Metals that surprise us
Some metals are soft. One is a liquid.
A knife and five metals
Iron and copper are hard solids. So you may think every metal is a hard solid. Let us put a knife to five metals.
What do you think a knife can do to metals?
What this lesson covers
The idea
Not all metals are hard and solid: sodium and potassium are soft enough to be cut with a knife, and mercury is a liquid at room temperature.
A knife and five metals
Iron and copper are hard solids. So you may think every metal is a hard solid. Let us put a knife to five metals.
What do you think a knife can do to metals?
- It cannot cut any metal
- It can cut a few soft metals
- It can cut every metal
Press the knife
Press the knife on each metal. First guess, then watch.
Exceptions
Not all metals are hard and solid. Sodium and potassium are so soft that they can be cut with a knife. Mercury is a liquid at room temperature.
You may have seen mercury in thermometers. It is poisonous: never touch it.
- Metal | The knife | It is
- Iron, copper | cannot cut it | a hard solid
- Sodium, potassium | cuts through | a soft solid
- Mercury | passes through | a liquid at room temperature
Notes
Not all metals are hard solids. Sodium and potassium are soft enough to be cut with a knife. Mercury is a liquid at room temperature.
Check yourself
Which metal is a liquid at room temperature?
Which metals are soft enough to be cut with a knife?
A friend says, "Every metal is a hard solid." What is the best reply?
A thermometer breaks in class and shiny mercury drops spill out. What should you do?
- Sodium. Sodium is a soft solid.
- Iron. Iron is a hard solid.
- Mercury — correct. Yes! Mercury is a liquid metal.
- Iron and copper. Both are hard. A knife cannot cut them.
- Sodium and potassium — correct. Yes! They are soft solids.
- Mercury and iron. Mercury is a liquid and iron is hard.
- Right. There are no exceptions.. There are exceptions: sodium and potassium are soft, and mercury is a liquid.
- Not every one: sodium and potassium are soft, and mercury is a liquid. — correct. Yes! Not all metals are hard solids.
- Right, but mercury is a gas.. Mercury is a liquid, not a gas.
- Pick up the shiny drops to play with them. Mercury is poisonous. Never touch it.
- Wipe it up with your bare hand. Never touch mercury, not even to clean it.
- Keep away and tell your teacher — correct. Yes! An adult will clean it up safely.