Chemthink Questions

1. The starting materials in a chemical reaction are the Reactants
2. The ending materials in a chemical reaction are the Products
3. The arrow indicates a Reaction has taken place
4. All reactions have one thing in common: there is a rearrangement of chemical bonds
5. Chemical reactions all involve breaking old bonds and forming new bonds, or both.
6. In all the reactions we still have all of the atoms at the end that we had at the start.
7. In every reaction  there can never be any missing or new atoms when the reaction is over
8. Chemical reactions only rearrange bonds in the atoms that are already there.
9. 2H2+O2--->2H2O
10. 2h2 + 2O2 = 4H2O
11. The idea is called Law of Conservation of Mass
12. There must be the same atoms and the same number of mass before the reaction (in the reactants) and after the reaction (in the products).
13. 2Cu + O2 = 2CuO
14. Reactants: Cu: 1 O: 2 Products: Cu: 1 O: 1
15. To balance this equation, we have to add CuO molecules to the products because this reaction doesn't make lone  atoms
16. When we added a molecule of CuO, now the number of O2 atoms is balanced but the number of Cu atoms doesn't match. Now we have to add a Cu atom.
17. 2Cu + 1O2 ---> 2CuO
18. 2CH4 + 3O2---> 2H2O + 2CO2
19. N2 + 3H2---> 2NH3
20. 2KClO3---> 2KCl + 3O2
21. 4Al + 3O2---> 2Al2O3

1) Chemical reactions always involve breaking bonds, making bonds, or both.
2) The Law of Conservation of Mass says that the same atoms must be present before and after the reaction.
3) To balance a chemical equation, you change the coefficients in front of each substance
until there are the same number of each type of atoms in both reactants and products

We did four experiments. Each one had a different result and a different chemical reaction. The first one we did was ethanol + oxygen + fire = carbon dioxide + water. Ethanol was in a 2 liter bottle and was shaken until it became a gas. The cap was removed from the bottle and the tip of the bottle was next to an open flame. The oxygen mixed with the ethanol. The ethanol, oxygen mixture caused the bottle to shoot backwards and increase the size of the flame. As a  product of this, carbon dioxide and water were made. I thought the bottle would implode from the pressure, but instead it shot backwards. This kind of reaction was combustion. It was combustion because fire was used to get the products water and carbon dioxide.

In the second one, baking soda and vinegar was poured into a beaker and carbon dioxide was formed. A candle was placed on the cart and the CO2, being heavier than air, poured out onto the candle. The carbon dioxide replaced the oxygen around the flame on the candle, eliminating one of the three essentials of fire-oxygen. It put out the flame because the CO2 replaced the oxygen. That is what I thought was going to happen so my hypothesis was correct. The chemical reaction in this one was acid and base because vinegar was an acid (the ph level was high) and the baking soda was a base because the ph level was lower.

In the third one, zinc was added to hydrochloric acid. My thoughts were that it would bubble up and produce large amounts of gas in the beaker it was in. The zinc did bubble up and because of that, the water turned green. After it kept bubbling for a few seconds, a flame was introduced, it sped up the process. The zinc bubbled faster and the flames only stayed on the top layer of the hydrochloric acid. Steam was also produced making it single displacement because the zinc combined with the chlorine and went away from the hydrogen.

In the fourth experiment hydrogen peroxide was added to potassium iodide. When dish soap was also added, a big tightly packed foam formed and spilled out of the container. Before the experiment started, I thought that something slimy and foamy would form and spill out of the container. The hydrogen peroxide and potassium iodide created gas and the dish soap trapped the gas in it. That is why the foam was created. The chemical reaction taking place was decomposition because in the chemical equation, H2O2 was broken down into H2O and O2.