"Click New Materials" Materials Around Us PPT Courseware

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"Click New Materials" Materials Around Us PPT Courseware

learning target

1. Understand some characteristics, applications and development prospects of nanomaterials, semiconductor materials, superconducting materials, and invisible materials.

2. Understand the impact of new materials on human life and social development

Core test points: Applications and characteristics of new materials

Preview before class

1. Nano is a unit of length, the size is _______________ meters. When the particles of material are as small as nanometers, significant changes will occur in ________. For example, gold is golden yellow under normal conditions, but its nanoparticles have turned into _________, and _________ has decreased significantly.

2. Nanotechnology has significant applications in various aspects such as _____, _____, _____, _____, _____, _____, etc.

3． When the temperature drops to a certain temperature, the resistance of some conductors will _____. This characteristic of the material is called superconductivity. In 1997, the zero-resistance temperature of the superconducting material developed in my country has reached _____K, which is at the world's advanced level. ．

4． Some materials can be stretched and twisted like springs when heated and remain __________ after cooling; when heated again, they return to their __________ shape. This alloy is called a shape memory alloy.

5. Objects coated with invisible materials can absorb most of the __________ emitted by radar, but very little __________.

Lectures in class

Knowledge point 1. Nanomaterials

(1) Nano is a unit of length, with a size of one billionth of a meter (10-9m). When the particles of a material reach nanometer size, the properties of the material will change significantly. Nanotechnology is widely used in industry, agriculture, energy, It is widely used in various aspects such as environmental protection, medical treatment, and national security.

(2) The application of nanotechnology is shown in the figure below,

[Example 1] Which of the following statements about nanotechnology is incorrect ( )

A. Using nanotechnology, molecules and atoms can be manipulated

B． Using nanotechnology, electron manipulation is possible with scanning tunneling microscopy

C． Devices made with nanotechnology are smaller, run faster and consume less energy

D. Nanotechnology can study the fine structure of DNA

[Exercise 1] Nanoceramics is a high-tech material with the characteristics of wear resistance, corrosion resistance, high temperature resistance, anti-penetration, and completely non-magnetic. Which of the following options can be made using nanoceramic materials ( )

A. High voltage transmission lines B. Container for concentrated sulfuric acid

C． Bank savings card D. LED light emitting diode

Knowledge point 2. Semiconductor materials

Objects whose conductivity is between conductors and insulators are called semiconductors. For example, germanium, silicon, gallium arsenide, etc. are all semiconductor materials. Semiconductors have very unique conductivities, such as: heat sensitivity, pressure sensitivity, photosensitivity, and one-way conductivity. Electrical properties and other properties. These properties have special uses in electronic components.

[Example 2] LED lamp is an efficient energy-saving light source, and its core component is a light-emitting diode. The main material of light-emitting diodes is ( )

A. Superconducting materials b. Alloy materials C. Semiconductor materialsD. magnetic materials

Knowledge point 3. Superconducting materials

(1)Superconductor

The resistance of metals increases (or decreases) as the temperature increases (or decreases). For example, when a "PZ220--60" light bulb is powered on and lights normally, the filament temperature is about 3000°C and its resistance is about 800 Q. When the circuit is disconnected and the filament temperature drops to room temperature, its resistance is only more than 200 ohms. ． It can be seen that the size of metal resistance is affected by temperature. Generally, the resistance is large when the temperature is high, and the resistance is small when the temperature is low.

In 1911, Dutch scientist Onnes first discovered that when mercury reaches a thermodynamic temperature of around 4.15 K (minus 269°C), its resistance suddenly drops to zero. Later, people gradually discovered that some metals and alloys have similar properties. We call the property that the resistance of materials suddenly becomes zero at low temperatures superconductivity, and objects with superconductivity are called superconductors.

(2)The significance of superconductors

Superconductors are of great significance. Since wires usually have resistance, they will generate heat when current passes through them. This consumes a lot of electrical energy. On the other hand, the heat will increase the temperature and cause other problems, such as To obtain a strong magnetic field, the number of turns and current of the electromagnet coil must be increased, but when it exceeds a certain value, the coil will burn out due to heat. If superconducting material is used to make a coil and it operates at a temperature without resistance, then the required strong magnetic field can be obtained.

Chapter 5 Review Lesson

Breakthrough in test points

Test point 1. Quality (high frequency test point)

Analysis of test points: This test point is a high-frequency test point for the Guangdong High School Entrance Examination. The focus of the test is on the attributes and estimation of mass. The questions are relatively simple. When reviewing, please note: (1) The mass of a substance does not depend on the temperature, state, shape and temperature of the substance. Changes due to changes in geographical location; (2) Memorize the approximate masses of some common objects.

1. (2010 Guangdong, 1, 3 points) Among the following options, the one with the closest mass to 50g is ( )

A. A table tennis ball B． A hen C. An egg D. a desk

2. (2012 Guangdong, 2, 3 points) After a bottle of mineral water is placed in the refrigerator and frozen, which of the following physical quantities does not change ( )

A. Quality b. Temperature c. Internal energy D. density

Test point 2. Measurement of quality (high-frequency test point)

Analysis of test points: This test point is a high-frequency test point for the Guangdong High School Entrance Examination. The test is relatively simple. The focus of the test is the use of a pallet balance. Knowledge points that should be noted: The correct way to use a pallet balance is: (1) Place the balance on a horizontal platform. Place the vernier at the zero-degree mark on the left side of the ruler. (2) Adjust the balance nuts at both ends of the beam so that the pointer points to the center line of the index plate. At this time, the beam is balanced. If the right arm of the beam is higher, the pointer will be biased toward the minute mark. To the left of the center line of the dial, the balance nut should be adjusted to the right at this time. (3) When weighing, place the object to be measured in the left pan, use tweezers to add or subtract weights to the right pan and adjust the cursor on the scale position until the beam returns to balance. (4) At this time, the mass of the object is equal to the total mass of the weights in the right disk plus the scale value corresponding to the upstream code of the ruler. To read the value corresponding to the running code, you should look at the running code The engraved line on the left.

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Update Time: 2024-07-02

This template belongs to Physics courseware Guangdong and Shanghai version of eighth grade physics volume 1 industry PPT template

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