Chemistry Ch. 1 + 2 Test 10/1/20

elements

made up of one type of atom with unique properties

Identify one element that is a solid at room temperature.

K

reactants

What goes into a chemical reaction

Pure substances

have definite and constant composition

Describe the difference between the three phases of matter in terms of particle arrangement.

solid - particles tightly packed, definite volume and shape liquid - particles are close, but not tight; definite volume but indefinite shape gas - particles are spread out, indefinite shape and volume

List the three common states of matter.

solid, liquid, gas

mixtures

the physical combination of 2 or more pure substances

compounds

2 or more atoms chemically combined together

Why would a student who wants to be a doctor need to study chemistry?

A doctor would need to know how the human body responds to chemicals, and how the chemical reactions in the body keep you healthy or how the change when you are sick.

Two clear liquids are placed in two different beakers. They are both allowed to evaporate. After evaporation, beaker A has a white solid at the bottom of it, and beaker B has nothing left in it. Which of the beakers contained a mixture and which one contained a pure substance? How did you determine this?

Beaker A has a mixture because it was a liquid mixed with whatever the white substance is. Beaker B is a substance because it all evaporated away.

Identify two elements that are liquid at room temperature.

Br, Hg

Chemistry is commonly called the central science. Explain this term.

Chemistry is considered a central science because it studies matter which is what makes up everything (except energy) around us.

Why does chemistry affect all aspects of life and most natural events?

Chemistry is the study of matter, and matter is anything with mass and volume, which is just about anything around us. Chemistry also studies the changes that matter undergoes, which will explain many natural events, like leaves changing color.

What is the difference between an extensive and intensive property of matter?

Extensive - physical property that depends on the amount of substance (mass, volume, area) Intensive property - physical property that does NOT depend on the amount of substance (density, color, temperature)

Identify three elements that are gases at room temperature.

H, He, N

You discover a new element. After studying it, you discover that it is a brittle solid that is a poor conductor of heat and electricity. Where on the periodic table would you place this element and why?

I would place this element on the right side of the periodic table because it has properties similar to the nonmetals.

State the law of conservation of mass. What does this imply about all matter in existence?

Matter cannot be created or destroyed in chemical or physical changes. This implies that all matter that is currently in existence has always been in existence and will continue to be in existence. It has just merely been ordered differently.

Define matter.

Matter is anything with mass and volume.

Identify three metals, non metals, and metalloids.

Metals - Li, Na, K nonmetals- N, O, F Metalloids - B, Si, Ge

Do compounds have properties identical to their constituent elements? Explain using the following reaction: sodium + chlorine -> sodium chloride.

No, compounds have properties different from their elements. Sodium is explosive in water but sodium chloride just dissolves in water. Chlorine is poisonous, but sodium chloride is not.

Read the following description of zinc and determine which properties are physical, and which properties are chemical. Zinc is a silver-gray colored metal, which melts at 420oC. When zinc granules are added to dilute sulfuric acid, hydrogen is given off. Zinc has a hardness of 2.5 and a density of 7.13 g/cm3 at 25oC. It reacts slowly with oxygen at elevated temperatures to form zinc oxide.

Physical = silver-gray color, melts at 420C, hardness 2.5, density 7.13 g/cm3 Chemical = react with sulfuric acid, reacts with oxygen

Jack mixes lead (ii) nitrate and potassium iodide. A solid yellow substance forms in the beaker. What would be the best term to describe this substance?

The substance is a precipitate.

How can a mixture be distinguished from a pure substance?

a substance has a fixed composition. The composition of a mixture may vary. Mixtures can also be separated by physical means and pure substances can not.

metalloids

brittle solids found between metals and non-metals, good conductors of electricity but not heat

Look at the following chemical reaction. Identify the reactants and the products. Carbon + Oxygen -> Carbon monoxide

carbon and oxygen are the reactants, and carbon monoxide is the product

How do chemical changes differ from physical changes?

chemical change results in new substances forming, but physical changes just change the appearance of a substance.

chemical reactions

chemical changes where new substances are formed

What are five common signs that a chemical reaction has occurred?

color change, precipitate forms, gas forms, odor is released, energy changes

Explain the difference between an element and a compound.

elements are made up of one type of atom with definite properties. Compounds are made up of two or more types of atoms with properties different from the elements that make them up.

homogeneous

mixture with uniform composition a.k.a. solution

heterogeneous

mixture without uniform composition

Look at your desk or table. List two intensive properties and two extensive properties of the surface.

intensive - color, texture, density, Extensive - size, mass, surface area

metals

most elements, solid at room temp, good conductors of heat and electricity, found to the left of the staircase

Define physical property and physical change. Compare these to chemical properties and changes.

physical properties can be observed without changing the identity of the substance, but chemical properties can only be observed by changing the identity of the substance. Physical changes are changes that do not change the identity of the substance, but chemical changes result in the identity of the substance changing. Both physical and chemical changes can be reversible or irreversible.

nonmetals

right side of the staircase, most are gases, poor conductors of heat and electricity

products

what comes out of a chemical reaction

Precipitate

when two liquids are put together and form a solid. A solid that forms from two liquids reacting