Introduction to Matter

1. Introduction to Matter

2. What is matter? • Matter is anything that has mass and takes up space. • The air you breathe • The water you drink • Matter makes up the materials around you • Light and sound are not matter

3. What is mass? • Mass is the amount of matter in an object.

4. How does mass differ from weight? • Weight is the measure of gravitational force on an object • Gravitational force keeps objects from floating into space. • Gravitational force depends on an objects mass. • The greater the mass the greater the gravitational force and the greater the weight will be • An object’s weight can change depending on location. • You would weigh less on the moon because the moon has less mass, and therefor less gravitational force, but you have the same mass in both places • An object’s mass does not change unless the amount of matter in the object changes.

5. Measuring space • All matter takes up space. The amount of space that object takes up is it’s volume. • Objects with the same volume do not always have the same mass.

6. What is density? • Mass and volume are properties of all substances. • Density is the measure of the amount of mass in a given volume. How is density determined?

7. Properties of matter

8. What are physical properties of matter? • They are used to describe a substance • A characteristic of a substance that can be observed and measured without changing the identity of the substance is called a physical property. • All of your senses can detect of physical change. Color, shape, size, and texture are a few physical properties. • Some properties can be measured like length, width, and height. • The temperature at which water boils is called the boiling point, and it is a physical property.

9. Common physical properties: • Electrical conductivity • Measure of how well an electric currant can move through a substance • Thermal conductivity • The rate at which a substance transfers heat • Density • Measure of the amount of mass in a given volume • Solubility • The ability of a substance to dissolve in another substance • Malleability • The ability of a substance to be tolled or pounded into various shapes • Magnetic attraction • Melting point • Point at which a substance changes from a solid to a liquid • Boiling point • Point at which a substance changes from a liquid to a gas

10. What are chemical changes? • A chemical property describes a substance’s ability to change into a new substance with different properties • The ability to rust is a chemical property. So is tarnish. • Flammability, the ability to burn, is a chemical property. • Reactivity, the ability of a substance to interact with another substance, is another chemical property.

11. How can physical and chemical properties identify a substance? • Characteristic properties can be physical or chemical properties • Characteristic properties stay the same regardless of the amount of the sample. • They can help identify a substance.

12. Physical and chemical changes

13. What are physical changes of matter? A physical change is a change that affects one or more physical properties of a substance. Physical changes occur when a substance changes from one form to another. The chemical identity remains the same.

14. Changes in observable properties The appearance, shape, or size of a substance may be altered during a physical change. Changes of state, and all physical changes, do not change the chemical makeup of the substance.

15. Examples of physical changes Stretching a rubber band Dissolving sugar in water Cutting your hair Melting butter Bending a paper clip Crushing an aluminum can

16. What are chemical changes of matter? A chemical change occurs when one or more substances change into entirely new substances with different properties. Be aware that chemical changes are not exactly the same as chemical properties. Burning is a chemical change, flammability is a chemical property. The chemical properties of a substance describe which chemical changes can or cannot happen to that substance. Chemical changes are the processes by which substances actually change into new substances.

17. Changes to the chemical makeup of a substance In a chemical change, a substance's identity changes because its chemical makeup changes. This happens as the particles and chemical bonds that make up the substance get rearranged. Because chemical changes involve changes in the arrangements of particles, they are often influenced by temperature.

18. How can you tell a chemical change has happened? Here are some signs that a chemical change may have occurred: Production of a gas Chemical changes often cause fizzing or foaming. It is important to note that some physical changes, such as boiling, can also produce gas bubbles. Therefore, the only way to know for sure whether a chemical change has taken place is to identify new substances. Production of an odor Formation of a precipitate Chemical changes may result in products in different physical states. Liquids sometimes combine to form a solid called a precipitate. Change in energy Chemical changes can cause energy to change from one form to another. A change in temperature is often a sign of a chemical changes. Change in color

19. What is the law of conservation of mass? In the 1770's, the French chemist Antoine Lavoisier studied chemical changes in which substances seemed to lose or gain mass. He showed that the mass was most often lost to or gained from gases in the air. Lavoisier demonstrated this transformation of mass by observing chemical changes in sealed glass bulbs. This was the first demonstration of the law of conservation of mass. The law of conservation of mass states that in ordinary chemical and physical changes, mass is not created or destroyed but is only transformed into different substances.

20. Pure substances and mixtures

21. How can matter be classified? Matter is made up of basic “ingredients” known as atoms. Atoms are the smallest unit of an element that maintains the properties of that element. The substances you encounter every day can be classified into one of the three major classes of matter: elements, compounds, and mixtures.

22. Matter can be classified into elements, compounds, and mixtures An atom is like a building block of matter. An element is made up of one or more of the same kind of atom chemically combined. A compound is made up of different kinds of atoms chemically combined. Compounds have different properties from the elements that make them up. A mixture contains a variety of elements and compounds that are not chemically combined with each other.

23. What are pure substances? Elements and compounds are pure substances. A pure substance that has definite physical and chemical properties such as appearance, melting point, and reactivity. No matter the amount of a pure substance you have, it will always have the same properties.

24. Pure substances are made up of one type of particle All elements are pure substances. Copper is a pure substance. The atoms that make up copper are all the same. No matter where is the world you find pure copper, it will always have the same properties Compounds are also pure substances. Two different kinds of atoms make up each chemically combined particle, or molecule.

25. Pure substances cannot be formed or broken down by physical changes Physical changes such as melting, freezing, cutting, or smashing do not change the identity of pure substances. The chemical bonds that hold atoms together cannot be broken easily. To break or form chemical bonds, a chemical change is required. A chemical change changes the identity of the substance. Individual atoms cannot be broken down into smaller parts by normal physical or chemical changes.

26. How can elements be classified? Differences in physical and chemical properties allow us to classify elements. By knowing the category to which an element belongs. You can predict some of its properties. Elements are broadly classified as metals, nonmetals, or metalloids. Most metals are shiny, conduct heat and electricity well, and can be shaped into thin sheets and wires. Nonmetals are not shiny and do not conduct heat or electricity well. Metalloids have some properties of both metals and nonmetals. There are over 100 elements known to exist. Each elements has a place in an arrangement called the periodic table. The periodic table is a useful tool that can help you identify elements that have similar properties. Metals, nonmetals, and metalloids occupy different regions in the periodic table. Metals start on the left and make up most of the elements in the periodic table. Nonmetals are at the right and are often shaded with a color different from that of the metals. The metalloids lie between the metals and nonmetals.

27. What are mixtures? A mixture is a combination of two or more substances that are combined physically but not chemically. When two or more materials are put together, they form a mixture if they do not change chemically to form a new substance.

28. Mixtures are made up of more than one type of particle Unlike elements and compounds, mixtures are not pure substances. Mixtures contain more that one type of substance. Each substance in a mixture has the same chemical makeup it has before the mixture formed. Unlike pure substances, mixtures do not have definite properties Mixtures do not have defined properties because they do not have a defined chemical makeup. Mixtures can be separated by physical changes.

29. How can mixtures be classified? A heterogeneous mixture is one that does not have a uniform composition A homogeneous mixture is when the substances are evenly spread throughout. Mixtures can be classified as suspensions, solutions, and colloids. Suspensions are mixtures in which the particles of a material are spread throughout the liquid or gas but are too large to stay mixed without being stirred or shaken. In a solution, one substance is dissolved in another substance. Colloids fall somewhere between suspensions and solutions. Unlike the particles in a suspension, colloid particles are small and do not settle out quickly. Colloids like homogeneous, but are considered heterogeneous.

30. States of matter

31. How do particles move in solids, liquids, and gases? All matter is made of atoms or groups of atoms that are in constant motion. This idea is the basis for the kinetic theory of matter.

32. In solids, particles vibrate in place A solid substance has a definite volume and shape. The particles in a solid are close together and do not move freely. The particles vibrate but are fixed in place. Often, the particles in a solid are packed together to form a regular pattern. For most substances, the particles in a solid are closer together than particles in a liquid.

33. In liquids, particles slide past one another A liquid substance has a definite volume but not a definite shape. Particles in a liquid have more kinetic energy than particles in a solid. The particles are attracted to one another and are close together. Particles in a liquid are not fixed in place and can move from one place to another.

34. In gases, particles move freely A gas does not have a definite volume or shape. A substance in a gaseous state has particles with the most kinetic energy of the three states. Gas particles are not close to one another and can move easily in any direction. There is much more space between gas particles than there is between particles in a liquid or a solid. The space between gas particles can increase or decrease with changes in temperature or pressure.

35. How does particle motion affect the properties of solids, liquids, and gases? Solids have a definite volume and shape The particles in a solid are in fixed positions and are close together. Although the particles vibrate, they cannot move from one part of the solid to another part. As a result, a solid cannot easily change shape or volume. If you force the particles apart, you can change the shape of a solid by breaking in into pieces. Each of those pieces will still be solid and have its own definite shape. Liquids have a definite volume but can change shape All liquids have a definite volume but no definite shape. The particles of a liquid are close together, but they are not tightly attached to one another. Particles in a liquid can slide past one another. Liquids can flow. Gases can change in volume and shape Gases do not have a definite volume or shape. The particles in a gas are very far apart. The amount of space between the particles in a gas change more easily.

36. What happens when substances change state? Ice, liquid water, and water vapor are different states of the same substance. As liquid water turn into ice or water vapor, the water molecules themselves do not change. What changes are the motion of the molecules and the amount of space between them.

37. The motion of the particles changes The particles of a substance, even a solid, are always in motion. As a solid is heated, its particles gain energy and vibrate faster. If the vibration is fast enough, the particle break loose and slide past one another. The process in which a solid becomes a liquid is know as melting. As the temperature of a liquid is lowered, its particles lose energy. Eventually, the particles move slowly enough for the attraction between them to cause the liquid to become a solid. This process is called freezing When substances lose or gain energy, one of two things can happen to the substance; its temperature can change or its state can change. But both do not happen at the same time. The energy that is added or removed during a change of state is used to break or form the attraction between particles.

38. Changes of state

39. What happens when matter changes state? Energy is gained or lost To change a substance from one state to another, energy must be added or removed. When a substance gains or loses energy, its temperature changes or its state changes. These two changes do not happen at the same time; the temperature remains constant until the change of state is complete. Particle motion changes All matter is made of tiny particles that are in constant motion. During a change of state, the motion of the particles change. Particles can break away from each other and gain more freedom to move. This happens when a solid changes to a liquid, or a liquid changes to a solid. Particles can also attract each other more strongly, and have less freedom to move. This happens when gas changes to a liquid, or a liquid changes to a solid. Energy is conserved During a change of state, a substance must gain energy from the environment or lose energy to the environment, but the total amount of energy is conserved.

40. How do solids and liquids change states? By freezing The change in state is which a liquid becomes a solid is called freezing. When a liquid is cooled, its particles have less energy than they did before. The particles slow down, and the attractions between particles increase. Eventually, the particles lock into the fixed arrangement of a typical solid. The temperature at which a liquid substance changes into a solid is the liquid's freezing point. Different substances have different freezing points. By melting Particles in a solid have an ordered arrangement. When a solid is wormed, its particles have more energy than they did before. The particles speed up, and the attraction between the particles decrease. Eventually the particles are able to slide past one another. This change of state from solid to liquid is called melting. The temperature at which the substance changes from a solid to a liquid is called the melting point.

41. How do liquids and gases change state? By evaporation or boiling As a liquid is warmed, its particles gain energy. Some particles gain enough energy that they escape from the surface of the liquid and become a gas. This process is called evaporation. Evaporation occurs slowly at the range of temperatures, but it can happen more quickly at higher temperatures. A rapid change from liquid to a gas, or vapor, is called boiling. This change takes place throughout a liquid, not just at the surface. As a liquid is warmed to a high enough temperature, bubbles form. The specific temperature at which this occurs in a liquid is called the boiling point. By condensation Particles in a gas have a very little attraction to one another. As a gas is cooled its particles lose energy. The attraction between particles overcomes the speed of their motion, and a liquid forms. This change of state from a gas to a liquid is called condensation. Condensation is the reverse of evaporation.

42. How do solids and gases change state? By sublimation The change from a solid state directly into a gas is called sublimation. By deposition Deposition is the change in state from a gas directly to a solid. When condition are right, deposition occurs when the particles of a gas lose energy. Attraction between particles locks the particles into a rigid structure of a solid. No liquid is formed in the process.

43. What happens to matter when a change of state occurs? Energy and motion or particles changes The energy of the particle, the movement of the particles, and the distance between them change. Mass is conserved The mass of a substance does not change when its state changes. Each state contains the same amount of matter.

44. Atoms and the periodic table

45. What makes up matter? Around 400 BC, a Greek philosopher named Democritus thought that you would eventually end up with a particle that could not but cut. He called this particle atomos, a Greek word meaning “not able to be divided.” Aristotle, another Greek philosopher, disagreed. He did not believe that such a particle could make up all substances found in nature.

46. Atoms An atom is the smallest particle into which an element can be divided and still be the same element. People used to think that atoms could not be divided into anything simpler. Scientists now know that atoms are made of even smaller particles. But the atom is still considered to be the basic unit of matter because it is the smallest unit that has the chemical properties of an element. You cannot see individual atoms, but they make up everything you do and see. There are many types of atoms that combine in different ways to make all substances. Atoms are so small that you cannot see them with an ordinary microscope.

47. Who developed the atomic theory? John Dalton Dalton's theory stated that all matter is made up of atoms. He also thought that atoms cannot be created, divided, or destroyed Dalton's theory also stated that all atoms of a certain element are identical, but they are different from atoms of all other elements. Dalton also thought that atoms join with other atoms to make new substances. J.J Thomson J.J. Thomson's experiments provided evidence that atoms are made up of even smaller particles. He found particles within the atom that have a negative charge. These negatively charged particles later became know as electrons. Thomson though that an atom was a positive sphere with the electrons mixed through it. Ernest Rutherford In 1909, Ernest Rutherford conducted an experiment to study the parts of an atom. His experiments suggested that atoms have a nucleus, a small, dense center that has a positive charge and is surrounded by moving electrons. Rutherford later found that the nucleus is made up of smaller particles. He called the positively charged particles in the nucleus protons. Niels Bohr Niels Bohr made observations that led to a new theory of how the electrons in the atom behaved. Bohr agreed that an atom has a positive nucleus surrounded by electrons. In his model, electrons move around the nucleus in circular paths. Each path is a certain distance from the nucleus Bohr's model helped scientists predict the chemical properties of elements.

48. What is the current atomic theory? Modern atomic theory is based on the work of many scientists. It keeps Dalton's ideas that atoms are the basic unit of matter and that the atoms of each element are unique. The experiments of Thomson and Rutherford showed that atoms are made of electrons and protons. James Chadwick was Rutherford's student. In 1932, Chadwick discovered that the nucleus contains uncharged particles called neutrons. In the current atomic theory, electrons do not move in circular paths around the nucleus as Bohr thought. Instead, the current theory suggests that electrons move within an area around the nucleus called the electron cloud.

49. What are the parts of an atom? Protons Protons are the positively charged particles of atoms. The relative charge of a single proton is often written as 1+. The masses of particles in the atom are so small that scientists made a new unit for them:the unified atomic mass unit (u). The mass of a proton is about 1 u. Neutrons Neutrons are particles that have no electric charge. They are a little more massive than protons are, but the mass of a neutron is still very close to 1 u. atoms usually have at least as many neutrons as they have protons. Together, protons and neutrons from the nucleus of the atom. The nucleus is located at the center of an atom. The volume of the nucleus is very small compared to the rest of the atom, but protons and neutrons are the most massive particles in an atom. So the nucleus is very dense The electron cloud The negatively charged particles of the atom are called electrons. Electrons move around the nucleus very quickly. Scientists have found that it is not possible to determine both their exact positions and speed at the same time. Compared with protons and neutrons, electrons have very little mass. The mass of an electron is so small that it is usually thought of as almost 0 u. The charge of a single electron is represented as 1-. The charges of protons and electrons are opposite, but equal. The number of protons in an atom equals the number of electrons. So the atom has a net, or overall, charge of 0. an atom can lose or gain electrons. When this happens we refer to the atom as an ion.

50. How can we describe atoms? By atomic number The number of protons distinguishes the atoms of one element from the atoms of another. The number of protons in the nucleus of an atom is the atomic number of that atoms. By mass number The atoms of a certain element always have the same number of protons, but they may not always have the same number of neutrons. Isotopes are atoms of the same element that have different numbers of neutrons. The total number of protons and neutrons in an atom's nucleus is its mass number.