Physical properties include the state of matter. We know these states as solid, liquid, or gas. Properties can also include color and odor. For example, oxygen is a gas. It is a major part of the air we breathe. It is colorless and odorless. Chlorine is also a gas. In contrast to oxygen, chlorine is greenish in color. It has a strong, sharp odor. Have you ever smelled cleaning products used around your home? If so, you have probably smelled chlorine. Another place you might smell chlorine is at a public swimming pool. The chlorine is used to kill bacteria that may grow in the water. Other physical properties include hardness, freezing, and boiling points. Some substances have the ability to dissolve in other substances. Some substances cannot be dissolved. For example, salt easily dissolves in water. Oil does not dissolve in water.

What are the physical properties of matter, and how many primary states are there for matter?

ATLANTA, Georgia (CNN) -- On a plot of soil, nestled against the backdrop of skyscrapers in downtown Atlanta, Georgia, a group of residents are turning a lack of access to fresh produce into a revival of old traditions and self-empowerment. Urban farming is a way for African-Americans to connect with the earth, says Cashawn Myers of HABESHA. HABESHA Gardens is one of many urban gardens sprouting up around the country. Fruits and vegetables are thriving in this community garden located in an economically depressed area of the city known as Mechanicsville. But the garden serves an even greater purpose. The harvest helps feed some of the neediest members of the neighborhood. "It's a reawakening going on. It's almost like it's a renaissance," says Cashawn Myers, director of HABESHA Inc. "There's a Ghanaian proverb that says Sankofa. Sankofa means return to your past so you can move forward. Even if you look at coming over here during our enslavement, we were brought here to cultivate the land because that's something we did on the continent. So really, that's what many of the people are doing now," he said. Myers believes urban farming is a way for many African-Americans to reconnect with their past. iReport.com: Show us your urban farm "They are going through a process of Sankofa and going to what they traditionally did, which is connect to the Earth so they can move forward and grow," he says. But HABESHA Gardens isn't unique. Former pro basketball player Will Allen, who is considered to be one of the nation's leading urban farmers and founder of Growing Power Inc., estimates that there are hundreds of thousands of urban gardens in inner cities across America. Urban farms help feed people, sustain neighorhoods " "It's beyond a movement at this point. Its more like a revolution," says Allen.

Are urban farms common?

It is not enough to describe some objects by their location. We may also need to know its direction. For example, a wind blows a storm over your school. Where is that storm coming from? Where is it going? How can we describe a direction? The most common way is by using a compass. A compass is a device with a floating needle (Figure 2.1). The needle is a small magnet. The needle aligns itself with the Earth's magnetic field. The compass needle always points to magnetic north. If you have a compass and you find north. You can then know any other direction. See the directions, such as east, south, west, etc., on a compass rose. The Earth has two poles. It has a magnetic north pole. It also has a geographic north pole. These two poles are close to each other but not the exact same place.
What might be some characteristics of a storm that we would want to be known?