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Chapter 6 Science!

Chemical Reactions

QuestionAnswer
How can matter and changes in matter be described? Matter can be described in terms of two kinds of properties—physical properties and chemical properties. Changes in matter can be described in terms of physical changes and chemical changes.
What is a physical property? A physical property is a characteristic of a substance that can be observed without changing the substance into another substance.
What is a chemical property? A chemical property is a characteristic of a substance that describes its ability to change into other substances.
What is a physical change? A physical change is any change that alters the form or appearance of a substance but that does not make the substance into another substance.
What is a chemical change? A change in matter that produces one or more new substances is a chemical change.
When do chemical changes occur? Chemical changes occur when bonds break and new bonds form.
How can you tell when a chemical reaction occurs? Chemical reactions involve two main kinds of changes that you can observe—formation of new substances and changes in energy.
What is a precipitate? A solid that forms from solution during a chemical reaction is called a precipitate
What is an endothermic reaction? A reaction in which energy is absorbed (frying an egg)
What is an exothermic reaction? A reaction in which energy is released (making ice cubes)
What is a chemical equation? A short easy way to show a chemical reaction , using symbols instead of words
What are reactants? Substances you have at the beginning of a chemical equation
What are products? New substances formed by the reactants
What is a "yield"? Equals
What is conservation of mass? The principle of conservation of mass states that in a chemical equation, the total mass of reactants must equal the total mass of products
What is a open system? Give an example. A system in which matter can enter from or escape to the surroundings. An example is a burning match.
What is a closed system? Give an example. A system in which you are able to measure before and after a reaction. An example is a closed jar.
What is a coefficient? A number placed in front of a chemical formula in an equation
What is a synthesis reaction? Give an example. A reaction in which two or more elements or compounds combine to make a more complaex substance. An example is the reaction between hydrogen and oxygen to make water.
What is a decomposition reaction? Give an example. A reaction in which compounds are broken down into more simpler products. An example is hydrogen peroxide breaking down into hydrogen and water.
What is a replacement reaction? A reaction in which one element replaces another in a compound, OR when two elements in different compounds trade places.
What is activation energy? The minimum amount of energy needed to start a chemical reaction.
What are the 5 ways chemists control rates of reactions? -increase surface area -increase temperature -increase concentration -use catalysts -use inhibitors
What is an example of increasing surface area to change the rate of the reaction? Chewing your food breaks it into smaller pieces that your body can digest more quickly and easily.
What is an example of increasing temperature to change the rate of the reaction? Heating a substance make the particles move faster.
What is an example of increasing the concentration to change the rate of the reaction? Addidng a small spoonful full of sugar to a glass of lemonade will make it sweet.
What is a catalyst? A material that increases the rate of a reaction by lowering the activation energy.
What are "biological catalysts" enzymes
What is an inhibitor? A material used to slow down the rate of a reaction.
Why does the surfarce area of a reactant influence the rate of a reaction? THE MORE SURFACE AREA, THE FASTER THE REACTION!!!
How do most inhibitors work? By preventing reactants from coming together
Created by: lp1213