1. Starting materials in a chemical reaction are called reactants
2. The ending materials in a chemical reaction are called products
3. The arrow indicates a chemical reaction has taken place
4. All reactions have one thing in common: there is a rearangment of chemical bonds.
5.Chemical reactions always involve old bonds breaking, new bonds being created, or both.
6. In all reactions we still have all of thesame reactants at the end that we had at the start.
7. In every reaction there can never be any destruction atoms or construction
8. Chemical reactions only rearrange the bonds in the atoms that are already there.
9.Let's represent a reaction on paper. For example, hydrogen gas (H2) reacts with oxygen gas (O2) to form water (H2O): H2 + O2 = H2O
If we use only the atoms shown, we'd have 2 atoms of H and 2 atoms of O as reactants. This would make 1 molecule of H2O, but we'd have 1 atom of O leftover. However, this reaction only makes H2O.
Remember: reactions are not limited to 1 molecule each of reactants. We can use as many as we need to balance the chemical equation.
A balanced chemical reaction show
a) What atoms are present before (in the reactants) and after (in the products)
b) How many of each reactant and product is present before and after.
10. So to make H2O from oxygen gas and hydrogen gas, the balanced equation would be:
2H2 + O2----> 2H2O2
whis is the same as:
11. This idea is called the The Law of Conservation of Mass
12. There must be the same molecules and the same number of molecules before the reaction (in the reactants) and after the reaction (in the products).
13. What is the balanced equation for this reaction? 2 Cu +1 O2 -----> 2CuO
14. Reactants- 2Cu, O2 Products- 2CuO
15. To balance this equation we would have to add CuO molecules because this reaction doesn’t make lone oxygen molecules.
16. When we add a molecule of CuO now the number of oxygen atoms is balanced but the number of Cu atoms don’t match. Now we have to add more cu atoms to the reactants.
17. the balanced reaction for this equation is 2 Cu +1 O2 -----> 2CuO
Reactants- 2Cu and 1 O2 Product- 2Cu and 1 O2
18. 2CH4 + 4O2----> 4H2O + 2CO2
19. N2+ 3H2----> 2NH3
20. 2KClO3-----> 2KCl + 3O2
21. 4Al + 3O2-----> 2Al2O3
summary
(1)Chemical reactions always involve the breaking or making of bonds.
(2)The Law of Conservation of Mass says that the same atoms must be used for reactants and products
(3)To balance a chemical equation, you change the atoms in front of each substance until there are the same number of each type of atoms in both reactants and products
2. The ending materials in a chemical reaction are called products
3. The arrow indicates a chemical reaction has taken place
4. All reactions have one thing in common: there is a rearangment of chemical bonds.
5.Chemical reactions always involve old bonds breaking, new bonds being created, or both.
6. In all reactions we still have all of thesame reactants at the end that we had at the start.
7. In every reaction there can never be any destruction atoms or construction
8. Chemical reactions only rearrange the bonds in the atoms that are already there.
9.Let's represent a reaction on paper. For example, hydrogen gas (H2) reacts with oxygen gas (O2) to form water (H2O): H2 + O2 = H2O
If we use only the atoms shown, we'd have 2 atoms of H and 2 atoms of O as reactants. This would make 1 molecule of H2O, but we'd have 1 atom of O leftover. However, this reaction only makes H2O.
Remember: reactions are not limited to 1 molecule each of reactants. We can use as many as we need to balance the chemical equation.
A balanced chemical reaction show
a) What atoms are present before (in the reactants) and after (in the products)
b) How many of each reactant and product is present before and after.
10. So to make H2O from oxygen gas and hydrogen gas, the balanced equation would be:
2H2 + O2----> 2H2O2
whis is the same as:
| # of atoms in Reactants | Element | # of atoms in Products |
| 4 | H | 4 |
| 2 | O | 2 |
11. This idea is called the The Law of Conservation of Mass
12. There must be the same molecules and the same number of molecules before the reaction (in the reactants) and after the reaction (in the products).
13. What is the balanced equation for this reaction? 2 Cu +1 O2 -----> 2CuO
14. Reactants- 2Cu, O2 Products- 2CuO
15. To balance this equation we would have to add CuO molecules because this reaction doesn’t make lone oxygen molecules.
16. When we add a molecule of CuO now the number of oxygen atoms is balanced but the number of Cu atoms don’t match. Now we have to add more cu atoms to the reactants.
17. the balanced reaction for this equation is 2 Cu +1 O2 -----> 2CuO
Reactants- 2Cu and 1 O2 Product- 2Cu and 1 O2
18. 2CH4 + 4O2----> 4H2O + 2CO2
19. N2+ 3H2----> 2NH3
20. 2KClO3-----> 2KCl + 3O2
21. 4Al + 3O2-----> 2Al2O3
summary
(1)Chemical reactions always involve the breaking or making of bonds.
(2)The Law of Conservation of Mass says that the same atoms must be used for reactants and products
(3)To balance a chemical equation, you change the atoms in front of each substance until there are the same number of each type of atoms in both reactants and products
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