358801
| Questão | Responda |
| What is the oceans and rivers sphere called? | The hydrosphere. |
| What is the earth sphere called? | The lithosphere. |
| What is the air sphere? | The atmosphere. |
| All molecules have a tendency to stick together, so why do O2 molecules not combine? | The attractive force is too weak, and so they don't stick because they're moving too fast for the force to keep them. |
| What is a covalent bond? | A strong bond that holds atoms together in molecules. |
| In what atoms do covalent bonds occur? | Non-metallic. |
| Describe the covalent bond. | Positive nuclei repel each other but are held together by their attraction for the negative electrons they share. |
| What is electrostatic attraction? | Covalent bonding, basically. |
| What are the four special properties of water? | Liquid at room temp despite smaller mass than O2, ice expands and so is less dense than water, good solvent for salts. |
| Why does the structure of the atoms in a water molecule cause its properties? | They're at an angle and the electrons aren't evenly shared in the covalent bond. Oxygen has more than its fair share and so is slightly positive on the H side and slightly negative on the O. |
| What is happening when a precipitate forms? | The opposite of dissolving - the two salts meet and combine into an insoluble salt. |
| What is an iconic equation? | An equation that only includes the ions that are being focussed on. |
| What test is used to identify metal ions in a precipitate? | Sodium hydroxide is added. |
| How do they found out what a non-metal precipitate is? | They add dilute nitric acid then silver nitrate solution, and then observe the colour change. Or if the precipitate is white they test again with barium chloride. |
| What are the two most common elements in the lithosphere? | Non-metals oxygen and silicon. |
| What is an ionic compound? | A combination of positive metals and negative non-metals. |
| What is ionic bonding? | Very strong ionic forces that hold the ions together in an ionic compound. |
| What is the structure of solid ionic compounds? | A giant ionic lattice. |
| Why do ionic compounds only conduct electricity when molten or dissolved in water? | When solid the ions aren't free to move, but when 'liquid' they can separate and carry charge. |
| What are the five properties that are the same for graphite and diamond? | They're solid carbon, they have a giant covalent structure, high melting point, high boiling point, insoluble in water. |
| What three properties of diamond are different from those of graphite? | Diamond is strong and hard, it doesn't conduct electricity and it doesn't work as a lubricant. |
| Describe the structure of diamond. | Carbon atoms are evenly spaced and joined to their four neighbours in three dimensions - a pyramid shape that goes on and on. |
| Describe the structure of graphite. | Carbon atoms are joined to their three nearest neighbours in flat hexagon sheets, with each atom having one 'spare' electron that just about holds the sheets together. |
| What are ores? | Rocks that contain useful minerals. |
| What are the four questions asked by a scientist when a company is considering digging up a new ore site? | How can the ore be reduced? Is there a good supply of ore? What are the energy costs? What is the environmental impact? |
| How is impure zinc (ZnS) refined into pure zinc (Zn)? | It's oxidised by heating to make ZnO then the reducing agent carbon is used to make Zn and CO2. |
| How is the relative formula mass of a compound calculated? | The relative atomic masses are found in the period table and added together. |
| You have Fe2O3 - Fe is 56 and O is 16. Calculate the relative formula mass. | (56 x 2) + (16 x 3) = 160 |
| When does electrolysis often take place? | When the metal holds on to oxygen too strongly for carbon to work as a reducing agent. |
| What is electrolysis? | The splitting up of a chemical into its elements by passing an electric current through it. |
| Draw (or mentally picture) an unlabelled diagram of electrolysis. | |
| How does electrolysis work? | The mixed elements separate and are attracted to the negative and positive electrodes. |
| What happens to the ions during electrolysis and why? | They turn back to atoms because at the electrode they gain or lose electrons. |
| What is the bonding between metals called? | Metallic bonding. |
| What are the four properties of metallic bonding? | Strong but flexible, conducts electricity, has a high melting point. |
| Describe the structure of a metallic bond. | The atoms lose electrons easily and become positive, whilst the sea of negative electrons holds it all together. The electrons are free, so can drift. |
| What are the two negative and two positive factors to consider in mining? | The risks to the environment and the miners, vs the advantages of more materials and jobs. |
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