Change:-A substance can be changed by heating it, adding water to it or by mixing another substance to it. The change that takes place can be either a chemical change or a physical change.Chemical Change:-Signs of a chemical change:-     -One or more new substances are formed for example,

Iron + sulfur = Iron sulfide

(Black) (Yellow Powder) (Black Solid)

     -The new substances usually look quite different from the starting substance.     -A chemical change is also known as a chemical reaction.     -Energy is taken or given out during the reaction.           -A reaction that takes in heat is known as an enactheumic reaction.           -A reaction that gives out heat is known as a exothermic reaction.        -Examples of a 'Chemical' change: Fireworks, Frying Egg.        -Examples of a 'Physical' change: Scissors & Paper, Melting Ice cube, Sugar and Salt in Water.

Physical Change:          -No new substances are formed.     -A physical change is usually easy to reverse.

True or False:1. With a physical change, no new substance is formed.     -True     -False2. With a chemical change, a chemical reaction occurs.     -True      -False3. With a physical change, energy is either given off or absorbed.     -True     -False4. A chemical change can be easily reversed.     -True     -False5. A catalyst speeds up a chemical reaction     -True      -False

Burning Of A CandleIncomplete combustion result in the function of:     -Carbon Monoxide     -Heat     -Water Vapor     -Soot

          -The above diagram shows an appertains used to test the gases produced when a candle is burnt.          -The presence of black particles on the sides of the funnel indicates that soot is produced when the candle burns.           -Ice cubes are used to condense water vapor to liquid water by cooling the vapor.          -Lime water (colorless liquid) can be used to test of carbon dioxide gas.          -In the presence of carbon dioxide, lime water turns milky (cloudy). 

Endothermic and Exothermic Reactions:

Endo  |  thermic

-Remember the word 'Enter'.

-Comes from the word thermal which means heat.

-An Endothermic reaction is a reaction which absorbs heat from the surroundings.

-An Endothermic reaction is a reaction which absorbs heat from the surroundings.

Exo   |   thermic 

-Remember the word 'Exit'.

-Comes from the word thermal which means heat.

   -An exothermic reaction is a reaction which gives out heat to the surroundings.

     -In an exothermic reaction the temperature of the surrounding increases and the reaction medium (reaction container) becomes hotter.

Combustion Reaction:Definition      -Combustion is the process when a  substance is burnt in the presence of oxygen.          -Combustion reactions are always exthermic (They give out heat)Hydrocarbons:Definition       -A hydrocarbon is a compound which contains the elements of hydrogen only.          -Hydrocarbonates burn in oxygen to produce carbon dioxide, water vapor and heat.          -During combustion reactions, fuels burn in oxygen to produce carbon dioxide, water vapor and heat.            -However, metals burn in oxygen to produce metal oxide and heat. Examples:    -Magnesium + Oxygen = Magnesium      -Methanol + Oxygen = Carbon Dioxide + Water Vapor + Heat     -Wood + Oxygen = Carbon Dioxide + Water Vapor + Heat      -Zinc + Oxygen = Zinc Oxide + Heat     -Organic Molecules (Hydrocarbon) + Oxygen = Carbon Dioxide + Water Vapor + Heat.Other Examples:    1. The burning of coal in a power station.    2. The burning of petrol in a automobile engine.

Combustion Reactions

Can Be

Complete Combustion

Incomplete Combustion

-Requires large supply of oxygen.-Products are:     -Carbon Dioxide     -Water Vapor     -Heat

-Limited supply of oxygen is available for burning.-Products are:     -Carbon Monoxide     -Soot (unburnt carbon)     -Water Vapor     -Heat

Write down the word equation for:     1.Complete combustion and methane.          Carbon Dioxide + Water + Heat     2.Incomplete combustion of methane.          Carbon Monoxide + Soot + Water Vapor + Heat

The Reactivity SeriesP- PotassiumS- SodiumC- CalciumM- MagnesiumA- AluminiumZ- ZincI- IronL- LeadC- CopperM- MercuryS- SilverG- Gold

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Down the Reactivity Series, Reactivity of the metals decreases.

A simple electrical cell 

A simple electrical cell can be made when the different metals are pushed in a fruit.

-In the above cell, a current is produced when to metals are in contact with the fruit juice.-As a result the cell converts chemical energy into electrical energy.-The amount of energy which is produced by the chemical reaction is measured as the voltage of the cell. -This voltage is recorded by a voltmeter. 

-Link between energy produced and the Reactivity Series.-Different electrical cells can be made by  using different pairs of metals. -However, the energy produced will be different in each chemical reaction.-As a result, the voltage will be different for each chemical reaction.-The greater the difference in reactivity between the two metals used in the cell, the greater the energy released and the higher the voltage produced by the cell.

A Link Between:

1) For each of the following pairs of metals identify which metal is more reactive.

     a. Sodium & Lead     b. Magnesium & Iron     c. Aluminum & Copper     d. Zinc & Iron     e. Calcium & Magnesium

2) 4 different electrical cells (A, B, C, & D) made using different pairs of metals as shown below.

Cell A --> Iron & CopperCell B --> Calcium & CopperCell C --> Magnesium & ZincCell D --> Aluminium & Lead

-Identify which cell will produce the highest voltage.-Explain your answer.

Simple Chemical Reaction:

-A process during which atleast one new substance is prone as a chemical change.

     -All chemical reactions can be represented using chemical equations.     -Examples are:-          1. Precipitation reaction          2. Displacement reaction          3. Neutralisation reaction

Precipitation Reaction:

     A precipitation reaction is a reaction which reserves in the formation of an insoluble product (solid) when two solutions are mixed.     For example:          Reaction between Potassium iodide and Silver nitrate.

Equation for the reaction:Potassium iodine + silver nitrate = silver iodine + potassium nitrate.

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