Question | Answer |
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 |