The same everywhere, or not?

The idea

A homogeneous mixture, or solution, has a uniform composition throughout and always remains homogeneous; a heterogeneous mixture is not uniform throughout.

First sip, last sip

You stir sugar into a glass of water until you cannot see it. You sip from the top. Later you sip from the bottom.

How will the two sips taste?

• Equally sweet
• The bottom sip is sweeter
• The top sip is sweeter

Take three sips

Look at sips from the top, middle and bottom. First with sugar, then with sand.

Uniform or not uniform

A mixture with a uniform composition throughout is a homogeneous mixture, or solution. A solution always remains homogeneous. A mixture that is not uniform is a heterogeneous mixture.

• Homogeneous (solution) | Heterogeneous
• sugar in water | sand in water
• vinegar (acetic acid in water) | oil and water
• soda (carbon dioxide in water) | tea leaves in water

Notes

A homogeneous mixture (solution) is uniform throughout and always remains homogeneous. A heterogeneous mixture is not uniform.

Check yourself

Stirred sand and water: the sand is easily visible and settles with time. This mixture is…

Which statement about a solution is true?

A fizzy drink such as soda is carbon dioxide dissolved in water. What kind of mixture is it?

• homogeneous. A homogeneous mixture is uniform and does not settle.
• heterogeneous — correct. Yes. It is not uniform.
• a solution. A solution is uniform.
• It has the same composition throughout and always stays that way — correct. Yes.
• It slowly separates into layers if left standing. A solution always remains homogeneous.
• Its particles are easily visible. The particles of a solution are not visible.
• Heterogeneous. The gas is dissolved evenly in the water.
• Homogeneous — correct. Yes. It is a solution.
• It is not a mixture. It is a mixture of carbon dioxide and water.