# Density and the Particle Theory of Matter

```Science 8/9
Density and the Particle Theory of Matter
We have learned that when we __________________ the temperature
of a substance, this causes the ___________________ of the substance
to increase in ________________, thus leading to the decrease in
____________________.
When you decrease ____________________ of a substance, you decrease the energy
of the particles, and ___________________ _____ _____ ______________________.
Temperature also effects density. If a temperature stays _______________ then density does
not change. As temperature increases, the particles begin to vibrate ______________. As the
particles move faster, the ______________ between them increases. Increasing the space
between the particles leads to an increase in _________________.
However, leading to an increase in volume does not mean that
there is an increase in the ___________________ ____
________________, which means that the density actually
decreases. This is the reason why warm water ____________ above
cold water. You will notice in a lake that there are patches of warm water on the surface.
Science 8/9
Density Review Questions
1. Use the particle theory to describe what is happening to the density of a substance
when it is cooled.
2. Most substances increase their density as they move from a gas to liquid to a solid.
Water is an exception, as it actually becomes less dense as it freezes. Without
measuring how would you know that ice is less dense than water?
3. How do you think temperature affects the density of a fluid such as air in a balloon?
4. Calculate the density of 27.1 g of mercury that displaces 2.0 mL of water.
5. A fluid is not only a liquid but also a gas, therefore, what does it mean to be a fluid?
6. Indicate two ways you can determine viscosity of a fluid.
```
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