Extensive & Intensive Physical Properties

Extensive & Intensive Physical Properties

Lesson Goal:

Learn the difference between the two and be able to identify examples of each.

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Physical Properties can be divided into two types:

• Extensive - the prefix "ex" means outside, like the outside or external properties.

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• Intensive - the prefix "in" means inside, like the inside or internal properties

Poll

Based on the prefixes, which do you think is an "inside" or intensive property?

• Volume

• Mass

• Color

• Shape

Poll

Just based on the prefix "ex", which do you think is an extensive, or "outside" property?

• Shape

• Density

• Color

• Luster (shininess)

Extensive Properties

• Definition: These are properties that depend on how much matter there is.

• So if you change how much matter there is, like by adding more or taking some away, these properties will change

• Think of it like a glass of water: if I drink half of it, which properties will change? Will it change color? Or mass? Volume? Density?

• These are "outside" properties because if the outside changes, they change too.

• Examples: Mass, volume, weight, size, length/height/width, surface area. If matter is taken away then there is less mass, less volume, less weight, etc.

Intensive Properties

• Definition: These are properties that do NOT depend on the amount of matter.

• So if you change how much matter there is, like by adding more or taking some away, these properties will stay the same

• Think of it like a glass of water: if I drink half of it, which properties will stay the same? Will it change color? Or mass? Volume? Density?

• These are "inside" properties, because they are "inside" the substance, they won't change no matter how much you add or take away from the outside of the substance.

• Examples: Color, boiling/freezing/melting point, temperature, luster, conductivity, hardness, malleability, and DENSITY

Multiple Choice

If I drink half of my water, the ______________ will decrease.

• mass

• color

• density

• boiling point

Multiple Choice

If I drink half of my water, the ____________ will stay the same.

• Mass

• Volume

• Density

• Weight

Multiple Select

If I break a glass into tiny pieces, what will stay the same about the glass?

• Hardness

• Volume

• Color

• Melting Point

• Surface area

Density - Why is it intensive?

• Because density is the ratio of how much mass is in a given space - If I drink half of the water, I'm taking away half of the mass, but also half of the volume, so the ratio stays the same!

• Let's use math to show that it doesn't change. The water in my glass is exactly 200mL of water and it has a mass of 200 grams.

• D=mass/volume therefore, density equals 200/200 = 1g/mL (which is the actual density of water)

• If I drink half of the water, then it's half the mass - 100g AND half the volume, so 100mL. D=m/v, so D= 100/100, or 1g/mL

• So, the density didn't change, which makes it intensive.

Why are all the phase change points (boiling, melting, freezing, etc.) intensive?

• If I want to freeze my glass of water it's always going to freeze at 0^oC (or 32^oF) whether I drink half of it or none of it.

• Sometimes it takes longer to freeze if there's a lot and lowering the temperature makes it freeze faster, but it would ALL still freeze at 0^oC.

• Same for boiling point! Water will boil at 100^oC no matter how much there is, but if there's a lot it takes longer for it to all boil.

• Melting point is the reverse of freezing point, so ice above 0^oC will start to melt whether it's an ice cube or a glacier.

How are luster, hardness, conductivity, and malleability all intensive?

• Luster - A small piece can reflect the same amount of light per square inch that a big piece can. Big pieces just seem more lustrous because we can see the reflected light better.

• Hardness - Sometimes we think bigger is stronger, but not necessarily! If you smash a glass those broken pieces are just as hard (or fragile) as the big piece.

• Conductivity - A short piece of wire can transport as much electricity as a long piece, it just doesn't go as far.

• Malleability - I can fold up, roll up, or ball up a big piece of aluminum foil as easily as a small piece.

Open Ended

Are there any properties you're confused about? Any properties you're not sure why they're extensive? Or intensive?