Class 9th Matter Around Us Pure (Prashant Kirad) PDF

Is Matter Around Us Pure?  Topics to be Covered Classification of matter Pure Substances Elements Mixture Compounds Solution Concentration of a Solution Physical Changes Chemical Changes Classification of Matter  Pure Substance Pure substances are defined as...

Is Matter Around Us Pure?  Topics to be Covered Classification of matter Pure Substances Elements Mixture Compounds Solution Concentration of a Solution Physical Changes Chemical Changes Classification of Matter  Pure Substance Pure substances are defined as substances that are made of only one type of atom or only one type of molecule.For Example, Diamond, Salt, Sulphur, Tin. Characteristics of Pure Substance: Definite Composition: A pure substance has a uniform and definite composition i.e. Homogeneous in nature. Inseparability by Physical Means: Pure substances cannot be separated into other kinds of matter by any physical means. For instance, pure water cannot be separated into hydrogen and oxygen by simple filtration or distillation. Consistent Properties: The physical and chemical properties of a pure substance are consistent and do not vary. This includes properties like density, color, and hardness.  Pure Substances chemical composition Elements Compounds Element is a basic form of matter Compounds are chemical substances that cannot be broken down into made up of two or more elements that simpler substances by chemical are chemically bound together in a fixed reactions. ratio. e.g. Gold, Sodium, Iron, etc. e.g. Salt, Carbon dioxide etc.  Elements and Matter Solid - Iron, copper, gold, silver Liquid - bromine, mercury Gas - oxygen, hydrogren Elements Metals Non Metals Metalloids Periodic Table  Properties of Metals Metals are lustrous (shiny) Metals conduct heat and electricity Metals have a silver-grey or gold-yellow colour We can hammer metals and form thin sheets (Malleability) We can convert metals into wires (Ductility) Metals always produce a ringing sound if they are hit (Sonorous)  Properties of Non-Metals (i) They display a variety of colours. (ii) They are poor conductors of heat and electricity. (iii) They are not lustrous, sonorous or malleable. Examples of non-metals are hydrogen, oxygen, iodine, carbon (coal, coke), bromine, chlorine etc. Properties of Metalloids Elements having intermediate properties between those of metals and non-metals are called metalloids. Examples: Boron, silicon, germanium etc.  Compounds It is a substance that consists of two or more substances chemically combined together in fixed proportion. For Example, Ammonium Sulphate, Sulphur Chloride, Water. Properties of Compounds: These substances are combined chemically with each other in fixed proportions. The properties of a compound are different from that of its constituents. The components of a compound can only be separated by chemical processes like electrolysis and cannot be separated by physical methods.  Is water an element or a compound? Water (H₂O) is a compound composed of two elements: hydrogen and oxygen. In this compound, hydrogen (H) and oxygen (O) are present in a fixed mass ratio of 1:8. The atomic mass unit (amu) of hydrogen (H) is 1 amu. The atomic mass unit (amu) of oxygen (O) is 16 amu. There are 2 hydrogen atoms and 1 oxygen atom. Therefore, the mass ratio of hydrogen to oxygen in water is 2 X 1 amu 2 = = 1:8 1 X 16 amu 16 This fixed proportion is a characteristic property of compounds, indicating that the elements in a compound are always combined in the same ratio by mass. Q. Classify the following into elements, compounds and mixtures. (a) Sodium (b) Soil (c) Sugar solution (d) Silver (e) Calcium carbonate (f) Tin (g) Silicon (h) Coal (i) Air (j) Soap (k) Methane (l) Carbon dioxide (m) Blood  Mixtures If two or more substances (elements or compounds) are mixed together in any proportion, and they do not undergo any chemical change but retain their properties, the resulting substance is called mixture. Homogeneous Mixtures Heterogeneous Mixtures  Difference between homogeneous and heterogeneous mixture Aspect Homogeneous Mixtures Heterogeneous Mixtures Components are uniformly mixed Components are not uniformly mixed Mixing of Components with no visible boundaries. with visible boundaries. Example Sugar in water. Oil and water. Distribution of Components Uniformly distributed. Not uniformly distributed. Cannot be separated by physical Separation of Components Can be separated by physical means. means. The ratio of compositions can vary, Example: Sand in water, where sand Variation in Composition e.g., different amounts of sugar in settles and can be separated by lemonade. filtration.  Difference between Mixture & Compounds Aspect Mixtures Compounds Formed by physically mixing two or more Formed by chemically combining two or Formation substances. more elements. Purity Considered impure substances. Considered pure substances. Composition Variable composition. Fixed composition. Nature Can be homogeneous or heterogeneous. Always homogeneous. Can be separated by physical methods (e.g., Can only be separated by chemical or Separation Methods filtration). electrochemical methods. Constituents lose their individual properties; Retention of Properties Constituents retain their individual properties. the compound has unique properties. Formation of New No new substances are formed; properties A new substance is formed with different Substances depend on the constituents. properties from its constituents. Melting and Boiling Points Do not have defined melting and boiling points. Have defined melting and boiling points.  Are alloys mixtures or compound? Alloys are combinations of two or more metals or a metal and a non-metal. They cannot be separated into their components by physical methods. Despite this, alloys are considered mixtures because they retain the properties of their constituent elements and can have varying compositions. For example, brass is an alloy made up of about 30% zinc and 70% copper.  Mixtures Homogeneous Mixtures Heterogeneous Mixtures Solution (True Solution) Colloids (Colloidal Solution) Suspension The particles are very small, less Particles are small, ranging from 1- Particles are larger than 100 nm. than 1 nm (10^-9 m). 100 nm (10^-9 m to 10^-7 m). Opaque. Transparent. Translucent. Particles can be separated by Particles cannot be separated by Particles cannot be separated by filtration. filtration. filtration. Scatters light significantly. Does not scatter the beam of light. Scatters a beam of light. Example: Sand in water. Example: Salt-water. Example: Milk A solution is a homogeneous mixture of two or more substances. Solution Example - Sugar solution, Salt water, Soft drinks, Tea, Coffee, etc. Solvent Solute The component that dissolves The component(s) that is/are the other component is called dissolved in the solvent is/are the solvent. called solute(s). For example - In salt water solution, salt is solute and water is solvent. Q. Identify solute and solvent in 80% solution of ethyl alcohol with water.  Concentration of a solution A solution may have a small amount of solute dissolved in it while and another solution may have large amount of solute dissolved in it. The concentration of a solution is the amount of solute present in a given amount of the solution. Concentration of a solution  Solubility The solubility of a solute in a solvent at a specific temperature refers to the maximum amount of the solute that can dissolve in 100 grams of the solvent at that temperature. Q. To make a saturated solution, 36g of sodium chloride is dissolved in 100g of water at 293 K. Find its concentration at this temperature. Q. A solution contains 60 g of sugar in 480 g of water. Calculate the concentration of solution in terms of mass by mass percentage of the solution. (CBSE 2010, 2012) Q. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution). (NCERT) (a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K? (b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain. (c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature? (d) What is the effect of change of temperature on the solubility of a salt?  Saturated solution Unsaturated solution A saturated solution refers to a An unsaturated solution refers to solution where no additional a solution where more solute can solute can be dissolved at a be dissolved at a specific specific temperature. temperature.  Effect of temperature on a saturated solution Case 1 : On increasing the temperature Case 2 : On decreasing the temperature  Colloidal solution In a colloid, particles of a substance are evenly spread throughout the solution. These particles are larger than those in a solution but smaller than those in a suspension. This makes a colloid seem uniform but it is actually a blend of different components. Dispersed Phase Dispersion medium Component present in smaller Component present in larger proportion. proportion. It is analogous to solute of a It is analogous to solvent of a solution. solution. Dispersed Dispersing Type Example Phase Medium Liquid Gas Aerosol Fog, clouds, mist Smoke, Solid Gas Aerosol automobile exhaust Gas Liquid Foam Shaving cream Liquid Liquid Emulsion Milk, face cream Dispersed Dispersing Type Example Phase Medium Milk of Solid Liquid Sol magnesia, mud Foam rubber, Gas Solid Foam sponge, pumice Jelly, cheese, Liquid Solid Gel butter Coloured Solid Solid Solid Sol gemstone, milky glass  Suspension A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Properties of a Suspension : Heterogeneous mixture. Particles visible to the naked eye. Scatters light, making its path visible. Particles settle over time, making it unstable. Can be separated by filtration. Does not scatter light once particles settle.  Tyndall Effect The phenomenon of scattering of a beam of light by colloidal particles, when passed through a colloidal solution, is called the Tyndall effect.  Physical Changes Chemical Changes Changes that do not result in the formation of new Changes that result in the formation of new substances are referred to as physical changes. substances are known as chemical changes. During a physical change, the substances involved During a chemical change, the substances undergo do not alter their identity. a transformation in their identity. Physical changes can typically be reversed by Chemical changes typically cannot revert to their using a physical process, indicating that they are original form, indicating that they are generally usually reversible. irreversible. Changes in the physical state, size, and shape of a Substances are converted into entirely new substance are examples of physical changes. substances during chemical changes. Examples: melting of ice, chopping of vegetables, Examples: burning of magnesium, burning of paper, boiling of water. rusting of iron. Burning of a candle is a physical or chemical change? Q. Which of the following are chemical changes? (a) Growth of a plant (b) Rusting of iron (c) Mixing of iron filings and sand (d) Cooking of food (e) Digestion of food (f) Freezing of water (g) Burning of a candle.  TOP 5 Questions 1. Which of the following will show “Tyndall effect”? a. Salt solution b. Milk c. Copper sulphate solution d. Starch solution  TOP 5 Questions 2. Which of the following statement are true for pure substances? (i) Pure substances contain only one kind of particles. (ii) Pure substances may be compounds or mixtures. (iii) Pure substances have the same composition throughout. (iv) Pure Substances can be exemplified by all elements other than nickel. a. (i) and (ii) b. (i) and (iii) c. (iii) and (iv) d. (ii) and (iii)  TOP 5 Questions 3. Two substances, A and B, were made to react to form a third substance, A₂B, according to the following reaction: 2A+B→ A₂B. Which of the following statements concerning this reaction are incorrect? a. The product, A₂B, shows the properties of substances A and B. b. The product will always have a fixed composition. c. The product cannot be classified as a compound. d. The product formed is an element.  TOP 5 Questions 4. Mercury and Bromine are both a. liquid at room temperature b. solid at room temperature c. gases at room d. both (a) and (b)  TOP 5 Questions 5. Classify Brass and Diamond as element or mixture?