Chapter 5 Properties of Matter

Lesson 1 Matter

What is matter made of? Everything around you is made up of matter. All matter is made of the same set of building blocks called chemical elements. An element is a material that cannot be broken down into anything simpler by chemical reactions

Most elements are solid, some are gases, and a few are liquid at room temperature. Elements that are more chemically reactive are more likely to combine with other elements to form new substances. Each element is made up of the same atoms. An atom is the smallest unit of an element that retains the properties of that element.

What are atoms and molecules made of? Atoms are made up of 3 different parts. The nucleus is the center of an atom. The nucleus is made up of protons and neutrons. A proton is a particle with a positive charge.

The number of protons in an atom is called the atomic number. The neutron is a particle that has no charge or neutral charge. Electrons are particles that have a negative charge. Electrons move around in the space outside the nucleus. Atoms usually have the same number of electrons and protons.

Molecules are particles with more than one atom joined together. When molecules form, atoms link together through their electrons. Chemical formulas describe molecules by combining letters and numbers. Water – H2o The numbers are subscripts and they describe the amount of each element.

How are elements grouped? All elements have a name and symbol. The symbol is always 1 or 2 letters. C is for Carbon and Au is for gold The elements are arranged according to their properties in the periodic table.

Lesson 2 Physical Properties

What are physical properties? A physical property is something that can be observed about an object without changing the identity of the object. Examples of physical properties are mass, volume, weight, density, color, hardness, odor, and magnetism.

Mass Mass is the amount of matter in an object. Mass is measured by using a balance. Mass is measured in grams (g) and kilograms (kg)

Weight Weight is how strongly gravity pulls on an object. Weight is measured in Newtons (N).

Volume Volume measures how much space matter takes up. Volume of a regularly shaped object is calculated by multiplying length, width, and height. Volume of irregularly shaped objects can be measured by placing the object in a graduated cylinder of water and seeing how much the water rises.

Volume Volume of water is measured in milliliters (mL). Volume of solids are measured in cubic centimeters.

What is density? Density is the amount of mass for each cubic centimeter of a substance. To measure density, divide its mass by its volume. Buoyancy is the resistance to sinking. Buoyancy depends on density.

If an object is less dense than the liquid around it, it will float. But remember density can change when you change the volume or mass of an object.

What are metals, nonmetals, and metalloids like? Most metals are shiny and can be reflective. Metals are conductors. Conductors are substances that allow both heat and electricity to flow easily. Insulators restrict the flow of heat and electricity.

Metals are malleable which means they are easy to shape without breaking. Nonmetals are poor conductors. They can break or crush easily. Many nonmetals are gases at room temperature.

Metalloids look like metals but they are not as shiny. They are not malleable. Metalloids are semiconductors which means they can conduct electricity but not as well as metals.

How are atoms arranged in different states of matter? There are 3 states of matter: solid, liquid, and gas.

Solids Particles vibrate in place and have very little freedom to move. Solids stay in a definite shape with a definite volume. Solids are the densest state of matter.

Liquid Particles are close together, but can flow past one another. Liquids have a definite volume, but not a definite shape.

Gases Particles are not close together and can move past one another very easily. A gas has no definite shape or volume. Gas is the least dense state of matter.

Lesson 3 Changes of State

How can matter change state? Changes in temperature occur when an object gains or loses heat. Heat is the energy that flows between objects with different temperatures. When particles gain energy, the particles move faster and spread apart.

When particles lose energy, the particles slow down and group together. Condensation is the changing of a gas into a liquid. Sublimation is the change of state directly from a solid to gas.

When does matter change states? Temperature of water does not rise while it is melting or boiling. Melting point is the temperature at which a substance melts. Water melts at 0 C or 32 F. Boiling point is the temperature at which a substance boils.

Boiling point of water is 100 C or 212 F. Freezing point is the temperature at which a substance freezes. Melting point and freezing point are the same temperature. Every substance melts and boils at specific temperatures. Evaporation is the slow change from liquid to gas at temperature well below the boiling point.

What are expansion and contraction? The volume of an object changes as it gains heat. This causes the object to grow. This is called thermal expansion. When a object loses heat, the object shrinks.

Thermal contraction is the decrease in an object’s volume due to a change in heat. Thermometers are an example of thermal expansion and contraction.

Lesson 4 Chemical Properties

What are chemical properties? A chemical property describes the way a substance reacts with other substances. Flammability is the chemical property of a substance that describes its ability to catch on fire or burn. Corrosion is when metals combine with nonmetals from the environment.

Example of corrosion – when iron corrodes by rusting.

What is the difference between a physical and chemical change? Physical change happens when matter changes size, shape, or state without changing what its identity. Example: ripping up paper, melting chocolate, or breaking a glass.

In a chemical change, the change will cause a new substance to form. There are some signs to look for if a chemical change has taken place. The substance may change color. Ex. Iron rusting There may be a formation of a gas. Ex. Mixing baking soda and vinegar will cause bubbles to form letting you know a gas (carbon dioxide) was formed.

There may be a formation of light and heat. Ex. Burning wood in a fire. Some other examples of chemical changes are baking a cake, tarnish on silver, car engines using fuel to burn.

Formation of light and heat

Change in color

Formation of a gas

Chemical change from mixing sulfuric acid and sugar

Tarnish on silver

Is the change reversible? Physical change can sometimes be reversed. Chemical changes cannot be reversed. Ex. Can you unburn toast?

What are acids and bases? Acids taste sour and cause blue litmus paper and natural indicators to turn pink. Examples of acids – lemon juice and vinegar

Bases tastes bitter and cause red litmus paper to turn blue and natural indicators to turn green. Bases tend to feel slippery. Examples of bases – chlorine bleach and baking soda. Indicators are material that change color when in the presence of an acid or base.

Litmus paper and red cabbage juice are indicators. The pH scale measures how acidic or how basic a substance is. The pH scale runs from 0 to 14. The lower the number the more acidic the substance is and the higher the number the more basic the substance is.

A substance with the pH of 7 is neutral. Example: water

pH Scale

Uses of acids and bases Acids are used in the production of plastics and explosives. Acids are used in your body to break down food. Bases are used mostly in cleaning products.

Bases can break down grease and oil easily. When acids and bases are mixed together, the reaction forms a salt and water. This process is called neutralization.