"Which material is hard" Materials around us PPT courseware 3

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"Which material is hard" Materials around us PPT courseware 3

We chose the four most common items around us: wooden strips, cardboard, nails and plastic to study.

Which of them is harder? Try to come up with a research method yourself first.

Compare hardness

You can prepare two wooden strips, cardboard, iron nails and plastic rulers each, and use one wooden strip to mark the other wooden strips, cardboard, iron nails and plastic ruler respectively. Can wood strips leave scratches on their surfaces? Repeat the experiment with cardboard, iron nails, and plastic rulers. Record the observed phenomena in a table.

Get to know metal

Metal is an important material with many important uses. Look around us, what objects are made of metal?

Objects made of metal include cars, airplanes, buckets, pots, spoons, etc.

some additional information

Metal

①Has metallic luster and color: This is because free electrons can selectively absorb and reflect visible light, giving metals different colors and lusters.

②Electrical conductivity and thermal conductivity of metal

Good electrical conductivity: Due to the directional movement of free electrons under the action of an external electric field, a current is formed. Therefore, metals easily conduct electricity.

Good thermal conductivity: Free electrons collide with metal ions during movement, and energy exchange occurs during the collision, causing the entire metal to reach the same temperature.

③The ductility of metal: When a metal is subjected to external force, the atomic layers in the crystal will slide relative to each other. Since the interaction between metal ions and free electrons has no directionality, the interaction is not destroyed after being subjected to external force. The metal only deforms without breaking, giving the metal good ductility

Metal products to consider

1. Whether it has the performance to meet this requirement

2. Is the price appropriate?

3. Is it beautiful?

4. Is it convenient (quality, volume)

5. Does it have any impact on people and the environment?

Information - The best of metals

1. What is the most abundant metallic element in the earth’s crust?

2. Which metal element is the most abundant in the human body?

3. Which metal has the best conductivity of electricity and heat?

4 Which metal has the highest melting point?

5. Which metal has the lowest melting point?

2. Alloy

1. Common alloys: (aluminum alloy, pig iron and steel)

Pig iron and steel are both alloys of carbon and iron

2. Comparison of properties between alloys and pure metals

Experiments show that most metals can react with oxygen, but the difficulty and intensity of the reaction vary.

Mobility: Magnesium, Aluminum > Iron, Copper > Gold

practise:

Titanium and titanium alloys are important metal materials in the 21st century. They have excellent properties, such as high melting point, low density, good plasticity, good mechanical properties, strong corrosion resistance, and good "compatibility" between titanium alloys and the human body. According to their main performance, the impractical use is ( )

A: Used in the manufacture of nuclear submarine equipment

B: Used to manufacture aerospace equipment

C: used to make fuses

D. Can be used to make artificial bones

think:

(1) Aluminum can react with oxygen at room temperature, but the aluminum tableware we use is corrosion-resistant. Why is this?

Metal slowly oxidizes at room temperature to form a dense oxide film, which prevents further oxidation of aluminum, so aluminum has good corrosion resistance.

(2) Why shouldn’t you use a steel brush to scrub aluminum tableware?

If you use a steel brush to scrub aluminum products, the oxide film will be easily removed and the protective effect will not be achieved.

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For more information about the PPT courseware "Which material is hard among the materials around us", please click the Materials around us ppt Which material is hard ppt label.

"Which material is hard" Materials around us PPT courseware 2:

"Which material is hard" Materials around us PPT courseware 2 There are many objects around us, and they are made of different materials. We are all familiar with wood, fiber, paper, glass, metal, plastic, rubber, etc. Characteristics of wood: yellowish white...

"Which material is hard?" Materials around us PPT courseware:

"Which material is hard" PPT courseware of materials around us. Based on the results we observed, arrange the wooden strips, iron nails and plastic rulers in order of hardness from large to small. Which material is the hardest? Iron nails, plastic rulers and wooden strips. Let’s take a look at the story of beverage cans on page 50 of the book..

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Update Time: 2024-10-20

This template belongs to science courseware Third Grade Science Volume 1, Textbook Edition industry PPT template

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