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Chem4kids.comGrading KeyProperties of Elements

1. What is matter?a. Matter is anything made of atoms and molecules; it has mass and takes up space. It is the amount of

stuff in an object. Even though matter can be found all over the Universe, you only find it in a few forms

As of 1995, scientists have identified five physical states of matter: solids, liquids, gases, plasmas, and

one state called the Bose-Einstein condensate (BEC).

2. What are the differences between chemical and physical properties (Properties and State are the same)? Giveexamples of each type.

a. A chemical property change happens when the atoms in a molecule are moved around or when atomsare added or taken away. Chemical changes happen when bonds between atoms are created or

destroyed. Changing physical states of matter is about changing densities, pressures, temperatures, and

other physical properties. The basic chemical structure does not change when there is a physical change

You can cause physical changes with forces like motion, temperature, and pressure.

i. A water molecule is made up of two hydrogen (H) atoms and one oxygen (O) atom. It has thesame molecular structure whether it is a gas, liquid, or solid. Although its physical state may

change, its chemical state remains the same.

ii. If the formula of water were to change, that would be a chemical change. If you could just add asecond oxygen atom, you would have hydrogen peroxide (H2O2).iii. When you step on a can and crush it, you have forced a physical change.iv. When you melt an ice cube (H2O), you have also forced a physical phase change by adding

energy.

v. When iron (Fe) rusts, the actual molecules change their structure (the iron oxidized) this is achemical change.

vi. Melting a sugar cube is a physical change, because the substance is still sugar.vii. Burning a sugar cube is a chemical change. Fire activates a chemical reaction between sugar and

reactions (O2). The oxygen in the air reacts with the sugar, and the chemical bonds are broken.

3. Describe the movement of atoms within a solid, a liquid, and a gas.a. Solids are usually hard, because their molecules have been packed together. In the same way that a

solid holds its shape, the atoms inside of a solid are not allowed to move around too much. This is one o

the physical characteristics of solids. The molecules in a solid are stuck in a specific structure or

arrangement of atoms. The atoms still spin and the electrons fly around, but the entire atom will not

change position.

b. Liquids are an in-between state of matter. They can be found between the solid and gas states. Onecharacteristic of a liquid is that it will fill up the shape of a container. Another trait of a liquid is that it is

difficult to compress. Liquids have their atoms close together making them hard to compress. Due to

Intermolecular, forces the molecules of liquids stick to each other creating a cohesive (sticky) force to

hold liquids molecules together.

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Chem4kids.comGrading Key6. What phase change occurs at a substances freezing point? At its melting point?

a. At a substances freezing point, the substance changes state from a liquid to a solid.b. At a substances melting point, the substance changes state from a solid to a liquid.

7. How does the temperature at which a substance melts compare tothe temperature at which it freezes?

a. Phase changes happen when certain points are reached.Sometimes a liquid wants to become a solid. Scientists use

something called a freezing point to measure the

temperature at which a liquid turns into a solid. There is a

special temperature for every substance called the melting

point. When a solid reaches the temperature of its meltingpoint, it can become a liquid. The reverse of the melting

process is called freezing.

8. Compare and contrast the effects of pressure on solids, liquidsand gases.

i. When the pressure surrounding a substance goes up, the freezing point and other special pointsalso go up. That means it is easier to keep things solid at higher pressures. Just remember that

there are some exceptions.

b. All matter can move from one state to another. It may require extreme temperatures or extremepressures, but it can be done. Sometimes a substance does not want to change states. You have to use

all of your tricks when that happens. To create a solid, you might have to decrease the temperature by a

huge amount and then add pressure.

c. What if you wanted to turn it into a solid but could not make it cold enough? You could increase thepressure to push those molecules together. The opposite works too. If you have a liquid at room

temperature and you wanted a gas you could use a combination of high temperatures and low

pressures to solve your problem.

9. If an unknown substance is made up of atoms in constant motion, has no definite shape or volume, and canspread out to fill a container, what is its state? How do you know?

a. Its physical state is water. Water is the only state with the characteristic of being able to fill up the shapeof a container that it is in due to having no definite shape of their own like a solid, also the atoms in a

liquid have more energy than the atoms in a solid meaning that they are in constant motion.

Periodic Nature of Properties

10.How is the placement of an element determined?a. The elements are placed in specific locations because of the way they look and act. If you have ever

looked at a grid, you know that there are rows (left to right) and columns (up and down). The periodic

table has rows and columns, and they each mean something different. In the periodic table, elements

have something in common if they are in the same row. Hydrogen (H) and helium (He) are special

elements. Hydrogen can have the talents and electrons of two groups: one and seven. To scientists,

hydrogen is sometimes missing an electron, and sometimes has an extra one. Helium is different from

all of the other elements. It can only have two electrons in its outer shell. Even though it only has two, it

is still grouped with elements that have eight (i.e., noble gases).

11.What is a period? How many periods are found in the periodic table?

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Chem4kids.comGrading Keya. All of the elements in a period have the same number of atomic orbitals. Every element in the top row

(the first period) has one orbital for its electrons. All of the elements in the second row (the second

period) have two orbitals for their electrons. It goes down the periodic table like that. At this time, the

maximum number of electron orbitals or electron shells for any element is seven, resulting in seven

periods on the Periodic Table.

12.What is a group? How many groups does the periodic table contain?a. The periodic table also has a special name for its columns. When a column goes from top to bottom, it is

called a group. The elements in a group have the same number of electrons in their outerorbital. Those

outer electrons are also called valence electrons. They are the ones involved in chemical bonds with

other elements. Every element in the first column (group one) has one electron in its outer shell. Every

element in the second column (group two) has two electrons in the outer shell. As you keep counting

the columns, you will know how many electrons are in the outer shell. There are some exceptions to the

order when you look at the transition elements, but you get the general idea. Transition elements start

to add electrons to the second-to-last shell. There are 18 groups on the standard periodic table.

13.How are the atomic structures of elements within the same period similar?a. All of the elements in a period have the same number of atomic orbitals, which are the paths that the

electrons are always moving in. Electrons spin very quickly around the nucleus of an atom. As the

electrons zip around, they can move in any direction, as long as they stay in their shell. Any directionyou can imagine upwards, downwards, or sideward electrons can do it. Electrons are constantly

spinning in those atomic shells and those shells, or orbitals, are specific distances from the nucleus.

Every element in the top row (the first period) has one orbital for its electrons. All of the elements in the

second row (the second period) have two orbitals for their electrons. It goes down the periodic table like

that. At this time, the maximum number of electron orbitals or electron shells for any element is seven.

14.How are the atomic structures of elements within the same group similar?a. The elements in a group have the same number of electrons in their outer orbital. Those outer electrons

are also called valence electrons. They are the ones involved in chemical bonds with other elements.

Every element in the first column (group one) has one electron in its outer shell. Every element in the

second column (group two) has two electrons in the outer shell. As you keep counting the columns, you

will know how many electrons are in the outer shell. There are some exceptions to the order when you

look at the transition elements, but you get the general idea. Transition elements start to add electrons

to the second-to-last shell. There are 18 groups on the standard periodic table.