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Friday, Oct. 4th: “A” DayMonday, Oct. 7th: “B” Day
AgendaHomework Questions/Collect Finish 2.3: “Measurements and Calculations in
Chemistry”Specific heat, scientific notation
Homework:Pg. 63: #1-8, 10, 11“Scientific Notation/Significant Figures” WSConcept review: “Measurements and Calculations
in Chemistry”
Homework Questions“Significant Figures Practice” worksheet“Additional Problems” worksheet
Problems/Questions?
Hand In
Specific HeatRemember, specific heat is the amount of
energy that must be transferred as heat to raise the temperature of 1 g of a substance by 1K or 1°C.
The amount of energy depends on:The nature of the materialThe mass of the materialThe size of the temperature change
Calculating Specific HeatThe specific heat of a substance at a given
pressure is calculated by the formula:
Cp = q_____ (m) (ΔT)
Cp is the specific heat at a given pressureq is the energy transferred as heat (Joules)m is the mass of the substance (grams)ΔT if the difference between the initial and
final temperatures (K)
Sample Problem B, pg. 61A 4.0 g sample of glass was heated from 274 K to
314 K and was found to absorb 32 J of energy as heat. Calculate the specific heat of this glass.
Cp = q_____
(m) (ΔT)q = 32 Jm = 4.0 gΔT = 314K – 274K = 40 K
0.20 J/g•K (2 sig figs)
Practice #1, pg. 61Calculate the specific heat of a substance if a
35 g sample absorbs 48 J as the temperature is raised from 293 K to 313 K.
Cp = q_____
(m) (ΔT)q = 48 Jm = 35 gΔT = 313K – 293K = 20 K
0.069 J/g•K (2 sig figs)
Scientific NotationChemists often make measurements and
perform calculations using very large or very small numbers.
To make calculations with these numbers easier, scientists use scientific notation.
In scientific notation, the exponent on the number 10 tells how many places the decimal point moves.
TTo change a number into scientific notation,
follow these steps:
1. Put a decimal point after the first non-zero digit.2. Add a multiplication sign and then the number 10.3. Count how many spaces the decimal point moved
and make that the exponent on the number 10.4. If the original number was less than 1, the sign on
the exponent is negative!5. If the original number was more than 1, the sign
on the exponent is positive!
Scientific Notation ExamplesWrite the following in scientific notation:
1. 123,000 grams 1.23 X 105 grams
2. 9,125,600 liters 9.1256 X 106 liters
3. 0.000931 meters 9.31 X 10-4 meters
Scientific Notation with Sig Figs Scientific notation eliminates non-significant
zeros.2,400 meters 2.4 X 103 meters
(the two 0’s are NOT significant)
When doing calculations, the answer must contain the correct # of sig figs.
5.44 X 107 = 671.6049383 8.1 X 104
6.7 X 102 (2 sig figs)
HomeworkSec. 2.3 review, pg. 63: #1-8, 10, 11“Scientific Notation/Significant Figures” WorksheetPAPERS DUE NEXT TIME!!Concept Review: “Measurements and
Calculations in Chemistry”Next time: Quiz over sec. 2.3 Ch. 2 test/concept review due:
“A” Day: Thurs. 10-17“B” Day: Fri. 10-18