AQA GCSE CHEMISTRY (9-1) GUARANTEED SUCCESS

AQA GCSE CHEMISTRY (9-1) GUARANTEED SUCCESS 1. What is the fundamental building block of matter, and what are its characteristics? Answer: Atoms are tiny particles that make up everything around us, with a radius of about 0.1 nanometers (1x10^-10 meters). They are incredibly small, with a 50p piece containing approximately 77 quadrillion atoms. 2. Can you compare the size of atoms to other objects? Answer: Yes, atoms are so tiny that they are almost unimaginable in size. To put it into perspective, the nucleus of an atom has a radius of about 1x10^-14 meters, which is roughly 1/10,000th the size of the entire atom. 3. What is the structure of an atom composed of? Answer: The nucleus is at the center of an atom, containing protons and neutrons. Protons have a positive charge, while neutrons have no charge. The electrons orbit around the nucleus in shells, covering a significant portion of space. 4. Why do atoms have no overall charge? Answer: The number of protons always equals the number of electrons in an atom, with protons having a charge of +1 and electrons having a charge of -1. This balance cancels out, resulting in an overall neutral charge. 5. What are the relative charges and masses of protons, neutrons, and electrons? Answer: Relative Charge: Proton = +1, Neutron = 0 (neutral), Electron = -1; Relative Mass: Proton = 1, Neutron = 1, Electron = very small. 6. What defines an element? Answer: An element is a substance composed only of one type of atom. 7. How many elements are known? Answer: There are approximately 100 known elements. 8. What distinguishes one element from another? Answer: Elements differ from one another based on the number of protons in their atoms. 9. How can elements be represented? Answer: Atoms of each element can be represented by a one or two-letter symbol. 10. What is a nuclear symbol for an atom? Answer: A nuclear symbol is the chemical symbol for an element with two numbers beside it. The top number represents the mass number, while the bottom number represents the atomic number. 11. What does "atomic number" refer to? Answer: The atomic number is the number of protons in an atom. 12. What does "mass number" refer to? Answer: The mass number is the total number of protons and neutrons in an atom. 13. How do you calculate the number of neutrons in an atom? Answer: You can calculate the number of neutrons by subtracting the atomic number from the mass number. 14. What are isotopes? Answer: Isotopes are different forms of the same element, characterized by having the same atomic number (number of protons) but different mass numbers (number of protons and neutrons). What is "relative atomic mass"? Many elements have more than one isotope. This means when referring to the masses of elements, relative atomic mass is used. This is an average mass taking into account the different masses of isotopes that make up the element, and how abundant each isotope is. This means it's not always a whole number. How do you work out the relative atomic mass of an element? Sum of (isotope abundance x isotope mass) ______________________________________________________________ Sum of abundances of all the isotopes What are compounds? Compounds are substances formed from two or more elements. The atoms of the elements are in fixed proportions throughout the compound and they're held together by chemical bonds. What can compounds be represented by? Compounds can be represented by formulas. The formulas are made up of elemental symbols in the same proportions that the elements can be found in the compound. What is the only way to separate a compound back into it's elements? A chemical reaction must take place to separate a compound back into it's elements. What happens when chemicals react? Bonds between atoms break and the atoms rearrange themselves to form different chemicals. What does the word "reactants" mean? The substances that react together.