Is Matter Around Us Pure-Notes
Chemistry - Notes
Pure Substance
A single form of matter consisting of only one type of particle (either atoms or molecules) and having a definite and uniform chemical composition.
Mixture
Mixtures are constituted by more than one kind of pure form of matter.
Homogeneous mixtures
A Mixture which has a uniform composition throughout. Such mixtures are called homogeneous mixtures or solutions.
Heterogeneous mixtures
Mixtures, which contain physically distinct parts and have non-uniform compositions. Such mixtures are called heterogeneous mixtures
| Difference Between Homogeneous and Heterogeneous Soltion | |
|---|---|
| Homogeneous Mixture | Heterogeneous Mixture |
| Uniform composition | Non-uniform composition |
| Only one phase seen | Two or more phases seen |
| No visible boundaries | Visible boundaries |
| Cannot be separated easily | Components can be separated |
| Example: Salt in Water | Example: Sand in Water |
Difference between Pure Substance and Mixture
| Pure Substance | Mixture |
|---|---|
| Pure substance consists of a single type of constituents | Mixture consists of two or more pure substances |
| Pure substances can not be separated into other substances by physical methods | Mixture can be separated into componetsa by physical methods |
| Pure substance has its own definite properties | Mixtures shows the properties of its components |
Solution
A solution is a homogeneous mixture of two or more substances. A solution has a solvent and a solute as its components
Solvent
The component present in larger amounts is called the solvent.
Solute
The component of the solution that is dissolved in the solvent.
Properties of a Solution
- A solution is a homogeneous mixture
- The particles of a solution are smaller than 1 nm (10-9 metres) in diameter. So, they cannot be seen with the naked eye.
- They do not scatter a beam of light passing through the solution. So, the path of light is not visible in a solution.
- The solute particles cannot be separated from the mixture by the process of filtration.
Saturated Solution
At any particular temperature, a solution that has dissolved as much solute as it is capable of dissolving is said to be a saturated solution.
Unsaturated Solution
If the amount of solute contained in a solution is less than the saturation level, it is called an unsaturated solution.
Concentration of a Solution
The amount of solute (the substance being dissolved) present in a given amount of solvent (the substance doing the dissolving) or the total solution.
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Mass by mass
$$\text{Mass by Mass }=\dfrac{\text{ Mass of Solute}}{\text{Mass of Solution}}$$
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Mass by Volume
$$\text{Mass by Volume }=\dfrac{\text{ Mass of Solute}}{\text{Volume of Solution}}$$
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Volume by Volume
$$\text{Volume by volume }=\dfrac{\text{ Volume of Solute}}{\text{Volume of Solution}}$$
Example
A solution contains 50 grams of sugar in 350 grams of water. Calculate the concentration in terms of mass percentage of the solution
Solution:\(\require{cancel} \begin{aligned} \text{Mass of the Solute (Sugar)} &= 50~grams\\ \text{Mass of the Solvent (Water)} &= 350~grams \\\text{Mass of the Solution} &= \text{Mass of the solute + Mass of the Solvent} \\&=50+350 \\&=400~grams\\\\\color{magenta}\text{Mass percentage of Solution} &\color{magenta}=\dfrac{\text{Mass of solute}}{\text{Mass of solution}}\times 100\\\\ &=\dfrac{40}{400}\times 100 \\\\ &= \dfrac{\cancelto{1}{40}}{\cancelto{\cancelto{1}{10}}{400}}\times \cancelto{10}{100}\\\\&=10\% \end{aligned}\)
Example
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Solution:\( \begin{aligned} \text{Mass of Solute (NaCl) } &= 36~g\\ \text{Mass of Solvent (Water)} &= 100~g\\ \text{Total weight of Solution } & = \text{Mass of Solute } + \text{ Mass of Soltion}\\&=36~g+100~g\\&=136~g\\\\ \color{blue}\text{Concentration of Solution } &\color{blue}= \left(\dfrac{\text{Mass of Solute}}{\text{Mass of Solution}}\right)\times 100\\\\ &=\left(\dfrac{36}{136}\right)\times 100\\\\ &\approx{26.47\%} \end{aligned} \)
This concentration value shows the mass percentage of sodium chloride in the saturated solution at 293 K, meaning no more sodium chloride can dissolve in the solution at this temperature.
Suspension
A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye.
Properties of a Suspension
- Suspension is a heterogeneous mixture.
- The particles of a suspension can be seen by the naked eye.
- The particles of a suspension scatter a beam of light passing through it and make its path visible.
- The solute particles settle down when a suspension is left undisturbed; that is, a suspension is unstable. They can be separated from the mixture by the process of filtration.
Colloidal Solution
The particles of a colloid are uniformly spread throughout the solution. Due to the relatively smaller size of particles, as compared to that of a suspension, the mixture appears to be homogeneous. But actually, a colloidal solution is a heterogeneous mixture
Tyndall effect
A phenomenon where light scatters when it passes through a medium containing light-scattering particles. particles.
Properties of a Colloid
- A colloid is a heterogeneous mixture.
- The size of particles of a colloid is too small to be seen individually with the naked eye.
- Colloids are big enough to scatter a beam of light passing through them and make its path visible.
- They do not settle down when left undisturbed; that is, a colloid is quite stable.
- They cannot be separated from the mixture by the process of filtration. But, a special technique of separation known as centrifugation
| Difference between Sol, Solution and and Suspension | |||
|---|---|---|---|
| Property | Sol (Colloid) | Solution | Suspension |
| Nature of mixture | Heterogeneous, but appears uniform | Homogeneous | Heterogeneous |
| Particle size | Intermediate (1-100 nm); bigger than solution | Smallest (less than 1 nm) | Largest (over 100 nm) |
| Particle visibility | Not visible to naked eye | Not visible to naked eye | Visible to the naked eye or under a microscope |
| Stability | Stable; particles don't settle | Most stable; never settles | Unstable; particles settle on standing |
| Filtration | Cannot be separated by filter paper | Cannot be separated by filter paper | Can be separated by filter paper |
| Light scattering | Shows Tyndall effect (scatters light) | Doesn't scatter light | May scatter some light |
| Examples | Milk, paints, blood | Sugar solution, salt solution | Muddy water, sand in water |
Dispersed phase and Dispersion medium
In a colloidal dispersion, the dispersed phase consists of the particles present in smaller quantities that are scattered throughout another substance.
The dispersion medium is the component present in a larger quantity, forming the continuous background in which the dispersed phase particles are suspended.
Dispersed Phase
The substance is distributed in the form of fine, discrete particles, often of colloidal size (1-1000 nm).
Dispersion Medium
The substance that acts as the solvent or continuous background in which the dispersed phase particles are suspended.
| Difference between Dispersed phase and Dispersion medium | |
|---|---|
| Dispersed Phase | Dispersion Medium |
| The substance that is distributed (in the form of small particles) throughout another substance. | The substance in which the dispersed phase is distributed. |
| It is present in a smaller amount. | It is present in a larger amount. |
| Example: In a milk colloid, tiny fat globules act as the dispersed phase. | In milk, water acts as the dispersion medium. |
Centrifugation
Centrifugation is a process that separates mixtures using centrifugal force. It's used in science, medicine, and everyday life.
Physical and chemical Changes
Physical Change
A physical change is a change in the physical properties of a substance, like its shape, size, or state, without changing its chemical composition.
Chemical Change
A chemical change is a change in a substance's chemical composition that produces a new substance. In a chemical change, the substance loses its identity and cannot be returned to its original form.
Elements
An element is a pure substance that can't be broken down into simpler substances by chemical or physical means. means. Each element is made up of only one type of atom.
Metals
Metals are solid substances that are shiny, hard, and conduct heat and electricity well. They are also malleable, ductile, and dense.
Properties of Metals
- They have a lustre (shine).
- They have a silvery-grey or golden-yellow colour.
- They conduct heat and electricity.
- They are ductile (can be drawn into wires).
- They are malleable (can be hammered into thin sheets).
- They are sonorous (make a ringing sound when hit).
Ductility
Ductility is a material's ability to stretch without breaking when force is applied. It's a physical property of materials that's important in engineering and manufacturing.
Malleability
Malleability" refers to the ability of a material, usually a metal, to be hammered or rolled into thin sheets without breaking, essentially allowing it to be shaped into different forms by applying pressure; It's a physical property where the material can deform under compressive stress without losing its integrity
Sonorous
The word 'sonorous' means capable of producing a sound. When metal strikes a hard surface, it produces sound. It is due to the sonorous property of metals.
Non-Metals
Non-metals are chemical elements that lack the characteristics of metals. They are poor conductors of heat and electricity, and are mostly gases and sometimes liquids.
Properties of Non-Metals
- They display a variety of colours.
- They are poor conductors of heat and electricity.
- They are not lustrous, sonorous or malleable.
Metalloids
A metalloid is a chemical element that has properties of both metals and nonmetals. Metalloids are located on the periodic table between the metals and non-metals.
Compound
A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion
| Diffrence between Mixtures and Compounds | |
|---|---|
| Mixtures | Compounds |
| Elements or compounds mix to form a mixture, and no new compound is formed. | Elements react to form new compounds. |
| A mixture has a variable composition. | The composition of each new substance is always fixed. |
| A mixture shows the properties of the constituent substances. | The new substance has totally different properties. |
| The constituents can be seperated fairly easily by physical methods. | The constituents can be separated only by chemical or electrochemical reactions. |
Important Points to Remember
- A mixture contains more than one substance (element and/ or compound) mixed in any proportion
- Mixtures can be separated into pure substances using appropriate separation techniques.
- A solution is a homogeneous mixture of two or more substances. The major component of a solution is called the solvent, and the minor component, the solute.
- The concentration of a solution is the amount of solute present per unit volume or per unit mass of the solution.
- Materials that are insoluble in a solvent and have particles that are visible to the naked eye form a suspension. A suspension is a heterogeneous mixture.
- Colloids are heterogeneous mixtures in which the particle size is too small to be seen with the naked eye, but is big enough to scatter light. Colloids are useful in industry and daily life. The particles are called the dispersed phase and the medium in which they are distributed is called the dispersion medium.
- Pure substances can be elements or compounds. An element is a form of matter that cannot be broken down by chemical reactions into simpler substances. A compound is a substance composed of two or more different types of elements, chemically combined in a fixed proportion.
- Properties of a compound are different from its constituent elements, whereas a mixture shows the properties of its constituent elements or compounds.
