Engage:

The teacher fills three bowls with ice cubes, water and hot water, respectively, and facilitates discussion.

Time: 5 minutes

What are some of the characteristics of each container?

Can you explain these differences?

Observe and describe the difference in the items in each bowl amongst themselves. Students are to write all answers down in pen (so they won’t change their answers when they hear the answers of another student).

The water is room temperature in one container and very hot in the other.

The water is frozen in one container.

Heat was applied to the water to make it hot.

Heat was removed from the water to turn it into ice.

The water was placed in the freezer to make ice cubes.

A physical change because the ice is hard and the water is not.

A chemical change because the only difference between the water in the three container is the bonding between the water molecules.

Explore:

The teacher takes a hammer or hard object and breaks a few ice cubes into smaller pieces.

Teacher designates one student from each group to cut the paper into any shape they choose.

Is this an example of a physical change or a chemical change?

Why?

Is this an example of a physical change or a chemical change?

Why?

How is the water able to change from one state to the other?

What is the difference between the molecules of the water in the three states?

A physical change because the ice is hard and the water is not.

A chemical change because the only difference between the water in the three container is the bonding between the water molecules.

When nothing is chemically altered or changed it is just a physical change.

Student cuts the paper.

Physical because the paper was only physically altered.

Physical because no heat was applied to the paper.

Chemical because when the paper was cut, some bonds holding the paper together was also cut.

Ice absorbs heat from its surroundings. It heats up and melts.

The molecules in the ice are not moving at all.

The molecules in the water are moving a little faster than the molecules in the ice.

The water molecules in the steam are moving very fast.

The three phases or physical states of matter are solid, liquid, and gas.

Explain

Discuss how kinetic energy changes the bonding of the atoms and molecules. The stronger the bonds (as in crystals), the more energy is needed to change them. Heat causes the molecules to move faster. Therefore the molecular motion (called Brownian motion) increases as water changes from a solid to a liquid to a gas.

Time: 10 minutes

What is kinetic energy?

Depending on the kinetic energy of its atoms or molecules, what are the three physical states or phases of matter?

The energy used to move a steam boat.

Energy used to break the ice cubes.

Kinetic energy is associated with motion. Specifically, in physics, it is a theory. The theory is that any substance is made of minute particles (molecules) that are constantly moving. As the particles encounter each other, they change velocity and direction. The movement of the molecules is sometimes referred to as Brownian motion.

The three phases or physical states of matter are solid, liquid, and gas.

Elaborate:

Chemically, water consists of two atoms of hydrogen and one atom of oxygen. Due to the molecular structure of the oxygen and the hydrogen atoms, they are able to share two pairs of elections covalently.

The two hydrogen atoms are connected to the oxygen at 105 degree angles which make one end of the water molecule slightly more negatively charged or positively charged than the other. This is an important property of water which makes it attract other substances carrying either a positive or negative charge. The attraction is effective with other water molecules as it is with other substances.

This attraction between a negative pole of one water molecule and a positive pole of another is due to a connection called HYDROGEN BONDING. (See overhead transparency.)

This type of bond is not as strong as the COVALENT BOND which keeps the oxygen connected to the hydrogen within a single water molecule.

The hydrogen (H) bonds formed between the positive and negative poles on water molecules cause surface tension and increases the bonds that must be broken before water can escape as steam when boiling.

Kinetic Energy

Matter is composed of small particles called atoms, ions, and molecules. These particles are in constant motion and, therefore, the matter possesses a kind of energy called kinetic. In other words, the average kinetic energy of a group of particles determines the group's temperature. If heat is added to an object, the kinetic energy of its particles increase. The greater the average kinetic energy, the higher the temperature of the material.

Time: 10 minutes

Evaluate:

Time: minutes