VALENCY OF COMMON METALS AND NON-METALS

Valency is the combining power of an element, which determines the number of electrons that an atom can gain, lose, or share when it forms chemical bonds. 

Here are the valencies of some common metals and non-metals: 

Metals	Symbol	Valency	Non-metals	Symbol	Valency
Sodium	Na	1	Hydrogen	H	1
Potassium	K	1	Carbon	C	4
Calcium	Ca	2	Nitrogen	N	3, 5
Magnesium	Mg	2	Oxygen	O	2
Aluminium	Al	3	Fluorine	F	1
Iron	Fe	2, 3	Chlorine	Cl	1, 3, 5, 7
Copper	Cu	1, 2	Bromine	Br	1, 3, 5, 7
Zinc	Zn	2	Iodine	I	1
Silver	Ag	1	Phosphorus	P	3, 5
Gold	Au	1, 3	Sulphur	S	2, 4, 6
Tin	Sn	2, 4
Lead	Pb	2, 4
Mercury	Hg	1, 2
Cobalt	Co	2, 3
Manganese	Mn	2, 3, 4, 6, 7
Barium	Ba	2
Lithium	Li	1

Class X: Acids, Bases and Salt

Class X: Acids, Bases and Salt

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ELEMENTS AND COMPOUNDS:

Elements and compounds are two types of substances that are important in chemistry.

An element is a pure substance that cannot be broken down into simpler substances by chemical means. Elements are the building blocks of matter, and each element is made up of atoms with a unique number of protons in their nuclei. There are currently 118 known elements.

A compound, on the other hand, is a substance made up of two or more elements that are chemically bonded together in a fixed ratio. Compounds can be broken down into their constituent elements by chemical means, such as through a chemical reaction. Examples of compounds include water (H₂O), table salt (NaCl), and carbon dioxide (CO₂).

The properties of compounds are often very different from the properties of the elements that make them up. For example, sodium (Na) is a highly reactive metal, while chlorine (Cl) is a toxic gas. However, when these two elements combine to form sodium chloride (NaCl), they produce a compound that is a common table salt and is safe to consume in small amounts.

In summary, elements are the basic building blocks of matter, while compounds are made up of two or more elements that are chemically bonded together in a fixed ratio.

ACIDS, BASES AND SALTS:

Acids and bases are two classes of chemicals that are important in many aspects of chemistry and everyday life.

Acids are substances that can donate hydrogen ions (H⁺) in a solution. They are typically characterized by their sour taste and ability to react with certain metals to produce hydrogen gas. Strong acids have a low pH and can be highly reactive, while weak acids have a higher pH and are less reactive.

Bases, on the other hand, are substances that can accept hydrogen ions (H⁺) in a solution. They are typically characterized by their bitter taste and slippery feel, and can often be found in cleaning products. Strong bases have a high pH and can be highly reactive, while weak bases have a lower pH and are less reactive.

Acids and bases have opposite chemical properties, and they can neutralize each other when they react. When an acid and a base react, they produce a salt and water in a process known as neutralization. This process is commonly used in the production of various chemicals, as well as in the regulation of pH levels in many different systems, including the human body.

In chemistry, salts are ionic compounds made up of positively charged ions (cations) and negatively charged ions (anions) that are held together by electrostatic attraction. Salts are typically formed by the reaction of an acid and a base, in a process called neutralization.

For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), they produce salt and water as follows:

HCl + NaOH → NaCl + H₂O

In this reaction, hydrochloric acid (HCl) is an acid, sodium hydroxide (NaOH) is a base, and the resulting product sodium chloride (NaCl) is a salt.

Salts can have a wide range of uses in industry, agriculture, and everyday life. For example, common table salt (sodium chloride) is used as a seasoning in cooking, as a food preservative, and in the production of various chemicals. Other types of salts, such as magnesium sulfate and calcium chloride, have uses in medicine, agriculture, and industry.

INDICATORS:

Indicators are substances that can be used to determine the acidity or basicity (alkalinity) of a solution. They are often used in chemistry and biology to help scientists identify the pH of a solution or to detect the presence of certain chemical compounds.

Natural, universal, and olfactory indicators are different types of indicators used to determine the acidity or basicity of a solution.

Natural indicators: These are indicators that occur naturally and can be found in plants or other natural sources. Examples of natural indicators include red cabbage (which contains anthocyanins that change color in response to pH), turmeric (which turns reddish-brown in acidic solutions and yellow in basic solutions), and beetroot (which changes from red to yellow in basic solutions).

Universal indicators: These are mixtures of different indicators that can be used to determine the pH of a solution across a wide range of values. Universal indicators produce a range of colors that correspond to different pH values, allowing scientists to determine the approximate pH of a solution.

Olfactory indicators: These are indicators that change odor in response to pH changes. Olfactory indicators are useful for detecting changes in pH in situations where color changes may be difficult to see or when the presence of color interferes with other analyses. Examples of olfactory indicators include vanilla (which smells sweet in acidic solutions and bitter in basic solutions), and cloves (which smell sweet in basic solutions and spicy in acidic solutions).

Overall, indicators are important tools in chemistry and can provide valuable information about the properties of a solution or sample. Natural, universal, and olfactory indicators all have unique advantages and can be useful in different contexts depending on the goals of the analysis.

Three Most Common Indicators:

The three most common indicators used in acid-base titrations are:

Litmus: Litmus is a natural indicator obtained from lichens that turn red in acidic solutions and blue in basic solutions.

Methyl orange: Methyl orange is a synthetic indicator that turns red in acidic solutions and yellow in basic solutions.

Phenolphthalein: Phenolphthalein is a synthetic indicator that is colorless in acidic solutions and pink in basic solutions.

Litmus Indicators:

Litmus is a natural indicator that is commonly used in chemistry to test the acidity or basicity of a solution. It is obtained from lichens, which are composite organisms that consist of a symbiotic relationship between fungi and photosynthetic algae or bacteria. The lichens are boiled in water to extract the litmus, which is then dried and ground into a fine powder.

Litmus is available in two forms: red litmus and blue litmus. Red litmus turns blue in basic solutions and remains red in acidic solutions, while blue litmus turns red in acidic solutions and remains blue in basic solutions. Litmus is a pH indicator that changes color based on the concentration of hydrogen ions (H+) or hydroxide ions (OH-) in a solution.

Litmus is a commonly used indicator in chemistry, biology, and other sciences. It is easy to use and provides a quick visual indication of the acidity or basicity of a solution. Litmus paper is a convenient form of litmus that is widely used in the laboratory. To use litmus paper, a small strip is dipped into the solution being tested, and the resulting color change is compared to a chart that indicates the pH range associated with each color.

While litmus is a useful indicator, it has some limitations. For example, it is not very accurate, and it is not precise enough for some applications. Additionally, litmus can only provide a rough estimate of the pH of a solution, as it does not provide a quantitative measurement of acidity or basicity. Nonetheless, litmus is still a valuable tool in the laboratory and is widely used to quickly and easily test the pH of a solution.

pH Scale:

The pH scale is a logarithmic scale used to describe the acidity or basicity of a solution. It ranges from 0 to 14, with 7 being neutral. Solutions with a pH below 7 are considered acidic, while solutions with a pH above 7 are considered basic (or alkaline).

The pH of a solution is determined by the concentration of hydrogen ions (H+) or hydroxide ions (OH-) in the solution. Acids release hydrogen ions (H+) when dissolved in water, while bases release hydroxide ions (OH-). The pH of a solution can be measured using a pH meter or by using an indicator, such as litmus paper, that changes color depending on the pH.

The pH scale is logarithmic, which means that a change in one pH unit represents a tenfold change in the concentration of hydrogen ions (or hydroxide ions). For example, a solution with a pH of 3 is ten times more acidic than a solution with a pH of 4, and 100 times more acidic than a solution with a pH of 5.

Some common examples of the pH of different substances include:

Battery acid: pH 1

Lemon juice: pH 2

Vinegar: pH 3

Pure water: pH 7

Baking soda: pH 9

Ammonia: pH 11

Bleach: pH 13

The pH scale is an important tool in chemistry, biology, and environmental science, as it can help scientists understand the behavior of different substances and the impact of pH on biological and chemical systems. Understanding the pH of a solution can also be important for industrial and agricultural applications, such as water treatment and crop management.

STRONG ACIDS AND WEAK ACIDS:

Acids are substances that donate hydrogen ions (H⁺) in aqueous solution, which means that they increase the concentration of hydrogen ions in solution, leading to a decrease in pH. Some common examples of acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and acetic acid (CH₃COOH).

Strong acids are acids that completely dissociate (or ionize) in water, meaning that they release all of their hydrogen ions in solution. This results in a high concentration of hydrogen ions and a low pH. Some common examples of strong acids include hydrochloric acid (HCl), sulphuric acid (H₂SO₄), and nitric acid (HNO₃).

Weak acids are acids that only partially dissociate in water, meaning that they release only some of their hydrogen ions in solution. This results in a lower concentration of hydrogen ions and a higher pH compared to strong acids. Some common examples of weak acids include acetic acid (CH₃COOH), citric acid (C₆H₈O₇), and carbonic acid (H₂CO₃).

The strength of an acid is determined by its ability to donate hydrogen ions in solution, which is related to its dissociation constant (Ka). A strong acid has a large dissociation constant, indicating that it donates hydrogen ions readily and completely, while a weak acid has a small dissociation constant, indicating that it donates hydrogen ions less readily and only partially.

In general, strong acids have a pH less than 3, while weak acids have a pH between 4 and 6. Acids with a pH greater than 6 are considered very weak and are not considered significant contributors to acidity.

Examples of strong acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and nitric acid (HNO₃), while examples of weak acids include acetic acid (CH₃COOH), citric acid (C₆H₈O₇), and carbonic acid (H₂CO₃) (weak mineral acid).

Mineral acids and organic acids are two types of acids with different chemical properties and sources. Mineral acids are usually inorganic acids that contain mineral elements, while organic acids are usually derived from organic compounds.

 

Mineral Acids:

Mineral acids are strong acids that dissociate completely in water to produce hydrogen ions (H+) and an anion. They are typically derived from mineral sources such as rocks, salts, and ores. Some examples of mineral acids include:

Hydrochloric acid (HCl): A colorless, pungent, and highly corrosive acid that is commonly used in chemical manufacturing, pickling, and as a laboratory reagent.

Sulphuric acid (H₂SO₄): A dense, oily liquid that is widely used in the production of fertilizers, detergents, and batteries.

Nitric acid (HNO₃): A strong oxidizing agent that is commonly used in the production of fertilizers, dyes, and explosives.

 

Organic Acids:

Organic acids are weak acids that contain one or more carboxyl (-COOH) functional groups. They are typically derived from living organisms, including plants, animals, and microorganisms. Some examples of organic acids include:

Acetic acid (CH₃COOH): A colorless liquid that is commonly used as a food preservative, flavoring agent, and solvent.

Citric acid (C₆H₈O₇): A weak acid found in citrus fruits that is commonly used as a flavoring agent, preservative, and chelating agent in the food industry.

Lactic acid (C₃H₆O₃): A weak acid that is produced during anaerobic respiration in animals and humans. It is commonly used as a food preservative, flavoring agent, and in the production of biodegradable plastics.

In summary, mineral acids are strong acids derived from mineral sources, while organic acids are weak acids derived from living organisms. Each type of acid has unique properties and applications in various industries. Only weak mineral acid is Carbonic Acid.

TEST YOUR KNOWLEDGE OF THE CONCEPT OF VECTORS IN PHYSICS

1. How do vector operations affect the displacement and velocity of an object in motion?
2. In what ways can we apply vector addition and subtraction in analyzing forces acting on a body?
3. Can you explain how the cross product of two vectors can be used to determine the direction of torque acting on a rigid body?
4. What is the significance of the dot product in determining the work done by a force on a body?
5. How can we use vector algebra to determine the magnitude and direction of resultant force acting on a system of forces?
6. How do we determine the position of an object relative to a given origin using vector quantities?
7. Can you explain how the parallelogram law of vector addition is used in calculating resultant displacement and velocity of an object?
8. How does the vector product of two vectors help in calculating the magnetic field around a current-carrying wire?
9. Can you explain the concept of vector projection and how it is used in physics?
10. In what ways can we use vector calculus to describe and analyze the behavior of electromagnetic waves?

LECTURE -3 : CLASS VIII : SCIENCE : CHAPTER 4 : DISPLACEMENT REACTIONS AND USES OF METALS AND NON-METALS

 CLASS VIII   |    SCIENCE    |    CHAPTER 4: 

METALS AND NON-METALS

      Notes prepared by Subhankar Karmakar

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• A more reactive metal displaces a less reactive metal from its salt solution. 
• When a more reactive metal is placed in a salt solution of a less reactive metal, then the more reactive metal metal displaces the less reactive metal from its salt solution.
• A displacement reaction, also known as a replacement reaction, is a type of chemical reaction in which one element replaces another in a compound.
• This type of reaction occurs when a more reactive element replaces a less reactive element in a compound.
• The displaced element is released as a free element, and the newly formed compound contains the element that did the displacing.
• Displacement reactions are often used to extract metals from their ores, and they are also important in organic chemistry reactions.
• One common example of a displacement reaction is the reaction of iron with copper sulfate to form iron sulfate and copper.

Example, Reaction of Iron Metal with Copper Sulphate solution: 

Copper Sulphate + Iron → Iron Sulphate + Copper 

CuSO₄ + Fe → FeSO₄ + Cu

METALS	NON-METALS
1.      1.    Metals form basic oxides.	1.    Non-metals form acidic oxides
2.       2.  Most metals react with water (or steam) to produce Hydrogen gas.	2.    Non-metals do not react with water.
3.      3.  Metals react with dilute acids to produce Hydrogen gas.	3.    Non metals do not react with dilute acids.

USES OF METALS:

Some of the most uses of metals are given below : 

1: Iron, copper, and Aluminium metals are used to make cooking utensils and water boilers for factories.

2: Copper metal is used for making electric wires for household wiring, electric motors, armature of dynamos, and many other electrical appliances. Aluminium metal is used for making electric cables and over-head electric transmission lines. 

3. Aluminium foils are used for packaging medicines, chocolates, food items, and many other materials. 

4. Aluminium metal in the form of alloys is used to make aeroplanes. 

USES OF NON-METALS:

Non-metals have many important uses in our daily lives. Here are some examples:

1. Oxygen (O) is a non-metal that is essential for life. It makes up about 21% of the air we breathe and is used by living organisms to produce energy through respiration.
2. Nitrogen (N) is another non-metal that makes up about 78% of the air we breathe. It is used in the production of fertilizers and as a coolant in certain industrial processes.
3. Carbon (C) is a non-metal that is found in all living organisms. It is used in the production of fuels, such as coal and oil, and is also used in the manufacturing of various products, including plastics, rubber, and textiles.
4. Chlorine (Cl) is a non-metal that is used as a disinfectant in swimming pools and water treatment plants. It is also used in the production of various chemicals, including PVC plastics.
5. Hydrogen (H) is a non-metal that is used as a fuel in vehicles and as a source of energy in fuel cells. It is also used in the production of ammonia, which is used in the production of fertilizers.
6. Sulfur (S) is a non-metal that is used in the production of sulfuric acid, which is a key component in the production of many chemicals and fertilizers. It is also used in the production of rubber and as a fungicide in agriculture.

QUESTIONS ON MOTION IN ONE DIMENSION

Questions on motion in one dimension so that objective of knowledge construction is achieved

1. What is the definition of motion in one dimension, and how does it differ from motion in multiple dimensions?

2. What are some common examples of motion in one dimension, and how can they be described using mathematical equations?

3. How does the concept of velocity relate to motion in one dimension, and how can it be calculated using distance and time measurements?

4. How does acceleration affect motion in one dimension, and what are some common examples of situations where acceleration is present?

5. How does the principle of inertia apply to motion in one dimension, and how can it be used to explain the behavior of objects in motion?

6. What is the difference between uniform and non-uniform motion in one dimension, and how can this be observed in real-world situations?

7. How do external forces, such as friction or air resistance, affect motion in one dimension, and how can they be accounted for in mathematical models?

8. What are some common misconceptions or misunderstandings about motion in one dimension, and how can they be addressed to promote a more accurate understanding of this concept?

9. How can motion in one dimension be applied to real-world scenarios, such as the motion of vehicles or the trajectory of a projectile?

10. What are some current research topics related to motion in one dimension, and how do they contribute to our understanding of this concept?

Questions on motion in one dimension that are designed to facilitate knowledge construction through case-based reasoning:

1. A car is moving in a straight line with a constant velocity of 20 m/s. How far will it travel in 5 seconds?

2. A ball is thrown upward with an initial velocity of 30 m/s. How long will it take to reach its maximum height? What is the maximum height that it will reach?

3. A train is traveling with a constant acceleration of 2 m/s^2. If it starts from rest, how long will it take to reach a velocity of 60 m/s? How far will it travel during that time?

4. A roller coaster starts at the top of a hill with an initial velocity of 0 m/s. It then travels down the hill with a constant acceleration of 5 m/s^2. How fast will it be traveling after 10 seconds? How far will it have traveled during that time?

5. A person is walking at a constant speed of 1.5 m/s. How long will it take for them to travel a distance of 500 meters?

6. A student throws a ball vertically upwards with an initial velocity of 20 m/s. How high does the ball go and how long does it take to reach its maximum height? What is the ball's velocity and acceleration at its maximum height?

7. A car is driving down a straight road at a constant speed of 60 km/hr. Suddenly, the driver applies the brakes and the car comes to a stop in 5 seconds. What is the car's acceleration during this time? How far does the car travel before coming to a stop?

8. A cyclist is riding down a hill with an initial velocity of 10 m/s. The cyclist then applies the brakes and comes to a stop after traveling 100 meters. What is the cyclist's acceleration during this time? How long does it take for the cyclist to come to a stop?

9. A ball is thrown off a building with an initial velocity of 30 m/s. If the building is 50 meters tall, how long does it take for the ball to hit the ground? What is the ball's velocity just before it hits the ground?

10. A rocket is launched vertically upwards from the ground with an initial velocity of 500 m/s. If the rocket's engine shuts off after 10 seconds, how high does the rocket go? What is the rocket's velocity and acceleration at its maximum height? How long does it take for the rocket to fall back to the ground?

For each of these questions, students can use the given information to construct a mental model of the situation, and then apply the relevant physics principles to arrive at a solution. By working through these case-based problems, students will develop a deeper understanding of the concepts of motion in one dimension, and will be better equipped to apply those concepts to new situations in the future.

THE FUNCTIONS OF KIDNEY IN HUMAN BEINGS

THE STRUCTURE OF A KIDNEY

• Each kidney is made up of a large number of excretory units called nephrons. 

• Each nephron has a cup shaped bag at its upper end which is called Bowman's capsule. 

• The lower end of Bowman's capsule is tube shaped and it is called a tubule. 

• The Bowman's capsule and the tubule taken together make a nephron. 

• One end of the tubule is connected to the Bowman's capsule and the other end is connected to a urine-collecting duct of the kidney. 

• The Bowman's capsule contains a bundle of blood capillaries which is called glomerulus.

• One end of the glomerulus is attached to the renal artery which brings the dirty blood containing the urea waste into it.   

THE FUNCTIONS OF KIDNEY IN HUMAN BEINGS

The kidneys are a pair of bean-shaped organs located in the abdominal cavity, and they play several crucial roles in maintaining the overall health and wellbeing of human beings. Some of the primary functions of the kidneys include:

Regulating fluid balance: The kidneys regulate the balance of fluids in the body by filtering excess fluids and removing them as urine.

Removing waste products: The kidneys filter waste products, such as urea, uric acid, and creatinine, from the blood and eliminate them through urine.

Maintaining electrolyte balance: The kidneys help maintain the balance of electrolytes, such as sodium, potassium, and calcium, in the body.

Regulating blood pressure: The kidneys play a role in regulating blood pressure by controlling the amount of fluid in the bloodstream.

Producing hormones: The kidneys produce hormones, such as erythropoietin and renin, that help regulate the production of red blood cells and control blood pressure, respectively.

Activating vitamin D: The kidneys play a role in activating vitamin D, which is essential for maintaining strong bones.

Overall, the kidneys are essential organs that play multiple vital roles in maintaining the overall health and homeostasis of the body. Dysfunction or failure of the kidneys can result in severe health consequences, such as fluid imbalances, electrolyte disturbances, and accumulation of waste products in the bloodstream.

Draw a well labelled diagram of L.S. of the human kidney