安裝中文字典英文字典辭典工具!
安裝中文字典英文字典辭典工具!
|
- What Is a Chemical? Definition and Examples
For example, pesticides in water or artificial colorings in food are “chemicals ” But, chemistry sees chemicals somewhat differently A chemical is a substance with a specific composition It is an element, an alloy, or a compound made up of two or more elements combined in a fixed ratio
- PubChem
Search chemicals by name, molecular formula, structure, and other identifiers Find chemical and physical properties, biological activities, safety and toxicity information, patents, literature citations and more
- Chemistry | Definition, Topics, Types, History, Facts | Britannica
Most of the materials that occur on Earth, such as wood, coal, minerals, or air, are mixtures of many different and distinct chemical substances Each pure chemical substance (e g , oxygen, iron, or water) has a characteristic set of properties that gives it its chemical identity
- Substance (chemistry) - Wikipedia
Chemical substances can exist in several different physical states or phases (e g solids, liquids, gases, or plasma) without changing their chemical composition Substances transition between these phases of matter in response to changes in temperature or pressure
- What is a Chemical ? | Nuclear Regulatory Commission - NRC
Chemical changes are different from physical changes, which don't result in a change in substances One example of a physical change is when water freezes into ice While ice may have different physical properties, it is still just water Another example is when you dissolve salt into a cup of water
- Chemicals, Pesticides and Toxics Topics | US EPA
Learn how to safely handle chemicals, the effects of certain toxins, which substances are controlled or managed, and safer alternatives
- What Is and Is Not a Chemical? - ThoughtCo
A chemical is any substance that is made of matter, like solids, liquids, or gases Light, heat, and sound are not chemicals since they are not made of matter Chemicals can be both natural, like oxygen, or artificial, like stainless steel
- 10 Types Of Chemicals and How to Manage Them
Chemicals are the backbone of countless industries—from manufacturing and agriculture to healthcare and research However, with their widespread use comes the inevitable risk of chemical hazards that can seriously affect human health and the environment
|
|
|