1. Midterm Review

2. What is matter?
Matter is anything that has mass and takes up space.

3. What is the difference between elements, compounds and mixtures
What is the difference between elements, compounds and mixtures? Draw a diagram/model of each.
Elements are matter made of one single type of atom.
Compounds are two or more different atoms that have been chemically combined.
Mixtures are two or more substances that have been mixed together but not chemically combined.

4. What is the difference between a physical property and a chemical property? Give two examples of each.
A physical property is a characteristic of matter than can be observed without changing the identity of the substance.
Ex: color, size, shape, texture
A chemical property is a characteristic of matter that can only be observed when the substance is changing into a new substance.
Ex: the ability to rust, the ability to react, the ability to burn

5. Describe the arrangement, motion and attraction between the particles that make up a solid, a liquid and a gas. Draw a diagram showing the particles of a solid, liquid and gas.
A solid has a strong attraction between particles. The particles move very slowly (vibrate) and are packed tightly together.
The particles of a liquid are not as strongly attracted to each other as in a solid. The particles move more quickly than in a liquid and flow past one another.
The particles in a gas are spread very far apart, have weak attractive forces and move very quickly.

6. How does adding or removing thermal energy affect the states of matter?
Adding thermal energy causes the particles of a substance to speed up and spread apart.
Removing thermal energy causes the particle of a substance to slow down and move closer together.

7. List the phase changes that occur when a solid changes to a liquid, when a liquid changes to a gas, when a gas changes to a liquid, and when a liquid changes to a solid.
Solid to Liquid-melting
Liquid to Gas-Vaporization (evaporation or boiling)
Gas to Liquid-Condensation
Liquid to Solid-Freezing

8. How does thermal energy change as each of the phase changes described above occur?
When a substance melts or vaporizes, thermal energy is added until the particles overcome the attractive forces between them. The particles break from their fixed positions and can now move past one another.
When a substance condenses or freezes, Thermal energy is removed until the particles can no longer overcome the attractive forces between them. The particles slow down until they can no longer move freely and remain in a fixed position.

9. How is thermal energy transferred between objects?
Thermal energy is always transferred from the object with a higher temperature to the object with the lower temperature.

10. What are the signs that a chemical change has occurred?
A new substance is formed
a spontaneous color change
a gas is released
an energy change occurs (temperature changes, light is produced, sound is produced)
an odor is released
a precipitate (solid) is formed

11. How are the products of a chemical reaction different from the reactants?
The reactants are the substances that start a reaction.
The products are the new substances that form at the end of a chemical reaction.
The products will have properties that are different than the properties of the reactants.

12. Illustrate a chemical reaction that shows the Law of Mass Conservation
Illustrate a chemical reaction that shows the Law of Mass Conservation. Explain why the diagram shows the Law of Mass Conservation.
16 g g  g g
This diagram shows the Law of Mass Conservation because the elements and number of atoms of each element are the same on the reactant and product side of the reaction. In addition, the mass of the reactants is the same as the mass of the products

13. Explain the difference between an endothermic and an exothermic reaction.
An exothermic reaction releases more energy than it absorbs, causing the temperature to rise.
An endothermic reaction absorbs more energy than it releases, causing the temperature to drop