AQA GCSE Chemistry Paper 1 Questions & Answers A+ 2024/2025

AQA GCSE Chemistry Paper 1 Questions & Answers A+ 2024/2025 What is an *atom*? - ANS-smallest part of an element What is an *element*? - ANS-a substance that contains only one type of atom What are *chemical symbols*? - ANS-- the letter or pair of letters that represents an element. - first letter is always capitalized What are *compounds*? - ANS-substances in which atoms of two or more elements, which are chemically combined What is a *chemical formula*? - ANS-a combination of symbols that shows the ratio of elements in a compound Why are *chemical formula* used? - ANS-- the different elements in a compound - how many atoms of each element one molecule of the compound contain How can *compounds* be separated? - ANS-Through chemical reactions What are *reactants*? - ANS-the starting materials in a chemical reaction (on the left) What are *products*? - ANS-the ending materials in a chemical reaction (on the right) What is always *equal* to each other in a *chemical reaction*? - ANS-products to reactants - no atoms are lost or made What is a *mixture*? - ANS-consist of two or more elements or compounds which are not chemically combined What are the *properties* of *mixtures*? - ANS-they retain their own properties from before e.g. colour How can *mixtures* be separated? - ANS-by physical processes - no new substances are made What is *filtration*? - ANS-- used to separate soluble solids from insoluble solids What is *crystallization*? - ANS-- used to obtain a soluble solid from a solution 1. Mixture is gently warmed 2. Water evaporates leaving crystals of pure salt What is *simple distillation*? - ANS-used to obtain a solvent from a solution *RP* Analysis and purification of water samples from different sources - ANS-1. Use a pH probe or indicator to analyze the pH of the sample 2. Set up the equipment 3. Heat a set volume to 100oC so that the water changes from liquid to gas 4. Water collects in the condenser and changes state from gas to liquid 5. measure the mass of solid that remains to find the amount of dissolved solids present in the sample What is *fractional distillation*? - ANS-- used to separate mixtures in which the components have different boiling points What is *chromatography*? - ANS-used to separate the different soluble, coloured components of a mixture What were *atoms* thought to be in *early models*? - ANS-Tiny spheres that could not be divided into simpler particles What did *Thomson* discover in 1898? - ANS-electrons - causing the representative of atoms to be changed What model did *Thomson* make ? - ANS-plum pudding model What was the *plum pudding* model made up of? - ANS-- atom contained tiny, negative electrons - surrounded by a positive charge What did *Geiger and Marsden* do? - ANS-measured the deflection of alpha particles bombarding gold foil What did *Geiger and Marsden* conclude about their experiment? - ANS-- some alpha particles deflected - some went straight through What did *Rutherford* conclude about the *alpha and gold foil* experiment? - ANS-- there must be a positive charge in the center of each atom (new model now called 'nuclear') What did *Bohr* do? - ANS-said that electrons were arranged in levels or orbits around the nucleus What did *James Chadwick* discover? - ANS-neutrons in the nucleus How big are *atoms*? - ANS-- very small - 0.1nm or 1 x 10^-10m What do all *atoms* contain? - ANS-protons, neutrons, electrons What is the *relative charge* and *mass* of a *proton*? - ANS-1 +1 What is the *relative charge* and *mass* of a *nucleus*? - ANS-1 0 What is the *relative charge* and *mass* of an *electron*? - ANS-very small -1 Where is most of the *mass* of an *atom*? - ANS-nucleus How much *smaller* is the radius of the *nucleus* compared to the rest of the atom? - ANS-1/10000 Why do *atoms* have no *overall charge*? - ANS-they contain an equal number of protons and electrons What do all atoms of a particular *element* have in common? - ANS-- they have the same number of protons What is the *atomic number*? - ANS-number of protons What is the *mass number*? - ANS-Number of protons and neutrons What are *isotopes*? - ANS-Atoms of the same element with different numbers of neutrons How can *atoms* become *ionic*? - ANS-- by losing or gaining electrons What do *metals* do to form *positive ions*? - ANS-lose electrons What do *non-metals* do to form *negative ions*? - ANS-gain electrons What is the *electron configuration* for the first twenty elements? - ANS-2,8,8 What did *John Newlands* do? - ANS-Octaves, he realized that for the first 16 elements, every eighth had similar properties. What was *wrong* with *John Newlands* periodic table? - ANS-- there was only 63 known elements at the time - some of the elements were in the wrong place How did *John Newlands* organize the elements? - ANS-- arranged known elements in order of atomic weight - put them in octaves according to similar properties What did *Dimitri Mendeleev* do? - ANS-Created the periodic table What did *Dimitri Mendeleev* do in order to make the *periodic table* correct? - ANS-left gaps for unknown elements How did *Dimitri Mendeleev* arrange the *periodic table*? - ANS-- left gaps to allow for discovery of new elements - each element placed in vertical group with elements that had similar properties What did *Mendeleev* do with his periodic table? - ANS-predicted new elements and their properties What was *revealed* about *Mendeleev's* periodic table after subatomic particles were discovered? - ANS-he arranged them in the order of increasing proton number (atomic number) What is another name for *Group 0*? - ANS-noble gases What are the properties of *Group 0*? (4 points) - ANS-- full outer shell of electrons - very stable electron configurations - very unreactive *non-metals* Continues...