Chemistry / Matter and Change

1. How does a pure substance differ from a mixture of substances such as lemonade?

- A pure substance has a uniform and unchanging composition. They are broken down into elements and compounds. - A mixture of substances, such as lemonade, are physically combined and can be separated into their original components.

NH,4OH =

1 nitrogen + 5 hydrogen + 1 oxygen

Ca,3(PO,4),2 =

3 calcium + 2 phosphorous + 8 oxygen

chemical change

A change in matter that produces one or more new substances

solvent

A liquid substance capable of dissolving other substances

heterogenous mixture

A mixture in which substances are not evenly mixed

How to find the ratio of mass A to mass B?

A/B = x/1 First, divide 1 by B. Next, multiple that with A. Answer goes in the X spot.

Physical Changes

Any change that DOES NOT alter the chemical composition of a substance.

extensive property & example

DO depend on the amount of matter/the substance present ex: volume, mass, energy

Solid

Definite shape and volume

7. Aluminum can combine chemically with various substances, but it never reacts to form simpler substances. Is aluminum an element, a compound, or a mixture? How do you know? Is aluminum a substance? Explain.

Element, because it is in its simplest form. It is a substance because it has a uniform and unchanging composition.

3 types of substances

Element, compound, & molecules

5. Suppose you measure the mass of an iron nail and find it to be 13.8g. You place the nail in a moist place for two weeks. When you retrieve the nail, it is covered with a crusty brown coating of rust. You then place the nail on a balance to measure its mass. Will the nail have a mass that is greater than, less than, or equal to 13.8g? Explain your answer.

Greater, because of the law of conservation. Mass of products = mass of reactants, and the nail moisture combines with air forms the rusty nail as a product. When iron rusts - in the presence of moisture and oxygen - iron-oxide is formed. There is an increase in the mass of the iron equal to the mass of oxygen that has gone into forming the rust.

Law of Conservation of Mass

Matter is neither created nor destroyed Mass reactants = Mass products

3. Can two different samples of the same substance have different physical properties? Can they have different chemical properties? Explain your answers to both questions.

No, all substances have a uniform and unchanging composition. All samples of a pure substance have the same chemical and physical properties.

9. The elements carbon and sulfur are solids at room temperature. Can you reasonably predict that a compound of these two elements will also be a solid at room temperature? Explain your conclusion.

No, they may chemically react to form a new product.

conservation of mass formula

SIGMA mr = SIGMA mp (sum of mass of reactants = sum of mass of products)

4. Write one statement each for a solid, a liquid, and a gas describing the particle arrangement and spacing in each state.

Solid: definite shape and definite volume Liquid: indefinite shape, definite volume Gas: indefinite shape and indefinite volume

8. The mineral cassiterite is mined as a commercial source of tin. It is a compound of the elements tin and oxygen. A 1.000-kg sample of pure cassiterite mined in Germany contains 788 g of tin. Is it possible to predict the mass of tin contained in a 43.5-kg sample of cassiterite mined in South America? Explain your reasoning.

Yes, find the mass by percent.

Law of Definite Proportions

a given compound always contains exactly the same proportion of elements by mass

Sand on the beach is an example of a compound a heterogeneous mixture a homogeneous mixture an element

a heterogeneous mixture

plasma

a hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons

Homogeneous Mixture

a mixture in which the composition is uniform throughout

Element

a substance that cannot be separated into simpler substances A pure substance made of only one kind of atom

compound

a substance that consists of two or more elements chemically combined represented by a formula

6. Identify each of the following examples as a physical change or a chemical change. a. Wood burns in a fireplace. b. A block of pewter is pounded and made into a bowl. c. A copper weather vane becomes green in a few years. d. Baking soda in cookie dough causes the cookies to puff with bubbles of gas when they are baked. e. A pan of water boils on a stove until the pan becomes dry. f. Soap and water are used to clean up a spill of grease. g. Mothballs vaporize in a closed closet.

a. chemical b. physical c. chemical d. chemical e. physical f. physical g. physical

Identify each of the following as an example of a homogeneous mixture or a heterogeneous mixture and a possible separation method for each substance: a. 70% isopropyl rubbing alcohol b. saltwater c. gasoline d. concrete

a. homogenous, distillation b. homogenous, crystallization c. heterogenous, filtration d. heterogenous, screening

Chemical Property

ability of a substance to combine with or change into one or more other substances

A solution of solids is a(n)___________.

alloy

A sample of an element contains only one kind of

atom

Distillation separates mixtures by their ____________.

boiling point

how to tell if matter is a mixture or substance

can physical separation occur? Yes: mixture No: substance

Physical Property

characteristic that can be observed & measured without changing the composition of the substance

Law of Definite Proportions​

compound always composed of the same elements in the same proportion by mass (ratio of element to compound)

________ is a separation technique that produces highly pure solids

crystallization

intensive property & example

do NOT depend on the amount of matter/the substance present ex: melting/boiling point, density

2 types of pure substances

elements and compounds

A technique that uses a porous barrier to separate heterogeneous mixtures is _______.

filtration

A vapor is a _________.

gas

What is evidence of a chemical reaction?

gas/precipitate, change in temperature, change in matter, color change, melting/boiling point

Periods are ___________ on the periodic table.

horizontal rows

liquid

indefinite shape and definite volume

Gas

indefinite shape and indefinite volume

Which would be an example of a homogeneous mixture? oily water sodium chloride soil (dust) kool-aid

kool-aid

Percent by Mass

mass of element/mass of compound x 100

(pure) substance

matter that has a uniform and unchanging composition

In the figure above, the volume of hydrogen gas is twice the volume of oxygen gas. What is the mass relationship between hydrogen and oxygen gas?

more info is required

Which of these is not a homogeneous mixture? oil and vinegar in salad dressing sugar dissolved in water oxygen and nitrogen gases in the air a silver mercury amalgam used to fill a tooth cavity

oil and vinegar in salad dressing

A(n) ____________ is a transition from one state of matter to another.

phase change

States of Matter

solid, liquid, gas

A heterogeneous mixture is poured through a piece of filter paper that is positioned over a beaker. What is the substance that is collected in the beaker?

solution

Which of the following is a substance? soda sugar water steam gun powder

steam

Which of the following is a vapor? hydrogen helium steam oxygen

steam

Matter that has a uniform and unchanging composition is a ___________.

substance

sigma means

sum of

An example of a mixture is hydrogen fluoride gold the air in this room purified water

the air in this room

Vapor

the gaseous state of a liquid or a solid at room temperature

Solute

the substance that is dissolved

how to tell if a mixture is homogenous or heterogenous

uniform composition? yes: homogenous no: heterogenous

A solution can be distinguished from a compound by its

variable composition