Question

physical science
science skills - density
name

1. define density.
2. write the formula for density.
3. give two different units for density

a.
b.

1. one cubic centimeter is the same volume as one
2. a materials density is the same no matter how large or small the sample is, or what its shape is, as long as it is a solid, uniform piece of material. explain and give an example.
3. the piece of wood below has a mass of 20 grams. calculate its volume and density. then use the table in your notes to determine what kind of wood it is.
4. the density of balsa wood is about 170 kg/m³. convert this to g/cm³. why do you think balsa wood is used for models over oak and ash? use the table in your notes for help
5. the density of maple wood is about 755 kg/m³. what is the mass of a solid piece of maple that has a volume of 640 cm³.

Explanation:

Step1: Define density

Density is the mass per unit volume of a substance.

Step2: Write density formula

The formula for density is $
ho=\frac{m}{V}$, where $
ho$ is density, $m$ is mass and $V$ is volume.

Step3: Give density units

a. $\text{kg/m}^3$
b. $\text{g/cm}^3$

Step4: Volume equivalence

One cubic - centimeter is the same volume as one milliliter.

Step5: Explain density constancy

Density is a characteristic property of a substance. For a uniform solid, the ratio of mass to volume is always the same. For example, a small gold cube and a large gold block have the same density because gold is a uniform material. The mass and volume change proportionally.

Step6: Calculate volume and density of wood

Volume of the wood $V = l\times w\times h=3\text{ cm}\times2\text{ cm}\times5\text{ cm}= 30\text{ cm}^3$.
Density $
ho=\frac{m}{V}=\frac{20\text{ g}}{30\text{ cm}^3}=\frac{2}{3}\text{ g/cm}^3\approx0.67\text{ g/cm}^3$.

Step7: Convert balsa - wood density and explain usage

Convert $170\text{ kg/m}^3$ to $\text{g/cm}^3$.
$1\text{ kg} = 1000\text{ g}$ and $1\text{ m}^3=(100\text{ cm})^3 = 1000000\text{ cm}^3$.
So, $170\text{ kg/m}^3=\frac{170\times1000\text{ g}}{1000000\text{ cm}^3}=0.17\text{ g/cm}^3$. Balsa wood is used for models over oak and ash because it has a low density, making models lighter and easier to handle.

Step8: Calculate mass of maple wood

First, convert the density of maple wood from $\text{kg/m}^3$ to $\text{g/cm}^3$. $755\text{ kg/m}^3=\frac{755\times1000\text{ g}}{1000000\text{ cm}^3}=0.755\text{ g/cm}^3$.
Using $
ho=\frac{m}{V}$, we can find $m=
ho V$.
$m = 0.755\text{ g/cm}^3\times640\text{ cm}^3 = 483.2\text{ g}$.

Answer:

1. Density is the mass per unit volume of a substance.
2. $

ho=\frac{m}{V}$

1. a. $\text{kg/m}^3$; b. $\text{g/cm}^3$
2. milliliter
3. Density is a characteristic property. For a uniform solid, mass and volume change proportionally. Example: small and large gold cubes have the same density.
4. Volume: $30\text{ cm}^3$, Density: $\frac{2}{3}\text{ g/cm}^3\approx0.67\text{ g/cm}^3$
5. $0.17\text{ g/cm}^3$. Balsa wood is used for models as it has low density, making models lighter.
6. $483.2\text{ g}$