PHYSICAL PROPERTIES OF MATTER

REFRESH YOUR MEMORY:

Substance = A substance, in physical science, is not really a specific object. Rather, it is the material(s) that make up specific objects. E.g., the plastic in a rubber ducky. Substance = A substance, in physical science, is not really a specific object. Rather, it is the material(s) that make up specific objects. E.g., the plastic in a rubber ducky. Sample = the amount you have of a substance, measured usually in g or mL. Sample = the amount you have of a substance, measured usually in g or mL. PRE-LESSON VOCABULARY Here you have three different substances. You have a sample of each substance.

In science, property does not mean objects that you own. In science, property does not mean objects that you own. (Ex., your backpack) A property does, however, mean a characteristic or feature that you own. A property does, however, mean a characteristic or feature that you own. Properties belong to you and make you who you are – they’re a part of your identity! Properties belong to you and make you who you are – they’re a part of your identity! Examples: green eyes, light brown skin tone, born Feb 20, Examples: green eyes, light brown skin tone, born Feb 20, PROPERTIES – WHAT ARE THEY?

Suppose you are going on a blind date. You don’t know what the person looks like, but you have a description of the person’s physical properties. Suppose you are going on a blind date. You don’t know what the person looks like, but you have a description of the person’s physical properties. You can use physical properties to identify the person. You can use physical properties to identify the person. Physical properties of substances work the same way! Physical properties of substances work the same way! – With an unknown substance, if you know some of its physical properties, you can use the physical properties to figure out what the substance is. – Physical properties, do NOT depend on sample size. No matter how much or little sugar you have, the density is always 1.59 g/cm 3 PHYSICAL PROPERTIES HELP US TO IDENTIFY: Salt?? Sugar?? Flour?? Baking Soda?? Density = 1.59 g/cm 3

Density Density Solubility Solubility Electrical Conductivity Electrical Conductivity Thermal Conductivity Thermal Conductivity Magnetism Magnetism Boiling Point Boiling Point Melting Point Melting Point 7 PHYSICAL PROPERTIES YOU NEED TO KNOW

How much matter (mass) is packed into a specific space (volume). How much matter (mass) is packed into a specific space (volume). Helps us to determine whether substances will float or sink. Helps us to determine whether substances will float or sink. DENSITY

Solubility = the ability to dissolve within (spread throughout) another substance (usually liquid) to form a mixture called a solution. Solubility = the ability to dissolve within (spread throughout) another substance (usually liquid) to form a mixture called a solution. – If a substance is soluble – it dissolves in water (Ex., Salt) – If a substance is insoluble (not soluble) in water – it does not dissolve (Ex., sand) SOLUBILITY

Solubility can be measured. Solubility can be measured. Terms you need to know: Terms you need to know: Solute = the substance that dissolves (ex. Sugar) Solute = the substance that dissolves (ex. Sugar) Solvent = the substance (usually water) that the solute dissolves in Solvent = the substance (usually water) that the solute dissolves in Solution = the mixture of solute and solvent Solution = the mixture of solute and solvent A solution is “saturated” if no more solute can dissolve in the solvent, and the solute then settles to the bottom. A solution is “saturated” if no more solute can dissolve in the solvent, and the solute then settles to the bottom. Saturated Solution

Whether we have a small sample of sand, or a large sample of sand, doesn’t matter. All sand is insoluble. Whether we have a small sample of sand, or a large sample of sand, doesn’t matter. All sand is insoluble. SOLUBILITY HELPS US TO IDENTIFY SUBSTANCES AND IS INDEPENDENT OF SAMPLE SIZE

Electrical conductivity = how well a substance conducts (moves) electricity through it. Electrical conductivity = how well a substance conducts (moves) electricity through it. Copper, like most metals, is a good conductor of electricity. Electricity flows easily through it. Copper, like most metals, is a good conductor of electricity. Electricity flows easily through it. That’s why most wires that hook up your TV, computer, etc. are copper. That’s why most wires that hook up your TV, computer, etc. are copper. Substances like plastic, wood, and glass are poor conductors of electricity. Electricity does NOT move easily through them. Substances like plastic, wood, and glass are poor conductors of electricity. Electricity does NOT move easily through them. That’s why copper wires are covered with plastic – so that you don’t electrocute yourself! That’s why copper wires are covered with plastic – so that you don’t electrocute yourself! ELECTRICAL CONDUCTIVITY

We test electrical conductivity with simple circuits that include a light bulb, battery, and wires that connect to the substance being tested. We test electrical conductivity with simple circuits that include a light bulb, battery, and wires that connect to the substance being tested. If the substance tested makes the bulb light up, the substance is a good conductor of electricity – ex., metals, salt solution If the substance tested makes the bulb light up, the substance is a good conductor of electricity – ex., metals, salt solution If the bulb doesn’t light up, the substance tested is a poor conductor of electricity –ex. plastic, sugar solution If the bulb doesn’t light up, the substance tested is a poor conductor of electricity –ex. plastic, sugar solution If the bulb is dim, the substance is a semi-conductor of electricity. If the bulb is dim, the substance is a semi-conductor of electricity. ELECTRICAL CONDUCTIVITY Sugar Water Solution Salt Water Solution

Electrical conductivity is independent of sample size Electrical conductivity is independent of sample size Electrical conductivity helps us to identify substances. Electrical conductivity helps us to identify substances. If we have a white powder that may be salt or sugar, we can test its conductivity, compare it to what we know, and figure out the identity. If we have a white powder that may be salt or sugar, we can test its conductivity, compare it to what we know, and figure out the identity. ELECTRICAL CONDUCTIVITY Sugar?Salt?

How well heat (not electricity) moves through a substance How well heat (not electricity) moves through a substance Why do you cook with wooden spoons, not metal spoons? Why do you cook with wooden spoons, not metal spoons? Metals heat up and transfer heat quickly because they are good thermal conductors Metals heat up and transfer heat quickly because they are good thermal conductors Plastics, wood, and glass slowly heat up because they are poor conductors of heat Plastics, wood, and glass slowly heat up because they are poor conductors of heat THERMAL CONDUCTIVITY

Melting point – the temperature (in ºC, ºF, or K) at which a substance in its solid state melts into the same substance in a liquid state. Melting point – the temperature (in ºC, ºF, or K) at which a substance in its solid state melts into the same substance in a liquid state. Boiling point – the temperature at which a substance in its liquid state evaporates into the same substance in its gas state. Boiling point – the temperature at which a substance in its liquid state evaporates into the same substance in its gas state. MELTING AND BOILING POINTS Water’s melting point is 0 º C Water’s boiling point is 100 º C Gold’s melting point is 1,064 º C Gold’s boiling point is 2,970 º C

Like all other physical properties, melting and boiling points are independent of sample size! Like all other physical properties, melting and boiling points are independent of sample size! MELTING AND BOILING POINTS Whether the sample size is large or small, water has the SAME boiling point Whether the sample size is large or small, water has the SAME melting point 100 º C 0ºC0ºC0ºC0ºC 0ºC0ºC0ºC0ºC

SubstanceBoiling Pt. Water100 ºC Alcohol78 ºC Hydrogen Peroxide 150 ºC Vinegar118 ºC * LIKE ALL OTHER PHYSICAL PROPERTIES, SINCE BOILING AND MELTING POINTS ARE INDEPENDENT OF SAMPLE SIZE, THEY NEVER CHANGE. * SO THEY CAN BE USED TO IDENTIFY SUBSTANCES. Water ? Alcohol ? Hydrogen peroxide? Vinegar? Boiling Point = 78 ºC

Magnetism = the property of being attracted to a magnet Magnetism = the property of being attracted to a magnet Only nickel, iron, and cobalt are magnetic Only nickel, iron, and cobalt are magnetic SO NOT ALL METALS ARE MAGNETIC!!! SO NOT ALL METALS ARE MAGNETIC!!! MAGNETISM Question: So, if Earth has a magnetic field… Then what is the Earth’s core made of? Iron

There are other types of properties called chemical properties. When chemical properties are observed, a new substance is created. There are other types of properties called chemical properties. When chemical properties are observed, a new substance is created. When physical properties are observed, or tested, they DO NOT CREATE A NEW SUBSTANCE!!! When physical properties are observed, or tested, they DO NOT CREATE A NEW SUBSTANCE!!! WHY DO WE CALL PHYSICAL PROPERTIES PHYSICAL? Melting Point. No new substance created. Still water, just melted. Solubility. No new substance created. Still salt in the solution Boiling pt. No new substance created. Still water, just in the form of vapor. Magnetism. No new substance created. Still iron... Density. No new substance. Still floats or sinks… Thermal conductivity. Wire doesn’t turn into a new substance Electrical conductivity Nothing new, still copper.