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