POS  Key Concept:  Thermal expansion  K2e:  Investigate and describe the effects of heating and cooling on the volume of different materials, and identify applications of these effects (use of expansion joints on bridges and railway tracks to accommodate thermal expansion

Materials  Ball and ring  Candle, lighter  Ice cubes/water/beaker  Balloons x2, blowdryer  Race to the top apparatus

Ball and Ring Magic Trick  The Ball does not fit through the ring. Or does it?

Unit C: Heat and Temperature Topic 4: Expansion and Contraction

When expansion occurs  Temperature rises  More space between particles  Increase in volume  Less dense  Particles move faster  Float  *exception: ice expands

When contraction occurs:  Temperature decreases  Less space between particles  Decrease in volume  More dense  Particles move slower  sink

 Can you think of technologies that rely on principles of expansion and contraction?

 Hot air balloon  Cement paving stones

Bimetallic strip  Different metals expand and contract different amounts depending on the temperature  We use this property in a coil to operate a thermostat

Table Reading Activity  Pg 211 #1, 2, 1, 2

Pg 211  #1  a) The similarities that we see as all substances warm is that they expand!  b) The materials react differently in that they expand different amounts.  c) The material that expands the most as it warms according to the table was lead  d) The material that expands the least as it warms according to the table was pyrex.

Pg 211  2. Expands the most  Lead  Aluminum  Brass  Copper  Steel  Glass  pyrex

Pg 211  1. The materials that expand the most contract the most. The lead also contracts the most.  2. The hole in the pie will be filled by the expanding pie, so the juice will not run out.

Bulging Balloons Activity  Pg 215  Balloons x2

Race for the top Activity  Pg 216

Practical Applications  Sagging wires  Railway tracks  Bridge expansion joints  Road construction

Expansion joint-bridge  Engineers need to design road and bridge joints that can allow for expansion and contraction

Electrical transmission lines

Power/phone lines  Summer: lines expand and droop  Winter: lines contract, pulling tight

Frost Heave

Mechanical Weathering  Water gets into cracks in rocks, freezes and expands, splitting the rock. Year after year, the cracks get bigger

Review Q’s T4  Pg 217 #4,5  Read and take your own notes Topic 5  *Evaporative cooling

Review pg 217  #4  a) Graph X is the warming curve. In the summer, items expand, so the volume increases. This means that as the temperature is increasing, the particles are moving faster, they have more energy, the spaces between them are greater.

Pg 217  4b) a) Graph Y is the cooling curve. In the winter, items contract, so the volume decreases. This means that as the temperature is decreasing, the particles are moving slower, they have less energy, the spaces between them are smaller.

 4c) When you put a thermometer in a bowl of hot soup, the increased temperature (thermal energy) will cause expansion of the liquid inside the thermometer, as the particles are moving faster, and further apart. Graph X illustrates this warming curve, as the volume will increase.

 4d) When you put a thermometer in a bowl of ice cream, the decreased temperature (thermal energy) will cause contraction of the liquid inside the thermometer, as the particles are moving slower, and closer together. Graph Y illustrates this cooling curve, as the volume will decrease.

Review pg 217  #5