Chemistry - GCSE AQA - Combined Science - Higher
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Chemistry - GCSE AQA - Combined Science - Higher - Marcador
Chemistry - GCSE AQA - Combined Science - Higher - Detalles
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| 🇬🇧 | 🇬🇧 |
| What is an atom? | The smallest particle to exist. |
| When did Dimitri Mendeleev make his periodic table and why? | He made it in 1869, and he changed it because it was originally arranged in atomic mass and didn't take into account properties. |
| What do groups in a periodic table show? | How many electrons are in the outer shell. |
| What do the columns in a periodic table show? | Elements with similar properties. |
| What is the radius of an atom? | 0.1 nanometres ( 1 × 10⁻¹⁰ m) |
| What and where is the nucleus? | Its in the middle of the atom and contains protons and neutrons. It has a radius of around 1 × 10⁻¹⁴ m and has a positive charge. The vast majority of the mass of the atom is concentrated there. |
| What and where is an electron? | They orbit the nucleus on shells and are negatively charged with a tiny relative mass. The size of their orbits depend on the size of the atom. |
| What do protons and electrons do to the charge of an atom? | Atoms have no charge because there is an equal amount of protons and neutrons. They have the same size charge and because they are both oppositely charged, they cancel each other out, leaving the atom with no charge. |
| What is atomic number? | The number of protons in an atom. It's the smallest number when shown on the atomic symbol. If the atom isn't an ion, the number of electrons will also be the same. |
| What is atomic mass? | The number of neutrons and protons in an atom. |
| What is the weight and charge of subatomic particles? | Protons, +1 charge, 1 relative mass; Neutrons, o charge, 1 relative mass; Electrons, -1 charge, 1/2000 relative mass (negligible). |
| What is an element? | A substance made up of only one type of atom. |
| How are atoms of each element represented? | By a one or two letter symbol. |
| What is an isotope? | An atom of an element that has the same number of protons but a different number of neutrons. |
| What is a compound? | A substance that's made up of two or more different elements that are chemically bonded. |
| How are compounds made? | When elements react with each other and the atoms combine with other atoms, making bonds. |
| What is a formula? | Something that shows what is happening to substances involved in chemical reactions. |
| What are word equations? | Writing chemical reactions with words instead of symbols. |
| What are reactants and products? | Molecules on the left-hand side of the equation because they react with each other. Molecules on the right-hand side of the equation because they have been produced. |
| What is a mixture? | Two or more elements or compounds that are physically mixed. There is no chemical bond. |
| What is chromatography? | The process that is used to separate mixtures of coloured compounds like dyes or inks. |
| What are the steps of chromatography? | 1. Draw the base line in pencil on the chromatogram, then different colours of dyes or inks. 2. Lower the chromatogram (stationary phase) into the solvent which should reach up to under the base line. 3. Wait for the ink to rise with the water into the different colours it may separate into. |
| What is Rf value and whats the equation for it? | Distance traveled by ink ÷ Distance travelled by water Both of these are from the base line |
| What is filtration? | Filtration is the separation of insoluble solids from a liquid. It can also be used for purification. |
| How can you separate soluble solids from solutions? | Evaporation/ Crystallization - You pour the solution into an evaporation disk and slowly heat the solution. The solvent will evaporate making the solution more concentrated. This forms crystals which will eventually be dry. You can filter the crystals and leave them in a warm place to dry, or use a drying oven or desiccator. |
| What is rock salt? | A mixture of salt and sand. |
| What is distillation? | Distillation is the separation of a liquid from a solution. The solution is heated so that the part that has the lowest boiling point evaporates first. The vapour cools and is condensed and collected while the rest of the solution is left in the flask. |
| What is a problem with simple distillation? | It only works if the liquids have very different boiling points. |
| What is fractional distillation? | Fractional distillation is the separation of mixtures of liquids even if their boiling points are similar. The mixture is heated in a flask with a fractioning column at the top. The liquid with the lowest boiling point evaporates first and will reach the top of the column. Liquids with higher boiling points may also evaporate, but the column is cooler towards the top, so the condense and run backdown into the flask. When the first liquid has been collected, you raise the temperature. |
| What is the Dalton model? | John Dalton described the atom as a solid sphere near the start of the 19th century. |
| What is the Plum Pudding model? | J.J Thompson said that the atom was a positively charged sphere with negatively charged electrons embedded within it in 1897. |
| What was the Alpha Particle Scattering Experiment? | In 1909 Ernest Rutherford conducted an experiment where a positively charged alpha ray was shot through the atom. Very few were bounded back and this created the idea of the nuclear model because he found the nucleus was a small point of the atom that positive. |
| What was Neil Bohr's nuclear model? | Neil Bohr figured out that electrons were on fixed energy levels (shells) and that they orbit the nucleus. |
| What did James Chadwick discover? | Chadwick discovered neutral particles, neutrons, in the nucleus. |
| What are alkali metals? | Group 1 elements. |
| Why are alkali metals called alkali metals? | Because they produce an alkaline solution, hydrogen gas and a metal hydroxide when reacted with water. |
| Why do alkali metals need to be stored in oil? | Because they are so reactive, they will react with the oxygen in the air. |
| What does aqueous mean? | Dissolved in water. |
| What colour do alkali metals turn when exposed to air and why? | They turn a dull grey colour because the air makes it oxidise. |
| Explain the reactivity trend in group 1 elements. (4 marks) | The reactivity in Alkali metals increases as you go down the series. This is because the number of shells and electrons increase as you go down the group, meaning the distance between them is getting bigger, and the electrostatic force of attraction between the nucleus and outer electron is weaker. This means that the electron can be lost easily, and the atom will react. |
| What are some properties of group 1 elements? | They are soft and have low melting and boiling points. They are very reactive and have low densities. |
| What are halogens? | Group 7 elements. |
| What are noble gases? | Group 0 elements. They are monatomic. |
| What are some properties of group 0 elements? | They are colourless, odourless and tasteless. They have full outer shells and are gases. They are inert. |
| What happens to the boiling point as you go down group 0? | It increases because the atoms get larger, and more energy is needed to overcome the intermolecular forces. |
| What does properties mean? | How something looks and/ or behaves. |
| What are halogens? | Group 7 elements. They are diatomic. |
| What type of molecules are group 7? | They are diatomic molecules - 2 atom molecules. |
| What happens to the reactivity of group 7 as you go down the series? | The reactivity decreases as you go down the group because the outer shell gets further from the nucleus. |
| What happens to the melting point of group 7 as you go down the series? | The melting and boiling point increases as you go down the group. |
| Explain why fluorine is more reactive than chlorine. (3 marks) | Fluorine has a smaller atom than chlorine since it has less electrons and shells. This means that the electrostatic force of attraction will be stronger with the nucleus and outer electron in fluorine. Because it's stronger, fluorine can gain an electron and make a full outer shel easier than chlorine, making it react. |
| What is displacement? | When a more reactive element displaces a less reactive element in a reaction. It can also be known as rearrangement. |
| Balance the equation, Mg + O₂ → MgO | Mg + O₂ → MgO Mg = 1 × 2 = 2 Mg = 1 × 2 = 2 O = 2 O = 1 × 2 = 2 = 2Mg + O₂ → 2MgO |
| Name the subatomic particles inside the nucleus of an atom. (3 marks) | Protons and neutrons. |
| Explain why the reactivity increases as you go down group1, but decreases as you go down in group 7. (4 marks) | The reactivity in group 1 increases as you go down the series because the electrostatic force of attraction between the further electron and the nucleus gets weaker as the atom size increases, meaning the electron can be lost easily, making it react. However, in Halogens, the reactivity would decrease as you go down the series because the electrostatic force between the outer electron and the nucleus weakens due to a larger atom size. This would make it harder for the atom to gain an electron and react. |
| What is the total number of electrons in a fluorine molecule? (1 mark) | Fluorine atom = 9 Fluorine molecule =18 = 18 |
| Aluminium reacts with bromine to form aluminium bromide. Complete the balanced equation; Al + Br₂ → AlBr₃ | Al + Br₂ → AlBr₃ Al = 1 × 2 = 2 Al = 2 Br = 2 × 3 = 6 Br = 3 × 2 = 6 = 2Al + 3Br₂ → 2AlBr₃ |
| When chlorine reacts with potassium bromide, it displaces bromine. Why is it more reactive? (3 marks) | Chlorine is more reactive than bromine because its electrostatic force of attraction between the nucleus and outer electron is stronger since its atom is smaller. This means that it can gain an electron easier, making it more reactive than bromine. |
| Complete the table to show when the subatomic particle was discovered. Date Particle 1897 1920 1932 | Date Particle 1897 Electron 1920 Proton 1932 Neutron |
| State why lithium and sodium are both in group 1. (1 mark) | They both have 1 electron in the outer shell. |
| What colour is fluorine and what's some of its properties? | It is a very reactive, poisonous, yellow gas. |
| What colour is chlorine and what's some of its properties? | It is fairly reactive, poisonous, green gas. |
| What colour is bromine and what's some of its properties? | It is a dense, poisonous, red-brown volatile liquid. |
| What colour is iodine and what's some of its properties? | It is a dark grey crystalline solid, or purple vapour. |
| What are ions? | Atoms or groups of atoms that have a charge because they lose or gain electron(s). |
| NA | NA |
| What forms negatively charged ions? | Non-metals form negatively charged ions. |
| What forms positively charged ions? | Metals form positively charged ions. |
| What are dot and cross diagrams? | Diagrams that show how ionic bonds are formed by showing the arrangement of electrons in an ion or atom. |
| Draw and explain the dot and cross diagram of Sodium Chloride. | The sodium atom gives the outer electron to have a full outer shell. It then becomes Na⁺. The chlorine atom then gains the electron to also have a full outer shell, and becomes Cl⁻. |
| What is an advantage of dot and cross diagrams? | It shows where electrons have moved from. It shows the electron arrangement. |
| What are some disadvantages of dot and cross diagrams? | It doesn't show how the ions are arranged. It doesn't show the size of the substance. |
| Draw a dot and cross diagram of Magnesium Chloride. | The magnesium atom gives two electrons to then have a full outer shell. It becomes Mg²⁺. The two chlorine atoms gain an electron each, so now they also have full outer shells. We now have two Cl⁻ ions. |
| What are ionic compounds called? | Giant ionic lattices. |
| What is a ball and stick model? | A model that shows the atoms and the bonds between them in a 3D representation of covalent structures. |
| What are some advantages of 2D models? | It is simple. It shows the atoms involved. It shows how the atoms are connected. |
| What are some disadvantages of 2D models? | It does show the shape. It doesn't show the size. |
| What are some advantages of ball and stick models? | It shows how atoms are arranged. It also shows the covalent bonds between ions. It shows the shape. |
| What are some disadvantages of ball and stick models? | There aren't actually gaps between the ions. It also doesn't show it to relative size. |
| What are some advantages of 3D ionic structures? | It shows how big the ions are compared to each other. It shows how they are ordered in a pattern. |
| What are some disadvantaged of 3D ionic structures? | It doesn't show the bonds between ions. It only shows the outside layers. |
| Why can ions not conduct when molten? | Because the ions are not free to move. |
| Why can ions conduct when molten or aqueous? | Because the ions are now free to move, they can carry charge throughout the structure. |
| What is an ionic bond? | The electrostatic force of attraction between oppositely charged ions. |
| What is empirical formula? | The ration of the different atoms in a compound in its simplest form. |
| What is the empirical formula of the ionic compound potassium oxide? | Potassium is in group 1, so it makes a 1+ ion. Oxygen is in group 6, so it makes a 2- ion. To make the charge neutral, we need 2 potassium ion for every 1 oxygen ion. = K₂O. |
| What are covalent bonds? | The sharing of electrons between non metals. They are very strong and have intermolecular forces keeping them together. |
| What are intermolecular forces? | Forces of attraction between molecules. They are weak. |
| What are the three different ways to draw covalent bonds? | Dot and cross diagrams, Displayed formula and 3D models. |
| What are some simple molecular substances? | Hydrogen, Chlorine, Oxygen, Nitrogen, Methane, Water and Hydrogen Chloride |
| What are simple molecular substances made up of? | Molecules containing few atoms joined by covalent bonds. |
| What are some properties of simple molecular substances? | They have low melting and boiling points. They have simple molecular structures. They are gases or liquids at room temperature. They don't conduct. |
| What is an advantages of (displayed) formulas? | They show how atoms are connected in large molecules. |
| What are displayed formulas and what are some disadvantages? | Something that shows the atoms and bonds of a compound, with the bonds shown as lines. They don't show the 3D structure. They don't show which atom the electron came from. |