In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. It can be solid, liquid, gas, or plasma. Chemical substances are often called ‘pure’ to set them apart from mixtures.
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American scientists conducted a study that showed that gastroesophageal reflux disease, one of the manifestations of which is heartburn, is associated with a high risk of developing cancer of the larynx and...