"Specific Heat Capacity" Content Energy PPT Courseware 2

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"Specific Heat Capacity" Content Energy PPT Courseware 2

review:

1. What is heat? What is the unit of heat?

During the heat transfer process, the amount of internal energy transferred is called heat, unit: joule (J)

2. Heat is always transferred from ______ object to ______ object until the temperature reaches ______.

3. Methods of changing the internal energy of an object: heat transfer and work

discuss

What factors determine how much heat an object absorbs?

1. Use the same fire to boil a large pot of water and a small cup of water respectively, and heat them to the same temperature. Which one takes longer to absorb heat? Who absorbs more calories?

2. When heating or boiling a pot of water, which situation requires absorbing more heat?

Explanation: The heat absorbed by an object is related to mass and temperature changes.

Questions and Thoughts

1. If the temperature of two glasses of water with masses of 50 grams and 100 grams increases by 30°C, do they absorb the same amount of heat?

The heat absorbed in this case is ______. The results show that the heat absorbed by the substance is related to the ______ of the substance.

2. Two glasses of water with a mass of 50 grams each absorb the same amount of heat if their temperatures increase by 20°C and 50°C respectively?

The heat absorbed in this case is ______. The results show that the heat absorbed by the substance is related to the ______ of the substance.

Take a guess

In addition to the mass of the object and the elevated temperature of the object, the amount of heat absorbed by an object may also be related to what other factors?

When different substances have the same mass and are raised to the same temperature, how much heat do they absorb?

Inquiry activities

Thoughts after the experiment

1. Which one has the stronger heat-absorbing ability, water or kerosene?

2. How to scientifically compare this characteristic of different substances?

In fact, it is very simple. It is to compare the heat absorption capacity of water and kerosene by comparing the heat absorbed by unit mass and rising by 1℃.

The thinking after the experiment is often more important than the experiment itself - Newton

About specific heat capacity

1. The specific heat capacity of a substance is similar to the density and is also one of the characteristics of the substance.

2. For a certain substance, the specific heat capacity is a certain value, which has nothing to do with the mass of the object, the temperature change, the shape, volume, position, etc. of the object. It is only related to the type and state of the substance.

3. Specific heat capacity can be used to identify the type of substance.

3. Physical meaning of specific heat capacity

For example: the specific heat capacity of water is: 4.2 × 103 J/(kg·℃)

It means that for water with a mass of 1 kilogram, the heat absorbed (or released) is 4.2 × 103 J for every 1 °C increase (or decrease) in temperature.

Exercise: The specific heat capacity of kerosene is 2.1 × 103 J/(kg·℃),

It means that when the temperature of kerosene with a mass of 1 kilogram increases (or decreases) by 1°C, the heat absorbed (or released) is 2.1 × 103 J.

Do the math

1. The specific heat capacity of water is 4.2×103 J/(Kg·℃). What is its physical meaning?

The heat absorbed (or released) by water with a mass of 1 kilogram when the temperature increases (or decreases) by 1°C is 4.2×103J.

2. The heat absorbed by 10 kilograms of water when the temperature increases by 1 degree Celsius is __________ joules.

3. The heat absorbed by 10 kilograms of water when the temperature rises by 10 degrees Celsius is __________ joules.

Class exercises

1. Regarding specific heat capacity, which of the following statements is correct ( )

A. The specific heat capacity of an object is related to temperature

B. The specific heat capacity of an object is related to the heat absorbed and released by the object

C. The specific heat capacity of an object is a characteristic of the substance itself

D. The greater the mass of an object, the greater its specific heat capacity.

2. Which of the following statements is correct ( )

A. If half of a cup of kerosene is used, its specific heat capacity will be reduced to half of its original value.

B. A substance that absorbs more heat must have a larger specific heat capacity.

C. High-temperature objects must release a lot of heat

D. Water and kerosene of equal mass absorb the same amount of heat. The temperature of kerosene rises greater than that of water.

3. In agricultural production, in order to protect the seedlings from freezing at night, more water should be poured into the rice fields in the evening. This is because of the ()

A.High density B.High specific heat capacity

C. High temperature D. Large thermal expansion

think about it

Why do seawater and sand have different temperatures at the same time?

Because seawater and sand receive sunlight for exactly the same amount of time, they absorb the same amount of heat. However, the specific heat of seawater is greater than that of sand, so seawater heats up more slowly than sand. When there is no sunlight, seawater cools down more slowly than sand.

Questions and Thoughts

Most of the earth's surface is covered by sea water. The impact of the ocean on the earth's environment is crucial. Please consider the following questions based on some relevant knowledge:

(1) What is the main reason for the big difference between inland climate and coastal climate?

(2) Imagine if the specific heat capacity of water is small, what will be the consequences on the earth? What significance does water's large specific heat capacity have to the earth's ecological environment?

(3), Reading: P:133 Climate and Thermal Pollution

summary:

1. Specific heat capacity:

1. Definition: The amount of heat absorbed by unit mass of a substance when its temperature rises by 1°C.

2. Unit: Joule per kilogram Celsius J/(kg·℃)

3. Specific heat capacity is a property of matter.

2. Calculation of heat

1. Endothermic: Q absorption=cm△t=cm(t-t0)

2. Heat release: Q release=cm△t=cm(t0-t)

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Update Time: 2024-11-18

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