Salts-1
Neutralisation is a chemical reaction in which an acid reacts with a base to form salt and water.
The compound formed by the reaction between an acid and a base is known as a salt. Salts like magnesium chloride, potassium nitrate, zinc carbonate and copper sulphate are useful to us in many ways.
Salts are ionic compounds which contain positively charged cations and negatively charged anions.
Salts formed from any hydroxide and:
Hydrochloric acid are called chlorides.
Sulphuric acid are called sulphates.
Nitric acid are known as nitrates.
Carbonic acid are known as carbonates.
Salts formed from:
b acids and b bases are called neutral salts.
b acids and weak bases are called acidic salts.
Weak acids and b bases are called basic salts.
Sodium chloride is obtained from the sea water by the process of evaporation. It is referred to as table salt.
Sodium chloride is used:
To preserve pickles, fish and meat.
To manufacture soap.
To melt ice formed on roads in cold countries and
As a raw material for the manufacture of other compounds.
Sodium hydrogen carbonate is used in the baking industryas an antacid, In soda acid fire extinguishers. Sodium carbonate is used to manufacture of glass, cleansing agents, soap, glass and paper, sodium compounds like borax.
Bleaching powder chemically known as calcium oxy chloride is used to bleach cotton, linen textiles and wood pulp, to disinfect drinking water,
Sodium hydroxide is produced by the electrolysis of aqueous solution of sodium chloride, called brine. The electrolysis of brine is called the ‘chlor-alkali’ process. In the process of electrolysis of brine hydrogen is collected at the cathode and chlorine at the anode.
The hydrogen formed in this process is used to manufacture fuels, margarine, and ammonia for fertilizers.
Chlorine is used for water treatment, in swimming pools, to manufacture chloro-flouro carbons, PVC, chemical compounds like chloroform, carbon tetra chloride, disinfectants, and pesticides.
Sodium hydroxide is used to manufacture soaps, detergents, paper, artificial fibres like rayon and dyes.
Some salts have a fixed number of water molecules as an essential part of their crystal. These water molecules which form the part of the crystal are called water of crystallisation and such salts are called hydrated salts.
Sodium carbonate decahydrate………Na2CO3.10 H2O
Ferrous sulphate heptahydrate FeSO4.7H2O
Zinc Sulphate heptahydrate ZnSO4.7H2O
Magnesium sulphate heptahydrate or Epsom salt MgSO4.7H2O
Potash alum K2SO4 Al2 (SO4)3 .24H2O.
Plaster of paris which is chemically called calcium sulphate hemihydrate is used as a bandage, proofing material, sealing agent, for making statues, toys and decorative articles and for smoothening wall surfaces
Tuesday, May 25, 2010
acids
CBSE Class X >> Science>> Acids
Acids
The word “acid” comes from the Latin word “acidus,” which means sour. Any substance that releases hydrogen ions when dissolved in water is an acid.
The word “acid” comes from the Latin word “acidus,” which means sour. Any substance that releases hydrogen ions when dissolved in water is an acid.
Acids obtained from food like curd, lemons, grapes, raw mango, citrus fruits and gooseberry are called organic acids. Hydrochloric acid, sulphuric acid and nitric acid are called inorganic or mineral acids.
Acids turn blue litmus red, methyl orange red and have corrosive action on skin, and are good conductors of electricity. The action of acids with water is exothermic as heat is generated on dilution.
Acids react with metals to form metal salts. In this reaction, hydrogen gas is liberated. Acids react with metal carbonates to form corresponding salts, carbon dioxide and water. Acids react with metal hydrogen carbonates and form corresponding salts, carbon dioxide and water. Acids react with metal oxide to form salt and water.
An acid base indicator is the one which exhibits different colour in acids and bases. Red cabbage is a visual indicator used to detect acids.
Onions are called olfactory indicators. Litmus is a natural indicator and is extracted from lichens.
Apart from natural indicators there are a few synthetic indicators, such as methyl orange and phenolphthalein.
•Methyl orange turns red in an acid and yellow in a base.
•Phenolphthalein does not change colour in an acid. It turns pink in a base.
•Sulphuric acid is used in the manufacture of fertilisers, paints, dyes, chemicals, plastics and synthetic fibres. It is also used in car batteries.
•Nitric acid is used in the manufacture of fertilisers, explosives like TNT, dyes and drugs.
•Hydrochloric acid is used before galvanising, to remove oxide film from steel and also as a descaling agent for boilers. It is also used in the textile, leather and food industry.
Acids
The word “acid” comes from the Latin word “acidus,” which means sour. Any substance that releases hydrogen ions when dissolved in water is an acid.
The word “acid” comes from the Latin word “acidus,” which means sour. Any substance that releases hydrogen ions when dissolved in water is an acid.
Acids obtained from food like curd, lemons, grapes, raw mango, citrus fruits and gooseberry are called organic acids. Hydrochloric acid, sulphuric acid and nitric acid are called inorganic or mineral acids.
Acids turn blue litmus red, methyl orange red and have corrosive action on skin, and are good conductors of electricity. The action of acids with water is exothermic as heat is generated on dilution.
Acids react with metals to form metal salts. In this reaction, hydrogen gas is liberated. Acids react with metal carbonates to form corresponding salts, carbon dioxide and water. Acids react with metal hydrogen carbonates and form corresponding salts, carbon dioxide and water. Acids react with metal oxide to form salt and water.
An acid base indicator is the one which exhibits different colour in acids and bases. Red cabbage is a visual indicator used to detect acids.
Onions are called olfactory indicators. Litmus is a natural indicator and is extracted from lichens.
Apart from natural indicators there are a few synthetic indicators, such as methyl orange and phenolphthalein.
•Methyl orange turns red in an acid and yellow in a base.
•Phenolphthalein does not change colour in an acid. It turns pink in a base.
•Sulphuric acid is used in the manufacture of fertilisers, paints, dyes, chemicals, plastics and synthetic fibres. It is also used in car batteries.
•Nitric acid is used in the manufacture of fertilisers, explosives like TNT, dyes and drugs.
•Hydrochloric acid is used before galvanising, to remove oxide film from steel and also as a descaling agent for boilers. It is also used in the textile, leather and food industry.
electric circuit
An electric circuit is a closed path for flow of electricity through which electricity can be converted into different forms. An electric circuit basically contains a source of electricity, a load resistance, a switch or a key for making the circuit on or off at ones convenience (which makes or breaks the circuit correspondingly). The diagrammatic representation of an electric circuit is called the circuit diagram. Each electric component in a circuit has a unique symbol through which it is represented in a circuit diagram. If a circuit is switched off, it is called an open circuit and if the circuit is switched on it is called a closed circuit. When two or more resistors are connected such a way that the terminus of one resistance is connected to the starting end of the other, such a combination of resistance is called the series connection and the circuit is called series circuit. On the other hand, if the starting ends of two resistors are joined to a point and the terminal ends of the two are combined and given connection to a source of electricity, such a combination is called parallel connection and the circuit is called parallel circuit. The potential difference or voltage drop across a resistance is the cause of electric current through it.
For a number of resistors connected in parallel, the electric potential drop across them remains the same and the electric current through each of them varies as their resistance.
For a number of resistors connected in series, the electric current through them remains the same and the potential drop across each of them varies as their resistance. The net resistance or equivalent resistance of a number of resistors connected in series is the sum of the individual resistances.
The reciprocal of the net resistance or equivalent resistance of a number of resistors connected in parallel is the sum of the reciprocals of the individual resistances.
Lesson Demo
For a number of resistors connected in parallel, the electric potential drop across them remains the same and the electric current through each of them varies as their resistance.
For a number of resistors connected in series, the electric current through them remains the same and the potential drop across each of them varies as their resistance. The net resistance or equivalent resistance of a number of resistors connected in series is the sum of the individual resistances.
The reciprocal of the net resistance or equivalent resistance of a number of resistors connected in parallel is the sum of the reciprocals of the individual resistances.
Lesson Demo
heating effect of current
Heating effect of electricity is one of the widely used effects in the world.
Heating effect of electricity is one of the widely used effects in the world. When electric current is passed through a conductor, it generates heat due to the resistance it offers to the current flow. The work done in overcoming the resistance is generated as heat. This is studied by James Prescott Joule and he enunciated various factors that affect the heat generated. The heat produced by a heating element is directly proportional to the square of the electric current (I) passing through the conductor, directly proportional to the resistance (R) of the conductor, time (t) for which current passes through the conductor. It is given by the expression H = I2Rt and is well known as Joule’s Law.
Applications of the heating effect of electric current include appliances like electric immersion water heater, electric iron box, etc. All of these have a heating element in it. Heating elements are generally made of specific alloys like, nichrome, manganin, constantan etc. A good heating element has high resistivity and high melting point. An electric fuse is an example for the application of heating effect of electric current. The rating of 3 A of an electric fuse implies the maximum current it can sustain is three ampere.
Heating effect of electricity is one of the widely used effects in the world. When electric current is passed through a conductor, it generates heat due to the resistance it offers to the current flow. The work done in overcoming the resistance is generated as heat. This is studied by James Prescott Joule and he enunciated various factors that affect the heat generated. The heat produced by a heating element is directly proportional to the square of the electric current (I) passing through the conductor, directly proportional to the resistance (R) of the conductor, time (t) for which current passes through the conductor. It is given by the expression H = I2Rt and is well known as Joule’s Law.
Applications of the heating effect of electric current include appliances like electric immersion water heater, electric iron box, etc. All of these have a heating element in it. Heating elements are generally made of specific alloys like, nichrome, manganin, constantan etc. A good heating element has high resistivity and high melting point. An electric fuse is an example for the application of heating effect of electric current. The rating of 3 A of an electric fuse implies the maximum current it can sustain is three ampere.
electricity
SATs Electricity Questions
What is electricity?
Electricity is made from the movement of electrons. Every single item in the whole world is made up of tiny, tiny things called atoms. Electrons are inside each of these tiny atoms. Electrons are so small that if you took a million of them, they would barely reach across the top of a small pin. These electrons have a negative charge causing them to move from one area to another, creating electricity.
Electricity flows easily through metals but not through other materials.
Electricity can flow when there is a complete circuit.
Metals are good electrical conductors.
The answers are on this page. Try and think of what you would say before clicking on the answers. How near were you to the correct answer?
1. What are the two places on a battery to which circuit wires can be attached called? AnswerTerminals (positive and negative).
2. What is the path electricity takes called? AnswerA circuit
3. Materials through which electricity can pass are called ___________ conductors Answerelectrical
4. Materials that do not allow electricity to pass through them are called electrical ____________ Answerinsulators.
5. True of False? Electricity is a flow of negative charge AnswerTrue
6. What do you use to measure a current in a circuit? AnswerAn ammeter
7. What components do you need to make a simple series circuit to light one bulb? AnswerOne bulb, one battery,one switch and some wire.
8. Which is the odd one out and why?
Steel
glass
iron
tin
AnswerGlass because it isn't a metal and thereforedoesn't allow electricity to pass through it.
9. Why are plug sockets covers made of plastic? Answerbecause plastic doesn't allow electricityto flow through it - it is an electrical insulator.
10. True of False? The lead of a pencil (graphite) can conduct electricity. AnswerTrue - graphite is one of the few non-metallicmaterials to conduct electricity fairly well.
11. If you put a second battery in a simple circuit, how will it affect the brightness of the bulb? AnswerThe bulb will be brighter.
12. What is happening when a switch is
What is electricity?
Electricity is made from the movement of electrons. Every single item in the whole world is made up of tiny, tiny things called atoms. Electrons are inside each of these tiny atoms. Electrons are so small that if you took a million of them, they would barely reach across the top of a small pin. These electrons have a negative charge causing them to move from one area to another, creating electricity.
Electricity flows easily through metals but not through other materials.
Electricity can flow when there is a complete circuit.
Metals are good electrical conductors.
The answers are on this page. Try and think of what you would say before clicking on the answers. How near were you to the correct answer?
1. What are the two places on a battery to which circuit wires can be attached called? AnswerTerminals (positive and negative).
2. What is the path electricity takes called? AnswerA circuit
3. Materials through which electricity can pass are called ___________ conductors Answerelectrical
4. Materials that do not allow electricity to pass through them are called electrical ____________ Answerinsulators.
5. True of False? Electricity is a flow of negative charge AnswerTrue
6. What do you use to measure a current in a circuit? AnswerAn ammeter
7. What components do you need to make a simple series circuit to light one bulb? AnswerOne bulb, one battery,one switch and some wire.
8. Which is the odd one out and why?
Steel
glass
iron
tin
AnswerGlass because it isn't a metal and thereforedoesn't allow electricity to pass through it.
9. Why are plug sockets covers made of plastic? Answerbecause plastic doesn't allow electricityto flow through it - it is an electrical insulator.
10. True of False? The lead of a pencil (graphite) can conduct electricity. AnswerTrue - graphite is one of the few non-metallicmaterials to conduct electricity fairly well.
11. If you put a second battery in a simple circuit, how will it affect the brightness of the bulb? AnswerThe bulb will be brighter.
12. What is happening when a switch is
Tuesday, May 18, 2010
Evaporation and Boiling
Mouseover the pictures to learn
Factors affecting evaporation | Interactive Assessment Worksheets
© by Alan & Hui Meng
When the water temperature reaches 100°C, bubbles of water vapour form (throughout the water) and rise to the surface of the water and break. In other words, water starts to boil and changes into water vapour. The temperature 100°C is called the boiling point of water.
When the hot water vapour (steam) meets the cold air above the boiling water, it condenses into tiny water droplets to form 'white clouds'.
Mouseover the pictures to learn
Factors affecting evaporation | Interactive Assessment Worksheets
© by Alan & Hui Meng
When the water temperature reaches 100°C, bubbles of water vapour form (throughout the water) and rise to the surface of the water and break. In other words, water starts to boil and changes into water vapour. The temperature 100°C is called the boiling point of water.
When the hot water vapour (steam) meets the cold air above the boiling water, it condenses into tiny water droplets to form 'white clouds'.
Factors affecting the rate of evaporation
Mouseover the pictures to learn more
Temperature
Wind
Exposed surface area
Humidity
"Water" Crossword | Evaporation and Boiling | Effect of Humidity & Temperature on Evaporation
Interactive Assessment Worksheets © by Alan & Hui Meng
Water molecules are always moving; at the water's surface, some molecules are bumped by molecules below them and gain enough speed to break free and escape into the air as gas [water vapour]. This escape of surface molecules is called evaporation ... it involves a change of state, from liquid to gas.
Evaporation takes place all the time and at any temperature.
The higher the temperature, the higher the rate of evaporation. When the temperature of water is increased (e.g., shining a powerful spotlight at it), the water molecules gain more energy, move faster and escape at a faster rate.
Mouseover the pictures to learn more
Temperature
Wind
Exposed surface area
Humidity
"Water" Crossword | Evaporation and Boiling | Effect of Humidity & Temperature on Evaporation
Interactive Assessment Worksheets © by Alan & Hui Meng
Water molecules are always moving; at the water's surface, some molecules are bumped by molecules below them and gain enough speed to break free and escape into the air as gas [water vapour]. This escape of surface molecules is called evaporation ... it involves a change of state, from liquid to gas.
Evaporation takes place all the time and at any temperature.
The higher the temperature, the higher the rate of evaporation. When the temperature of water is increased (e.g., shining a powerful spotlight at it), the water molecules gain more energy, move faster and escape at a faster rate.
Planting trees in your neighborhood really is one of the best things you can do for the local environment and for the planet. It�s no secret that trees help the environment, but you may be surprised by all the benefits that planting trees can provide. Besides producing oxygen and removing carbon dioxide and contaminants from the air, trees have many other social, economic, and environmental benefits.
Environmental Benefits of Planting Trees
Trees are like the lungs of the planet. They breathe in carbon dioxide and breathe out oxygen. Additionally, they provide habitat for birds and other wildlife. But that�s not all trees do for us! To see just how much trees are essential to the planet and to humans, let�s look at the following statistics:
CO2 is one of the major contributing elements to the greenhouse effect. Trees trap CO2 from the atmosphere and make carbohydrates that are used for plant growth. They give us oxygen in return. According to ColoradoTree.org, about 800 million tons of carbon are stored in the trees that make up the urban forests of the U.S. This translates to a savings of $22 billion in control costs. Mature trees can absorb roughly 48 pounds of CO2 a year. The tree in turn releases enough oxygen to sustain two human beings.
Trees also help to reduce ozone levels in urban areas. In New York City, a 10 percent increase in urban canopy translated to a reduction of peak ozone levels by around 4 parts per billion. (Source: Luley, Christopher J.; Nowak, David J. 2004. Help Clear the Smog with Your Urban Forest: What You and Your Urban Forest Can Do About Ozone.)
Trees reduce urban runoff and erosion by storing water and breaking the force of rain as it falls. The USDA reports that 100 mature trees can reduce runoff caused by rainfall by up to 100,000 gallons!
Trees also absorb sound and reduce noise pollution. This is especially important for people who live near freeways. In some cases, a well planted group of trees can reduce noise pollution by up to 10 decibels. (Source: New Jersey Forest Service.)
Additionally, trees shade asphalt and trees, reducing what is know as the �Heat Island� effect. The EPA has some great information on how planting trees and other vegetation can help to reduce the urban heat island effect.
Just being around trees makes you feel good. Can you imagine your community without trees? Trees, especially in urban areas, have numerous social benefits. For example, the addition of trees to a neighborhood or a business district can greatly improve the mental and physical health of residents and workers.
Environmental Benefits of Planting Trees
Trees are like the lungs of the planet. They breathe in carbon dioxide and breathe out oxygen. Additionally, they provide habitat for birds and other wildlife. But that�s not all trees do for us! To see just how much trees are essential to the planet and to humans, let�s look at the following statistics:
CO2 is one of the major contributing elements to the greenhouse effect. Trees trap CO2 from the atmosphere and make carbohydrates that are used for plant growth. They give us oxygen in return. According to ColoradoTree.org, about 800 million tons of carbon are stored in the trees that make up the urban forests of the U.S. This translates to a savings of $22 billion in control costs. Mature trees can absorb roughly 48 pounds of CO2 a year. The tree in turn releases enough oxygen to sustain two human beings.
Trees also help to reduce ozone levels in urban areas. In New York City, a 10 percent increase in urban canopy translated to a reduction of peak ozone levels by around 4 parts per billion. (Source: Luley, Christopher J.; Nowak, David J. 2004. Help Clear the Smog with Your Urban Forest: What You and Your Urban Forest Can Do About Ozone.)
Trees reduce urban runoff and erosion by storing water and breaking the force of rain as it falls. The USDA reports that 100 mature trees can reduce runoff caused by rainfall by up to 100,000 gallons!
Trees also absorb sound and reduce noise pollution. This is especially important for people who live near freeways. In some cases, a well planted group of trees can reduce noise pollution by up to 10 decibels. (Source: New Jersey Forest Service.)
Additionally, trees shade asphalt and trees, reducing what is know as the �Heat Island� effect. The EPA has some great information on how planting trees and other vegetation can help to reduce the urban heat island effect.
Just being around trees makes you feel good. Can you imagine your community without trees? Trees, especially in urban areas, have numerous social benefits. For example, the addition of trees to a neighborhood or a business district can greatly improve the mental and physical health of residents and workers.
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