Grade Nine Science Properties of Matter II

The Plan for Today To do: –Get out your pencil or pen –Open your Textbooks to page 18 –Put your name and date at the top of a page in your note book Subjects that will be covered –Chemical Properties of Matter –Density (more in depth)

1.2 Chemical Properties of Matter II. Chemical property: describes the behaviour of a substance as it becomes a new substance. 1. Combustibility (flammable): the ability of a substance to burn when exposed to a flame (react with oxygen to produce carbon dioxide, water and energy). –When a flame is brought close to gasoline and air, the gasoline ignites and burns. –List some materials that are flammable/nonflammable.

1.2 Chemical Properties of Matter 2. Reaction with acid: Whether or not a substance reacts when exposed to acid. –When magnesium is exposed to acid, it bubbles. –When gold is exposed to acid, it does nothing.

1.5 Density Which is heavier: a 12 inch bar of gold or a pillow full of feathers? A 12 inch bar of gold weighs more than a pillow full of feathers even though the pillow takes up more space. Why? Gold is more dense. It has more matter per unit volume.

1.5 Density Density is the amount of matter per unit volume of that matter. Density(D) = Mass(m) / Volume(V) If you know any two of the three variables (D,m, or V), you can solve for the third. m = D x V V = m / D

Sample density question #1 If a rock has a mass of 49 g and occupies a volume of 7 cm 3, what is the density? D = m / V = 49 g / 7 cm 3 = 7.0 g/ cm 3

Solve these sample density questions 1.An object has a mass of 250 g and occupies a volume of 14.5 cm 3, what is the density? 2.A piece of wood occupies a volume of 46 cm 3 and it has a mass of 100 g. What is the density of the wood?

Answer to question #1 D = m / V = 250 g / 14.5 cm 3 = g/ cm 3

Answer to question #2 D = m / V = 100g / 46 cm 3 = 2.17 g/ cm 3

3.An unknown metal has a density of 2.6 g/cm 3 and a mass of 15 g. How much volume does this piece of metal occupy? 4.A sample of a particular liquid has a density of 6.85 kg/L and it occupies a volume of 3.4 L. How much does this particular sample weigh?

Answer to question #3 D = m / V V = m / D = 15 g / 2.6 g/cm 3 = 5.77 cm 3

Answer to question #4 D = m / V M = D x V = 6.85 kg/L x 3.4 L = kg **Note that volume can be expressed as cm 3, m 3, ml or even L.

Water is more dense than ice! Why is this so important? –It means that ice floats in water instead of sinking. Think of the poor fish if this was the not the case. Why is ice less dense than water? –When water freezes, it expands which means that the same mass of water is spread over a greater volume.

More Review Questions Answer questions 2,3,4 on page 25 of the text.