Chemical and Physical Properties

Properties of Matter

•Properties are the “identifying characteristics” of substances.

•All substances have their own properties unlike any other substance.

•You can identify all substances if you know enough of the properties

Properties of Matter

•There are two types of properties•Physical & Chemical

Two Types of Properties•Physical:•Describe the physical characteristics / attributes of

the substance.

•Qualitative: what the substance looks like, feels like, tastes like, smells like, sounds like.

•Quantitative: numerical properties such as phase at certain temperatures, density, melting/freezing point, etc.

•Describe the physical properties of your pencil.

•On the periodic table there are a lot of metals, describe some of the physical properties of metals.

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Some Physical Properties of Metals

•Conduct heat and electricity

•Can bend without breaking (malleable/ductile)

• Shiny (luster)

Problem!!!• Just like twins, sometimes the substances all look the

same – how can you tell which is which then? (Sugar vs Salt)

• Sometimes it’s a bit difficult to determine the substance simply because they look too much alike.

• Another way we can tell them apart is by how they react with other substances.

•Chemical Properties:•How a substance reacts with other substances.

Chemical Properties Recap

• Chemical:• How a substance reacts with other substances.

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Fizzing

•Examples of some Chemical Properties: • i.e. iron will react with oxygen to produce rust.• i.e. Silver reacts with sulfur to form tarnish• i.e. Gold does NOT react with oxygen or sulfur• i.e. Baking Soda is NOT flammable (does not

react to oxygen)

What causes certain chemical reactions?

It has to do with valence electrons.

A valence electron is an electron in the outermost shell/ring.

All atoms want to have a full outer shell.

Review:

• How many electrons can fit in the 1st shell (closest to the nucleus)?

• How many electrons can fit in the 2nd shell?

Periodic Table

• Periodic means repeating/patterns. The number of valence electrons can be determined from looking at which column the element is in.

• For example, carbon is in the 4th column (we are skipping the middle section) – This means it has 4 valence electrons

• Oxygen is in the 6th column (again we skipped the middle section) –How many valence electrons does it have?

• If carbon has 4 valence electrons, how many does it need to get a full shell?

• Carbon needs 4 electrons so it will make 4 bonds or connections with other atoms to get electrons from them.

• Oxygen already has 6 valence electrons so it needs 2 more. Magnesium has 2 valence electrons so it will be easier to give away 2 than to steal 6. Magnesium will give its two extra electrons to oxygen.