Physical Change

1. Physical Change • Physical changesoccur when objects change but do not change into a different substance. A physical change involves a change in physical properties. Examples of physical properties include: texture, shape, size, color, odor, volume, mass, weight, and density. Examples of physical change are shape, size, state(phase), and mixture (solute into solvent).

2. Solute – a substance dissolved into another substance (solvent). Ex. Food coloring, salt Solvent- a substance, solid, liquid, or gas that dissolves another solid, liquid, or gas. Ex: water Solution-a mixture of a solute and a solvent that are mixed to the molecular level.

3. Thermal Expansion of Solids Temperature- the average kinetic energy of its particles. Thermal energy-the total kinetic energy of the particles of a sample. Thermal expansion- the increase in size of an object due to the increase in temperature. The size of a solid, liquid, or gas depends on how hot or cold it is. Hot = bigger andcold = smaller.

4. Examples are railroad tracks expanding because of the heat of a hot summer day or concrete squares of a road getting bigger because the day is hot.

5. Volume-is the amount of space a substance fills. Volume relates to Thermal Expansion because thermal expansion involves an increase in volume. The particles of matter are like the following: In gas the particles are far apart. In liquid the particles are close together but still fluid. In a solid the particles are bunched tightly together.

6. *Gas particles bounce against each other and the side of the container keeping it in the shape of the bottle. *Gas particles contract when cold and cannot keep the bottle in shape. The air on the outside of the bottle presses the bottle shrinking it. *The gas particles have a lot of energy and force the bottle to expand outward with the increased pressure. *The greater the temperature the greater the pressure. The lower the temperature the lower the pressure.

7. Pressure-the amount of force exerted in a per unit area. When gas particles in a flexible bottle have more pressure and thus more volume, they hit the side of the container more and more often expanding the bottle. When gas particles are put into a less flexible container or when they are pumped into an area of limited space such as a basketball or a tire the pressure increases and the volume decreases. As pressure decreases volume increases. See the chart to the right.

8. Temperature and State (Phases) of Matter There are three main states of matter: • Solids where atoms are densely packed together. • Liquids where atoms have more energy and are farther apart than a solid and more fluid. • Gases where atoms have a lot of energy, move around quickly, and are very far apart. Review the chart here.

9. Changing State: Processes Freezing-particles losing energy (heat) and bunching together tightly forming a solid. Melting-particles gaining energy (heat) and moving away from each other becoming fluid. Vaporization- particles in a liquid gaining energy (heat) enough to change from a liquid to a gas. Condensation- particles losing energy (heat) and coming together to form a liquid. Sublimation-the process in which a solid becomes a gas without first turning into a liquid. Deposition-the process in which a gas becomes a solid without first being a liquid. Water freezes at 32oF(0oC) & boils at 212oF(100oC)