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substances & mixtures
• A substance is matter that is always made up of the same combination of atoms.
• There are two types of substances— elements and compounds.
• The composition of elements and compounds doesn’t change. Therefore, all elements and compounds are substances.
substances
substances
substances
• A mixture is two or more substances that are physically blended but are not chemically bonded together.
• The relative amounts of each substance in a mixture can vary.
• Granite, a type of rock, is a mixture. Granite contains bits that are white, black, and other colors. Two pieces of granite will have different amounts of each color bit. The composition of rocks varies.
mixture
GRANITE
• Air is also a mixture. Air contains about 78 percent nitrogen, 21 percent oxygen, and 1 percent other substances.
• This composition varies. Air in a scuba tank can have more than 21 percent oxygen and less of the other substances.
mixture
AIR
heterogeneous / homogeneous mixtures
• Rocks and air are examples of the two different types of mixtures—heterogeneous and homogeneous.
• It’s not always easy to identify a mixture. A rock looks like a mixture, but air does not.
heterogeneous mixtures
• A heterogeneous mixture is a mixture in which substances are not evenly mixed.
• Often, you can see the different substances and parts of a heterogeneous mixture with unaided eyes. Sometimes you can see them only with a microscope.
heterogeneous mixtures
• Blood looks evenly mixed—its color and texture are the same throughout.
• Suppose you compare two samples of blood under a microscope. They will look different. The samples will contain different amounts of the components (plasma, rbc, wbc, platelets)
homogeneous mixtures
• A homogeneous mixture is a mixture in which two or more substances are evenly mixed on the atomic level but not bonded together.
• The individual atoms or compounds of each substance are mixed.
• Air is a homogeneous mixture.
• Another name for a homogeneous mixture is solution.
H20
H20
H20
C6H12O6
C6H12O6
C6H12O6
heterogeneous mixture
homogeneous mixture
also called solutionscan see different parts with an unaidedfruit saladlooks the same throughoutsalt watersubstances not evenly mixed bloodevenly mixed but not bondedgraniteone colour and texturesoilsugar water
how do compounds and mixtures differ?
• The substances that make up a mixture are not chemically bonded.
• Mixing is a physical change. The substances that exist before mixing still exist in the mixture.
how do compounds and mixtures differ?
SUBSTANCES KEEP THEIR PROPERTIES• Substances that make up a mixture are not changed chemically.
• You can observe some of their properties in the mixture.
• Sugar water is a mixture of two compounds—sugar and water. After the sugar is mixed in, you can’t see the sugar in the water, but you can still taste its property of sweetness. You can also observe some properties of the water, such as its liquid state.
how do compounds and mixtures differ?
COMPOUNDS DO NOT KEEP THEIR PROPERTIES• The properties of a compound can be different from the properties of the
elements that make it up.
• Sodium and chlorine bond and form table salt. Sodium is a soft, opaque, silvery metal. Chlorine is a greenish, poisonous gas. You cannot observe any of these properties in table salt.
how do compounds and mixtures differ?
MIXTURES CAN BE SEPARATED• The substances that make up a mixture are not bonded together.
• As a result, you can separate them from each other using physical methods.
• The physical properties of one substance are different from those of another. You can use these differences to separate the substances.
• In contrast, you can separate compounds only by a chemical change that breaks the bonds between the elements.
mixtures
