Question

Use the table to identify the phase and phase changes of the elements under the given conditions. Write the name of the substance, phase, or phase change.
When the temperature in a room increases from
25°C to 33°C,
______ changes from a solid
to a liquid.
In a lab, methane and nitrogen are cooled from
-170°C to -200°C. The methane freezes and the
nitrogen _____
.
When gold is heated to 2,856°C it changes from a liquid to a ____

Answer 1

See attached picture of the right responses to the phase change question.

Answer 2

Answers:

1. When the temperature in a room increases from25°C to 33°C, galium changes from a solid to a liquid.

2. In a lab, methane and nitrogen are cooled from -170°C to -200°C. The methane freezes and the nitrogen condenses.

3. When gold is heated to 2,856°C it changes from a liquid to a gas

Explanations:

The melting and boiling point of the substances permit to state whether a susbstance will be solid, liquid or gas at certain conditions (temperature in this case).

Melting point: is the temperature at which a solid becomes liquid.

Boiling point is the temperature at which a liquid becomes gas.

Hence:

• if the temperature is below the melting point, the substance is solid.

• if the temperature is between the melting and the boiling points, the substance is liquid.

• if the emperature is above the boiling point the substance is gas.

The names of the phase changes dealt with in this question are:

• Condenstation: pass from gas to liquid.

• Boiling (Vaporization): pass from liquid to gas

• Freezing: pass from liquid to solid.

• Melting (fusion): pass from solid to liquid

With that let us go through the three statements:

1. When the temperature in a room increases from25°C to 33°C,

______ changes from a solid to a liquid. Answer: galium.

You need to find in the table a substance whose melting point is between 25°C and 33°C.

This is Gallium, whose melting point is indicated to be 30°C, meaning that at 25°C it is solid and at 33°C it is liquid.

2. In a lab, methane and nitrogen are cooled from -170°C to -200°C. The methane freezes and the nitrogen _____. Answer: condenses.

Since the boling point of nitrogen is - 196°C, at  -170°C nitrogen is gas.

Since, the melting point is - 210°C, at -200°C, nitrogen is liquid.

So, nitrogen condenses when it is cooled from - 170°C to - 200°C.

3. When gold is heated to 2,856°C it changes from a liquid to a ____. Answer: gas.

Since, 2856°C is the boiling point of gold, it will start fo pass from liquid to gas at this temperature.