Chemistry Flashcards (not accurate)

## Elements, Compounds & Mixtures

Elements

Pure substance with only one type of atom.
Cannot be broken down by chemical methods.
Classified by metallic properties and physical states.
Exist as atoms or molecules.
Metals and noble gases exist as monatomic elements (e.g., Na, Al, He, Ar).

- Some exist as diatomic molecules (e.g., H $2$ , N $2$ , O $2$ , F $2$ , Cl $2$ , Br $2$ , I $_2$ ).

Compounds

Pure substance with two or more elements chemically combined in a fixed ratio.
Made up of molecules or ions.
Fixed composition of atoms (e.g., H $_2$ O always has a 2:1 ratio of hydrogen to oxygen).

- Broken down by chemical methods (electrolysis, thermal decomposition).

Mixtures

Two or more elements or compounds not chemically combined.
Separated by physical methods (distillation, filtration).

- Composition is not fixed, and components are not chemically bonded.

Types of Mixtures

Solution: solute dissolved in a solvent (e.g., salt in water).
Alloy: mixture of metal with another metal/non-metal (e.g., steel, brass, bronze).

## Apparatus and Accuracy

Time

Apparatus: Stopwatch or stop clock
Units: Seconds (s) or minutes (min)

- Accuracy: Nearest second

Temperature

Apparatus: Thermometer
Units: Degrees Celsius (°C)

- Accuracy: Record to 0.5 °C (half of smallest division)

Mass

Apparatus: Electronic balance
Units: Grams (g) or kilograms (kg)

- Accuracy: Depends on instrument

Volume of gas

Apparatus: Gas syringe
Units: Cubic centimeters (cm³)

- Accuracy: Approximate and variable volumes of gases

Volume of liquid

Apparatus: Measuring cylinder
Units: Cubic centimeters (cm³)

- Accuracy: Approximate and variable volumes of liquids (record to half the smallest division)

Volume of liquid

Apparatus: Burette
Units: Cubic centimeters (cm³)

- Accuracy: For variable and accurate (record to the nearest 0.05 cm³) volumes of liquids

Volume of liquid

Apparatus: Pipette
Units: Cubic centimeters (cm³)
Accuracy: For fixed and accurate (record to the nearest 0.1 cm³) volumes of liquids
*Measuring volume of gases: Gas syringes
Reactions:-
Acid + Metal -> salt + hydrogen gas
Acid + Carbonate

Collection of Gases

Method depends on:
- Solubility of gas in water.

- Density of gas compared to air.

Method A: Downward delivery

Suitable for gases denser than air.

- Examples: chlorine (Cl $2$ ), carbon dioxide (CO $2$ ).

Method B: Upward delivery

Suitable for gases less dense than air.

- Examples: ammonia (NH $3$ ), hydrogen (H $2$ ).

Method C: Water displacement

Suitable for gases insoluble in water.
Examples: hydrogen (H $*2$ ), nitrogen (N $*2$ ).

Drying of Gases

Moist gas dried by passing through a drying agent.
- Examples:-
- Solid: quicklime (calcium oxide), anhydrous calcium chloride.
- Liquid: concentrated sulfuric acid.

Kinetic Particle Theory

States that all matter is made of tiny particles in constant random motion.
'Kinetic' refers to motion; more kinetic energy means faster movement.
Particles can be atoms, molecules, or ions.

- Three common states of matter: solid, liquid, and gas.

Solid

Arrangement: Closely packed in orderly arrangement
Movement: Vibrate and rotate in fixed positions
Forces of attraction: Very strong
Shape: Fixed

- Volume: Fixed

Liquid

Arrangement: Closely packed (but not as closely packed as solid), in a disorderly arrangement
Movement: Move freely and slide over one another throughout the liquid
Forces of attraction: Strong
Shape: No fixed shape

- Volume: Fixed

Gas

Arrangement: Far apart in disorderly arrangement
Movement: Move rapidly in all directions
Forces of attraction: Weak
Shape: No fixed shape
Volume: No fixed volume
- Gases have the most kinetic energy, followed by liquids. Solids have the least.

Inter-conversion of States

- Occurs through gain or loss of energy.

Solid to Liquid (Melting)

Temperature increases, particles gain kinetic energy and vibrate faster.
At melting point, energy is used to overcome forces of attraction.
Particles move further apart and slide past each other.

- Once all particles overcome attraction, temperature increases.

Liquid to Gas (Boiling)

Temperature increases, particles gain kinetic energy and move faster.
At boiling point, energy overcomes forces, and particles move far apart.

- Once all particles overcome attraction, temperature increases.

Liquid to Solid (Freezing) & Gas to Liquid (Condensation)

As temperature decreases, particles lose kinetic energy and move slower.

Methods of Separation

To identify the separation and purification techniques for the components of the following types of mixtures
- solid-solid
- solid-liquid

- liquid-liquid (miscible)

Solid and Liquid (Solid Insoluble)

Method: Filtration

- Solid collected as residue, liquid as filtrate.

Solid and Liquid (Solid Soluble)

Method: Crystallization

- Heat to saturation, cool for crystals, filter, wash, and dry.

Solid and Liquid (Solid Soluble, Solvent Wanted)

Method: Simple Distillation

- Solvent collected as distillate.

Two Miscible Liquids

Method: Fractional Distillation

- Lower boiling point liquid collected first.

Small amount of mixtures

Method: Paper Chromatography
The more soluble the component of the mixture is, the further than it will travel in the solvent, the further away it will travel from the start line

## Determining Purity

Pure Solid

- Melts sharply at a fixed temperature.

Impure Solid

Melting point is lower and occurs over a wider range.

Ionic Bonding

Atoms form ions to achieve stable electronic structures (duplet or octet).
Positive ion (cation): more protons than electrons.
Negative ion (anion): more electrons than protons.
Positive ions retain element names (e.g., sodium ion).
Negative ions use suffix "ide" (e.g., bromide ion).
Metal atoms lose electrons; non-metal atoms gain electrons.
Ionic bond: electrostatic force between oppositely charged ions.

- Ionic compound: formed by electron transfer from metal to non-metal.

Properties of Ionic Compounds

High melting and boiling points due to strong electrostatic forces.
Do not conduct electricity in solid state.
Conduct electricity in molten or aqueous states due to mobile ions.
Soluble in water but insoluble in organic solvents.

Covalent Bonding

Atoms share electrons to attain noble gas electronic structure.
Covalent bond: attraction between nuclei and shared electrons.
Shared electrons are in pairs.

- Molecule: formed by two or more atoms covalently bonded.

Properties of Covalent Compounds

Low melting and boiling points due to weak intermolecular forces.
Do not conduct electricity in any state.

- Not soluble in water but soluble in organic solvents.

Physical properties of metals

Malleable and ductile.
Good conductors of heat and electricity.
Generally have high melting and boiling points.

Alloys

Mixture of a metal with other metals or non-metals (e.g., brass, bronze, steel).
Have different properties than their constituents.

## Atoms

Atomic structure

- Electrically neutral because the number of positively charged protons equals the number of negatively charged electrons.

Subatomic particles

Proton: +1 charge, mass 1
Neutron: 0 charge, mass 1

- Electron: -1 charge, negligible mass

Location

- Protons and neutrons are found in the nucleus of an atom, while electrons move around the nucleus in electron shells.

Numbers

Proton (atomic) number: number of protons in an atom
Nucleon (mass) number: total number of protons and neutrons in an atom
Number of neutrons = nucleon number - proton number

- For atoms, number of electrons = number of protons

Electron shells

The innermost electron shell holds a maximum of 2 electrons, while subsequent shells can hold up to 8 electrons each.

Isotopes

Atoms of the same element with the same number of protons but different number of neutrons.

- Isotopes have similar chemical properties but slightly different physical properties.

Relative atomic mass

The relative atomic mass of an element is the average mass of one atom of the element compared to 1/12 of the mass of one carbon-12 atom.

## Mole Concept and Stoichiometry

Relative atomic mass (Ar)

- Average mass of an atom of an element compared to 1/12 of the mass of one carbon-12 atom.

Isotopes

- Atoms of the same element with the same number of protons but different number of neutrons.

Relative molecular mass (Mr)

- Average mass of one molecule of an element or compound compared to 1/12 of the mass of one carbon-12 atom.

One mole

- One mole (collective noun) of matter contains $6.02 \times 10^{23}$ particles and is given a special name: Avogadro constant. Particles refer to molecules, atoms, ions O electrons.

Molar mass

- Molar mass is the mass of 1 mole of a substance in grams.

Balanced chemical equation

A balanced chemical equation tells us important information about a reaction:-
the ratio of the number of moles of the reactants and the products
the physical states of the reactants and products

Fuels

a fuel is a substance which releases heat energy when it burns
during combustion, the carbon and hydrogen atoms in the fuel molecules combine with oxygen molecules from the air to form carbon dioxide and water
Examples of fuels:-
- coal
- petroleum
- natural gas
- biofuels

Acids and Bases

A
base is a compound which can react with an acid to form salt and water only.
When a base dissolves in water to produce hydroxide, $OH^-$ , ions, the solution formed is called an

alkali. $OH^-$ ions are responsible for alkaline properties.

Reactions

Alkalis react with acids to form salt and water only.
Alkalis react

Chemistry Flashcards (not accurate)

## Elements, Compounds & Mixtures

- Some exist as diatomic molecules (e.g., H∗2*2∗2, N∗2*2∗2, O∗2*2∗2, F∗2*2∗2, Cl∗2*2∗2, Br∗2*2∗2, I2_22​).

- Broken down by chemical methods (electrolysis, thermal decomposition).

- Composition is not fixed, and components are not chemically bonded.

## Apparatus and Accuracy

- Accuracy: Nearest second

- Accuracy: Record to 0.5 °C (half of smallest division)

- Accuracy: Depends on instrument

- Accuracy: Approximate and variable volumes of gases

- Accuracy: Approximate and variable volumes of liquids (record to half the smallest division)

- Accuracy: For variable and accurate (record to the nearest 0.05 cm³) volumes of liquids

Collection of Gases

- Density of gas compared to air.

- Examples: chlorine (Cl∗2*2∗2), carbon dioxide (CO∗2*2∗2).

- Examples: ammonia (NH∗3*3∗3), hydrogen (H∗2*2∗2).

Drying of Gases

Kinetic Particle Theory

- Three common states of matter: solid, liquid, and gas.

- Volume: Fixed

- Volume: Fixed

Inter-conversion of States

- Occurs through gain or loss of energy.

- Once all particles overcome attraction, temperature increases.

- Once all particles overcome attraction, temperature increases.

Methods of Separation

- liquid-liquid (miscible)

- Solid collected as residue, liquid as filtrate.

- Heat to saturation, cool for crystals, filter, wash, and dry.

- Solvent collected as distillate.

- Lower boiling point liquid collected first.

## Determining Purity

- Melts sharply at a fixed temperature.

Ionic Bonding

- Ionic compound: formed by electron transfer from metal to non-metal.

Covalent Bonding

- Molecule: formed by two or more atoms covalently bonded.

- Not soluble in water but soluble in organic solvents.

Alloys

## Atoms

- Electrically neutral because the number of positively charged protons equals the number of negatively charged electrons.

- Electron: -1 charge, negligible mass

- Protons and neutrons are found in the nucleus of an atom, while electrons move around the nucleus in electron shells.

- For atoms, number of electrons = number of protons

Isotopes

- Isotopes have similar chemical properties but slightly different physical properties.

## Mole Concept and Stoichiometry

- Average mass of an atom of an element compared to 1/12 of the mass of one carbon-12 atom.

- Atoms of the same element with the same number of protons but different number of neutrons.

- Average mass of one molecule of an element or compound compared to 1/12 of the mass of one carbon-12 atom.

- One mole (collective noun) of matter contains 6.02×10236.02 \times 10^{23}6.02×1023 particles and is given a special name: Avogadro constant. Particles refer to molecules, atoms, ions O electrons.

- Molar mass is the mass of 1 mole of a substance in grams.

Fuels

Acids and Bases

alkali. OH−OH^-OH− ions are responsible for alkaline properties.

- Some exist as diatomic molecules (e.g., H $2$ , N $2$ , O $2$ , F $2$ , Cl $2$ , Br $2$ , I $_2$ ).

- Examples: chlorine (Cl $2$ ), carbon dioxide (CO $2$ ).

- Examples: ammonia (NH $3$ ), hydrogen (H $2$ ).

- One mole (collective noun) of matter contains $6.02 \times 10^{23}$ particles and is given a special name: Avogadro constant. Particles refer to molecules, atoms, ions O electrons.

alkali. $OH^-$ ions are responsible for alkaline properties.