Chemistry Notes PDF

**Beginner Stuff:** In a **chemical reaction**, new substances are always produced. Chemical reactions are usually difficult or impossible to reverse. **Physical changes** are things like changes in state. They are easier to reverse. No new substances are produced in a physical change.  Physica...

**Beginner Stuff:** In a **chemical reaction**, new substances are always produced. Chemical reactions are usually difficult or impossible to reverse. **Physical changes** are things like changes in state. They are easier to reverse. No new substances are produced in a physical change.  Physical Changes Chemical Changes ----------------------------------- --------------------------------- Ice cream melting Car rusting (colour change) Draining water from rice Boiled egg (solid is produced)  Stirring sugar into a cup of tea. Burning toast (colour change) **Indicators of chemical reactions:** A colour change; a gas is given off; a new solid is produced; an energy change. **Energy Changes include:** Heat being given out or taken in; light being produced; sound being produced. When heat energy is produced, temperature increases. [EXOTHERMIC] reaction gives out energy, while [ENDOTHERMIC] reaction takes in energy.  **Effervescence:** When bubbles of gas are produced in a liquid **Precipitate:** A new solid formed when clear solutions are mixed. **Solute**: The substance being dissolved **Solvent:** The liquid that is doing the dissolving e.g water, alcohol, petrol **Solution:** A liquid with something dissolved in it **Saturated Solution:** A solution which cannot dissolve a further amount of solute at a certain temperature. **Solubility**: [SOLUBLE] chemicals dissolve well in solvents, and [INSOLUBLE] chemicals do not dissolve well.   Separating mixtures: **Filtration:** Used to separate an insoluble solid from a liquid. **Evaporation:** Used to separate dissolved solutes from the solution.  **Distillation:** Used to separate liquids with different boiling points. **Chromatography:** Used to separate mixtures of similar substances e,g coloured inks or sugars **Word Equations:** **Reactants:** Chemicals that react together **Products:** Chemicals that are produced in a reaction. E.g: Carbon Carbonate  ➕ Hydrochloric acid ➡️ Calcium Chloride ➕ Carbon dioxide ➕ water **Rules**: The reactants are on the left, and the products are on the right. Equations have to be written to be read from left to right. **Rates:** The **rate of reaction** is the speed of a reaction. Reaction rate can be affected by: **Particle:** Decreasing the particle size makes the reaction faster. Smaller particles = bigger surface area. Bigger surface area, faster reaction. **Temperature: ** The higher the temperature, the faster the reaction rate.  **Concentration:** Is a measure of how much solute is dissolved in one litre of solution. The higher the concentration, the faster the rate of reaction. **Catalyst:** Speeds up a chemical reaction without being used up. Enzymes are biological catalysts (made of protein) **Measuring rate:** We measure how a quantity changes over time (often mass or volume). To measure volume of gas, we can use an upside down measuring cylinder of water or a gas syringe. We can measure mass by doing a reaction on a balance(set of scales). The mass goes down if gas escapes from the flask. **Method:** **Upside down measuring cylinder:** in a conical flask, will be the reactions mixture. A delivery tube will go from the flask to a trough of water. There will be a measuring cylinder upturned in the trough, as well as a clamp on it, to keep it from moving its position. The gas produced from the reactants in the conical flask, will go down the delivery tube, and into the cylinder, pushing the water down. The less water, the more gas. The empty space is basically the gas.  **The gas syringe** is inserted into a conical flask with reactants. The gas goes up the syringe, and we can measure the amount of gas.  **Measuring mass loss:** When a gas is given off, the mass of the chemicals inside lowers, as the gas was produced from those chemicals. We can put a conical flask with those chemicals on a scale, and a piece of cotton on the top of the flask. It will allow gas formed to escape, but not liquid. We can see the mass leftover at the end of the experiment. **Comparing Rates:** **(Average) Rate Calculation:** See figure 6. Units can be like this. If the quantity is cm cubed and time is seconds. We do either cm cubed/ s or cm(cubed)s(mini minus 1).  Rate graphs: When the line is straight, the reaction is over. The steeper the gradient, the faster the rate of reaction. **Atomic Structure** See figure 1. Subatomic Particle  Mass (a.m.u)  Charge Where it is found --------------------- --------------- -------- ---------------------------- Proton 1 1+ In the nucleus  Neutron 1 0 In the nucleus  Electron  (Almost) 0 1- Orbits around the nucleus. Atoms are stable and neutral because they have the same number of negative electrons and positive protons. They do not have an electric charge. **Atomic Number:** Number of protons Atoms are neutral  so the **number of protons** is the same as the number of neutrons. Atomic number = protons = electrons **Mass number**: Number of protons + Number of neutrons. Electrons aren't added in this some because their mass is almost 0. **Number of neutrons** = mass number - atomic number. **Nuclide Notation ** See figure 2. **Isotopes:** Isotopes are atoms with the same number of protons, but a different number of neutrons OR Isotopes are atoms with the same atomic number, but different mass number but different mass number (same definition just with the mass scientific mass and atomic number lingo). See figure 3.  Relative atomic mass: The relative atomic mass (RAM) is the average atomic mass, taking into account how abundant(common) each isotope is. **Ions:** An unbalanced atom. Formed when an atom loses or gains electrons. It is no longer neutral, as the number of electrons and the number of protons is not equal. **Negative ions** have [more] electrons in the atom. **Positive ions** have [less] electrons in the atom. See figure 4. **Electron arrangement:** The electron arrangement shows how the electrons are arranged in energy levels (or shells of electrons), starting closest to the nucleus. **Target Diagram Rules:** The shells are filled in order, starting from the one closest to the nucleus. The first shell has a max of 2 electrons. They can go anywhere. There are 4 points to put the electrons in the next shells ( 2nd, 3rd...) We fill them singularly, 1,2,3,4, like north, south, east, West Point on a circle. Then we go again for pairing them up ( max 8 electrons in these shells). Apply up to element 20, calcium??? Target diagrams and electron arrangement in figure 5.  **Outer electron diagrams:** Similar to the target diagrams, but only outer electrons are shown (last number of the electron arrangement). Basically a target diagram, but we only do the last shell in the diagram. See figure 7.   **Periodic Table:** - Elements are arranged in the periodic table in order of increasing atomic number. - Arranged with their own unique symbol.  - The physical properties of an element is linked to the position of the element in the periodic table. - Elements with similar chemical properties are placed together in vertical groups.  - A row of elements is called a period. - All matter is made from atoms  - An element contains only ONE TYPE of atom. - Compounds contain more than one element chemically combined together. - Divided into metals and non-metals - metals conduct electricity when solid or liquid. Non metals do not. However carbon (as graphite) is the only non-metal which conducts electricity. **Group 1 (Alkali Metals) ** They are very reactive metals, and react with water e.g sodium + water ➡️ sodium hydroxide + hydrogen **Transition Metals:** Have the typical properties of metals (stuff like shiny and silver, malleable, unreactive, and good conductors of heat and electricity) **Group 7 (Halogens)** They are reactive non-metals They exist as diatomic molecules (see diatomic molecules. The gen-u-ine elements) e.g. F₂ **Group 0 (Noble Gases)(Also known as Group 8)** Very unreactive non-metals They are gases **Gaseous elements** at room temperature: Hydrogen, Helium, Nitrogen, Oxygen, Fluorine, Chlorine, Neon, Argon, Krypton, Xenon, and Radon. **Liquid** **Elements** at room temperature: Mercury and Bromine All the rest are solid. **Chemical Formula**: Shows us which elements are in a substance, and in what ratio. E.g. Carbon dioxide = CO₂ **From a picture:** See figure 8. **Using prefixes:** The prefix tells you how many of an element there is. We use this for chemical formula when there is an element with at least one prefix. If one element has a prefix, and the other doesn't, the one without the prefix is just one of the element. E.g. Carbon [Di]oxide = CO₂ Prefix  Number --------- -------- Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 **Valency**: If there is no picture, and no prefix, we use valency. Valency is the number of chemical bonds and atom can make. It is the same as the number of unpaired electrons, in the outer electron shell.  Group Number 1 2 3 4 5 6 7 0 -------------- --- --- --- --- --- --- --- --- Valency 1 2 3 4 3 2 1 0 For the swap and drop method, see figure 9. **Roman Numerals and Valency:** Transition Metals don't have group numbers, so they don't have a specific valency. We are given it for each specific question, in Roman numerals. E.g Iron(III) chloride. The III means a valency of 3. Then the process is the same. - In the case of transition metals, the same element can have different valencies. - A valency of II is most common. - This type of valency is also used from some other elements (particularly when they break valency rules. E.g tin(II) chloride (even though tin isn't a transition metal) **Group Ions:** Group ions are groups of atoms which act as a unit in a chemical formula. On page 8 of data book. The thing at the top ( two negative, one positive, three negative...) shows the valency. Two negative means valency of 2. Name Formula Valency ------------ --------- --------- Nitrate NO₃ 1 Sulfate SO₄ 2 Phosphate PO₄ 3 Carbonate CO₃ 2 Ammonium NH₄ 1 Hydroxide  OH 1 If while making a chemical formula with valency swap and drop, and we had a group ion. Use this as the element name, not nitrogen, for nitrogen, for example. Also, say we have NH₄, and we get 2 of them during valency swap and drop, we don't right NH₄₂. It looks like 42 Ammonium atoms! We do instead (NH₄)₂. If there is only one, there is no need for a bracket. **Diatomic Molecules:** While usually elements are just written as stuff like iron = Fe. However, some are diatomic (Two atoms in a molecule). The are the gen-u-ine elements. They end in either -gen, or -ine. Hydrogen = H₂. However, FORGET about adding the 2 in compounds. In something like the chemical formula of a compound, don't add the tiny 2.   **Elements in compounds:** If the 2nd element ends in-ide, then there are [two elements].  E.g. Calcium Nitride ➡️ Calcium + Nitrogen If the 2nd element of the compound ends in -ate or -ite, then it [also contains oxygen. ] E.g. Sodium Sulphate ➡️ Sodium + Sulphur + Oxygen [Others] Hydroxide is Oxygen and Hydrogen. Ammonium is Nitrogen and Hydrogen. **Word Equations to Formula Equations summary: ** - **Elements:** Write element symbols, not forgetting the diatomic molecules. - **Compounds:** Use prefixes, if no prefix, use swap and drop. E.g. See figure 10. **State Symbols**: Show what state the element/compound is in. \(s) = solid \(l) = liquid \(g) = gas (aq) = aqueous (dissolved in water/ in solution) **Balancing Equations: ** This equation is balanced: C + O₂ ➡️ CO₂ This equation is not balanced H₂ + O₂ ➡️ H₂O We can use big numbers like to balance the equation. E.g. ****H₂ + O₂ ➡️ ****H₂ + O₂ E.g. H₂ + Cl₂ ➡️ ****HCl We can also use fraction and decimal big numbers. Basically, we are just multiplying the elements by the number that we add. We CANNOT use tiny numbers **Outer Electron Bonding Diagrams: ** Atoms can achieve a (stable) filled outer shell in two ways: - Covalent: Sharing electrons - Ionic: Gaining/ Losing Electrons **Covalent in detail:** Why do they share electrons? Why do they connect; why are they attracted to each other and don't pull apart. Because, each positive nucleus is attracted to the shared negative electrons. **Covalent** compounds are made when NON-METALS share electrons.  Most covalent compunds are the gen-u-ine molecules. **Ionic compounds:** are when metals transfer electrons to non metals, making the positive and negative ions, which are attracted to each other, making a bond. [Electron arrangement]: When they gain or lose electrons, the electron arrangement gains or loses electrons accordingly. Non metals GAIN electrons, giving it a negative charge, because it is more electrons. Metals LOSE electrons, giving it a positive charge, because it is more protons than electrons. They obtain a **Noble gas electron arrangement** by doing this process of losing and gaining electrons. Noble gases are stable, as they have a full outer electron shell. **Bonding diagrams**: See figure 11. If you are told to draw a diagram of a molecule of something. I think usually a gen-u-ine molecule **Double and Triple Bonds:** H --- H is a single bond (2 shared electrons in the middle)  O = O is a double bond (4 shared electrons in the middle) N three lines N is a triple bond ( 6 shared electrons in the middle) This is when more than one covalent bond is formed. E.g It is a double bond if 4 electrons are shared. E.g. Figure 12 **Shapes of molecules:** 4 types of arrangements: Linear, Angular/Bent/V-shaped, Trigonal Pyramidal, and Tetrahedral. See figure 13,14,15, and 16. **eginner Stuff:** In a **chemical reaction**, new substances are always produced. Chemical reactions are usually difficult or impossible to reverse. **Physical changes** are things like changes in state. They are easier to reverse. No new substances are produced in a physical change.  Physical Changes Chemical Changes ----------------------------------- --------------------------------- Ice cream melting Car rusting (colour change) Draining water from rice Boiled egg (solid is produced)  Stirring sugar into a cup of tea. Burning toast (colour change) **Indicators of chemical reactions:** A colour change; a gas is given off; a new solid is produced; an energy change. **Energy Changes include:** Heat being given out or taken in; light being produced; sound being produced. When heat energy is produced, temperature increases. [EXOTHERMIC] reaction gives out energy, while [ENDOTHERMIC] reaction takes in energy.  **Effervescence:** When bubbles of gas are produced in a liquid **Precipitate:** A new solid formed when clear solutions are mixed. **Solute**: The substance being dissolved **Solvent:** The liquid that is doing the dissolving e.g water, alcohol, petrol **Solution:** A liquid with something dissolved in it **Saturated Solution:** A solution which cannot dissolve a further amount of solute at a certain temperature. **Solubility**: [SOLUBLE] chemicals dissolve well in solvents, and [INSOLUBLE] chemicals do not dissolve well.   Separating mixtures: **Filtration:** Used to separate an insoluble solid from a liquid. **Evaporation:** Used to separate dissolved solutes from the solution.  **Distillation:** Used to separate liquids with different boiling points. **Chromatography:** Used to separate mixtures of similar substances e,g coloured inks or sugars **Word Equations:** **Reactants:** Chemicals that react together **Products:** Chemicals that are produced in a reaction. E.g: Carbon Carbonate  ➕ Hydrochloric acid ➡️ Calcium Chloride ➕ Carbon dioxide ➕ water **Rules**: The reactants are on the left, and the products are on the right. Equations have to be written to be read from left to right. **Rates:** The **rate of reaction** is the speed of a reaction. Reaction rate can be affected by: **Particle:** Decreasing the particle size makes the reaction faster. Smaller particles = bigger surface area. Bigger surface area, faster reaction. **Temperature: ** The higher the temperature, the faster the reaction rate.  **Concentration:** Is a measure of how much solute is dissolved in one litre of solution. The higher the concentration, the faster the rate of reaction. **Catalyst:** Speeds up a chemical reaction without being used up. Enzymes are biological catalysts (made of protein) **Measuring rate:** We measure how a quantity changes over time (often mass or volume). To measure volume of gas, we can use an upside down measuring cylinder of water or a gas syringe. We can measure mass by doing a reaction on a balance(set of scales). The mass goes down if gas escapes from the flask. **Method:** **Upside down measuring cylinder:** in a conical flask, will be the reactions mixture. A delivery tube will go from the flask to a trough of water. There will be a measuring cylinder upturned in the trough, as well as a clamp on it, to keep it from moving its position. The gas produced from the reactants in the conical flask, will go down the delivery tube, and into the cylinder, pushing the water down. The less water, the more gas. The empty space is basically the gas.  **The gas syringe** is inserted into a conical flask with reactants. The gas goes up the syringe, and we can measure the amount of gas.  **Measuring mass loss:** When a gas is given off, the mass of the chemicals inside lowers, as the gas was produced from those chemicals. We can put a conical flask with those chemicals on a scale, and a piece of cotton on the top of the flask. It will allow gas formed to escape, but not liquid. We can see the mass leftover at the end of the experiment. **Comparing Rates:** **(Average) Rate Calculation:** See figure 6. Units can be like this. If the quantity is cm cubed and time is seconds. We do either cm cubed/ s or cm(cubed)s(mini minus 1).  Rate graphs: When the line is straight, the reaction is over. The steeper the gradient, the faster the rate of reaction. **Atomic Structure** See figure 1. Subatomic Particle  Mass (a.m.u)  Charge Where it is found --------------------- --------------- -------- ---------------------------- Proton 1 1+ In the nucleus  Neutron 1 0 In the nucleus  Electron  (Almost) 0 1- Orbits around the nucleus. Atoms are stable and neutral because they have the same number of negative electrons and positive protons. They do not have an electric charge. **Atomic Number:** Number of protons Atoms are neutral  so the **number of protons** is the same as the number of neutrons. Atomic number = protons = electrons **Mass number**: Number of protons + Number of neutrons. Electrons aren't added in this some because their mass is almost 0. **Number of neutrons** = mass number - atomic number. **Nuclide Notation ** See figure 2. **Isotopes:** Isotopes are atoms with the same number of protons, but a different number of neutrons OR Isotopes are atoms with the same atomic number, but different mass number but different mass number (same definition just with the mass scientific mass and atomic number lingo). See figure 3.  Relative atomic mass: The relative atomic mass (RAM) is the average atomic mass, taking into account how abundant(common) each isotope is. **Ions:** An unbalanced atom. Formed when an atom loses or gains electrons. It is no longer neutral, as the number of electrons and the number of protons is not equal. **Negative ions** have [more] electrons in the atom. **Positive ions** have [less] electrons in the atom. See figure 4. **Electron arrangement:** The electron arrangement shows how the electrons are arranged in energy levels (or shells of electrons), starting closest to the nucleus. **Target Diagram Rules:** The shells are filled in order, starting from the one closest to the nucleus. The first shell has a max of 2 electrons. They can go anywhere. There are 4 points to put the electrons in the next shells ( 2nd, 3rd...) We fill them singularly, 1,2,3,4, like north, south, east, West Point on a circle. Then we go again for pairing them up ( max 8 electrons in these shells). Apply up to element 20, calcium??? Target diagrams and electron arrangement in figure 5.  **Outer electron diagrams:** Similar to the target diagrams, but only outer electrons are shown (last number of the electron arrangement). Basically a target diagram, but we only do the last shell in the diagram. See figure 7.   **Periodic Table:** - Elements are arranged in the periodic table in order of increasing atomic number. - Arranged with their own unique symbol.  - The physical properties of an element is linked to the position of the element in the periodic table. - Elements with similar chemical properties are placed together in vertical groups.  - A row of elements is called a period. - All matter is made from atoms  - An element contains only ONE TYPE of atom. - Compounds contain more than one element chemically combined together. - Divided into metals and non-metals - metals conduct electricity when solid or liquid. Non metals do not. However carbon (as graphite) is the only non-metal which conducts electricity. **Group 1 (Alkali Metals) ** They are very reactive metals, and react with water e.g sodium + water ➡️ sodium hydroxide + hydrogen **Transition Metals:** Have the typical properties of metals (stuff like shiny and silver, malleable, unreactive, and good conductors of heat and electricity) **Group 7 (Halogens)** They are reactive non-metals They exist as diatomic molecules (see diatomic molecules. The gen-u-ine elements) e.g. F₂ **Group 0 (Noble Gases)(Also known as Group 8)** Very unreactive non-metals They are gases **Gaseous elements** at room temperature: Hydrogen, Helium, Nitrogen, Oxygen, Fluorine, Chlorine, Neon, Argon, Krypton, Xenon, and Radon. **Liquid** **Elements** at room temperature: Mercury and Bromine All the rest are solid. **Chemical Formula**: Shows us which elements are in a substance, and in what ratio. E.g. Carbon dioxide = CO₂ **From a picture:** See figure 8. **Using prefixes:** The prefix tells you how many of an element there is. We use this for chemical formula when there is an element with at least one prefix. If one element has a prefix, and the other doesn't, the one without the prefix is just one of the element. E.g. Carbon [Di]oxide = CO₂ Prefix  Number --------- -------- Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 **Valency**: If there is no picture, and no prefix, we use valency. Valency is the number of chemical bonds and atom can make. It is the same as the number of unpaired electrons, in the outer electron shell.  Group Number 1 2 3 4 5 6 7 0 -------------- --- --- --- --- --- --- --- --- Valency 1 2 3 4 3 2 1 0 For the swap and drop method, see figure 9. **Roman Numerals and Valency:** Transition Metals don't have group numbers, so they don't have a specific valency. We are given it for each specific question, in Roman numerals. E.g Iron(III) chloride. The III means a valency of 3. Then the process is the same. - In the case of transition metals, the same element can have different valencies. - A valency of II is most common. - This type of valency is also used from some other elements (particularly when they break valency rules. E.g tin(II) chloride (even though tin isn't a transition metal) **Group Ions:** Group ions are groups of atoms which act as a unit in a chemical formula. On page 8 of data book. The thing at the top ( two negative, one positive, three negative...) shows the valency. Two negative means valency of 2. Name Formula Valency ------------ --------- --------- Nitrate NO₃ 1 Sulfate SO₄ 2 Phosphate PO₄ 3 Carbonate CO₃ 2 Ammonium NH₄ 1 Hydroxide  OH 1 If while making a chemical formula with valency swap and drop, and we had a group ion. Use this as the element name, not nitrogen, for nitrogen, for example. Also, say we have NH₄, and we get 2 of them during valency swap and drop, we don't right NH₄₂. It looks like 42 Ammonium atoms! We do instead (NH₄)₂. If there is only one, there is no need for a bracket. **Diatomic Molecules:** While usually elements are just written as stuff like iron = Fe. However, some are diatomic (Two atoms in a molecule). The are the gen-u-ine elements. They end in either -gen, or -ine. Hydrogen = H₂. However, FORGET about adding the 2 in compounds. In something like the chemical formula of a compound, don't add the tiny 2.   **Elements in compounds:** If the 2nd element ends in-ide, then there are [two elements].  E.g. Calcium Nitride ➡️ Calcium + Nitrogen If the 2nd element of the compound ends in -ate or -ite, then it [also contains oxygen. ] E.g. Sodium Sulphate ➡️ Sodium + Sulphur + Oxygen [Others] Hydroxide is Oxygen and Hydrogen. Ammonium is Nitrogen and Hydrogen. **Word Equations to Formula Equations summary: ** - **Elements:** Write element symbols, not forgetting the diatomic molecules. - **Compounds:** Use prefixes, if no prefix, use swap and drop. E.g. See figure 10. **State Symbols**: Show what state the element/compound is in. \(s) = solid \(l) = liquid \(g) = gas (aq) = aqueous (dissolved in water/ in solution) **Balancing Equations: ** This equation is balanced: C + O₂ ➡️ CO₂ This equation is not balanced H₂ + O₂ ➡️ H₂O We can use big numbers like to balance the equation. E.g. ****H₂ + O₂ ➡️ ****H₂ + O₂ E.g. H₂ + Cl₂ ➡️ ****HCl We can also use fraction and decimal big numbers. Basically, we are just multiplying the elements by the number that we add. We CANNOT use tiny numbers **Outer Electron Bonding Diagrams: ** Atoms can achieve a (stable) filled outer shell in two ways: - Covalent: Sharing electrons - Ionic: Gaining/ Losing Electrons **Covalent in detail:** Why do they share electrons? Why do they connect; why are they attracted to each other and don't pull apart. Because, each positive nucleus is attracted to the shared negative electrons. **Covalent** compounds are made when NON-METALS share electrons.  Most covalent compunds are the gen-u-ine molecules. **Ionic compounds:** are when metals transfer electrons to non metals, making the positive and negative ions, which are attracted to each other, making a bond. [Electron arrangement]: When they gain or lose electrons, the electron arrangement gains or loses electrons accordingly. Non metals GAIN electrons, giving it a negative charge, because it is more electrons. Metals LOSE electrons, giving it a positive charge, because it is more protons than electrons. They obtain a **Noble gas electron arrangement** by doing this process of losing and gaining electrons. Noble gases are stable, as they have a full outer electron shell. **Bonding diagrams**: See figure 11. If you are told to draw a diagram of a molecule of something. I think usually a gen-u-ine molecule **Double and Triple Bonds:** H --- H is a single bond (2 shared electrons in the middle)  O = O is a double bond (4 shared electrons in the middle) N three lines N is a triple bond ( 6 shared electrons in the middle) This is when more than one covalent bond is formed. E.g It is a double bond if 4 electrons are shared. E.g. Figure 12 **Shapes of molecules:** 4 types of arrangements: Linear, Angular/Bent/V-shaped, Trigonal Pyramidal, and Tetrahedral. See figure 13,14,15, and 16. **eginner Stuff:** In a **chemical reaction**, new substances are always produced. Chemical reactions are usually difficult or impossible to reverse. **Physical changes** are things like changes in state. They are easier to reverse. No new substances are produced in a physical change.  Physical Changes Chemical Changes ----------------------------------- --------------------------------- Ice cream melting Car rusting (colour change) Draining water from rice Boiled egg (solid is produced)  Stirring sugar into a cup of tea. Burning toast (colour change) **Indicators of chemical reactions:** A colour change; a gas is given off; a new solid is produced; an energy change. **Energy Changes include:** Heat being given out or taken in; light being produced; sound being produced. When heat energy is produced, temperature increases. [EXOTHERMIC] reaction gives out energy, while [ENDOTHERMIC] reaction takes in energy.  **Effervescence:** When bubbles of gas are produced in a liquid **Precipitate:** A new solid formed when clear solutions are mixed. **Solute**: The substance being dissolved **Solvent:** The liquid that is doing the dissolving e.g water, alcohol, petrol **Solution:** A liquid with something dissolved in it **Saturated Solution:** A solution which cannot dissolve a further amount of solute at a certain temperature. **Solubility**: [SOLUBLE] chemicals dissolve well in solvents, and [INSOLUBLE] chemicals do not dissolve well.   Separating mixtures: **Filtration:** Used to separate an insoluble solid from a liquid. **Evaporation:** Used to separate dissolved solutes from the solution.  **Distillation:** Used to separate liquids with different boiling points. **Chromatography:** Used to separate mixtures of similar substances e,g coloured inks or sugars **Word Equations:** **Reactants:** Chemicals that react together **Products:** Chemicals that are produced in a reaction. E.g: Carbon Carbonate  ➕ Hydrochloric acid ➡️ Calcium Chloride ➕ Carbon dioxide ➕ water **Rules**: The reactants are on the left, and the products are on the right. Equations have to be written to be read from left to right. **Rates:** The **rate of reaction** is the speed of a reaction. Reaction rate can be affected by: **Particle:** Decreasing the particle size makes the reaction faster. Smaller particles = bigger surface area. Bigger surface area, faster reaction. **Temperature: ** The higher the temperature, the faster the reaction rate.  **Concentration:** Is a measure of how much solute is dissolved in one litre of solution. The higher the concentration, the faster the rate of reaction. **Catalyst:** Speeds up a chemical reaction without being used up. Enzymes are biological catalysts (made of protein) **Measuring rate:** We measure how a quantity changes over time (often mass or volume). To measure volume of gas, we can use an upside down measuring cylinder of water or a gas syringe. We can measure mass by doing a reaction on a balance(set of scales). The mass goes down if gas escapes from the flask. **Method:** **Upside down measuring cylinder:** in a conical flask, will be the reactions mixture. A delivery tube will go from the flask to a trough of water. There will be a measuring cylinder upturned in the trough, as well as a clamp on it, to keep it from moving its position. The gas produced from the reactants in the conical flask, will go down the delivery tube, and into the cylinder, pushing the water down. The less water, the more gas. The empty space is basically the gas.  **The gas syringe** is inserted into a conical flask with reactants. The gas goes up the syringe, and we can measure the amount of gas.  **Measuring mass loss:** When a gas is given off, the mass of the chemicals inside lowers, as the gas was produced from those chemicals. We can put a conical flask with those chemicals on a scale, and a piece of cotton on the top of the flask. It will allow gas formed to escape, but not liquid. We can see the mass leftover at the end of the experiment. **Comparing Rates:** **(Average) Rate Calculation:** See figure 6. Units can be like this. If the quantity is cm cubed and time is seconds. We do either cm cubed/ s or cm(cubed)s(mini minus 1).  Rate graphs: When the line is straight, the reaction is over. The steeper the gradient, the faster the rate of reaction. **Atomic Structure** See figure 1. Subatomic Particle  Mass (a.m.u)  Charge Where it is found --------------------- --------------- -------- ---------------------------- Proton 1 1+ In the nucleus  Neutron 1 0 In the nucleus  Electron  (Almost) 0 1- Orbits around the nucleus. Atoms are stable and neutral because they have the same number of negative electrons and positive protons. They do not have an electric charge. **Atomic Number:** Number of protons Atoms are neutral  so the **number of protons** is the same as the number of neutrons. Atomic number = protons = electrons **Mass number**: Number of protons + Number of neutrons. Electrons aren't added in this some because their mass is almost 0. **Number of neutrons** = mass number - atomic number. **Nuclide Notation ** See figure 2. **Isotopes:** Isotopes are atoms with the same number of protons, but a different number of neutrons OR Isotopes are atoms with the same atomic number, but different mass number but different mass number (same definition just with the mass scientific mass and atomic number lingo). See figure 3.  Relative atomic mass: The relative atomic mass (RAM) is the average atomic mass, taking into account how abundant(common) each isotope is. **Ions:** An unbalanced atom. Formed when an atom loses or gains electrons. It is no longer neutral, as the number of electrons and the number of protons is not equal. **Negative ions** have [more] electrons in the atom. **Positive ions** have [less] electrons in the atom. See figure 4. **Electron arrangement:** The electron arrangement shows how the electrons are arranged in energy levels (or shells of electrons), starting closest to the nucleus. **Target Diagram Rules:** The shells are filled in order, starting from the one closest to the nucleus. The first shell has a max of 2 electrons. They can go anywhere. There are 4 points to put the electrons in the next shells ( 2nd, 3rd...) We fill them singularly, 1,2,3,4, like north, south, east, West Point on a circle. Then we go again for pairing them up ( max 8 electrons in these shells). Apply up to element 20, calcium??? Target diagrams and electron arrangement in figure 5.  **Outer electron diagrams:** Similar to the target diagrams, but only outer electrons are shown (last number of the electron arrangement). Basically a target diagram, but we only do the last shell in the diagram. See figure 7.   **Periodic Table:** - Elements are arranged in the periodic table in order of increasing atomic number. - Arranged with their own unique symbol.  - The physical properties of an element is linked to the position of the element in the periodic table. - Elements with similar chemical properties are placed together in vertical groups.  - A row of elements is called a period. - All matter is made from atoms  - An element contains only ONE TYPE of atom. - Compounds contain more than one element chemically combined together. - Divided into metals and non-metals - metals conduct electricity when solid or liquid. Non metals do not. However carbon (as graphite) is the only non-metal which conducts electricity. **Group 1 (Alkali Metals) ** They are very reactive metals, and react with water e.g sodium + water ➡️ sodium hydroxide + hydrogen **Transition Metals:** Have the typical properties of metals (stuff like shiny and silver, malleable, unreactive, and good conductors of heat and electricity) **Group 7 (Halogens)** They are reactive non-metals They exist as diatomic molecules (see diatomic molecules. The gen-u-ine elements) e.g. F₂ **Group 0 (Noble Gases)(Also known as Group 8)** Very unreactive non-metals They are gases **Gaseous elements** at room temperature: Hydrogen, Helium, Nitrogen, Oxygen, Fluorine, Chlorine, Neon, Argon, Krypton, Xenon, and Radon. **Liquid** **Elements** at room temperature: Mercury and Bromine All the rest are solid. **Chemical Formula**: Shows us which elements are in a substance, and in what ratio. E.g. Carbon dioxide = CO₂ **From a picture:** See figure 8. **Using prefixes:** The prefix tells you how many of an element there is. We use this for chemical formula when there is an element with at least one prefix. If one element has a prefix, and the other doesn't, the one without the prefix is just one of the element. E.g. Carbon [Di]oxide = CO₂ Prefix  Number --------- -------- Mono- 1 Di- 2 Tri- 3 Tetra- 4 Penta- 5 Hexa- 6 **Valency**: If there is no picture, and no prefix, we use valency. Valency is the number of chemical bonds and atom can make. It is the same as the number of unpaired electrons, in the outer electron shell.  Group Number 1 2 3 4 5 6 7 0 -------------- --- --- --- --- --- --- --- --- Valency 1 2 3 4 3 2 1 0 For the swap and drop method, see figure 9. **Roman Numerals and Valency:** Transition Metals don't have group numbers, so they don't have a specific valency. We are given it for each specific question, in Roman numerals. E.g Iron(III) chloride. The III means a valency of 3. Then the process is the same. - In the case of transition metals, the same element can have different valencies. - A valency of II is most common. - This type of valency is also used from some other elements (particularly when they break valency rules. E.g tin(II) chloride (even though tin isn't a transition metal) **Group Ions:** Group ions are groups of atoms which act as a unit in a chemical formula. On page 8 of data book. The thing at the top ( two negative, one positive, three negative...) shows the valency. Two negative means valency of 2. Name Formula Valency ------------ --------- --------- Nitrate NO₃ 1 Sulfate SO₄ 2 Phosphate PO₄ 3 Carbonate CO₃ 2 Ammonium NH₄ 1 Hydroxide  OH 1 If while making a chemical formula with valency swap and drop, and we had a group ion. Use this as the element name, not nitrogen, for nitrogen, for example. Also, say we have NH₄, and we get 2 of them during valency swap and drop, we don't right NH₄₂. It looks like 42 Ammonium atoms! We do instead (NH₄)₂. If there is only one, there is no need for a bracket. **Diatomic Molecules:** While usually elements are just written as stuff like iron = Fe. However, some are diatomic (Two atoms in a molecule). The are the gen-u-ine elements. They end in either -gen, or -ine. Hydrogen = H₂. However, FORGET about adding the 2 in compounds. In something like the chemical formula of a compound, don't add the tiny 2.   **Elements in compounds:** If the 2nd element ends in-ide, then there are [two elements].  E.g. Calcium Nitride ➡️ Calcium + Nitrogen If the 2nd element of the compound ends in -ate or -ite, then it [also contains oxygen. ] E.g. Sodium Sulphate ➡️ Sodium + Sulphur + Oxygen [Others] Hydroxide is Oxygen and Hydrogen. Ammonium is Nitrogen and Hydrogen. **Word Equations to Formula Equations summary: ** - **Elements:** Write element symbols, not forgetting the diatomic molecules. - **Compounds:** Use prefixes, if no prefix, use swap and drop. E.g. See figure 10. **State Symbols**: Show what state the element/compound is in. \(s) = solid \(l) = liquid \(g) = gas (aq) = aqueous (dissolved in water/ in solution) **Balancing Equations: ** This equation is balanced: C + O₂ ➡️ CO₂ This equation is not balanced H₂ + O₂ ➡️ H₂O We can use big numbers like to balance the equation. E.g. ****H₂ + O₂ ➡️ ****H₂ + O₂ E.g. H₂ + Cl₂ ➡️ ****HCl We can also use fraction and decimal big numbers. Basically, we are just multiplying the elements by the number that we add. We CANNOT use tiny numbers **Outer Electron Bonding Diagrams: ** Atoms can achieve a (stable) filled outer shell in two ways: - Covalent: Sharing electrons - Ionic: Gaining/ Losing Electrons **Covalent in detail:** Why do they share electrons? Why do they connect; why are they attracted to each other and don't pull apart. Because, each positive nucleus is attracted to the shared negative electrons. **Covalent** compounds are made when NON-METALS share electrons.  Most covalent compunds are the gen-u-ine molecules. **Ionic compounds:** are when metals transfer electrons to non metals, making the positive and negative ions, which are attracted to each other, making a bond. [Electron arrangement]: When they gain or lose electrons, the electron arrangement gains or loses electrons accordingly. Non metals GAIN electrons, giving it a negative charge, because it is more electrons. Metals LOSE electrons, giving it a positive charge, because it is more protons than electrons. They obtain a **Noble gas electron arrangement** by doing this process of losing and gaining electrons. Noble gases are stable, as they have a full outer electron shell. **Bonding diagrams**: See figure 11. If you are told to draw a diagram of a molecule of something. I think usually a gen-u-ine molecule **Double and Triple Bonds:** H --- H is a single bond (2 shared electrons in the middle)  O = O is a double bond (4 shared electrons in the middle) N three lines N is a triple bond ( 6 shared electrons in the middle) This is when more than one covalent bond is formed. E.g It is a double bond if 4 electrons are shared. E.g. Figure 12 **Shapes of molecules:** 4 types of arrangements: Linear, Angular/Bent/V-shaped, Trigonal Pyramidal, and Tetrahedral. See figure 13,14,15, and 16.