Topicmd3528c46302815e2_1528449000663_0Topic

How do we calculate the heat required to change the temperature, to melt or evaporate the body?

Levelmd3528c46302815e2_1528449084556_0Level

Second

Core curriculummd3528c46302815e2_1528449076687_0Core curriculum

The student uses the concept of specific heat, heat of melting and heat of evaporation together with its unit.

Timingmd3528c46302815e2_1528449068082_0Timing

45 minutes

General objectivemd3528c46302815e2_1528449523725_0General objective

Introducing the concept of specific heat, melting heat and evaporation heat.

Specific objectivesmd3528c46302815e2_1528449552113_0Specific objectives

1. Introducing the concept of specific heat.

2. Presenting the concept of melting heat.

3. Presenting the concept of evaporation heat.

Learning outcomesmd3528c46302815e2_1528450430307_0Learning outcomes

The student:

- using the concept of specific heat, melting heat and evaporation heat,

- determining the heat required to heat the body.

Methodsmd3528c46302815e2_1528449534267_0Methods

1. Flipped classroom.

2. Learning through the application of the acquired rules and solving problem tasks.

Forms of workmd3528c46302815e2_1528449514617_0Forms of work

1. Individual work.

2. Working in groups on solving problem tasks.

Lesson stages

Introductionmd3528c46302815e2_1528450127855_0Introduction

Please answer the following questions:

1. What is the specific heatspecific heatspecific heat and what is its unit?

2. Specify the formula with which you can determine the heat required to heat the substance with mass m by Δt.

3. What is the heat of meltingmeltingmelting of substances and what is its unit?

4. Present the method for determining the heat required to melt the body with mass m at the meltingmeltingmelting point.

5. What is the heat of evaporationevaporationevaporation of substances and what is its unit?

6. Present the method for determining the heat required to evaporate liquids with mass m.

Proceduremd3528c46302815e2_1528446435040_0Procedure

[Slideshow]

In groups prepare the answers to the following questions:

Question 1
Specific heatspecific heatSpecific heat - the amount of thermal energy required to increase the heat one kilogram of substance by one degree Celsius (one Kelvin). It is the quantity which characterizes a given substance. In the SI system the unit of specific heat is $\left[\frac{J}{kg\cdot K}\right]$.

This definition can be written using the following formula:

where:
$c_w$ - is the specific heatspecific heatspecific heat of the substance,
Q - the heat that must be added to heat the body,
m - the mass of heated body,
Δt – the change in temperature of the body.

Teacher's comment:

The specific heatspecific heatspecific heat of a substance depends on the type of substance and its state of matter. Table 1 shows sample values of specific heat.

[Table 1]

Question 2
By converting the definitional formula of specific heat, we get the formula for the heat required to heat the body with mass m to obtain the temperature change of Δt:md3528c46302815e2_1527752263647_0Question 2
By converting the definitional formula of specific heat, we get the formula for the heat required to heat the body with mass m to obtain the temperature change of Δt:

Question 3
Heat of meltingmeltingmelting - the amount of heat (energy) which should be added to 1 kilogram of substance to melt it. This is the quantity which characterizes a given substance. In SI system the unit of melting heatmelting heatmelting heat is $\left[\frac{J}{kg}\right]$.

This definition can be written using the following formula:

where:
L – the melting heatmelting heatmelting heat of a substance,
Q - the amount of heat added to a substance during the meltingmeltingmelting process,
m – the mass of the melted body.

Question 4
By converting the definition formula of the melting heat we get:md3528c46302815e2_1527752256679_0Question 4
By converting the definition formula of the melting heat we get:

Teacher's comment:

The melting heatmelting heatmelting heat depends mainly on the type of substance. Table 2 shows example values of melting heatmelting heatmelting heat.

[Table 2]

Question 5
Evaporation heatevaporation heatEvaporation heat - the amount of heat (energy) which should be added to 1 kilogram of substance to make it evaporate. This is the quantity which characterizes a given substance. In SI system the unit of melting heatmelting heatmelting heat is $\left[\frac{J}{kg}\right]$.

This definition can be written using the following formula:

where:
R – the evaporation heatevaporation heatevaporation heat of a substance,
Q - the amount of heat added to the substance during the evaporationevaporationevaporation process,
m – the mass of the eaporated body.

Question 6
By converting the definition formula of the evaporation heat we get:md3528c46302815e2_1527712094602_0Question 6
By converting the definition formula of the evaporation heat we get:

Teacher's comment:

The evaporation heatevaporation heatevaporation heat depends primarily on the type of substance. Table 3 shows sample evaporation heatevaporation heatevaporation heat values.

[Table 3]

Lesson summarymd3528c46302815e2_1528450119332_0Lesson summary

- The amount of heat energy Q for heating the body depends on the temperature change we want to observe, as well as on the mass of the heated body and the type of substance.

- Specific heat is used to compare the thermal properties of bodies.

- Specific heat - the amount of thermal energy required to heat one kilogram of substance to be raised by one degree Celsius (one Kelvin). Specific heat is the quantity that characterizes a given substance.

- In order to melt a solid, energy must be added, and in order to solidify the liquid (to change its state from the liquid to solid), energy must be taken away from it.

- Melting heat is the amount of heat (energy) which should be added to 1 kilogram of substance to melt it. This is the quantity which characterizes a given substance.

- Freezing heat is the amount of energy that should be taken away to solidify 1 kilogram of a substance.

- Evaporation of liquids and boiling (evaporation in the whole volume of liquid) requires a supply of heat energy to the liquid, whereas condensation requires energy abstraction from the substance in the gas phase.

- Evaporation heat - the amount of heat (energy) which should be added to 1 kilogram of substance to make it evaporate (to change its state from the liquid to gas). This is the quantity which characterizes a given substance.

- Condensation heat - the amount of heat (energy) which should be abstracted to condense 1 kilogram of a substance. This is the quantity which characterizes a given substance.

Selected words and expressions used in the lesson plan

evaporationevaporationevaporation

evaporation heatevaporation heatevaporation heat

liquidliquidliquid

meltingmeltingmelting

melting heatmelting heatmelting heat

solidsolidsolid

specific heatspecific heatspecific heat

thermal insulationthermal insulationthermal insulation