7.2 Fluids and Density

7.2 Fluids and Density

What are fluids?

A fluid is any form of matter that can flow.

Liquids and gases are fluids. (They are able to flow, because they do not have a fixed shape)
Solids are not fluids. (They have a fixed, rigid shape)

How does temperature affect density?

As energy is added to the air inside the balloon, the heated air gets less dense than the air outside the balloon.

his means that a substance gets less dense as energy is added to it.

Solid, liquid and gas density

Why are gases less dense than liquid?

Density is the mass of a given volume.
Density describes how closely packed together the particles are in a material.

You can find density of a substance if you know its mass and volume.
Measuring the volume a solid object depends on its shape.

Ex: a block (rectangular)
Multiply the length and by its width and by its height.
Ex: Length =4cm width= 3cm height= 2cm
Volume of a block= 4×3×2= 24

Displacement

If the object has an irregular shape, you can use a technique called displacement.

Displacement is the amount of space that an object takes up when it is placed in a fluid.
The amount of fluid that is displaced by an object is equal to the volume of the object.

Calculating Density

Once you know the mass and volume of a substance, you can calculate the density.

※ You can calculate both fluids and solids.

Density equals the mass of something divided by its volume.

The mass units for solids, liquids and gases are often grams (g) or kilograms (kg)

If the object is solid, the volume units are often cubic centimeters.

If the object is a fluid, the volume units are often milliliters (mL)

7.1 States of Matter

7.1 States of Matter
What is matter?
Oxygen, glass, and water are all examples of matter.
Matter is the amount of material that makes up an object.Anything that has mass and volume is called matter.


Volume is the amount of space that a material takes up.
Ex: a basketball has a greater volume than a basketball.The volume of a liquid is usually measured in milliliters (mL), litres (L) or cubic centimeters.


Mass is the quantity of matter that a substances or object contains.
Ex: the more matter the greater the massMass is usually measured in grams (g) or kilograms (kg).


The states of matter
The three common states of matter are solid, liquid and gas.

• Solid is the state of matter that has a definite shape and volume. (ex: bowling ball)



• A liquid has a distinct volume and a shape is determined by its surrounding. (ex: water in the beaker or on the ground)



• Gas is the state of matter that has its volume and shape determined by its surrounding. (Ex: helium in a balloon.)
  

What happens to matter when its temperature changes?

• When you add energy to a matter, its temperature rises.
  Expansion is an increase in the volume of something when its temperature rises. (Ex: balloon become bigger)



• When you take energy away from matter, its temperature falls. (Ex: balloon become smaller)
  Contraction is a decrease in the volume of something when its temperature falls.
  If the temperature of matter keeps rising or falling, the state of matter can change.
  
  

Why does matter change volume or state?
Matter is made up of tiny particles. The particles have kinetic energy. This mean they are always moving.

• Particles of a solid are packed close together. They can’t move freely. They can only vibrate.



• Particles of a solid are spaced a bit farther apart. They can slide past each other.

Particles of a gas are spaced very far apart.They move around quickly.

The kinetic molecular theory
Kinetic energy is the energy of motion.
The kinetic molecular theory explains how these particles act when energy is added or removed.

All particles in every solid, liquid and gas are always moving. So they have kinetic energy.

• Add energy to particles→move faster, move farther apart→matter expands →liquid become gas



• Energy removed from particles→move slowly, closer together→matter contract
  

A model in science is a way to think about and interrupt natural events and objects.

Thermal expansion and contraction

When you add energy to a material, you increase the kinetic energy of the particles.
Any kind of matter expands when its temperature increase. This effect is called thermal expansion.

The matter contracts, or decreases in volume. This effect is called thermal contraction.


The difference between heat and temperature
Heat is the energy transferred from one material or object to another.
(Ex: when you touch a warm cup of tea, you can feel the heat transfer from the cup to your hand.)

Temperature is a sampling the average kinetic energy of its particles.
(Ex: two object with different temperature.)



Change state
Evaporation= liquid to gas

Condensation= gas to a liquid

Melting= solid to a liquid

Solidification=liquid to a solid

Sublimation= solid directly into gas

Deposition= a gas to a solid

Melting point= temperature at which a solid turns to liquid.

Boiling point= temperature at which a liquid turns to gas.

Freezing point= temperature at which solidification takes place for any type of matter.