Physical and Chemical Properties Jaeda Aldridge, Corrie Beck, Sydney Beatty, and Josh Brown 7th Period
Physical properties • Physical properties don’t change the matter being studied when you observe and measure them. Physical properties are characteristics that can help identify a substance. You can see physical properties.
Melting point • The melting point is the temperature in which a solid melts into a liquid. The temperature that melts a pure substance never changes under the same conditions. It is the melting point for a pure substance, and is a physical property for identification.
Boiling point • The boiling point is the the temperature that makes a liquid boil. Boiling turns a liquid into a gas as the liquid starts to form bubbles and they rise to the top and burst open. The temperature of the liquid stays the same as long as the liquid is boiling. The boiling point stays the same for each substance under constant conditions.
Density • Density describes the relationship between the mass and volume of a material. The substances that have higher densitys have more matter. No matter how large or small the substance, the density of it will always stay the same.
Color • Color can be used to help identify a substance, along with other properties. • By itself color is significant identifier of a substance. • Absence of color is also a physical property.
Chemical Properties • Chemical properties can be seen only when substances react or do not react chemically with one another, that is, when they undergo a change in composition. A chemical property of one substance usually involves its ability to react or not react with different substances.
Reacting with Oxygen • The ability of a substance to burnis a chemical property that involves a substance reacting quickly with oxygen to produce light and heat. Reacting with oxygen slowly occurs when iron rusts or apples turn brown.
Reacting with Acids • The ability of a substance to react with an acid is a chemical property. Some metals react with diffrent acids to form compounds. All metals do not react with all acids. Bases react with acids to form water and neutralize the acid.
Physical Changes • When physical changes occur, the composition of the substances don’t change, but the physical properties. TO
Change in State of Matter • As a substance changes from one state of matter to the next, the composition of the substance stays the same, Example (liquid to gas, gas to liquid, liquid to solid) • When a substance changes directly from a gas to a solid (skipping liquid) or a solid to gas, this changing of the state is called sublimation. This is still a physical change because the composition of the substance stayed the same. TO
Change in Size or Shape • As a substance changes its size or shape, its composition doesn’t change (example: tearing, cutting, dissolving, stretching etc.)
Chemical Change • When one or more new substances change and have new chemical and physical properties.
Color Change • When the color of a substance changes, its chemical composition may have changed. • Examples: Apples turn brown when they react with oxygen in the air, marshmallows turn black when burned, iron turns reddish-brown when it rusts • However, it is also possible to have a color change without chemical change. • Example: adding food coloring to water
Temperature Change • When substances are combined, the temperature may increase or decrease • Example: When wood burns in to ash & gases, the temperature increases. • The temperature can change without a chemical change. • Example: Warming of the water in a pond
Formation of a Precipitate • The combination of two solutions can for a solid substancecalled a precipitate. (indicates that a chemical change has occurred) • Example: when carbon dioxide is combined with aqueous calcium hydroxide (limewater), solid calcium carbonate (chalk) is formed as the precipitate. • A precipitate can be in the form of very small particles, which appear in cloudiness in solution, or as a solid that settles to the bottom of a container.
Formation of a gas • When solids or liquids are combined, they can create gas bubbles. • Formation of a gas may indicate that a chemical reaction has taken place. • Example: When vinegar & baking soda are mixed, it forms carbon dioxide bubbles.