Chapter 2

1. Chapter 2 Matter

2. AtomsSection 2-1 pg. 38 ques. 1-7 • What are atoms? -Atoms are the building blocks of matter. So, what is matter? -Matter is anything that has a mass and takes up space. • Matter surrounds us, and could take the form of solid, liquid or gas. • What are some examples of matter? • Rocks • Desks • Air • Water

3. Atoms (continued) • Is fire matter? No. What about light? No. Neither one of these things is matter because they don’t take up any space.

4. Atoms (continued) • Is all matter visible? • No. Air is matter as well as other colorless gasses like butane, or propane. • What causes matter to take these various forms and shapes? • Its all depends on the way their atoms are put together and also the shape that their atoms take on. • In your body has several types of atoms that combine in different ways. These atoms form proteins, DNA, tissues and other things that makes you a person.

5. Also, many other objects you see around you are composed of many different types of atoms. • However thee are things that are only made up of one type of atom. These things are called the elements. • Elements are substances that are made of only one type of atom and cannot be broken down into simpler substances by ordinary chemical means.

6. Minerals • Along with elements combining to make up things you see everyday, they also make up the Minerals that compose the Earths crust. • Minerals are usually combinations of atoms that occur naturally in a crystal solid form. • However some minerals are only composed of element and they are called native elements. - Examples of native elements are Copper and Silver. What things do you know of that are made of these native elements.

7. The Atomic Model • If you cant see atoms, then how are we able to study them. • We use something called an atomic model. • All atoms of an element contain the same type of atom. Ex: All atoms of the element Carbon are carbon atoms.

8. The Atomic Model • Every atom is composed of three different particles. 1) Protons- which are positively charged particles, located inside the nucleus of the atom. 2) Neutrons- which is a particle with no charge. Also located inside the nucleus. • Because there is no negative charges inside the nucleus to counter act the positively charged protons, the overall charge of the nucleus is positive. 3) Electrons- These are particles that have a negative charge and are found outside the nucleus.

9. Electrons • Electrons have some special features that we need to look at. • First, we need to know that they are grouped into energy levels, and that each level contains a specific number of electrons. • Second, electrons float in a kind of cloud around the nucleus of the atom. Try to think of it like a beehive. The hive is the nucleus and all the swarming bees around the hive are the electrons.

10. Counting Atomic Particles • Not every atom has the same amount of atomic particles (protons, neutrons, and electrons). So how do we count them. • We use a table called the Periodic Table of Elements.

11. Counting Protons • We are able to count the number of protons in an atom by using the Atomic Number of an element. • The number of Protons in an atom of an element is always equal to the Atomic Number. • Carbons Atomic Number is 6 therefore an atom of Carbon has six Protons.

12. How to count electrons • In a neutral atom, the number of electrons will always be equal to the number of protons. • However, some atoms can lose or gain electrons and continue to remain the same element.. • If you lose an electron the overall charge of the atom becomes positive. • If you lose a proton the overall charge of the atom becomes negative.

13. How to count Neutrons • We count the amount of neutrons in an atom by using the elements mass number. • Mass Number- equals the number of protons plus the number of neutrons. • So to find the # of neutrons, subtract the atomic number from the mass number.

14. Isotopes • Atoms of the same element that have different number of neutrons is called an isotope. • Ex: Normal carbon C12 has 6P 6N & 6E. • An isotope of Carbon C14 has 6P 8N & 6E • Isotopes can sometimes be radioactive. - We use these radioactive isotopes to treat cancer, date rocks and label proteins.

15. Anatomical InteractionsSection 2-2 H.W. pg. 44 ques. 1-5 • So we know that substances that only have one kind of atom is called an element. • There are 90 different elements that occur naturally on Earth, meaning they are not man made. • So with only 90 elements, how is it that so many different things on Earth are made? • They are made by the infinite number of possible combinations that the elements can form.

16. Anatomical Interactions • These combinations that are made when the atoms of more than one element combine are called compounds. • Water is a compound made of what 2 elements? • H 2 0. This way of writing water is called its chemical formula. • NaCl is sodium chloride. Does anyone know what NaCl’s common name is?

17. Chemical Properties • A chemical property is a property that describes a change that occurs when one substance reacts with another. Ex: when electricity is passed through water, water breaks up into hydrogen gas and oxygen gas. This is a chemical property of water.

18. Bonding • Chemical bonds- are the forces that hold the atoms together in a compound. • These bonds form between the outermost electrons of two or more different atoms. • The outermost electron level of an atom can only have 8 electrons. If an atoms highest electron level has fewer than 8 electrons it will interact with other electrons of a different atom to form a compound. • If an atoms outermost electron level is occupied by 8 electrons than it will not readily react with other atoms to form compounds.

20. Four types of bonds • Covalent bonds- These occur when the atoms of two different elements share electrons. • A group of atoms connected by covalent bonds is called a molecule. • An example would be the covalent bonds between Hydrogen and oxygen in a water molecule.

21. Four types of bonds 2) Ionic bonds- These occur when atoms of two or more elements exchange electrons. • These bonds occur when an atom becomes either positively or negatively charged. • Atoms become positive or negative by losing or gaining electrons. When that happens when call them ions. • These ions are attracted to each other when they have opposite charges. • And when ions combine they form electrically neutral compounds. • An example is NaCl. Na has a positive charge and Cl has a negative charge, so they join to make a neutral NaCl molecule

23. Four types of bonds 3) Hydrogen bonds- These bonds form without the interactions of electrons. - These bonds make a molecule polar, meaning that the molecule has a partially positive end and a partially negative end. • An example would be the hydrogen bonds between water molecules. The partially negative end of a water molecule is attracted to the partially positive end and allows two or more water molecules to bond. • These H-bonds are very weak and are broken easily.

25. Mixtures • A mixture is composed of two or more substances that are not chemically combined. • Two types of Mixtures: 1) Heterogeneous mixture- the components of this type of mixture are not mixed evenly and each component retains its own properties.

26. Mixtures 2) Homogeneous Mixture- These types of mixtures are evenly mixed throughout. And individual components cannot be seen. -They are also called solutions. An Example would be how salt dissolves in water.

27. Separating Mixtures & Compounds • Componants of a compound or a mixture can be separated by either physical or chemical means. • If you boil a salt water mixture, the water will evaporate away and the salt will remain in the glass. (Physical) • The components of a compound must be separated by chemical means. Ex: HCL + CaCO3 -------- CO2

28. Properties of MatterSection 2-3 H.W. Pg. 56ques. 1-18 • Physical Properties- properties that you can observe without changing a substance into a new substance. -Ex: A physical property of you hair might be that its red or brown, curly or straight. One physical property that you would use to describe matter would be density. Density – is a measure of the mass of an object divided by its volume. The measurement used for density is g/cm3. -So if 1cm3 of water has a mass of about 1g this means its density is 1g/cm3

29. Properties of Matter • If an object is more dense than water it will sink in water. • If an object is less dense than water it will float.

30. Density problem Problem: You want to find the density of a small cube. It measures 1cm x cm x 2cm and has a mass of 8g. What's the density of the cube. What you know: mass: m= 8g volume: v= 1cm x 1cm x 2cm= 2cm3 Density: d= m/v What you want to find: Density: d How to solve: If d=m/v just substitute the numbers you have for v and m into the equation. D=8g/2cm3 D= 4g/cm3 To check your answer multiply the your answer by the given volume of 2cm3 and you get 8g.

31. States of Matter • There are four states of matter, solid, liquid, gas and plasma. • Solids- solid matter occurs when particles are in fixed positions relative to each other. Here, individual particles vibrate but they don’t switch positions with each other. - Solids take up a definite volume and have a definite shape.

32. States of Matter 2) Liquids- particles in liquid form are attracted to each other, but are not in fixed positions. • The reason why liquid particles are not fixed is because of their energy. Liquid particles have more energy than solid particles and causes them to move around and change positions with each other. • The particles in a liquid will always change position in order to fit the container that is holding them.

33. States of Matter 3) Gases- the particles that make up gases have enough energy to overcome any attractions between them. This allows them to move freely and independent of each other. • Unlike liquids and solids, gases spread out and fill whatever container they are placed in. Like a balloon.

34. States of Matter 4) Plasma- Plasma is the most common state of matter in the universe. This state is associated with high temperatures. • Plasma is composed of ions and electrons, and forms when high temperatures cause some electrons to escape the cloud its in around the nucleus of an atom. Ex: Sun, Stars, and lightning bolts.

35. Changing the State of Matter • Matter is changed from a liquid to a solid at its freezing point. • Matter is changed from a liquid to a gas at is boiling point. • The freezing point of water is 0 °C and its boiling point is 100 °C. • Water is the only substance on Earth that occurs naturally in all three states of matter.

36. Changing the State of Matter • Changes is states occur due to and increase or decrease in energy. • If you increase energy you increase the movement of particles. Ex: Boiling Water • This increase in energy causes heat which melts an ice cube and evaporates the puddle left behind. • Pressure could also effect changes in state. A decrease in pressure will lower the boiling points of liquids. • When pressure increases solids melt faster.

37. Changes in Physical Properties • When a molecule of water changes states its chemical composition does not change. Liquid, gas or solid water molecules are always water molecules. • However waters physical properties do change. Ex: When water is frozen as ice it becomes less dense than liquid water. That’s why ice cubes float in a glass of water.

38. Test on Chapter 2 in one week!!!!!!!