Transcript Document

Specific Heat Lab
pg 6
Record the temperature of the boiling water
(Ti of metal = T of boiling water)
Put 50 mL of distilled water in the calorimeter
(m of water in cup = 50 g)
Record the starting temperature of the calorimeter
(Ti of water in cup)
Place one of the hot metals in the calorimeter (quickly).
Gently stir with temperature probe until the temperature remains
constant , then record .
(Tf of metal = Tf of water in cup)
Dry & record mass of the metal and return to the boiling water
Repeat steps for the other metal. (Each pair does two metals/4)
Metal 1
Mass of
Metal 2
58 g
metal
Ti of metal
Boiling water ~ 100oC
Tf of metal
ΔT = Tf – Ti
of metal
Mass of
water
Ti of water
Tf of water
ΔT = Tf – Ti
of water
50 g
Rm temp water ~ 20oC
Metal 3
Metal 4
Metal
Ti = (B. pt. ~ 100 0C)
Transfer
→
Hot Metal ↓T
+
Cold Water↑T
Water 50 ml
(Ti = ? 0C)
Room Temp Metal Tf = Water Tf
~ 20 0C
= ? 0C
Temperature
(“Degree of hotness”)
- is the distribution of energy through
the molecules.
- related to the motion (speed) of molecules.
Heat ≠ Temperature
Heat (“Quantity of hotness”)
- is a form of energy. [units: Joules (J)]
- related to both the motion and mass of
molecules.
Q = m
x ∆T x c
Heat = mass x ∆T x Cp
oC
J
g
J/g oC
Specific heat (Cp) = amount of heat energy
required to raise 1 g of a
substance 1 oC.
Specific heat for water = 4.18 J/g oC
Thermal calories
1 cal = 4.18 J
vs.
Food Calories
1 Cal = 1000 calories
= 1 kcal
Practice
A 110.0-g sample of iron at 55.5 oC raises the
temperature of 150.0 mL of water from 23.0 oC
to 25.5 oC. Determine the specific heat of the
iron in J/g oC.
Heat = mass x T x spec. heat
Heat gain (H2O) = heat loss (metal)
Heat gained by H2O:
Heat = 150.0 g x 2.5C x 4.18 J/gC
( 25.5- 23.0)
= 1567.5 J (2 sigs) =
1600 J
Heat gained by H2O = heat lost by metal
1600 J = 1600 J
Heat lost by metal:
Heat = mass x T x spec. heat
1600 J = 110.0 g x 30.0C x spec.heat
(55.5 – 25.5)
1600 J
= Spec.heat (Cp) = 0.48 J/goC
110.0 g x 30.0C
For each metal calculate:
pg 7
oC
𝐶
=
4.18
J/g
1. Heat gained by the water
𝑤𝑎𝑡𝑒𝑟
𝑄𝑤𝑎𝑡𝑒𝑟 = 𝑚𝑤𝑎𝑡𝑒𝑟 𝐶𝑤𝑎𝑡𝑒𝑟 ∆𝑇𝑤𝑎𝑡𝑒𝑟
2.Remember that
Heat gained by the water = Heat lost by the metal
𝑄𝑤𝑎𝑡𝑒𝑟 = 𝑄𝑚𝑒𝑡𝑎𝑙
3.Solve for the specific heat of the metal
𝑄𝑚𝑒𝑡𝑎𝑙
𝐶𝑚𝑒𝑡𝑎𝑙 =
𝑚𝑚𝑒𝑡𝑎𝑙 ∆𝑇𝑚𝑒𝑡𝑎𝑙
4. Identify the metal: Cu or Pb or Sn or Zn
Given:
Cu
Pb
Sn
Zn
0.385 J/g0C
0.129 J/g0C
0.228 J/g0C
0.388 J/g0C
5. Calculate % error for each metal:
𝐴𝑐𝑡𝑢𝑎𝑙 − 𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙
% 𝑒𝑟𝑟𝑜𝑟 =
× 100%
𝐴𝑐𝑡𝑢𝑎𝑙