chemistry 1 yousef berbar

S e c t i o n o n e & t w o

B y :

Y o u s s e f B e r b a r

Total amount of energy in universe stays the same

When matter undergoes the change , there is often change of energy

In A heat energy goes in and chemicals gain energy

In B hear energy is released and the chemicals lose energy .

When you add heat energy to something, the particles inside it gain the energy , so it move faster .

The extra energy could also change the bonds that exist between atoms or molecules.

Bonds holding a molecule together : hold the atoms in an individual molecule together .

Attractive forces (between molecules ) : hold the molecules of solids and liquids together and prevent them from separating to form a gas .

chemical bonds are much stronger than the intermolecular forces of attraction so it takes a lot more energy to break bonds in any chemical reaction

Perspective of the energy change

Endothermic : A process when the matter absorbs heat energy.

Exothermic : A process when the matter releases heat energy.

Organization of particles When a substance changes the origination of its

molecules also changes .

Chemists choose to measure, or speak in disorganization.

From 1 to 2 the (disorder) or(spread) of particles of substance increases .

Chemists quantify “spread” or disorder under the name entropy

Entropy (S): The disorder of particles in a substance.

Gases have their molecules very spread out , because reactions that create gases from solids and liquids have an increase in disorder

CaCO3(s) + energy →CaO(s) + CO2(g)That means One mole of calcium carbonate will produce one mole of calcium oxide and one mole of carbon dioxide when it goes to completion. With the entropy values, it can be seen mathematically that the total entropy increases.

Balanced chemical equation Balanced chemical equations are an example of

the Law of Conservation of Matter.

Law of Conservation of Matter : the amount of matter present before and after a chemical change

remains the same. Or matter cannot be created or destroyed, but it can be changed from form to another .

When chemical equations are written, the quantity of an element on the reactant side must equal the quantity of that element on the product side

How to balance an equation For example : Balance the equation for the reaction of

iron(III) oxide with hydrogen to form iron and water.

First : write the equation without balancing

Fe2O3+H2→Fe +H2O

Note : you can’t change the formula of the product so Use coefficients to balance an equation. Never change subscripts.

For example : when you write equation of water you may start by : H2+O2→H2O then add the

coefficients it will be 2H2+O2→2H2O .

To balance this equation, some people may want to change the formula of the product to H2O2 so it will

give hydrogen peroxide not water.

H2+O2→H2O2

Thanks for listening

Yousef Berbar