用实验测定物质的密度，必须先测出它的____ 和____ ，最后用公式____ 求出它的密度。

阅读下面的诗歌。
                                                                                              滁州西涧
                                                                                                韦应物
                                                                                        独怜幽草涧边生，
                                                                                       上有黄鹂深树鸣。
                                                                                       春潮带雨晚来急，
                                                                                        野渡无人舟自横。

下列做法中，没有注意食品安全的是（　　）