- Students will know that matter is anything that takes up space, has mass, and has properties that you can observe and describe. Elements are pure substances that are often called the "building blocks" of matter. They are made of atoms of matter. All matter has mass (the amount of matter in an object), volume (the amount of space an object takes up), and density (the property of matter that compares the mass to the volume).
- Students will know some of the other physical properties of matter. Physical properties can be measured or observed without changing the matter into something else. Most of these properties remain constant and can be used to help identify matter.
- Students will recognize some physical properties of metals. About 3/4 of the elements are metallic. Elements like copper, gold, silver, aluminum, iron, and nickel are metals. All metals except mercury are solid at room temperature. Most metals look shiny and are found in the earth's ground. Most metals are malleable, which means they can be hammered into thin sheets or pulled into long, thin wires. Some metals are light and bendable like copper and aluminum, which are often used to make wire. Some metals, like iron, are heavy, hard, and very strong.
- Students will recognize some physical properties of nonmetals. About 1/4 of the elements are nonmetals. Most nonmetals are not shiny, heat and electricity do not pass through them easily, and they cannot be hammered into sheets or pulled into a wire. Most nonmetals are brittle.
- Students will understand other common physical properties of matter.
- Conductivity is the ability to pass energy along from one particle to another. When matter can move electrical energy from one particle to another, it is called an electrical conductor. Most metals are electrical conductors. Matter that is unable to conduct much electricity is called an electrical insulator. Most non-metallic substances are electrical insulators. Some materials conduct heat very well. Metals conduct or transfer heat very quickly. Other materials insulate against the passage of heat, which means they do not readily permit heat to flow. Many metallic substances conduct sound very well, but non-metallic substances, like glass or even water, conduct sound well too.
- Whether or not a substance is magnetic is another physical property of matter. Objects made from iron and steel are magnetic.
- Students will know some of the chemical properties of matter. Chemical properties describe the ability of matter to react or combine with other matter to form a new substance. Chemical properties are often hard to observe. Some elements react with an acid to produce a gas. This can be used to tell pyrite and gold apart. Combustibility is the ability to burn. Flame tests can help distinguish one element from another by the color of the flame.
- Students will understand that a physical change is a change in state, shape, or size, without the formation of a new substance.
- Most objects around us are not pure substances but mixtures. A mixture is two or more parts blended together yet keeping their own properties. Mixtures can be separated using their physical properties like size, shape, color, volume, density, and state. This is called a physical separation. Using a filter to separate a mixture of different-sized matter is one example. A filter is a tool used to separate things by size.
- Some mixtures are not easily separated. These are called solutions. A solution is a mixture in which the substances are completely blended so that the properties are the same throughout. The substances are mixed evenly so they stay blended. When one material forms a solution with another material, we say it dissolves. Some solids dissolve in water and some do not. Solubility is a measure of the amount of a material that will dissolve in another material. Liquid solutions are usually transparent, evenly colored, and never separate into layers.
- Students will understand that a chemical change occurs when atoms link together in new ways. This is called a chemical reaction. During chemical reactions, the atoms in the substances that were put together rearrange to form a new substance with different properties. The changes in the linking patterns of the atoms create the new substances. These new substances have properties different from the original substances from which they were formed. There are signals that a chemical change is happening. They include the formation of a gas, a color change, or light and heat changes caused by the release of energy. Burning a candle, rust formation, and tarnishing silver involve chemical changes. In general, chemical changes are difficult to reverse.
- Students will realize that sometimes it is difficult to tell if something is a physical change or a chemical change. Sometimes many of the signs are similar. The key to something being a chemical change is the formation of new matter or substances-not just altering or mixing the existing substances.
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