Chemical changes Flashcards
What is chemical change?
Process where new substances of different chemical properties are formed
What are the common attributes of chemical reactions? (PIECOLT)
- Bubbles of gas are formed (effervescence)
[New odour or smell noticed] - The change is difficult or impossible to reverse
- A new colour appears
- Thermal or light energy is given off/ absorbed
- A solid material (precipitate) is formed in a solution
What law do chemical changes obey?
The law of conservation of mass
What is combustion?
AKA burning
- Reaction with oxygen to release energy
- Involves oxygen as a reactant
- Releases energy, (usually thermal)
What is oxidation?
-Addition of oxygen to a substance
- No energy is released
- Can cause rusting
What is decomposition thermal?
- Involves the breakdown of a compound into simpler substances through strong heating.
- Requires an activation energy
What is decomposition electrolysis?
- Involves the breakdown of a compound into simpler substances
- through passing of electricity
What is neutralisation?
Acid + Alkali = Salt + water
What is photosynthesis?
- Process by which green plants transform light energy into chemical potential energy
What is respiration?
Process by which cells in living organisms get energy
What is the law of conservation of mass?
- Atoms are not created or destroyed in a reaction. They are only rearranged. Mass is conserved.
What is precipitation?
- `When 2 solutions are mixed, a solid may form
- This white chalkiness is called white precipitation,
It involves the formation of a solid when 2 solutions are mixed
What do elements in the same group have in common in terms of valence electrons?
They all have the same number of valence electrons
What do elements of the same group have in common in terms of chemical properties?
- Since chemical properties of elements depend on the number of valence electrons an element has and elements in the same group have the same number of valence electrons, elements in the same group have similar chemical properties.
What are the unique features of noble gases? (MSVGFB)
- They are monoatomic elements
- They are relatively stable chemically
- They are in group 18 and have 8 valence electrons
- Since their valence shell is full
- They do not bond with other atoms
What is chemical bonding?
- It is the electrostatic force of attraction
What is involved in chemical changes?
- Only valence electrons are involved in chemical changes (to become stable)
What do the formation of chemical bonds depend on?
- Atoms forming chemical bonds depend on the electronic configuration of atoms
What type of ions will bond?
- Only opposite ions will bond (ionic transfer)
What is an ionic bond?
- It is the electrostatic force of attraction between oppositely charged ions
- Metal atoms transfer electrons to the non metal atoms
- 1 valence will transfer 1 electron
- 2 valence will transfer 2 electrons
Are metals and non metals negatively or positively charged?
- Non metals are negatively charged
- Metals are positively charged
What is the order in which the chemicals are written in for ions?
The formula for a positive ion is written before that of a negative ion
- EG: Sodium sulfate is Na2S not SNa2
What is a covalent bond?
It is the electrostatic force of attraction between the shared pair of electrons and the positive nuclei of the 2 atoms
- this bond is formed when 2 non-metal atoms share electrons
What are the types of covalent bonds?
- SINGLE BOND
— 1 pair of shared electrons - DOUBLE BOND
— 2 pairs of shared electrons - TRIPLE BOND
— 3 pairs of shared electrons - Refer to note called BOOKMARKED [CC] pg 1 titled Slide 24 for more info
What are the 2 different forms for the drawing of covalent bonds?
- Dot can cross
- Involves the usage of dots and crosses - Structural formula
- Involves the usage of lines
- Refer to note called BOOKMARKED [CC] pg 1 titled Slide 25 for more info
What is the prefix as the number of atoms in each second element in a compound changes?
- Mono
- Di
- Tri
*reminder that this only applies for covalent compounds