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# Unit 1 Questions JK

Question | Answer |
---|---|

What are significant digits? | Significant digits are the certain digits in a measurement as well as one uncertain digit which you have estimated. |

What is percent error and why is it important | It is calculated by dividing the difference between the true value and the measured value by the true value and multiplying by 100. This takes human error into account, as humans can never be 100% accurate |

What are important things to remember when recording measured results? | Record to the correct number of sig figs |

How many estimated digits may you have at the end of a measured result? | You may have one estimated digit |

What do significant digits pertain to? | They pertain to all measurements |

What is the total number of digits you record determined by? | The number of sig figs is determined by the precision of the instrument |

How do you know how many sig figs to use in the answer when multiplying and dividing sig figs? | When multiplying or dividing sig figs, the measurement with the fewest sig figs determines the number of sig figs in the answer |

What are exact numbers and what are some examples? | Numbers with no uncertainty in their value, such as "a dozen" or "1" |

How do you know how many sig figs to use in the answer when adding and subtracting sig figs? | When adding and subtracting, the measurement with the fewest digits after the decimal place determines how many sig figs are allowed to trail the decimal place in the answer |

What is the rule to remember when rounding fives? | If the last sig fig before the five is odd, round up. If the last sig fig before the five is even, round down. If the five is followed by non-zero digits, round up |

In science, why is math different? | The rules of math must be adapted to handle quantities |

What is the rule involving addition and subtraction of quantities? | Only like quantities can be added and subtracted |

Why are units important? | Units are important because they name the quantity measured |

Why are the SI Units important to measurement? | They ease communication among scientists throughout the world |

What is the basic unit of length? | A meter |

What are the SI prefixes used in converting units? | mega, hilo, hecto, deka, deci, centi, milli, micro, nano, pico |

Why are derived quantities needed? | The basic SI units do not describe all dimensions |

What is area and why does it require derived quantities? | Area is the amount of surface something covers, and requires 2 dimensions to measure it |

What is volume and why does it require derived quantities? | Volume is area times height, and requires 3 dimensions to measure it |

Why is it necessary to record information in different manners (tables and graphs)? | It makes interpretations easier to make |

In what situations are graphs useful? | Graphs are useful when portraying a proportional relationship |

Why is graphing real data difficult, and what can be done? | A perfect curve or line rarely happens with real data; a best-fit line or equation can help make interpretations easier to make |

What is the most common reason for uncertainty in measurements? | Measuring tools are limited |

What is a best-fit line? | A line drawn to represent where points would be if there were no uncertainty in them, drawn so there are as many points above the line as below it |

What is density? | The proportion between mass and volume m/v |

How do you graph density? | Graph the proportion m/v as the slope |

How can you use graphs to find density? | The slope of the line is the density |

What are the properties of matter? | Characteristics that allow you to distinguish one kind of matter from another |

What is a chemical change? | A change that produces a new kind of matter with different properties |

How are physical changes different from chemical changes? | They do not produce new matter and can be reversed by physical means |

What are some everyday chemical changes? | Baking soda and vinegar forming bubbles, liquid bleach cleaning stains |

How are solids, liquids, and gasses different? | Solids don't flow like liquids. Liquids can't be compressed like gasses. Gasses flow, unlike solids. |

How is the particle model for matter useful? | It can help explain the difference between the three states of matter. |

What is solid? | A substance with definite volume and shape |

What is a liquid? | A substance that flows and takes the shape of its container` |

What is a gas? | A substance that takes the shape of and fills its container |

What is a mixture? | Matter that can be physically separated into component parts |

What is a pure substance? | Matter that CANNOT be physically separated into component parts |

What are means of separating substances? | Distillation, electrolysis, heat |

How do you purify water? | Distillation` |

What are solutions? | Mixtures that look uniform throughout and do not scatter light. |

What happens to the solids dissolved in a solution? | They exist in an aqueous state |

What are techniques for separation of solutions? | Distillation |

What are characteristics of pure substances? | Boiling point, freezing and melting point |

How does melting and freezing point identify a pure substance? | Pure substances have a constant melting and freezing point; mixtures do not |

How does a boiling point identify a pure substance? | Pure substances have a constant boiling point; mixtures do not. |

How do you decompose pure substances (compounds)? | Electrolysis, heat |

Why is knowing if a substance conducts electricity important? | Because if it conducts elecricity, electrolysis can be used |

What is electrolysis? | Passing an electric current through a substance, causing it to decompose into new kinds of matter |

What does the electrolysis of water do? | It separates it into components; Hydrogen and oxygen |

How are decomposition and distillation different? | Distillation is a physical process, the other is chemical |

How do pure substances differ? | If it can be decomposed further, it is a compound. If it can't, it is an element |

What is an element? | One of 109 substances that can be broken down no further, and is a building block of the universe |