http://www.youtube.com/watch?v=QaJ_Yxj9bG8 - no captions

http://www.ripleys.com/weird/daily-dose-of-weird-wtf-blog/amazing-

science/disappearing-spoon-trick/ - captions

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.