cbs science worksheet – Flashcards
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why do all chemists read a chemical equation in the same way?
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because the equations have to have a definite structure
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what does a chemical formula show in the case of molecular compounds
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it shows the number and the kind of atom in the molecule
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what does a chemical formula show in the case of ionic compounds?
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the ratio of different ions that are present.
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what does a subscript show in a chemical formula?
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the number of atoms of an element in molecule or the ratio of elements in a compound
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if a symbol in a chemical formula doesn't have a subscript what is understood about the symbol
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it is understood that the number 1 is there.
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how many atoms of each kind of element are there in a molecule of carbon dioxide (co2)
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2 oxygen atoms 1 carbon atom.
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what is a catalyst
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the materail that increases the rate of a reaction by lowering the activation energy
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catalysts are not always permanently changed in what
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a reaction
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what is a biological catalyst called
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enzymes
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what is an inhibitor?
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material used to decreate the rate of a reaction.
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why does endothermic reaction need additional energy to keep going, while exothermic reactions do not?
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the materials absorb energy as products are fomed, exothermic reactions don't need additional energy because energy is given off as the reaction takes place.
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hwat are the 3 factors that can be changed to affect the rate of the chemical reaction
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1. concentration 2. temperature 3. surface area 4. catalyst is a part of this without being changed in the reaction
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the amount of one material in a given volume of another material is called
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concnetration
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to increase the rate of a reaction why would you increase the concentration of the rectants?
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to make mart particles to react
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what are the factors that would increact the rate of reaction
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add heat increase surface are.
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what is the evidence of chemcial reactions
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color change substance reflect different colors of light, heat change when the container may get hotter or colder gas produced when bubles or smoke are observed percipate formed solid might form in a liquid
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what is the reason why chemical reactions need a certain amount of energy to get started?
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to puch them over the hump
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what is the activation energy of a chemical reaction
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the minimum amount of energy needed to start a chemcial reaction
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the reaction that makes water from hydrogen and oxygen where does the activation energy come from
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electrical sparks
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tell why this chemical equation is not balanced? h2 + 02 = H2O
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2 in reactant 1 in product
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write the balanced equation for this reactioN: hydrogen reacts with oxygen to form water
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2 H2 + O2 = 2H2O
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how can chemical reactions be classified
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3 categories: synthesis, decomposition, and replacment. By what happen to there reactants or products
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what are the categories of chemical reactions
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synthesis, decomposition, replacement
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Describe synthesis and give an example
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two or more substance combine to make a more complex compound. ex: A+B=AB
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Describe decomposition and give an example
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compounds are broken down into simpler products AB=A+B
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Describe replacement and give an example
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one element replaces another in a compound or two elements in different compounds trade places AB+C = AC +B AB + CD = AD + BC
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what are the materials you have at the beginning of a chemcial reaction are called what
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reactants
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The materials you have when a chemical reaction is complete are called
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products
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a chemical equation uses symbols and formulas to show the reactants and the products of what?
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chemical reaction
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what do you read the arrow in a chemical equation as meaning
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yield
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at the end of a chemcial reaction what is the total mass of reactants compared to the total mass of the products
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must equal product + reactant
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what is the principle called the conservation of mass
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it is the amount of matter involved in a chemcial reaction does not change. the total mass of the reactants must equal the total mass of the products
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a number in front of the chemical formula in a chemical equationis called what
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coefficient
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what does coefficient tell you
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how many atoms or molecules of each reactant and product take part in the reaction.
