Element, Compound, and Mixture Notes

Element, Compound and Mixture

Matter and its States

• Objects around us are made up of matter.
• Matter can exist in three states: solid, liquid, and gas.
• Examples:
  • Steel almirah (solid)
  • Plastic bucket (solid)
  • Water, mustard oil, syrup (liquids)
  • Air (gaseous mixture)
  • Fumes from vehicles (mixture of solid particles and gases)

Activity: Sound and Shape Observation

• Experiment: Drop a one rupee coin and a piece of charcoal on a concrete floor.
• Observe the sound and any changes in shape/size.
• Fill a table with observations, noting which objects produce a metallic sound and can be bent into thin sheets versus those that turn into powder when hit.

Characteristics of Substances

• Metallic substances:
  • Make a metallic sound when hit.
  • Can be bent into thin sheets.
• Non-metallic substances:
  • Do not make a metallic sound when hit.
  • Break down into powder when hit.

Metals and Non-metals

Sunlight and Temperature Experiment

• Place steel plate, brass saucer, and aluminum bowl in sunlight.
• Observe how sunlight reflects and feel the temperature change after five minutes.
• Compare observations with a plastic bowl.

Observations

• Steel: [Fill observation here]
• Brass: [Fill observation here]
• Aluminum: [Fill observation here]
• Plastic: [Fill observation here]

Blacksmith Workshop Observations

• Iron pieces are heated and hammered to make different objects.
• Reason: Iron has properties suitable for this purpose.
• Charcoal and plastic cannot be used in the same way because their properties differ from iron.

Common Properties of Metals

• Shine in the light.
• Produce a metallic sound when hit.
• Good conductors of heat and electricity.
• Can be bent easily.
• Can be hammered into sheets.

Metals vs. Non-metals

• Metals: iron, copper, aluminum, brass.
• Non-metals: charcoal.
• Metals are usually solid (except mercury, which is liquid at room temperature).
• Non-metals can be solid, liquid, or gaseous.
• Graphite (non-metal) is a good conductor of heat and electricity.
• Diamond (non-metal) is a good conductor of heat.

Classification Activity:

• Classify the following substances into metals and non-metals:
  • Gold
  • Silver
  • Aluminum
  • Sulfur
  • Zinc
  • Nitrogen
  • Oxygen

Table for Classification

Pure Substance and Mixture

Air Composition

• Air contains:
  • Nitrogen
  • Oxygen
  • Carbon dioxide
  • Moisture
  • Inert gases (argon, helium, neon, etc.)

Milk Boiling Observation

• Milk becomes thicker when boiled, releasing water through evaporation.
• Covering boiled milk with a plate shows water droplets accumulating.

Mixtures

• Air and milk contain more than one substance in a mixed state, hence they are mixtures.

Salt and Water Experiment

• Mix spoonfuls of salt in a glass of water and note the difference in salty taste between the first and last mixtures.

Identification of Mixtures

• Identify mixtures from the following list:
  • Syrup of sugar
  • Cold drinks
  • Honey
  • Gunpowder
  • Oil paint

Pure Substances

• Substances containing only one type are pure substances.
• Examples: sulfur, iron, water, oxygen, carbon dioxide, sugar.

Element and Compound

Electrolysis of Water Experiment

• Set up: Water in beaker, two nails in rubber, copper wires connected to a battery (torch cells only).

• Observation: Gas bubbles form at each nail.

• Result: Water breaks into hydrogen and oxygen due to electricity.

  • Caution: Use only torch cells, not electrical mains.

Elements

• Iron, copper, aluminum cannot be broken down into new substances.
• Elements: substances containing only one type of atom (e.g., iron).
• Oxygen and hydrogen are elements that combine to form water.
• Water is liquid; hydrogen and oxygen are gaseous.
• Properties of water differ from those of oxygen and hydrogen.

Air vs. Water

• Air is a mixture of nitrogen, oxygen, carbon dioxide, etc.
• Water contains oxygen and hydrogen.
• Air and water are different types of substances.

Oxygen Properties in Air

• Oxygen supports respiration and combustion.
• These properties are maintained even when mixed with other gases in the air.

Candle and Glass Experiment

• Light a candle and cover it with a glass.
• Observation: The candle blows out after a while.
• Reason: Oxygen within the glass is consumed, and combustion stops.

Water and Combustion

• Pouring water on a lighted candle extinguishes it.
• Oxygen and hydrogen are constituents of water, but water does not support combustion.

Properties Comparison: Hydrogen, Oxygen, and Water

• Hydrogen and oxygen do not maintain their properties in water.
• Water is a compound formed by a chemical reaction between oxygen and hydrogen.

Definition of Compound

• A compound is formed when more than one element combine chemically.

Magnesium Burning Experiment

• Hold a magnesium strip with forceps and place it in fire.
• Observation: Light and heat are evolved, and a white powder forms.
• The white powder is magnesium oxide, a new compound.
• Magnesium oxide is produced by the chemical reaction between oxygen and magnesium.

Carbon Dioxide

• Carbon dioxide is a compound made of carbon and oxygen.

Properties Comparison: Carbon, Oxygen, and Carbon Dioxide

Mixtures vs. Compounds

• In mixtures, constituents maintain their individual properties.
• Quantity of constituents may vary in a mixture.

Air Composition Variations

• Question: Does the quantity of air constituents remain the same everywhere and in every season?

Explanation Examples

Pure Substances

• Pure substances are made of only one constituent.
• Examples: pure iron, copper, gold, silver, carbon.

Iron Pieces in Bottles Experiment

• Three bottles contain iron of the same mass but in different piece sizes.
• Questions:
  • Which bottle contains the largest pieces of iron?
  • Which bottle contains the maximum number of pieces of iron?
  • Where are the pieces of iron not individually visible?
  • Where is it difficult to count the pieces individually?

Atomic Representation with Coloured Spheres

• Diagrams depict atoms as colored spheres (for understanding – atoms have no color).

Table Completion: Compound Constituents and Atom Numbers

Symbol, Formula and Valency

Element Symbols

• Symbols are short representations of elements.
• First letter of the element's name is used as the symbol (capitalized).
• Examples: Hydrogen (H), Oxygen (O), Carbon (C).

Symbol Writing Activity

Elements with Similar Initial Letters

• When elements have the same first letter, the first two letters are used (e.g., Calcium - Ca).
• First letter is capital, second is small.

Table Completion for Element Symbols

Elements with Pink-Highlighted Letters

Symbols from Latin Names

• Some elements use symbols derived from their Latin names.

Table Completion for Latin-Based Symbols

Formulae

• Atoms of inert gases can stay in a free state.
• Molecules can exist in a free state and are made of atoms of elements or compounds.
• A molecule of hydrogen consists of two hydrogen atoms, written as H₂.

Table Completion for Molecular Formulae

Atomicity

• Number of atoms present in a molecule of an element is called Atomicity of that molecule.
• Formula of water is H₂O.

Valency

• Combining capacity of an element is called its Valency.
• Number of hydrogen atoms that combine with one atom of an element to form a compound is called the valency of that element.

Table Completion for Valency

Valency with Respect to Hydrogen

• Valency is determined by assuming the valency of hydrogen to be unity (1).

Solutions

Mixtures and Solutions

• When two or more substances are mixed, they form a mixture.
• Solution is a kind of mixture.
• Sugar or salt dissolved in water forms a solution.

Solute and Solvent

• Substance dissolved is called the Solute.
• Substance in which it dissolves is called the Solvent.

Table Completion: Solute and Solvent

Types of Solutions

• Solutions can be formed by: dissolving a solid in a liquid, mixing two or more liquids, or dissolving a gas in a liquid.
  Mixing components of different states.
  Examples:
• Oxygen is soluble in water and helps aquatic life survive.
• Sugar particles are not visible after dissolution because they are made of billions of invisible sugar molecules.
• Water separates sugar molecules from a collection and mixes them throughout the solution.
• In the solution, both sugar and water remain in a mixed state with their chemical properties unchanged. If the sugar is heated, it is caramelized.

Examples of Aqueous Solutions

The Sugar Experiment

• Can sugar be perfumed by the solution? No sugar is not found after dissolution.
• Weigh water and sugar separately before dissolution. Then, prepare the two solutions. You will see that the two masses are equal. Besides this, the difference of of water and sugar solution can help us to understand that Water cannot taste before dissolution but after dissolution tastes sweet indicating that sugar, although mixed, is present in the solution still. Do the above with salt for another example.

Oil and Water Experiment

What did we find to identify if salt is more soluble in water or in oil?

• Take oil and water in a bottle. Close and shake it well. Keep aside for some time
  Record all observations

Separation of Components of a Mixture

Decantation and Filtration

• Muddy water kept aside settles the mud, then pour the clear water from the upper portion process is called decantation.
• Water obtained in this process is clear to the naked eye but may still contain tiny particles.
  Filtration using a piece of cloth/chutti may still not be clean enough.
  Separating water from its solute.
  Liquid and solid form.
  Sieve is too big of a perforation to be separated. What is of smaller form to use? A very special paper… called filter paper.

Filtration Process

Filter Paper Folding

Fold a circular filter paper into four folds open one fold and put the cone-shaped paper in a funnel with the help of glass rod, use a few drops of water to set it properly. Then pour muddy water into it

Table Completion: Filtration Observations

What you see : [Fill Here]

Why do you think it happens: [Fill Here]

Filter Paper Effectiveness

• Filter paper works better than cloth because it only allows the liquid to pass through, retaining solid particles.
  This is cleaner from decantation and sedimentation.

Definitions of Filtrate and Residue

• Filtration: Separating a liquid and a solid from a mixture using a filter paper.
• Filtrate: Clear liquid obtained through filtration.
• Residue: Solid left on the filter paper.

Water Filter Function

Water filter work by
Passing liquid through sand and gravels of different size.

Water cannot see the sugar due to small particles

Table Completion: Particle Size and Separation Process

crystallization.

Using Crystallization to Separate a Mixture

From your experience, is salt and water unable to separate by the one process.

Let is see how we can separate them by there mixture.

Salt Water Boiling Experiment

Boil salt water in a container-Solution will be concentrated as time pass.
-Allow the solution to cool in the end.
-Some granular salt separate from the mixture called its crystals.

Crystallization Process

• Crystallization: Process in which crystals of solid are obtained from a solution.

Separating Mixture by Using Magnet

• Separation of Iron Powder from any mixture is needed.
  Handpeeking and winnowing can be used to separate

Magnet Use

Take from the back of the speaker.

Activity.
Take a mixture of salt and iron powder on a sheet of paper. Then hold a magnet near it and see what happens.What will you see. Components of what other mixtures can be separated in this way?