a substance that is composed of only one type of atom, typically characterized by specific physical and chemical properties
化学元素
(chemistry) a process in which several chemicals combine and form different substances
反应
(chemistry) a combination of two or more substances without forming a chemical bond or any chemical reaction
混合物
a water-soluble chemical substance that contains Hydrogen and has a sour taste or corrosive feature with a PH less than 7
酸性物质
(chemistry) a substance that can accept protons, donate electrons, or release hydroxide ions in aqueous solution
基础
to make something change from a particular state, condition or position to another
改变
a quantitive mesasure used for determining how acidic or alkanic something is on a scale of 0 to 14
酸碱度