"Exploration-Specific Heat Capacity of Matter" Mechanical energy, internal energy and their conversion PPT courseware

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"Exploration-Specific Heat Capacity of Matter" Mechanical energy, internal energy and their conversion PPT courseware

think

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

Do different types of substances absorb the same heat and have the same temperature increase?

learning target

1. Try to use specific heat capacity to explain simple natural phenomena.

2. Understand the concept of specific heat capacity and know that specific heat capacity is a property of matter.

1. Experimental research

Questions and conjectures

It takes longer to boil a kettle of water than to boil half a kettle of water, that is, it requires more heat to boil a kettle of water.

For the same substance with different masses, they will raise (or lower) the same temperature and absorb (or release) different amounts of heat.

think

When different types of substances with the same mass raise (or lower) the same temperature, do they absorb (or release) the same amount of heat?

experiment procedure

Take two identical beakers and fill them with 400g of water and 400g of kerosene respectively. Use an alcohol lamp to heat them, let them rise to the same temperature, and compare the heating times.

Experimental results

Heating materials of the same mass and different types, causing them to rise to the same temperature, takes different heating times, indicating that they absorb different amounts of heat.

When different types of substances increase (or decrease) the same temperature, the heat absorbed (or released) is not only related to the mass, but also to the type of substance.

2. Specific heat capacity

1. We call the heat absorbed (released) when the temperature of a unit mass of a substance increases (decreases) by 1°C as the specific heat capacity of the substance. Symbol: c.

2. Commonly used units: Joule/(kg·℃)

3. Unit symbol: J/(kg · ℃)

Read as: Joules per kilogram Celsius

The specific heat of several substances[J/(Kg·℃)]

Water 4.2×10³ Sand and gravel 0.92×10³ Iron and steel 0.46×10³

Ice 2.1×10³ Glass 0.67×10³ Copper 0.39×10³

Kerosene 2.1×10³ Rubber 1.7×10³ Mercury 0.14×10³

Alcohol 2.4×10³ Water vapor 1.88×10³ Aluminum 0.88×10³

Glycerin 2.5×10³ Dry soil 0.84×10³ Lead 0.13×10³

What pattern can you find from the above table?

1. Water has the highest specific heat.

2. The same substance has different specific heats in different states.

3. The specific heat of the same substance is the same, while the specific heat of different substances is generally different.

think about it

1. 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 capacity 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.

2. According to relevant experts' predictions, after the Three Gorges Hydropower Station, my country's largest hydropower station, is fully completed, the temperature in the Three Gorges Reservoir area will be affected to a certain extent: it will drop by about 2°C in summer and rise by about 2°C in winter. Why?

Answer: This is because the water in the reservoir area has a large specific heat. It absorbs heat slowly and rises slowly in summer, releases heat slowly and cools down slowly in winter, and the temperature changes are small.

3. Causes of sea and land breezes

4. Heat island effect

5. Rice seedling cultivation

Rice is a temperature-loving crop. When raising rice seedlings in March and April every year, in order to prevent frost, some water is often poured into the rice fields overnight in the evening. After the sun rises the next day, the water in the rice fields is drained. Can you explain the reason? ?

Irrigation in the evening is because the water has a large specific heat capacity and releases heat and cools slowly, so it will not cause freezing damage; watering is done during the day because the rice fields have a small specific heat capacity and absorb heat and heat up quickly, so that the seedlings can have better growth conditions.

Summary of this lesson

What did you learn from this lesson?

Specific heat capacity

1. Definition: The heat absorbed (released) when the temperature of a unit mass of a substance increases (decreases) by 1°C is called the specific heat capacity of the substance.

2. Characteristics: Specific heat capacity is one of the characteristics of a substance. It is only related to the type and state of the substance.

Practice in class

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

A. The higher the temperature, the greater the specific heat capacity

B． The more heat a substance releases, the greater its specific heat capacity

C. The greater the mass of a substance, the smaller its specific heat capacity

D． The specific heat capacity of a substance is independent of mass and temperature

2. Among the following four phenomena, the one that has a great relationship with the specific heat capacity of water is ( )

A. Car engines are cooled by circulating water

B． Hot water is often used for heating in daily life

C. Use water to wash clothes in daily life

D． The temperature difference in tidal flats and wetlands is small

3. If one-third of a cup of kerosene is used, then its ( )

A. Specific heat remains unchanged

B. Specific heat is one-third of the original value

C. Specific heat is two-thirds of the original value

4. On hot days, under the same sunlight, the temperature of dry land rises faster than that of paddy fields. This is because ( )

A. Dry land absorbs more heat

B. Paddy fields are not easy to absorb heat

C. The specific heat capacity of water is greater than the specific heat capacity of soil.

D. The quality of dry land and paddy fields is different

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Update Time: 2024-11-22

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