Question

give two examples where expansion and contraction of metals utilised

Answer 1

*making of cartwheels
*making of plough

Answer 2

Expansion: freezing water and hot air in a balloon 
Contraction : melting ice and cooling air in a balloon

Examples Of Contractions

concrete roads are left with an expansion joint 
ice in pot holes freezes and expands and makes the pot hole larger 
freezing ice also aids erosion and weathering of rocks 
sidewalks are made in smaller blocks for expansion 
a bi-metal strip is used in thermostats to control heat 
water in food expands breaking cell structure 
bridges made of metal leave an expansion joint 
use hot water to help get a top off a jar, using the expansion of the metaal top 
water expands in a coffee pot causing the percolating