R E V I E W A N D R E T E AC H I N G

FORMATIVE ASSESSMENT #2

QUESTION #1 (PS 1.6)

• Mixtures are combinations of matter that are physically combined.

• Mixtures can be separated by physical means such as:• Filtering Using a magnet• Evaporating Straining• Sorting

• Examples of mixtures are:• Sand on a beach• Trail mix• Kool Aid or Lemonade

QUESTIONS #2-3 (PS 1.7-1.8)

• In a physical change, you have the same substance before and after the change occurs.

• Examples: • Water freeing, melting, evaporating• Crushing chalk• Breaking glass

• Physical changes are often, but not always, reversible by physical means

QUESTIONS #2-3 (PS 1.7-1.8)

• In a chemical change, something new, with new properties, is produced:

• Indicators of a chemical change include:• Change of heat, light, or temperature• Formation of a new type of solid• Formation of a new type of gas• Change of color or odor

• Example of a chemical change: Mixing baking soda and vinegar to get carbon dioxide gas.

• Chemical changes are sometimes reversible, but it is often a difficult or impractical process.

• Most changes that occur in nature have both physical and chemical properties.

QUESTION #4 (PS 1.9)• The law of conservation of mass states that matter

cannot be created or destroyed. Therefore, the mass of substances before a reaction will equal the mass of the substance after a reaction.

• Even if some of the product of a reaction escapes and cannot be measured (for example, in an open system), conservation of mass still applies.

5 g 10 g 15 g

5 g

3 g

12 g10 g

QUESTION #5 (PS 2.2)

• In an open system, mass and energy can enter and exit the system.• Most systems on Earth are open systems.

• Example: An ecosystem.

• A closed system, does not allow matter or energy to enter or exit the system.• It is difficult to identify real-life examples of closed

systems.

• Example: A sealed tin can of baked beans.