Expansion in solids and liquids One of the effects of heat is expansion. Nearly all materials expand when heated. That is, they take up more space when heated and less space when cooled. Expansion is an increase in the size of a material while the opposite is contraction, which is the decrease in size. In solids, we call it as linear expansion that is an increase in length and in liquids & gases, we call it as volume expansion.
Linear Expansion When solids are heated, their length increases or they elongate. They contract when they are cooled. This means the length of solids increases as temperature increases and their length decreases as temperature decreases. Finding the increase in length or elongation: L = Lt where L ( change in length ) ( coef. of linear expansion ) L original length t ( change in temperature )
Coefficient Of linear expansion Coefficient Of volume expansion The table below shows the constants for coefficient of linear & volume expansion of some substances! Material Coefficient Of linear expansion Coefficient Of volume expansion Aluminum 2.2 x 10-5/C 7.5 x 10-5/C Brass 1.9 x 10-5/C 5.6 x 10-5/C Iron or steel 1.2 x 10-5/C 3.5 x 10-5/C Lead 2.9 x 10-5/C 8.7 x 10-5/C Concrete 3.6 x 10-5/C Gasoline 950 x 10-6/C Mercury 180 x 10-6/C Ethyl Alcohol 1100 x 10-6/C Water 210 x 10-6/C Air 3400 x 10-6/C
Linear Expansion Example 1: A steel rod is measured to be 3m long at 15C. How much does it expand when heated to a temperature of 150C? Given = ? Example 2: A metal rod that is 100cm long at 10C is observed to be 100.2cm at a temperature of 80C. What is its coefficient of linear expansion? Given = ?
In construction of railways and roads Application of Linear Expansion In construction of railways and roads In construction of bridges In making jewelries In making glass wares
Volume Expansion On the other hand, liquids expand or increase in volume when heated. Finding the increase in volume! V = V t V ( change in volume ) V original volume ( coef of volume expansion ) t ( change in temperature )
Volume Expansion Example 1: A motorist fills the 60-liter tank of his automobile with gasoline at 60F. The automobile is left in the sun, and the temperature of the gasoline rises to 110 F. How much gasoline is lost to overflow caused by expansion?
Example 2: If the volume of water is 50ml at 30 C then to what temperature will its volume change to 50.3ml?
☻ When the mercury or alcohol in a thermometer is heated, it expands. ☻ When the mercury in a sphygmomanometer is heated, it rises or it expands. Application of Volume Expansion ☻ When the mercury or alcohol in a thermometer is heated, it expands. ☻ When heat is applied in a hot air balloon, it expands.
#1 Red #2 Blue #3 Black EXERCISE : Expansion Everybody will solve #9! 1. A tall iron flagpole gets 5.1mm taller when the average temperature increases by 5C. How tall is the flagpole? 2. A certain liquid that is 20ml in volume at 30C has been observed to be 20.3ml at 70C. What is its coefficient of volume expansion? 3. A road engineer noted that a concrete wall has a length of 5 meters at 40C. When it is exposed under the sun, the wall elongates by 0.05m. At what temperature will this happen? 4. Thirty ml of ethyl alcohol was heated at a certain initial temperature. After a few seconds, its volume became 30.5ml at 35C. Find the initial temperature. If the volume of mercury in a close container is 5ml at 37C and it rises by 0.25ml when heated then what is the final temperature of the liquid? A steel rod which has a length of 6 inches is heated from 10 C to 120 C, how long will it be after the heating process. A certain liquid that is 10ml in volume at 60 F has been noted to be 10.20 ml at 200 F. Find the coefficient of volume expansion. Find the original volume of tank of gasoline which has an increase of 0.10 ml when it was heated from 300K to 305K. What is the elongation of an aluminum wire which originally measured 5cm when it is heated from 290K to 120 F. Find the increase of volume in 15ml of alcohol when it is heated from 50 F to 290K.