Unit 3 : CHEMICAL CHANGES Flashcards
Definition of Matter:
Matter is anything that has mass AND takes up space
Particles that can make up matter:
Ions, Molecules and Atoms (IMA)
Definition of chemical change:
When atoms of chemical substances Break apart, Rearrange, and Combine chemically to form new substances.
Definition of Physical change:
A physical change is a change in a substance without changing its compostition or identity.
What causes chemical changes?
Chemical reactions
Definition of Chemical reaction:
A process by which one or more substances are changed into one or more DIFFERENT substances with DIFFERENT properties.
A substance has…
a composition and identity
What is the law of conversion of mass
The total mass before and after a chemical change must remain the same.
Characteristics of a Chemical change:
- Permenant colour change
- Formation of an insoluble solid (precipitate)
- Formation of effervescence in the solution (gas)
- A transfer of energy as heat and light (Glowing, Explosive, Hot, Cold)
- Not easily reversable
In a chemical reaction, ________ can be _________ or ________ to the surroundings during a chemical reaction.
In a chemical reaction, energy can be taken in or given out to the surroundings during a chemical reaction.
Definition of a Reactant in an equation:
A substance that is present at the start of the reaction
Definition of a product in an equation:
A new substance that is produced by the reaction
What is one KEY thing about atoms
- The cannot be created nor destroyed (chemical reaction follows the law of convertion of mass)
- When reactant collide together, atoms simply rearrange and combine chemically.
Conditions to trigger a Chemical change (5 types)
- Heat or an increase in temperature
- Interaction with oxygen
- Using an electric currenmt
- Exposure to light
- Mixing substances
Definition of Combustion:
It is a chemical reaction that occurs when a substance is heated/gains heat in the presence of oxygen to form one or more new substances.
Two chemical changes caused by Exposure to Light:
- Photosynthesis
- Photochemical Degradation (When a substance undergoes degradation when exposed to light (particularly ultra-violet rays) or visible light.
The 4 types of chemical reactions:
- Combustion
- Thermal Decomposition
- Neutralisation
- Oxidation
Definition of Thermal Decomposition:
When a single compound breaks into two or more of its constituent elements when it is heated.
[e.g Lime production]
Definition of Oxidation:
It is a chemical reaction in which a substance gains oxygen (can occur with or without combustion)
[e.g Rusting of Iron]
Common acids used in the lab (3 types):
- Sulfuric acid (H2SO4)
- Hydrochloric acid (HCI)
- Nitric acid (HNO3)
What is precipitate/precipitation?
The formation of a solid (precipitate) from a solution during a chemical reaction, often indicated by a cloudy or turbid appearance.
Two chemical changes caused by heat or increase in temperature:
- Combustion
- Thermal Decomposition
Chemical change caused by using an electric current:
- Electroplating
Types of Combustions (2 types):
- Complete Combustion: When sufficient amount of oxygen used to burn a substance -> Carbon dioxide produced
- Incomplete Combustion: When insufficient amount of oxygen used to burn a substance -> Carbon Monoxide and/or Soot produced.
