Some properties of metals
“It is impossible to foresee the boundaries of scientific knowledge”
D.I. Mendeleev
Goals:
Educational - to provide an understanding of the properties of metals and their relationship with the structure of the atom and crystal lattice.
Developmental
- continue to develop the ability to work with a textbook;
- the ability to establish cause-and-effect relationships between the structure of a substance and its properties;
- Develop the ability to draw conclusions;
- Develop cognitive interest.
Educational
- cultivate interest in independent work;
- ability to work in a team.
Equipment : metal samples, tabular data ( appendix )
II. Learning a new topic
Oral survey.
- What two groups can all the substances you know be divided into?
- What two groups can simple substances be divided into?
- What is special about the structure of metal atoms?
- What types of communication do you know?
- What is special about metal bonding?
Teacher. Indeed, a special feature of metals is the presence of common electrons, sometimes called electron gas. From life experience you know that metals have common properties. Today we will take a closer look at some of the properties of metals.
The teacher names the topic of the lesson, the students write it down in their notebooks, and names the purpose of the lesson.
Teacher. In ancient times, mankind knew 7 metals; it was believed that they appeared on Earth under the influence of seven planets:
Gold – Sun
Silver – Moon
Copper – Venus
Iron – Mars
Tin – Jupiter
Lead – Saturn
Mercury – Mercury
The guys have prepared short messages for us about these metals
(Children’s performance with stories about metals)
Teacher. We listened to the guys' speech about metals known in ancient times, and now open the periodic table and see how many metals are now known to humanity? Indeed, much more metals are known than non-metals; there are 88 metals in total and they all share similar properties.
What are these properties?
Students name properties (ductility, hardness, metallic luster, electrical conductivity, thermal conductivity, density, melting point)
Teacher. Using the material given to you, as well as the textbook page 69-72
Explain why metals have plasticity?
Which metal has the greatest ductility? (3 minutes to prepare)
(Students' answers)
Teacher. Using the provided reference table, as well as the textbook, answer the following questions: Why are metals hard?
Which metal is the exception?
Which metal is the hardest?
What are the softest metals called?
In which group of the table of chemical elements are they located? (4 minutes to prepare)
(Students' answers)
Teacher. You and I use electrical appliances, but how is electric current delivered to us? By wires, but what are they made of? Will they conduct electric current if they are made of copper or silver?
(Students' answers)
Teacher. From your answers we can conclude that all metals conduct electricity, why?
Why do all metals conduct electricity?
Which metal has the highest electrical conductivity?
How does the electrical conductivity of metals change when heated?
To answer these questions you need to work with the textbook and the reference literature provided. (3 minutes to prepare)
(Students' answers)
Teacher. Now look at the spoons that I hold in my hands, try to determine which one is metal and which one is plastic? How did you determine the material from which the spoons were made?
(Guys' answer)
Teacher. Why do metals have a metallic luster?
To answer this question you need to work with literature again (3 min)
(Students' response)
Teacher. Guys, what will happen to a metal spoon if we keep it in boiling water?
What if we take a wooden spoon?
Therefore, metal has thermal conductivity, but why?
Working with literature (3 min.)
Student response
Teacher. What is the reason for the presence of common properties in metals?
Students. Because there are free electrons in the crystal lattice of metals
Teacher. Why are there free electrons in the crystal lattice?
Students . Because the radius of metal atoms is large and there are few electrons at the outer energy level, so they are easily separated from the atom.
Teacher. Are the structure of metals and their properties related to each other?
Students. Yes connected. The structure of the atom determines the structure of the crystal lattice, and the structure of the crystal lattice determines the properties of substances.
III . Reflection.
Teacher. To summarize, I will ask you to fill out a table using metal samples and reference materials.
| № | Metal | Thermal conductivity | Shine | Electrical conductivity | Plastic | melting temperature | Density |
| 1 | A.I. | ||||||
| 2 | Zn | ||||||
| 3 | Cu |
Homework: paragraph 13. Exercise 1. 4.
Literature
- Ivanova R.G..Chemistry lessons in grades 8-9:. Methodological manual for teachers (R.G. Ivanova. - 3rd edition, revised - M.: Education, 2003.-123s
16.06.2012
Source: https://urok.1sept.ru/%D1%81%D1%82%D0%B0%D1%82%D1%8C%D0%B8/617721/
The most ductile metal is gold
Gold is the most popular metal in history, in culture, in economics. For its possession, rivers of blood were shed, family discord broke out, and even wars were fought. Its significance for the entire human civilization is based on its unique chemical and physical properties, on the features of its internal structure.
Gold is the most ductile metal. This quality makes it in demand everywhere: from jewelry to microelectronics.
The most "metallic" metal
Gold contains all the most obvious properties, which scientists call metallic. In terms of electrical conductivity, it is second only to silver, copper and pure palladium. In terms of thermal conductivity - the same as silver, copper and cobalt.
In its ability to absorb thermal energy, gold is second only to exotic bismuth, ahead of mercury and silver. In terms of other “metallic” properties - malleability and light reflection - it is a champion.
Gold is the most ductile metal in the world, and its shine is a legendary concept.
The molecular structure of gold is also very “metallic”. It is a geometrically regular crystal lattice with positive ions at the nodes and a cloud of “electronic” gas between them, dense in concentration.
This part of the atom consists of free electrons located at the outer energy level. They create an attractive force between the lattice nodes, which ensures the ability of the metal to deform without violating its overall integrity.
This is how the most ductile metal works.
From the Greek Πλαστική (“sculpting”, “modelling”) comes the word “plasticity”, which gave the root to others associated with changing the shape of a solid body. Plasticity is the property of a solid body to change shape and size and maintain residual deformation after the cessation of external forces without changing volume or compromising integrity.
For metals, this is one of the most important characteristics that allows them to be used in practice. Without the ability to shape metal blanks into the desired shape, it would be impossible to create even the simplest household items. Gold is the most ductile metal, and products made from it are an example of the shape that can be given to a fairly pliable material by forging, pressing, rolling, drawing, drawing, etc. The opposite property of the material is fragility.
Plasticity test
The ductility characteristics of metals are usually determined by static tests. The most revealing is the tensile test. To find out which metal is the most ductile, it is necessary to subject samples of the same size to this effect under similar temperature conditions. The amount of deformation that a metal sample can withstand before failure is an objective indicator of ductility.
The numerical expression of the tensile test result is two main coefficients. Relative elongation is the percentage ratio of the increased length of the sample after rupture caused by deformation to the original one. The most ductile metal - gold - has an indicator of 65%. For comparison: for iron – 40-50, for aluminum – 30-40.
The second indicator of plasticity is the relative narrowing of the cross section of the sample. For gold, the initial cross-section of the sample is 90% larger than what it had before breaking. For aluminum this figure is 80%, for copper – 75%.
Soft, viscous and durable
On the Mohs hardness scale, gold scores 2.5–3.7. In its pure form, this metal is much softer than many widely used materials and can be scratched with a knife or even a fingernail.
Therefore, in order to avoid rapid wear of gold products, special strengthening alloy elements, usually silver or copper, are added to the metal for their production. Gold also has harmful impurities.
The most ductile metal on the periodic table becomes brittle in the presence of lead, platinum, cadmium or sulfur.
The softness of gold is of a special nature; it is complemented by its viscosity and malleability. The convenience of molding and technological processing of parts is complemented by high tensile strength - 3300 kg/cm2. This unique combination of physical and mechanical characteristics of gold has been used since ancient times. An example is gold leaf.
Domes in Russia are covered with pure gold
Despite the centuries-old history of gold mining, this metal has always been considered rare and precious. This is the most ductile metal. This quality makes the use of gold foil for decorative finishing of interior elements or even for covering church domes cost-effective. To cover a large area, very little precious metal is required: 1 gram of plate can be forged into a sheet with an area of 1 m2.
Even the manual method of producing sheets for gilding makes it possible to achieve a thickness of a thousandth of a millimeter. This thickness allows the gold plates to adhere to the surface due to molecular attraction. The technology for producing tinsel has improved significantly. Now robotic lines are used to flatten gold sheets, but the process is based on the high plasticity of the source material.
Golden thread
Gold's ability to withstand tensile stress without breaking has been known since its commercial use.
The production of such wire for jewelry was established in ancient times - the ancient craftsmen already knew which metal was the most ductile.
In the middle of the 20th century, a microwire with a gold core was produced, which, even with plastic insulation, was 7 times thinner than a human hair. From 1 gram of metal a continuous gold thread about 3.5 km long was drawn.
Today's technologies have brought the thickness of gold wire to several microns, and further development of the technological advantages of the metal continues.
Source: https://FB.ru/article/222675/samyiy-plastichnyiy-metall---zoloto
How metals differ from non-metals - features, properties and characteristics:
In everyday life, a person interacts with many substances. All elements can be classified according to physical and chemical qualities. In the article we will look at how metals differ from non-metals, their properties and concept.
Definition of metal and its properties
Every day we deal with metals and this is not without reason. Most elements of the periodic table are them. They all have their own characteristics and properties.
As a rule, metals are elements that conduct heat and electricity well. Metals are also very ductile, which allows them to change their shape by forging, and they also have a high hardness coefficient. A distinctive feature of this element is its luster, which is called metallic. The properties of the metal are divided into two main fractions, such as:
- Physical properties.
- Chemical properties.
How do metals differ from metals in physical characteristics? Physical properties include:
- Color. Metals, as a rule, have a dense structure that does not allow light to pass through. And their color is determined by the reflection of light from its surface. Thus, metals in most cases have colors ranging from gray to silver. But there are exceptions, such as copper, which is red, and gold, which is yellow.
- State of shape, hardness and density. Metals themselves have a solid state of aggregation, but are capable of turning into liquid at high temperatures. Thus, metals melt at temperatures from 40 to 3400 degrees Celsius. But there are metals whose main state of aggregation is liquid. These elements include mercury.
- Electrical conductivity. A special feature is its decrease with increasing temperature of the substance.
- Thermal conductivity and boiling/melting point.
How do metals differ from metals in chemical properties? This group includes:
- Oxidability. Metals also oxidize, and the oxide film on the surface can give them a different shade.
- Reaction with non-metals, acids, water, salts.
How do metals differ from each other?
Many people do not know how metals differ from metals. Their differences can be classified:
- Metals differ in color from each other, such as gold and copper.
- Metals also melt at different temperatures. Some metals, such as tin and lead, can be melted at home, but others require higher temperatures.
- Metals are divided into two groups: heavy and light. Heavy metals include those whose density is from 5 g/cm3, light metals have a density less than 5 g/cm3. Light metals include lithium, which has a density of 0.2 g/cm3; the place of the heaviest metal is shared by osmium and iridium. Their density is 22.6 g/cm3.
- Metals differ from each other in ductility and electrical conductivity. Some of them are very flexible. For example, from just 1 gram of gold you can make a thin wire of 3.5 kilometers. It will be flexible and will not break. It will not be possible to repeat this with a less ductile metal.
- Also, some metals conduct current better than others. The most electrically conductive metals are copper, silver and aluminum. They are most often used as conductive elements.
How do nonmetals differ from metals?
Non-metals are commonly called elements that have non-metallic properties. How do metals differ from non-metals? Let's take a closer look:
- Form. So non-metals have three states of aggregation: liquid, solid and gaseous.
- Electrical conductivity. Nonmetals do not conduct current like metals and have lower thermal conductivity.
- Visual differences. Metal is easy to distinguish visually from non-metal, since the former has a metallic sheen. Nonmetals include elements such as bromine, sulfur and hydrogen.
- Chemical structure. It is also easy to distinguish them by their structure. Metals have a clear crystal lattice. Nonmetals have an ionic structure.
- Entry into reactions. Nonmetals have a larger number of unoccupied electrons located in outer levels. This is what allows them to have a high oxidizing capacity compared to metals.
How is wood similar to metal and what are their differences?
Wood is a plant material. Metal is the result of a natural chemical compound. What is the difference between wood and metal:
- Wood does not conduct electricity and ignites at a fairly low temperature compared to metals.
- Wood does not melt when exposed to high temperatures.
- Wood also conducts heat poorly, unlike metals.
- Wood is elastic, but not flexible. Metals have a lower elasticity coefficient, but they are more ductile. This way you can easily fold the wire in half without breaking it; the wood will break in half under this impact.
- Another distinguishing feature of wood from metal is that it does not corrode. There are wood species that can remain in water for a long time without rotting. Under such conditions, metals become covered with rust.
- The density of wood is quite low compared to metals. Although some metals have a density lower than wood, they are classified as light metals.
How do semiconductors differ from metals?
Semiconductors are non-metals that have some metallic properties. Metals and semiconductors are similar in that both are capable of conducting current.
But semiconductors have a distinctive feature, which is that their electrical conductivity can increase several times depending on external factors. Thus, a semiconductor conducts current better as the temperature increases. In metals, electrical conductivity decreases with increasing temperature. The electrical conductivity can also be affected by the presence of foreign impurities. Thus, in metals, impurities reduce electrical conductivity, and in semiconductors they increase.
Semiconductors, unlike metals, can have positive and negative electrical conductivity. Semiconductors themselves, in terms of their ability to pass current through themselves, stand between metal and elements that do not conduct current at all.
The difference between metal and steel
It is a mistake to think that metal and steel are completely different elements. In fact, steel is also a metal. What is the difference between metal and steel?
The fact is that metals are a whole group of elements that have metallic properties. This group also includes iron. Steel is nothing more than an alloy of iron with elements belonging to the group of metals.
Most often, in addition to iron, steel contains elements of the periodic table such as molybdenum, chromium and vanadium. Steel also contains carbon. It is used to increase the strength of iron.
Thus, by varying the amount of carbon in the alloy, a very strong material can be obtained. But the stronger the steel, the more brittle it becomes. Thus, under prolonged dynamic load, steel breaks easily. Adding other impurities to it helps to achieve resistance to any influences.
So, the article examined how metals differ from metals and non-metals. The characteristics of all elements can be compared in terms of chemical and physical properties. Every day a person uses such elements and creates new substances to improve the quality of life.
Source: https://www.syl.ru/article/372332/chem-metallyi-otlichayutsya-ot-nemetallov---osobennosti-svoystva-i-harakteristiki
Metallurgy Terms: Definition of plasticity 2020
Ductility is a measure of a metal's ability to withstand tensile stress—any force that pulls two ends of a material away from each other. The game of tug of war serves as a good example of tensile strength applied to a rope.
Plasticity is the plastic deformation resulting from such deformations. The term "ductile" literally means that a metallic substance is capable of being stretched into a thin wire and it does not become weaker or brittle in the process.
Metals with high or low ductility
Metals with high ductility, such as copper, can be drawn into long, thin wires without breaking. Copper has historically been an excellent conductor of electricity, but the metal can conduct almost anything. Metals with low ductility, such as bismuth, instead rupture when they are subjected to tensile stress.
Strength and bendability
In contrast, malleability is a measure of a metal's ability to withstand compression such as impact, rolling, or extrusion. Although the two concepts may seem similar on the surface, metals that are ductile are not necessarily malleable.
A common example of the difference between these two properties is lead, which is highly malleable but not very ductile due to its crystalline structure. The crystal structure of metals dictates how they will deform under stress.
The atomic particles that matting metals can deform under stress either slide over each other or are pulled apart from each other.
The crystal structure of more ductile metals allows the metal atoms to stretch further, a process called "twinning." More ductile metals are those that are more easily close, and they also deform more easily in other directions.
Effect of temperature
Plasticity in metals is also related to temperature.
When metals are heated, they typically become less brittle, resulting in plastic deformation. In other words, most metals become more ductile when heated and are easier to pull into wires without breaking. Certificate is an exception to this rule as it becomes more brittle as it heats up.
What are the most malleable metals?
While it is difficult to compare ductility between metals, gold and platinum are considered the most ductile. It is said that gold can be drawn into wires so beautifully that one ounce of the metal can reach up to fifty miles.
Source: https://ru.routestofinance.com/ductility-explained-tensile-stress-and-metals
