Physical versus Chemical Properties

Unit II - Part 1The study of matter

• Matter: anything that has mass and takes up space– Mass – the amount of matter in something– Volume – the amount of space something

occupies

• Which of the following is matter?– A car?– A box?– You?

Reviewing MATTER

What is a property?

• Property: a characteristic of a substance that can be observed

Physical Property

Physical property: a property that can be observed without changing the identity of the substance.

Examples:

• luster

• malleability: the ability to be hammered into a thin sheet

• ductility: the ability to be stretched into a wire

• melting point

• boiling point

• density

• solubility

• specific heat

Density Pre-Question

Which of the following object do you think will float in water?

Density

Density is the amount of mass per unit of volume.

• Density can be used to identify a substance.

• The density of water is 1.0g/mL

Density Discovery

Proposed Questions:

1.What do floating objects have in common?

2.What do sinking objects have in common?

- We will find out using gizmo.

How does liquid density affect whether objects float or sink?

Let’s find out through gizmo.

Answer:

- If the density of the liquid increases the buoyancy of objects increase.

- Buoyancy: The ability of an object to float.

How can you predict whether an object will float or not?

• Calculations:D = m/V = g/mL = g/cm3

• Ex: A cube has a mass of 2.8 g and occupies a volume of 3.67 ml. Would this object float or sink in water?

Mass = 2.8 g Volume = 3.67 mLD = 2.8g/3.67 mL= 0.76 g/mL

– This object would float in water because its density is less than water (1.0 g/mL).

Let’s practice density!!!

NCDPI Practice

Solubility

What happens when you stir a spoonful of sugar into hot water?

- Solubility: The ability of a substance to dissolve in a liquid.

- Three PartsSolute + Solvent = Solution(Kool-Aid Mix) (Water) (Kool-Aid)

Why don’t some substances mix?

Make a list of substances that don’t mix:- Oil and water

- Gasoline and water

Why? Because they don’t like each other?

No

Polarity: - Polar molecules mix with other polar molecules.

- Non-polar molecules don’t mix with polar molecules.

“Like Dissolves Like”

How does temperature of the solvent affect solubility?

What is your opinion?

Let’s find the answer using our Gizmo.

Chemical Properties

• Chemical property: a property that can only be observed by changing the identity of the substance

Examples:

•flammability

•ability to rust

•reactivity with vinegar

More Density Calculations

• Ex: A liquid has a mass of 25.6 g and a volume of 31.6 mL. Use the table below to identify the substance.

Substance Density (g/ mL)

Mercury 13.6

Water 1.00

Ethanol 0.81

M=25.6 g V=31.6 mL

D = 25.6 g/31.6 mL

D= 0.81 g/mL

The substance is ethanol.