for student use only

for student use only

Composition of Matter

Substance – type of matter with a fixed composition that cannot be separated by physical means.

Element – substance made up of atoms with the same identity

Example: gold, helium, aluminum

Compound – atoms of two or more elements combined

Examples: water (H2O), carbon dioxide (CO2)

for student use only

for student use only

States of Matter

Matter anything that has mass and takes up space.

Kinetic theory – explains how particles in matter behave

• All matter is composed of particles • Particles have constant random motion • Particles collide with each other and walls of container

States of Matter State Characteristics Particles SOLID Definite shape and

definite volume Closely packed in geometric arrangement

LIQUID Indefinite shape and definite volume

Have more space and slide past each other

GAS Indefinite shape and indefinite volume

Have energy to spread about in the container

The state of a sample of matter depends on the temperature.

Temperature – related to the average kinetic energy of the atoms or molecules

Thermal expansion- increase the size of a substance when the temperature increases and contracts when cooled

• Exception to rule: water- when cooled it expands

for student use only

for student use only

for student use only

CHANGES IN STATES OF MATTER

MELTING : FROM SOLID -> LIQUID Melting – change from a solid state to a liquid state

Melting point – temperature at which a solid melts

FREEZING : FROM LIQUID -> SOLID Freezing – changing from a liquid state to a solid state

Freezing point – temperature at which an object freezes

VAPORIZATION : FROM LIQUID -> GAS Vaporization – changing from a liquid state to a gaseous state

Boiling point – temperature at which liquid begins to vaporize

*Evaporation can occur at the surface of a liquid without heating the liquid (water in a cup will eventually evaporate)

CONDENSATION : FROM GAS -> LIQUID Condensation – changing from a gaseous state to a liquid state

Condensation point – temperature at which a gas condenses

for student use only

B

E

C

D

A

F

for student use only

Heat, Temperature, and Transfer

Students will do an activity in which heat is transferred from hot water to metal washers and then from hot metal washers to water. http://www.middleschoolchemistry.com/multimedia/chapter2/lesson1

1. The temperature of the water in your cup changes more than the water in the control cup because…

www.middleschoolchemistry.com/multimedia/chapter2/lesson1#heated_spoon

2. When the spoon is placed in the hot water, on the molecular level the energy is moving…. Hot Water vs Cool Spoon

for student use only

4. Why did the metal washers get warmer? Why did the water get cooler?

www.middleschoolchemistry.com/multimedia/chapter2/lesson1#cooled_spoon 5. When the hot spoon is placed in the cool water, on the molecular level the energy is moving…. .

Hot Spoon vs Cool Water

6. Why did the hot metal washers get cooler? Why did the water get warmer?

7. You saw an animation that showed that temperature is a measure of the average kinetic energy of the atoms of molecules of a substance. Does this mean that all of the molecules in a cup of water are moving at the same speed or at a variety of speeds? Explain.

8. Let’s say that you put a cup of cold water in one room and a cup of hot water in another room. Both rooms are room-temperature. Why does the cold water get warmer and the hot water get cooler?

for student use only

Freezing

www.middleschoolchemistry.com/multimedia/chapter2/lesson4#ice_bomb

1. In the video, you saw a round metal container filled with water and placed in a very cold liquid mixed with dry ice. What happened when the water inside the container froze?

Before After

What caused this to happen? 2. Use the example of what happens to the metal container to explain why Roads are likely to develop potholes during cold winters?

www.middleschoolchemistry.com/multimedia/chapter2/lesson4#ice_structure www.middleschoolchemistry.com/multimedia/chapter2/lesson4#ice_at_di'erent_angles www.middleschoolchemistry.com/multimedia/chapter2/lesson5#ice_and_water 3. What are some of the differences between liquid water and solid ice?

Write captions under the pictures to explain how the movement and position of molecules changes as the water freezes to become ice.

Liquid Ice

for student use only

You have seen molecular model animations of water and ice. Fill out the chart to compare how the molecules move in water and ice. Select one of the options in each row and write it under “water” or “ice” in the chart.

4. The temperature at which a substance freezes is called the freezing point. Different liquids have different freezing points. Here are a few examples. Water (H20) 0 °C Corn oil (CH3CH2CH2COOH) about –20 °C Isopropyl alcohol (C3H8O) –88.5 °C Why do you think different liquids have different freezing points?

The shape and size of the atoms and molecules that make up a substance affect the freezing point.

www.middleschoolchemistry.com/multimedia/chapter2/lesson4#fost

www.its.caltech.edu/~atomic/snowcrystals/movies/movies.htm 5. Freezing is the process that occurs when a liquid changes to a solid. Frost forms through a process called deposition. What happens during the process of deposition?