Middle school year 2 · first unit
Characteristic Properties of Matter
Two cups of clear liquid that look the same: one is water, one is ethanol. How can they be told apart without tasting? Look for the values that are fixed for each substance and serve as its name tag.
The same size, yet they weigh differently in the hand
A board to arrangeWhat exactly does it mean to say iron is heavier than wood? Drag the blocks onto the scale, and into the water too.
Water and ethanol, equally clear, are heated
A board to runDo they boil at the same temperature? Does a larger amount change it? Drag the burner under a beaker.
Sugar dissolves better in hot water
A board to adjustHow much better? Spoon in potassium nitrate, then heat it and cool it.
To separate what has been mixed
A board to joinFind the way in which the mixed substances differ. Drag from the dot of a mixture on the left to the dot of a method on the right.
What to take away from this unit
- Something made of one substance is a pure substance; two or more mixed is a mixture. A value fixed for each substance, whatever the amount, is a characteristic property. Density, boiling point, melting point and solubility are such values.
- Density is mass divided by volume. For the same material it is the same at any size. Less dense than water floats; denser sinks.
- Boiling point and melting point differ from substance to substance. A larger amount only takes longer to boil; it boils at the same temperature.
- Solubility is the most that will dissolve in 100 g of water at a given temperature. Most solids dissolve more as the temperature rises.
- A mixture is separated by a property in which its parts differ: boiling point for distillation, density for the separating funnel, solubility for recrystallisation, speed of travel for chromatography.