Integrated Physical Sciences: Section 2 Lessons 4-8

chemical change

when a change in chemical composition occurs

chemical reaction

a process where chemical bonds are formed or broken

physical change

when matter changes in appearance without changing in chemical composition

products

the new substances formed by a reaction

reactants

substances that go into a chemical reaction

What is rubbing alcohol evaporating off your skin an example of?

a physical change

What is a windshield shattering when a rock is thrown at it an example of?

a physical change

When a candle burns by changing paraffin wax into carbon dioxide and water, what is this an example of?

a chemical change

When a copper statue turns green by forming a layer of new substances containing copper atoms, what is this an example of?

a chemical change

When a tree uses energy from sunlight to convert water from the soil together with carbon dioxide from the air into sugars used for its growth, what is this an example of?

a chemical change

In which type of changes are atoms rearranged and new substances formed?

chemical changes

When water changes from ice to liquid water, what is this an example of?

a physical change

2H2(g)+O2(g)→2H2O(l)

Is the chemical reaction that forms water from hydrogen and oxygen a chemical change or a physical change?

a chemical change

Liquid methanol (CH3OH) becomes gaseous methanol (CH3OH).

Is the change a chemical change or a physical change?

physical change

Liquid nitrogen, which is very cold, can be used to turn a mixture of cream and sugar into ice cream. Is the transition of cream and sugar into ice cream a chemical change or a physical change?

physical change

ion

an atom with a net electric charge

How could a Cu2+ ion form?

A Cu2+ ion could form if a Cu atom loses two electrons.

When an atom loses an electron to become an ion, which electron is lost?

the one farthest from the nucleus

When an atom loses electrons, which type of ion forms?

a positively charged ion

When an atom gains electrons, which type of ion forms?

a negatively charged ion

ionic bond

when a strong, attractive force occurs between the two ions because one is positively charged and the other is negatively charged, and the unlike charges are attracted to one another

covalent bond

when two nonmetals react, neither one fully transfers electrons to the other; instead, the sharing of electrons provides the attractive force that holds the atoms together

metallic bond

when metal atoms are bonded, the valence electrons move freely from one metal atom to another

Which type of bonds form when electrons are transferred from one atom to another?

ionic bonds

Which type of bonds form when electrons are shared between atoms?

covalent bonds

What are the compound elements for an ionic compound?

both metals and non metals

What is the chemical bond type for a molecule?

covalent bond

period

rows in the periodic table

group

columns in the periodic table

family

elements within a group that have the same number of valence electrons

Which class of elements generally has the highest conductivity?

metals

Which class of elements has intermediate conductivity?

metalloids

Which class of elements has low conductivity?

nonmetals

Which properties are common to most metals?

malleable, ductile, shiny

What are the properties of a solid metalloid?

shiny and brittle

Which type of change occurs when sugar dissolves?

a physical change

A plastic bottle is filled with water and placed in a freezer. The water expands when it freezes, causing the bottle to burst. What is an explanation for this observation?

Water molecules must be spaced farther apart in ice than in liquid water.

What do we know about the conservation of matter and physical changes?

When a solid melts into a liquid, the amount of mass the solid loses must be exactly equal to the mass of liquid that forms.

In the hypothetical chemical reaction below, reactants A and B form product C.

A + B react to form C

A + B → C

If 5 g of A reacts with 3 g of B, how many grams of C will be formed?

8

What does the law of conservation of matter apply to?

both chemical and physical changes

In a chemical reaction, what is the mass of products?

the same as the mass of the reactants.

coefficients

indicate the ratio of chemicals that participate in a reaction; the coefficient is written before the chemical formula; no coefficient indicates a ratio of one.

subscripts

(the numbers written below the line) indicate the ratio of atoms in a compound; no subscript indicates that only one of that atom is present.

How many total H and O atoms are present in the 3 H2O molecules?

6 H and 3 O

Which type of change is the formation of rust (oxidation)?

a chemical change

233 g of oxygen (O2) reacts with 100 g of iron (Fe) and forms rust, as described by the following equation.

4Fe + 3O2 → 2Fe2O3

233 g + 100 g → ?

How much rust is produced?

333g

temperature

a measure of the average kinetic energy per particle

If the average kinetic energy of Sample B is greater than that of Sample A, what can be concluded about the temperature of samples?

sample B has a higher temperature

What describes the energy of particles in a solid?

low energy

What describes the shape of liquid?

not fixed

How do the particles move in a gas?

move rapidly

What describes the spacing of particles in a liquid?

close together

What describes the volume in a gas?

not fixed

thermal energy

the total kinetic energy of all the particles that make up the gas

heat

thermal energy that is transferred from one substance to another

What is the total (instead of average) energy of an object that its particles have?

thermal energy

What is the energy that transfers from hot objects to colder objects when you bring them in contact called?

heat

evaporation

the process by which a liquid turns into a gas

condensation

a process that occurs when particles in the gas phase no longer have sufficient energy to overcome attractive forces between them and turn into liquid

phase change

a change from one state to another

melting

the process of turning from a solid into a liquid

freezing

the process that occurs when a liquid turns into a solid

How does heating the inside of a clothes dryer help dry the clothes faster, even though the temperature is not high enough to make water boil?

At a higher temperature more of the water molecules have the kinetic energy needed to evaporate.

If you buy a cup of hot coffee at a fast food restaurant and want to keep it hot for as long as possible, you place a thin plastic lid on it. Why does this help keep the coffee hot even though the thin plastic is not very effective in preventing heat from being transferred across it?

It reduces cooling by evaporation.

During the condensation phase, does the energy of the particles increase or decrease?

it decreases

During the evaporation phase, does the energy of the particles increase or decrease?

it increases

During the melting phase, does the energy of the particles increase or decrease?

it increases

During the freezing phase, does the energy of the particles increase or decrease?

it decreases

At 0°C, the solid ice cube starts to become a liquid. What is this phase change called?

melting

What happens to the motion of the water molecules as the water becomes a liquid?

increases

At 100°C, the water molecules begin to undergo their second phase transition to the gas phase. What is this phase change called?

boiling

What happens to the motion of the water molecules as the water becomes a gas?

increases

Water changed from a solid to a liquid, and then to a gas. Did the water absorb heat or did the water release heat during this process?

the water absorbed heat

If water changed from a gas to a liquid, and then to a solid, what two phase changes would be seen?

condensation and freezing

You often feel hotter on a humid day than a dry day even if the temperature is the same. Why?

On a humid day water evaporates more slowly, which means that heat is transferred more slowly away from your skin when you sweat.

Temperatures below the temperature at which water freezes can harm citrus trees. When temperatures below freezing are expected, Florida citrus growers protect their trees by turning on sprayers to keep them wet. How does having the plants covered with liquid water help to protect the orange trees?

The liquid water releases thermal energy while freezing.

During melting and evaporation, the energy of particles increases. How must the energy be transferred?

from the environment to the particles.

Water can be changed from a liquid to a solid or a gas, and back to a liquid, by adding thermal energy to it or by removing thermal energy from it. During evaporation, what happens to the thermal energy?

It is absorbed from the surroundings to the water.

In dry climates, swamp coolers are sometimes used to cool the air. By allowing water to evaporate, what does the swamp cooler do?

it absorbs heat from the environment

Ice can form when water freezes on a window. What happens during this process?

heat is released by the ice

During a spring thaw, ice melts off a pond. What happens to heat when the ice melts?

it is absorbed

On a humid day, water condenses on a cold drink. What happens to heat when water condenses?

it is released

When the sun comes out after a rainstorm, what happens to water on wet pavement?

it evaporates

The water vapor rises and joins cooler, more humid air in the upper atmosphere. As a result, what happens to the vapor?

it condenses

When NaCl forms, each Na atom transfers one electron to a Cl atom. When this occurs, the Na and Cl atoms become ions. What is the charge of each Na ion?

+1

Before water begins to boil, thermal energy _____.

increases

What type of change is occurring as the water boils?

physical

If a liquid evaporates below its boiling temperature to change into a gas by evaporation, it _____ thermal energy from its surroundings.

absorbs

How does a physical change differ from a chemical change?

A chemical change produces new substances.

Which of these is true about a chemical change?

The change rearranges which atoms are bonded to which.

3 multiple choice options

After analyzing different eggs you conclude that egg whites each have about 50 mg of sulfur in them. Based on the relative mass of iron and sulfur atoms, you conclude that the 50 mg of sulfur can react with 92 mg of iron to form FeS.

50 mg of sulfur (S) can react completely with 92 g of iron (Fe) to produce FeS. The equation describing the change that makes eggs sometimes look greenish is:

S + Fe → FeS

What should you do to determine the mass of FeS produced?

Add the 50 mg for the S to the 92 mg for the Fe.

When shaking salt from a salt shaker, you see that the salt, which is sodium chloride (NaCl), is in the form of many small crystals.

What holds the Na particles and Cl particles in place inside the crystals?

Ionic bonds between sodium and chlorine

Salt dissolves in water to form saltwater. Is this considered a chemical change or a physical change?

this is a physical change

The fuel in a lighter is butane. When butane burns, the following change takes place.

2C4H10 + 13O2→8CO2+ 10H2O

Is this a chemical change or a physical change?

a chemical change

Two atoms of nitrogen bond together to form N2. Which type of chemical is N2?

a compound

Cu+1 is an ion of copper with a charge of plus one. If Cu+1 loses one electron, what will be formed?

Cu+2

Which type of bond forms when electrons are shared?

Covalent

Bronze is an alloy of copper and tin. Which type of bond holds bronze together?

metallic bond

What happens to the electrons when a metallic bond is formed?

Electrons float free in an electron sea.

Which of the following statements about metalloids is true?

Metalloids are shiny and have intermediate conductivity.

3 multiple choice options