"Studying the Specific Heat Capacity of Substances" Internal Energy and Heat Engine PPT Courseware 2

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"Studying the Specific Heat Capacity of Substances" Internal Energy and Heat Engine PPT Courseware 2

1. What is heat? What is the unit? What letters represent calories?

The amount that can be changed in an object during heat transfer is called heat

Unit J, heat is represented by Q

2. What is the calorific value of fuel? What letters represent calorific value? What is the unit of calorific value?

The heat released by the complete combustion of 1 kilogram of a certain fuel is called the calorific value of the fuel.

Represented by the letter q, the unit is J/Kg or J/m3

3. The calorific value of kerosene is 4.6×107J/Kg. What is its physical meaning?

The heat released by complete combustion of 1 kilogram of kerosene is 4.6×107J

Different substances of the same mass absorb different amounts of heat when the temperature rises by the same degree. This shows that the heat absorbed by the object is also related to the type of substance. This is what we are going to learn today.

Inquiry activities

Design experiments based on conjectures

Option 1: Take water and kerosene of equal mass and the same initial temperature, heat them for the same time (equal heat absorption), and compare the temperature changes.

Option 2: Take equal masses of water and kerosene, raise them to the same temperature, and compare the heating time (the amount of heat absorbed).

Experimental requirements:

1. The quality of kerosene and water is the same as the initial temperature

2. The heating sources should be the same

In the experiment: If the heating methods are exactly the same, it can be considered that the heat absorbed by the substance in the same time is the same.

In order to express the difference in the heat absorption and release properties of different substances, the physical quantity of specific heat capacity is introduced in physics.

Experiments show that the heat released when the temperature of a unit mass of a certain substance decreases by 10C is equal to the heat absorbed by a 10C increase in temperature.

We compare the heat absorption capacity of water and kerosene by comparing how much they absorb or release heat when the temperature rises or decreases by 1°C per unit mass.

Specific heat capacity (C) - The amount of heat absorbed or released by a unit mass of a substance that increases or decreases its temperature by 1°C, is called the specific heat capacity of this substance.

Definition formula: C=Q/m△t

Unit: J/(Kg 0C)

The specific heat capacity of a substance is related to the type of substance. The specific heat capacities of different substances are generally different;

Water has the largest specific heat capacity;

The specific heat capacity of a substance is not only related to the substance and type, but also related to the state of the substance. For example, the specific heat capacity of water and the specific heat capacity of ice are not equal;

The specific heat of water is___________

Its physical meaning is:_______________

Specific heat capacity is a characteristic of matter, just like density is a characteristic of matter. The specific heat capacity of the same substance in the same state is constant and does not change with the amount of heat absorbed or released by the object, its mass, or the rising or falling temperature.

If the temperature of 5Kg of water increases by 10°C, how much heat will be absorbed?

1. To heat 2kg of water at 20°C to 100°C, how much heat must be supplied?

Known: c water = 4.2 × 103J/(kg · ℃), m = 2kg

Initial temperature t1=20 ℃, final temperature t2=100 ℃

Request: Q suck

Solution: According to Q=ｃｍ△t=ｃｍ（t-t0）

Q suction = 4.2×103J/(kg · ℃) ×2kg×(100-20)℃

=6.72×105J

A steel ingot with a mass of 100kg and the temperature drops from 1.3×103 ℃ to 30 ℃, how much heat is released?

Known: c steel=0.46×103J/(kg · ℃), m=100kg

Initial temperature t1= 1.3×103 ℃, final temperature t2=30 ℃

Request: Q release

Solution: According to Q=ｃｍ△t=ｃｍ(t0-t)

Q discharge = 0.46×103J/(kg · ℃) ×100kg×(1300-30)℃

=5.84×107J

Compare to see who is the smartest?

1. People choose to use water to cool their engines and heat their engines. Why is this?

2. There is a large temperature difference between day and night in desert areas, but not much in coastal areas. What is the reason for this?

Water has a large specific heat capacity. Under the conditions of a certain quality, water absorbs (or releases) a lot of heat when it rises (or decreases) to a certain temperature. Using coolant or heating with water has a good effect.

It can be seen from the specific heat capacity table that among various substances, water has the largest specific heat capacity. This means that the temperature of water changes less when it is heated or cooled.

Because the specific heat capacity of seawater is large and that of sand and gravel is small, seawater absorbs or releases the same heat as sand and gravel, and the temperature rises or falls less. When exposed to the same sunlight during the day, the temperature change of seawater is smaller. The temperature in coastal areas rises more slowly than in inland areas. It releases heat at night and the temperature in coastal areas decreases less. Therefore, during the day, the temperature changes little in coastal areas and large in inland areas. Similarly, inland areas are hotter than coastal areas in summer and colder inland areas during winter.

practise:

1. The specific heat capacity of water is 4.2×103J/(kg·℃). Heating water with a mass of 4kg from 20℃ to 70℃ requires absorbing _____J heat. If half of the water is poured out, its specific heat capacity will be _____J/(kg.℃)

2. The specific heat capacity of water is twice that of kerosene. If the mass ratio of water and kerosene is 1:2, and the ratio of heat absorbed is 2:3, then the ratio of the rising temperatures of water and kerosene is ()

A:3:2 B:2:3 C:4:3 D:3:4

Thermal balance relationship: Q release = Q absorb

When two objects with different temperatures are put together, the high-temperature object will release heat and the temperature will decrease; the low-temperature object will absorb heat and the temperature will increase; finally, the two objects have the same temperature, which is called thermal equilibrium.

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For more information about the PPT courseware "Internal Energy and Heat Engine to Study the Specific Heat Capacity of Substances", please click the "Internal Energy and Heat Engine ppt to Study the Specific Heat Capacity of Substances" ppt tag.

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"Studying the Specific Heat Capacity of Substances" Internal Energy and Heat Engine PPT Courseware:

"Studying the Specific Heat Capacity of Substances" Internal Energy and Heat Engine PPT Courseware Learning Objectives 1. Understand the concept of specific heat capacity, know that specific heat capacity is a characteristic of a substance, a physical quantity that reflects the heat absorption and release properties of a substance, know that the unit of specific heat capacity is J/(kg.℃) and that the specific heat capacity unit...

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Update Time: 2024-08-16

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