Calories and Heat

Monday 1/23 : Heating Curves

•Pick up a packet on side table

•Thurs 1/26- Quiz 1- states of matter, heating curves, heat calculations

• Tues 1/31- Quiz 2- gas laws

Thurs 2/2 Unit 8 test

• Fri 2/3- PLD day

• announcements • Unit 7 shout outs
• PPT- Heating Curves, heat

calculations

Announcements/Reminders:

Agenda:

Bellwork:

Learning check on GC

HW:

1. packet page 4

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liquid
water

ice&water

water&
steam

ice

steam

Melting Point

The first horizontal line is the constant temperature for change of solid to liquid. This the the melting point e.g. mp water = 0^oC

Copyright © Cengage Learning.
All rights reserved
24

Heating/Cooling Curve

Page 3

Multiple Choice

Between which points is the temperature of the substance remaining constant?

• A-B only

• A-B, C-D, and E-F

• B-C only

• B-C and D-E

Multiple Choice

The melting point of the sample is

• -60 ºC

• 20 ºC

• 60 ºC

• 100 ºC

Multiple Choice

Which letter indicates where water is in both the solid and liquid phase at the same time?

• A

• B

• C

• D

• E

Multiple Choice

A measure of the average kinetic energy of the particles in an object is called

• Heat

• Temperature

• Kinetic energy

• Enthalpy

Multiple Choice

In which region(s) does temperature increase?

• Region C only

• Regions B and D

• Regions A, C, and E

• Regions A and B

Multiple Choice

In which region(s) of the heating curve would water be a liquid and a gas at the same time?

• A

• B

• C

• D

• E

Multiple Choice

The energy transferred between objects that are at different temperatures is called

• Heat

• Temperature

• Energy

• Friction

Multiple Choice

Describe the substance at letter A.

• Solid

• Liquid

• Melting

• Evaporating

Multiple Choice

In a heating curve, diagonal lines indicate temperature is __________, while flat lines indicate temperature is __________.

• Constant, changing

• Changing, constant

Multiple Choice

At which letter is the substance changing its state of matter?

• A only

• A, C, and E

• D and E

• B and D

Multiple Choice

NaCl was heated starting at an initial temperature of 0°C. The heating curve is shown in the picture. What is the melting point of this substance?

• 0°C

• 801°C

• 1000°C

• 1465°C

Multiple Choice

Describe the substance at letters D.

• Gas

• Liquid

• Melting

• Evaporating

HEAT – measure of the amount of energy transferred from one substance to another

- measured in units of joules (SI unit) or calories
- 4.184 J = 1 calorie

Calorimeter - device used to measure heat

How do we calculate heat?

specific heat ( C ) - amount of heat energy required to raise the temperature of 1 g of material 1C (or 1 K )

Heat of Vaporization ( Hv) - amount of energy
needed to vaporize 1 g of a liquid at its boiling point

Hv for water = 2260 J/g

Heat of Fusion ( Hf) - amount of energy needed to melt 1 g of a solid at its melting point

Hf for water = 334 J/g

Problem 1: How many joules are required to
vaporize 1000g of water?

q= 1000 g X 2260 J = 2260000 J = 2.26 X 106 J
g

Problem 2: If we melted 70 g of ice to water, how
much energy would the ice need to absorb?

melting or freezing is
heat of fusion

Q = 70 g X 334 J = 23,380 J
g

page 4

Some text here about the topic of discussion

Answer the following questions using the chart above.

1. What is the freezing point of the substance?

2. What is the
boiling point of the
substance?

3. What is the
melting point
of the substance?

B

B

D

4. What letter represents the range
where the solid is being warmed?
A
5. What letter represents
the range where the
liquid is being warmed?
C
6. What letter represents
the range where the
vapor is being warmed?
E
7. What letter represents
the melting of the solid?
B

8. What letter represents the
vaporization of the liquid?
D
9. What letter(s) shows a
change in potential energy?
B and D
10. What letters(s) shows a
change in kinetic energy?
A, C, and E