Chemistry

Solid distinguishing properties

Fixed volume and shape

Packed very closely, regular arrangement

More dense

Particles vibrate in fixed positions but cant change location

Liquids distinguishing properties

Fixed volume, takes shape of the container

Particles very close together but arranged irregularly

Usually less dense than solids but more than gasses

Particles can move and slide past each other

Gas distinguishing properties

No fixed volume, take shape of the container

Low density

Far apart move randomly and quickly in all directions

Can be compresses

Collide with each other and sides of the container

Melting

Solid changes into a liquid

Requires heat energy which transforms into kinetic energy allowing particles to move and slide past each other and not only vibrate in fixed positions

Occurs only at the melting point

Freezing

Liquid into solid

Requires loss of heat energy which leads to less kinetic energy so particles don’t have enough energy to move and only vibrate in fixed positions

Occurs only at freezing point

Evaporation

Liquid turns into a gas over a range of temperatures

Only at the surface of the liquid where high energy particles escape below the boiling point

Larger surface area and warmer temperature increase evaporation

Boiling

Liquid changes into gas

Requires heat which causes bubbles of gas to form below the surface of the liquid

Occurs at a specific temperature, the boiling point

Condensation

Gas changes into a liquid over a range of temperatures,

When gas is cooled, its particles lose energy so they bump into each other and lack energy to bounce away so they clump together to form a liquid

Why is there no increase in temperature during a change of state

Thermal energy is used to overcome attractive forces between particles rather than increase the kinetic energy

Why is there no decrease in temperature during a change of state

Thermal energy lost is used to build intermolecular forces rather than decrease kinetic energy

Combined Gas Law

(P1V1)/T1 = (P2V2)/T2

Why does temperature increase the volume of a gas

As the temperature increases, the kinetic energy will also increase

The gas particles will move faster and spread out

Why does Pressure affect the volume of a gas

As the pressure increases, the particles will collide more frequently

Same number of particles in a lower space

So lower volume

Diffusion definition

Net movement of particles from a region of higher concentration to lower concentration due to their random movement

Molecular mass effect on diffusion

Bigger molecules diffuse slower as they have a higher mass so move slower and travel less in the same amount of time

Physical Changes

New chemical substance is not produced

Easy to reverse and separate

Chemical Changes

New Chemical Substance is formed that have different properties to reactants

Difficult to reverse

Signs like colour change, temperature change and effervescence

Factors effecting Rate of reaction

Concentration

Pressure

Surface Area

Temperature

Catalyst

What does a catalyst do

Increases the rate of reaction and is unchanged by the end of the reaction

Collision Theory

In order for reactions to occur, the particles must collide with each other with sufficient energy

How to increase successful collisions

Number of particles per unit volume

Frequency of collisions per particles

Kinetic energy of particles

Activation Energy

How increasing concentration affects rate of reaction

More reactants in a given volume→ more collisions per second → more successful and frequent collisions→ Rate of reaction increases

How increasing pressure affects rate of reaction

Same number of particles in a smaller volume →more collisions per second →more frequent and successful collisions per second → rate of reaction increases

How increasing surface area affects rate of reaction

Greater area of particles exposed to reactant → more collisions per second→ more frequent and successful collisions per second → rate of reaction increases

How increasing temperature affects rate of reaction

Particles have more kinetic energy →more collisions per second → more frequent and successful collisions per second→ rate of reaction increases

How catalysts affects rate of reaction

Different reaction pathway with lower activation energy → higher proportion of particles have energy greater than the activation energy→ more successful reactions per second

How to measure the time

Stopwatch

How to measure temperature ?

Thermometer

How to measure mass

Digital Balance

How to measure approximate volumes of a liquid

Measuring Cylinder

How to accurately measure a fixed volume of liquid

Volumetric Pipette

How to accurately measure a variable volume of liquid

Burrettes

How to measure volume of Gas precisely and accurately

Gas Syringe

Disadvantage of Gas Syringe

Limited volume

Expensive

Fragile

Solvent

Substance that dissolves a solute

Solute

Substance that is dissolved in a solvent

Solution

Mixture of one or more solutes dissolved in a solvent

Saturated Solution

Solution containing the maximum concentration of a solute dissolved in the solvent at a specific temperature

Residue

Substance that remains after evaporation, distillation, filtration or any other substance

Filtrate

Liquid or solution that has passed through a filter

Chromotography process

Pencil line is drawn on chromatography paper and spots of the sample are placed on it

Paper is lowered into to the solvent container, ,making sure the pencil line sits above the level of the solvent so the samples don’t was into solvent container

Solvents travel up the paper taking some of the substance with it, different substances have different so they will travel at different rates causing them to spread apart#

Substance with higher solubility will travel farther

Substances with the same solubility will be

The same substance

Substances with multiple substances will have

produce more than one spot

Locating Agent

Used to see spots which aren’t visible with the human eye

Rf

Distance travelled by substance/ Distance travelled by solvent

How to identify carbon dioxide?

Using limewater, turns cloudy

How to test for chlorine

Bleaches damp litmus paper

How to test for hydrogen

Squeaky pop of lighted splint

How to test for oxygen

Glowing splint goes out than relights

How to test if substance is pure or impure

Fixed boiling/ melting points if pure, range of temperatures if not

How to use a suitable solvent to separate

Solids with different solubility, one dissolves in solvent other doesn’t

Place both in solvent

One will dissolve other won’t

How to use Filtration for separation

Used on mixture containing a insoluble solid in a liquid or solution

Filter paper placed in funnel above another beaker

Mixture powered placed in filter funnel above beaker

Filter paper will only let small liquid particles through into the filtrate

Solid particles will be too large too pass and stay behind as residue

Crystillisation

Dissolved solid from a solution

Solution heated allowing solvent to evaporate and leave a saturated solution behind

Dip clean dry cold rod into solution, crystals should begin to form when removed and allowed to cool

Saturated solution is allowed to cool

Solid will come out the solution as solubility decreases, crystals growing

Crystals collected by filtration

Washed with distilled water to purify, then allowed to dry

Simple Distillation

Liquid and soluble solid from a solution

Solution is heated, and the substance with the lower boiling point evaporates and boils producing a vapour which rises through the neck of the round bottom flask

Vapour passes through the condenser where it condenses and turns into pure water collected in a beaker

Only solid solute left

Fractional Distillation is used instead of simple distillation when

The liquids have a closer boiling point or a greater degree of accuracy is needed

Fractional Distillation

Used for miscible liquids

Substance raised to the boiling point of the substance with the lower boiling point

This substance will evaporate first

Rise and pass through fractionating column

Passes through condenser where they will cool and condense

Condensed liquid is collected in beaker

All of the substance is evaporated and collected

Exothermic Energy

Transfers thermal energy to surroundings leading to an increase in the temperature of the surroundings. Enthalpy change is negative

Endothermic Energy

Takes in thermal energy from surroundings leading to a decrease in the temperature of the surroundings. Enthalpy change is positive

Activation Energy

Minimum energy particles must have to react

Bond breaking is an_____ process

endothermic

Bond making is a _____ process

Exothermic

Enthalpy Change=

Bond breaking - Bond Making

Exothermic Reaction pathway diagram

Endo thermic reaction pathway diagram

Label

Red arrow is enthalpy Change

Green arrow is activation energy

Enthalpy Change

Transfer of thermal energy during a reaction

Are sodium salts soluble

Yes

Are Potassium salts soluble

Yes

Are Ammonium salts soluble

Yes

Are Nitrates Soluable

Yes

Are Chlorides soluble

Yes except pms

Are Sulfates soluble

Yes except pms and casr ba

Are Carbonates Soluble

No except with other soluble things

Are Hydroxides Soluble

No

Electrolysis

Decomposition of an ionic compound when molten or in an aqueous solution through the passage of an electric current

Anode

Positive Electrode

Cathode

Negetive Electrode

Electrolyte

Molten or aquaeous substance that goes electroysis

Which substance can be formed at the cathode

Metal and Hydrogen

What is formed at the anode

Non metals except hydrogen

Why might metals might be electroplated

Improve their appearance and resist corrosion

How do electrons move through the external circuit to transfer charge

Electrons flow from the negative terminal of the power supply to the cathode giving the cathode its negative charge

How does charge transfer during electrolysis from loss or gain of electrons at the electrodes

At the cathode, cations gain electrons to form atoms

Anions move to the anode and lose electrons

These electrons then flow back to the external circuit back to the power supply completing the circuit

Where do cations move to?

The cathode

Where do anions move

Anode

Identify products made in the electrolysis of molten lead (II) bromide

Brown Bromine Gas is given off

Grey lead deposits on the surface of the electrode

Identify the products made in the electrolysis concentrated aqueous sodium chloride

Hydrogen gas made at the negative electrode

Chlorine gas made at the positive electrode

Na + ions and OH- ions react to form NaOH solution which is left behind

Identify substances produced in electrolysis of dilute sulfuric acid

Hydrogen gas produced at cathode

Oxygen gas and water produced at anode

Sulfuric acid stays in electrolyte

What will form at the anode if concentrated group 7 elements are present

halogen will be formed

What will form at the anode if there are no halogens or dilute halogens

Oxygen

What will form at the cathode if it the metal is more reactive than hydrogen

Hydrogen gas

What will happen in the metal is less reactive than hydrogen

Metal will produce and plate onto the cathode

Describe the electrolysis of aqueous copper sulfate using inert carbon electrodes

Copper forms at the Cathode and will coat the cathode in a pink-brown colour

Oxygen will form at the anode

Blue colour of copper sulfate solution fades over time

OH- ions are oxidized to form oxygen in the equation

4OH- → O2 + 2H2O + 4e-

Describe the electrolysis of aqueous copper sulfate with a copper electrode

Copper is formed at the Cathode increasing its mass

Blue colour of copper sulfate remains the same

Anode decreases in mass as it dissolves as copper atoms are oxidised there by the battery taking away electrons

Copper plated on Cathode is the same lost at the anode

Copper sulfate concentration reamins the same

How does electroplating happen

Surface of one metal coats another metal

The cathode gets electroplated

The anode is made from the pure metal which will coat the other substance

The electrolyte is an aqueous solution of a soluble salt of the pure metal at the anode