Do NowThursday, January 08,

2015

You heat a balloon filled with air. What

happens to the pressure inside of the

balloon? Why?3.5 minutes

Do Now Check

By the end of the day today, IWBAT…• Explain and calculate specific heat

Why it matters in LIFE: Explains why certain objects are made out of certain materials

Why it matters in THIS CLASS: This is the last topic we are covering before spring break – you will have a mastery quiz on Monday so let’s hit 85%!

Agenda

Do Now 5 min

Thermometer Lab Wrap Up

5 min

Specific Heat C-Notes 10 min

Specific Heat Practice Problems

30 min

Thursday, 01/08/15TEKS:

P.6E: Describe how the macroscopic properties of a thermodynamic system such

as temperature, specific heat, and pressure are

related to the molecular level of matter, including

kinetic or potential energy of atoms

By the end of today, IWBAT…

Explain and calculate specific

heat

Essential Question:

What is specific heat?

Topic:Specific Heat

Thermometer Lab Wrap Up

What were the two systems you dealt with in this lab? Which system is transferring energy into the water? How do

you know? After you turned the hot plate on, what happened to the

molecules on the surface of the plate? What type of energy is being transferred from the hot plate to

the water? How does this transfer of energy affect the molecules of water? How does this transfer of energy affect the molecules of the

liquid inside the thermometer? As particles of water strike the thermometer and transfer their

energy into the liquid inside, what happens to the pressure of the thermometer’s liquid?

How does this change in pressure allow us to use a thermometer to measure the temperature of a system?

Specific Heat

In the last step of your lab, you calculated the total heat that was put into your system in order to raise the temperature of the water

In order to be able to do this, you needed to know the SPECIFIC HEAT of the water

Specific Heat

Specific heat is a property of matter that describes the amount of energy required to raise the temperature of one gram of a substance by 1 °C

Specific Heat

Specific heat is a constant that relates heat and temperature change per kilogram

Different materials have a different specific heat

A low specific heat means heat is conducted through an object quickly

INSULATORS: Do NOT change heat easilyHigh Specific HeatRequire LOTS of energy to change temp

Specific Heat

CONDUCTORS: change heat easily

Low Specific Heat

Require little energy to change temp

Specific Heat

Material C

Water 4184

Plastic Foam 2010

Air, 200 K 1650

Aluminum 897

Iron 449

Brass 375

Insu

lato

rs Con

du

ctor

s

Recall the “Fire Proof Balloon”Specific Heat Demonstration

We have two balloons – one filled with water and one filled with air

Based on what you learned yesterday about temperature and pressure, what actually happens to the balloon?

Specific Heat – Equation

Q = mCDTQ = mC(Tf – Ti)

Q = heat (joules-J)m = mass (kg)

C = specific heat (J/kg °C)DT = change in temp (°C)

Specific Heat Demo

Why did the balloon filled with water not explode?

The water balloon does not explode because the water inside absorbs the heat better than the air does

Water has a HIGHER specific heat, which means it has a HIGH heat capacity It takes a lot more energy to change the

temperature of the water than it does for the air

Practice Problem - Q = mCDT If the specific heat of methanol is 251

J/kg˚C, how many Joules of heat are needed to raise the temp of .250 kg of methanol from 18˚C to 33˚C?

Group Practice

A .625 sample of water was cooled from 50˚C to 10˚C. How much heat was lost? The specific heat of water is 4,184 J/kg˚C.

Group Practice

The heat capacity of lead is 130 J/kg˚C. How much heat (in J) is required to raise the temperature of 15 g of lead from 22˚C to 37˚C?

Group Practice

 What is the specific heat of a substance that absorbs 250 J of heat when a sample of 10 kg of the substance increases in temperature from 10˚C to 70˚C?

Exit Ticket

Complete the exit ticket questions INDEPENDENTLY

You are not getting enough INDIVIDUAL practice before assessments, which is one of the reasons why the grades are so low

You don’t really know it unless you can do it ON YOUR OWN