CHEMICAL REACTIONS

DURING CHEMICAL REACTION,SUBSTANCES CALLED REACTANTS BREAK APART & NEW SUBSTANCES CALLED PRODUCTS FORM.ENERGY IS TAKEN INTO BREAK THE BONDS BETWEEN THE REACTANTS ATOMS.AS THE ATOMS LINK UP AGAIN IN DIFFERENT COMBINATIONS TO MAKE THE PRODUCTS, NEW BONDS FORM THE ENERGY IS GIVEN OUT.

THERE ARE MANY KINDS OF REACTIONS.THEY ARE DESCRIBED BELLOW-

1. EXOTHERMIC REACTIONS-

IN AN EXOTHERMIC REACTION,SUCH AS BURNING,MORE ENERGY IS GIVEN OUT THAN IS TAKEN IN FROM THE SURROUNDINGS.

2. ENDOTHERMIC REACTIONS-

MOST OF THE REACTIONS THAT OCCUR IN COOKING ARE ENDOTHERMIC,WHICH MEANS THAT MORE ENERGY IS TAKEN IN THAN IS GIVEN OUT.

3. OXIDATION & REDUCTION-

WHEN IRON RUSTS, A REACTION OCCUR BETWEEN THE IRON & OXYGEN IN THE AIR.THE IRON GAINS OXYGEN, AND AN ORANGE-BROWN COMPOUND CALLED IRON OXIDE FORMS.A REACTION IN WHICH A SUBSTANCE GAINS OXYGEN IS CALLED OXIDATION.WHEN OXIDATION OCCURS, THERE IS A SIMULTANIOUS REACTION CALLED REDUCTION, IN WHICH A SUBSTANCE LOSES OXYGEN.WHEN IRON OXIDIZES, THE AIR IS REDUCED AS IT LOSES OXYGEN TO IRON.

4. REVERSIBLE REACTIONS-

MANY CHEMICAL REACTIONS PERMANENTLY CHANGE THE REACTANTS, BUT REVERSIBLE REACTIONS CAN GO BOTH FORWARDS AND BACKWARDS.FOR EXAMPLE WHEN NITROGEN DIOXIDE IS HEATED, IT BREAKS DOWN INTO NITROGEN MONOXIDE AND OXYGEN.COOLING THIS MIXTURE MAKES THE TWO GASES REACT TO FORM NITROGEN DIOXIDE AGAIN.