(6) Matter and energy. The student knows matter has physical properties that can be used for classification. The student is expected to:
(6B) Calculate density to identify an unknown substance.
Supporting Standard PRIOR KNOWLEDGE
MASS: the amount of matter, and is not affected by the force of gravity
Use appropriate units, grams (g) and practice using triple beam balance
Measure the mass of 1 mL of water (it will be 1 gram) Practice weighing techniques on a balance. Mass is NOT affected by the force of gravity. Regarding mass, location in universe does not affect it. Ex. If an object's mass is 60g on Earth, the mass will also be 60g on Moon.
Compare and contrast mass vs. weight. Use a spring scale to model how weight is affected by the force or pull of gravity. VOLUME: amount of space that the matter takes up. milliliters (mL) = graduated cylinder
cubic centimeters (cm3) = ruler (V= L x W x H)
measure the volume of solids, liquids and a gases
review the word “capacity” (how much it will hold) of a graduated cylinder and teach how to read a meniscus (eye level, flat surface, read bottom of the bubble)
teach different volume increments on glassware or syringes (lines could be measures of 1mL, 2mL, or possibly 5mL)
review terms associated with solutions and solubility: solute solvent dissolving insoluble (oil and water) precipitate a solution is a well-mixed mixture, and some solutions can be separated into their component parts, ex. saltwater
demonstrate in lab: Density of pure water = 1 gram/mL 1 mL of water has a mass of 1 gram 50 mL of water has a mass of 50 grams PHYSICAL PROPERTIES AND CHANGES
Make observations and test physical properties for all 3 states of matter (solids, liquids, and gases): mass, length, volume, shape, texture, smell, hardness, color, luster, streak, malleability, melting, freezing, boiling, evaporating, density, buoyancy, solubility, magnetic or nonmagnetic, malleability, ductility, conductivity or ability to insulate, etc.
Compare physical properties of metals, nonmetals, and metalloids: use aluminum foil, copper wire, iron nails, etc.
Most metals have low specific heat values; therefore, they give up (or gain) their heat quickly, they get hot and cold very fast.
Most metals are good conductors of heat and electricity.
Nonmetals are good insulators of heat and electricity– they hold on to heat (or cold). Properties of matter are constant, but each "state" (solid, liquid, gas) can behave a little differently.
Teach how to use the Phase Change Chart – substances can pass through their melting point, freezing point, boiling point, condensation point – all are physical changes – changes in the state of the matter
Note: Regarding phases of matter, there are actually 5 phases of matter. The fourth phase, called plasma, is found in stars. The fifth phase is called Bose-Einstein condensates, is a relatively newly discovered state of matter
DENSITY (Physical Property of Matter)
Show location of the density formula on the STAAR Formula Chart.
Suggestion: Poster-size it for classroom wall.
Determine the density of various substances using formula, D = m/v.
Use examples of solids, liquids, gases - using triple beam balance, ruler, graduated cylinder & overflow can (practice measurement techniques).
Practice lab techniques using measurable objects (ex. sugar cube)
Include irregular or asymmetrical objects (ex. rock, bolt) using water displacement (graduated cyclinder).
Understand the specifics about density:
Stress how density refers to how tightly packed the particles are in a substance.
Practice sequencing objects in order of their densities (have them make predictions), making connections to what the substance is made of. Ex. The greater the density, the more it will sink in water.
Associate the density of substance with an application.