Chemical Reactions and Types of Reactions

Question 1

What is a chemical reaction?

Answer 1

When one or more chemicals change to form different substances.

Question 2

What is the evidence of a chemical change?

Answer 2

• Energy change: All chemical reactions involve a change in energy: temperature change(thermal E), emission of light, emission of sound, and electrical energy.
• Odour change: in some reactions, odours change.
• Colour change: In some reactions, colors change.
• Formation of gas: In some, gases formed.
• Formation of a solid(precipitate) in a solution: In solution, new substance, no longer soluble, forms solid(precipitate).

Question 3

How do you know a chemical change has occured?

Answer 3

Two or more evidences will prove a chemical change. However, the best indicators of whether or not a chemical reaction has occurred are:

• A new substance has formed.
• The reaction cannot be reversed.

Question 4

What is chemical reaction and energy change?

Answer 4

In all chemical reactions, energy needs to be either absorbed or released.

• Exothermic reaction: reactions that release energy, energy is a product.
• Endothermic reaction: Reactions that absorb energy, energy is a reactant.

Question 5

What is the law of conservation of energy?

Answer 5

• Energy can be converted from one form to another, but the total energy of the universe remains constant. In order for this to be true, energy is linked to the formation or breakdown of chemical bonds.
• Breaking chemical bonds is endothermic.
• Forming new chemical bonds is exothermic.

Question 6

What is the law of conservation of mass?

Answer 6

During a chemical reaction, the total mass of the reacting substances(the reactants) is always equal to the total mass of the resulting substances(the products)

Question 7

Who was Antoine Lavoisier(1743-1794)?

Answer 7

• The father of modern chemistry.
• Lavoisier developed the law of conservation of mass based on a series of closed system experiments using test tubes.
• Closed system: does not allow exchange of matter between the system and its surrounding.
• Open system: allows the exchange pf substances between the system and its surrounding.

Question 8

What are the types of chemical reactions?

Answer 8

Chemical reactions involve the mixing of two or more reactants the form one or more products.
1. Formation(synthesis) reaction: Reactions involve two elements reacting to form one compound.
2. Decomposition reaction: involve one compound decomposing to form two different elements.
3. Single replacement reaction: involve one compound reacting with one elements to form one new compound and one new element.
4. Double replacement reaction: Involve two compounds reacting to form two new compounds.
5. Combustion reaction: combustion reactions often are ineradicable reactions that we think of as “burning” but in reality, they are when any substance react with oxygen.
A. Hydrocarbon combustion: Hydrocarbon combustion reactions are a specific type of combustion reactions involves one hydrocarbon reacting with oxygen gas to form carbon dioxide and water.
6. Neutralization reaction: Neutralization reactions involved an acid reacting with a base to form water and an ionic salt.