Elements, compounds and mixtures元素，化合物和混合物.ppt

Homogeneous Mixture Mixtures that mix very well Solutions where substances dissolve well into each other Can not visually see any separation of the ingredients Examples: Gasoline, Soda Pure substance and mixtures Comparison: both are composed of elements Contrast: Pure substance is composed of an element or compound whose composition is fixed. Mixture is composed of a combination of pure substances whose composition can vary WHAT IS THE DIFFERENCE BETWEEN HETEROGENEOUS AND HOMOGENEOUS MIXTURES? Heterogeneous and homogeneous mixtures Comparisons: both mixtures Contrast: Heterogeneous materials do not mix well or evenly. They are easily separated. Homogeneous mixtures do mix well and evenly, not easily separated Difference… Heterogeneous mixtures: are mixtures of 2 or more substances that are not completely soluble (bits of each are seen in mixture) Homogeneous mixtures: are mixtures of 2 or more substances that are completely soluble (blend completely, can not tell components) Miscible mixture Extremely homogeneous Dissolves completely Example: Air Miscibilitity How well substances mix together The greater the ability to mix (solubility), the more miscible it is. Oil and water are immiscible (insoluble) Carbon dioxide and water (very soluble) Immiscible mixture Extremely heterogeneous Don’t mix well at all Examples water and granite Immiscible Mixture Gasoline, Soda Solubility Measurement of the ability of one substance (solute) to dissolve into another substance (solvent) WHAT IS AN ALLOY? Alloy An alloy is a solid homogenous mixture of two or more metals. The there is not chemical reaction occurring, and the original materials can be recreated by melting. There are thousands of different alloys, and people use them for many different purposes. Different common alloys Alloy Composition Properties Representative Uses Brass, copper, zinc Corrosion resistance Instruments castings Bronze copper, tin Good for casting Castings Pewter