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The two metals look alike, but are not the same… How can you identify an unknown substance?
The melting point of the element Gallium (Ga) is 85.59°F (29.77°C)
The room temperature is about 72 °F or 22°C. So, neither metal melts in room air, but gallium melts in the heated water (or in your hand)
The melting point of silver (Ag) is 1,763°F (961.8°C)
What properties will BEST help you distinguish between two substances that LOOK identical?!!
Mass
Volume
Density
Boiling point
Melting point
Reactivity
What is the melting point of water? What is the boiling point of water? Do you think any other chemical has the same MP and BP as water?
http://www.harcourtschool.com/activity/hotplate/index.html
A characteristic property is a property that is unique to a particular substance. It can be used to identify the substance. These numbers are kind of like the “profile” of the substance.
Characteristic properties include:
1) Density: mass/volume usually measured in g/cm3
2) Solubility: A measure of the ability of a substance to
dissolve in another substance (usually water). Substances
that are highly soluble tend to “disappear” in water. Insoluble
substances tend to remain visible as solids (precipitates).
3) Melting Point (MP): The temperature at which the
substance changes from a solid to a liquid. Ex. MP of water
is 0C.
4) Boiling Point: The temperature at which the substance
changes from a liquid to a gas. The BP of water is 100C.
5) Reactivity: The tendency of a chemical to react. Ex.
Baking soda and vinegar react to form bubbles. Baking soda
and water do not react.
There are other properties that are NOT characteristic. They CANNOT
be used to identify the substance.
The following ARE NOT characteristic properties.
1) Mass
Ex. A 5g piece of gold would have less mass than a 10g piece of gold.
Both samples are still gold and would have the same density, melting
point, and boiling point.
Ex. 5g of gallium and 5g of silver would have different densities, melting
points, and boiling points.
2) Volume
Ex. A 10mL beaker of water would have less volume than a 100mL water.
Both samples are water and would have the same density, melting point,
and boiling point.
Ex. The gallium spoon and a silver spoon could both have the same
volume. However, they would have different densities, melting point, and
boiling points.
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