Created: October 21, 2024 1:55 PM Class: Science
- Periods - elements in the same row with the same amount of electron shells
- Group - elements in the same column sharing similar chemical properties and have the same amount of electrons in outer shell
- Blocks - (s,p,d,f) based on electron configuration. Also explain chemical reactivity and bonding
- Metals, non metals, metalloids - Metals on the left, metalloids in between and non metals on right
When atoms of the same element join together we get a molecule of that element
Oxygen is like this. Two oxygen atoms join together to make an oxygen molecule. Most of the oxygen in the air is in this form. Hydrogen and chlorine also have molecules with two atoms.
- Number of protons in the nucleus of an atom
- The average mass of protons, neutrons and electrons in an atom.
- Refers to how elements bond with each other
- Determined by the number of electrons in its outermost shell
- To have a stable configuration, it sometimes loses them to achieve a positive valency or gain them giving them a negative valency
- Electrons are negative
- Protons are positive
- Neutrons are neutral
A compound is made when atoms of different elements join together by chemical bonding.
- Properties are often very different from the elements they contain. E.g
- Hydrogen and oxygen are both gases at room temp, but water is a liquid
A mixture is an impure substance created when 2 chemicals aren’t chemically bonded but rather mixed together.
- Name metal first
- Name the non-metal component second and remove the last part of the word and add the suffix of “-ide”
- Oxygen becomes oxide
- Chlorine becomes chloride
- List of some anions
- Ammonium
$\text{NH}_4$ - Bromide
$\text{Br}$ - Chloride
$\text{CI}$ - Hydroxide
$\text{OH}^-$ - Iodide
$\text{I}$ - Nitrate
$\text{NO}_{3}^-$ - Carbonate
$\text{CO}_{3}^{2-}$ - Oxide
$\text{O}$ - Sulphate
$\text{SO}_{4}^{2-}$ - Sulphide
$\text{S}$ - Phosphate
$\text{PO}_4^{3-}$
- Ammonium
Compounds have constant composition with respect to mass because they are composed of atoms in fixed ratios
An ion is an atom that has gained or lost one or more electrons
Positive ions are ions that have lost electrons. They have more protons than electrons, so they carry a positive electrical charge.
Negative ions are atoms that have gained electrons. They have more electrons than protons so they carry a negative electrical charge.
The valency of an ion is the charge that is formed when an atom changes into being an ion
E.g. Magnesium atom (
OR
Oxygen atom (
| Atom | Atom symbol | Electrons exchange | Ion symbol |
|---|---|---|---|
| Lithium | Li | 1 lost | Li+ |
| Magnesium | Mg | 2 lost | Mg2+ |
| Aluminium | Al | 3 lost | Al3+ |
| Nitrogen | N | 3 gained | N3- |
| Oxygen | O | 2 gained | O2- |
| Chlorine | Cl | 1 gained | Cl- |
Sulphate, phosphate, nitrate and hydroxide will be the main 4 you will need to know and use. The process is similar, however we need to use brackets when there are 2 or more of sulphate, phosphate nitrate and hydroxide.
- Group 1 has +1 charge
- Group 2 has +2 charge
- Group 13 has 3+ charge
- Group 14 has
${\pm}4$ charge - Group 15 has -3 charge
- Group 16 has -2 charge
- Group 17 has -1 charge
- Group 18 is neutral (noble gases)
- Physical change, matter changes its appearance but not its composition
- Chemical change matter does change its composition
- Change in colour
- Bubbles of fizzing which means a gas is being made
- A change in temperature
- chemicals become hotter or colder
- A precipitate which is an insoluble solid substance being made
- The reacting chemicals slowly disappear, or new chemicals appear
The reacting chemicals are called reactants or reagents. They are consumed and used in the chemical reaction.
- The mass of reactants will always equal to the mass of products.
- Attraction between 2 atoms that have gained or lost electrons to become charged ions.
- Only between negatively charged and positively charged ion
- The negative ion gives electrons to the positive to form a neutral compound
- They have the following in common
- Made up of positive and negative ions
- Usually solids are room temperature
- Very high melting points because of electrostatic force of attraction between ions is very strong
- Usually dissolve in water to form aqueous solution
- Attraction between 2 atoms that secured by sharing electron/s from each of the atoms
- Bond over non metal atoms
- Properties include
- Exist as gases, liquids or solids with low melting points because the forces of attraction between the molecules are weak
- Generally don’t conduct electricity because they aren’t made up of ions
- Usually insoluble in water
- Metallic bonds only exist in a group of metal atoms. They are responsible for maintaining the metal atoms in a solid form.
- They are described as the nuclei of metal atoms in a sea of electrons. This “sea of electrons” is the reason that metals are such good conductors of electricity and heat.
| Ionic | Covalent | Metallic | |
|---|---|---|---|
| Electrons | Transferred | Shared, evenly or unevenly | Electron sea |
| Bond | Metal to nonmetal | Nonmetal to metal | Metal to metal |
| Electronegativity differences | Differences greater than 2 | Differences between 0 and 2 | NA |
| Make compounds | Yes by attraction of opposite charged ions | Molecules or molecular elements | No |
| State (STP) | Crystalline solid | Liquid, gas or solid | Malleable and ductile solid |
| Melting point | high | low | low |
| Conductivity | Liquid and aqueous state, yes | no | yes |
| Water solubility | high | low | no |
-
Substances on the left side are reactants and the right are products
-
State the state of each reactant next to the formula
-
Abbreviations
- Gas (g)
- Liquid (l)
- Solid (s)
- Aqueous (aq)
Chemical reactions
-
The total amount of energy stored in a substance is called enthalpy which is made up of:
- Kinetic energy
- Relates to the motion of the electrons and the atom.
- Temperature is a measure of the average kinetic energy in atoms
- When a substance rises in temperature, its atoms move faster and therefore higher kinetic energy
- Potential energy
- Attractions and repulsions present in the atom as well as the attractions present between different atoms
- The extent of the bonds it forms with other atoms
Exothermic reactions
- Chemical reaction that releases energy
- Often causes an increase in temperature
- Energy is released as heat
Endothermic
- A reaction in which energy is absorbed
- Energy must be added to the reaction
- Causes a drop in temperature so they can take up energy
- Absorb energy
- E.g Photosynthesis is the most important endothermic reaction
- Kinetic energy
Combustion
- Fast reaction of chemical with oxygen
- Releases the stored chemical energy in form of heat, therefore exothermic reaction.
- If the reactant is a metal, the product will always be a metal oxide
- If the product that is being combusted is an organic material (eg. glucose), the products will always be carbon dioxide and water
Complete combustion
- When hydrocarbons or alcohols burn in lots of oxygen, carbon dioxide and water are produced
- this is called complete combustion
- Produce heat energy which is able to be harnessed
Incomplete combustion
-
If supply of oxygen is limited, then incomplete combustion may occur
- Characterised by black smoky flames.
-
Two reactions occur simultaneously:
- Methane + oxygen → carbon monoxide + water
$$ \text{{2CH}}{\text{4}}(\text{g})+\text{3O}{2}(\text{g})\rightarrow \text{2CO(g)}+\text{4H}_{2}\text{O(g)} $$
- Methane + oxygen → carbon + water
$$ \text{CH}_{4}\text{(g)}+\text{O}_2(\text{g})\rightarrow \text{C(s) + 2H}_2\text{O(g)} $$
- The body needs a constant supply of energy which comes from digestion
- Glucose from digested carbohydrates is an important substance that contains stored chemical energy
- Living cells use a process called respiration to release energy from digested food (glucose), as it occurs in cells we call it cellular respiration
Glucose + oxygen → carbon dioxide + water + energy
- Reactants
- Glucose from digestive system
- Oxygen from respiratory system
- Waste products
- Carbon dioxide exhaled
- Water exhaled
Similarities
- Release energy
- Require oxygen and a fuel source
- Product the same products
- Carbon dioxide and water
Differences
| Combustion | Respiration |
|---|---|
| takes place in open | Takes place in cells |
| Occurs in single step | Many steps |
| No enzymes | Controlled by enzymes |
| Energy release is vigorous and not under control | Energy release is more gradual and under control |
| Energy is released in form of heat and light (flame can result) | Energy is released in form of heat and energy rich compound |
- Contain hydrogen
- React with metals to create salt and hydrogen gas
- React with carbonates to create salt, carbon dioxide and water
- Examples
- Hydrochloric acid
$\text{HCI}$ found in the stomach - Sulfuric acid
$\text{H}_2\text{SO}_4$ found in car batteries - Nitric acid
$\text{HNO}_3$ - Acetic acid
$\text{CH}_3\text{COOH}$ found in vinegar - Carbonic acid
$\text{H}_2\text{CO}_3$ found in soft drinks
- Hydrochloric acid
- Group of substances that neutralise acids, reacting with acids to form salts and water.
- Common bases used in classrooms
- Sodium hydroxide
$\text{NaOH}$ - Potassium hydroxide
$\text{KOH}$
- Sodium hydroxide
- Sodium chloride is found in oven cleaners and drain unclogging agents
- Ammonium hydroxide floor cleaners
- Sodium bi-carbonate in bi-carbonate soda
- Sodium hydroxide is found in household soap
- Magnesium hydroxide found in antacid tablets
-
Chemicals that turn different colours in acid and base solutions
- Red and blue litmus paper
- Universal indicator
- Phenolphthalein
- Red cabbage
- Measures how acidic or basic a substance is
- Scale of 1-14
- Acid < 7 pH
- Base > 7 pH
- Neutral = 7 pH
- Relates to how many H ions in the solution
- When an acid reacts with a base. Water is always a product in a neutralisation reaction as is salt
- Acid + Base → Salt + Water
- Applications
- Ant and bee stings are acidic so need to be neutralised with a basic solution
- Tooth paste is slightly basic which neutralises acids made by tooth decay
- Always react with a metal to produce salt and hydrogen gas
$\text{H}_2$ - Represented by general word equation
- ACID + METAL → SALT + HYDROGEN GAS
- Different acids produce different salts. E.g
- Hydrochloric acid produces chloride salts
- Sulfuric acid produces sulfate salts
- Nitric acid produces nitrate salts
- Carbonate is a substance containing
$\text{CO}_3$ - Acids always react with carbonates to produce a salt, water (
$\text{H}_2\text{O}$ ) and carbon dioxide gas($\text{CO}_2$ )
- When sodium chloride is dissolved in water to form an aqueous solution, it seems to ‘disappear’.
- The sodium ions and the chloride ions separate when they dissolve in water. Ions in aqueous solutions are therefore separate entities and are able to react independently.
- When two solutions containing dissolved ions are mixed together, these ions are able to come into contact with each other.
- Oppositely charged ions attract. In some cases, the attraction is strong enough to form ionic bonds and hence a new ionic compound.
- Some of these compounds are insoluble (unable to dissolve in water) and so a solid forms. This solid is called a precipitate.
- Chemical reactions in which precipitates form are called precipitation reactions.
- Reaction where one substance is broken into 2 or more new substances
- E.g Hydrogen peroxide is decomposed into water and oxygen
- 3 main factors that affect the rate
- Concentration
- Surface area
- Temperature
- Chemical factors that affect reaction rate are called catalysts in non-organic and enzyme in organic