion

Answer 3

Axle shrinks when cooled by liquid nitrogen. When gear and axle are placed at room temperature, axle regains original size by expansion giving a good fit

Question 4

Opening a metal lid by expansion

Answer 4

Put metal lid in hot water, lid will expand more than glass jar. Opens

Question 5

Bimetallic strip

Answer 5

When temperature of iron increases above certain value, brass expands more than iron causing strip to bend and break contact, turning the heater off, so temperature stops rising
When the temperature of iron decreases, the strip straightens back switching back the heater

Question 6

Precautions of overhead cables by expansion

Answer 6

Overhead cables must be loose to allow contraction in winter.

Question 7

Railway tracks

Answer 7

Spaces must be left between tracks to allow free expansion in supper. To prevent buckling

Question 8

Airport runway

Answer 8

Add bitumen spaces between concrete blocks to allow expansion and contraction in summer in winter. To prevent cracks in concrete

Question 9

Bridges

Answer 9

Rollers are to allow free expansion for bridge in summer and free contraction in winter