105 Changing States-Mid

Changing States FOCUS Question How does matter change from one state to another?

Everything Changes When ice melts in a glass of lemonade, it changes from solid to liquid Ice is a kind of matter. All matter takes up space and has weight. When matter changes state, it changes from one form to another. It might look different. But the tiny molecules that make it up remain the same. Water is still water, even when it is solid ice. The way molecules are organized and how they move changes in each state of matter. In solids, molecules are tightly packed. They move very slowly, In liquids, molecules are farther apart and bump into each other. Molecules in gases are spread even farther. They can crash into one another at high speeds.

Critical Moments Substances can change state, which is also called a phase change. This happens when heat is added or removed. The melting point is the temperature at which a solid changes to a liquid. At the boiling point, a liquid changes to a gas. At the freezing point, a liquid changes to a solid Pressure can also affect phase changes. Air pressure is lower at higher elevations, where the air is thinner. Thinner air makes it easier for water molecules to escape the liquid and turn to water vapor. So in the mountains, water boils at a lower temperature. At sea level, the air pressure is higher. The water molecules must work harder to spread out. So it takes a higher temperature to change from liquid water to water vapor.

Solid and Liquid Think of ice cream on a hot summer day. Solids turn to liquids when enough heat is added to reach the melting point. Heat energy makes the molecules move faster. Eventually, the molecules break away from one another. They spread out. The solid melts and becomes a liquid Generally, ice turns to water when it warms up to 0 degrees Celsius (32°F). The reverse happens when liquid water turns to ice. At the freezing point, molecules lose heat. They slow down and join together.

Liquid and Gas At high temperatures, liquids can turn into gases. This process is called vaporization When a liquid heats up slowly, it evaporates. Sunlight can warm the water in a puddle. The water evaporates as it warms. During boiling a liquid heats up and changes to a gas quickly. When a gas loses heat, it becomes liquid again. This state change is called condensation. Tiny drops of water fog up your bathroom. This is an example of condensation. The vapor from the hot shower cools and becomes liquid again. Science in Your World Liquid mixtures reach their boiling point at different temperatures. Water boils at 100°C (212°F), apple juice boils at 160°C (320°F), and olive oil boils at 572°C (1,062°F).

Solid and Gas Usually, a solid goes through the liquid state before becoming a gas. But a solid can change directly into a gas. This process is called sublimation. Dry ice is a kind of ice made of carbon dioxide, not water. At room temperature, dry ice changes directly into a gas. If heat leaves a gas quickly, the gas can become a solid right away. This process is called deposition On cold nights, water vapor becomes solid ice, or frost. You can see frost on plants and other surfaces. Frost forms without becoming liquid water first. Wowser At- 218.8°C (361.8°F), it is possible to produce solid oxygen from its gaseous state.