Unit 1: Matter & Density

Question 1

In your own words, define chemical change

Answer 1

The reaction creates a new compound entirely.

Ex. Rust on a car

Question 2

List three different physical and chemical changes and one physical and chemical change.

Answer 2

Physical change: ice, water (liquid), stem

Chemical change: burning, rusting, decomposing

Both: baking cookies, digestion

Question 3

Elements

Answer 3

Made of one kind of atom, distinguished by atomic number, which corresponds to the number of protons in the nucleus.

Question 4

Compounds/molecule/formula unit

Answer 4

Group of atoms that are bonded together. These are made up of different atoms

Question 5

Pure Substances

Answer 5

Only one type of atom or molecule, no impurities

Question 6

Mixture

Answer 6

Two or more substances that are mixed together pm nut not bonded

Question 7

Heterogenous Mixture

Answer 7

Mixtures that do no appear to be the same throughout ( different )

Question 8

Homogeneous Mixtures

Answer 8

Mixtures that appear to be the same thought ( same )

Question 9

Provide four evidences of a chemical change

Answer 9

1) change in heat
2) CHANGE in color
3) gas formed
4) precipitate (ppt) formed ➡️ forms a solid

Question 10

In your own words, define physical property

Answer 10

Come back to

Question 11

In your own words, define chemical property

Answer 11

A quality of substance that can be measured or noticeable throughout a chemical reaction.

Question 12

Significant Digits (figures)

Answer 12

The number of digits that are believed to be accurate, including one estimated digit
➡️telling us how precise a measurement is and should be carefully considered

Question 13

Why do we use significant digits?

Answer 13

To help us report our data, and show how accurate our measurements/reports are.
➡️along with increased accuracy, they also increase the rigor of our findings.

Question 14

Exact Numbers

Answer 14

Counting numbers ➡️ number of markers (no decimals)
Definition number
‼️have infinite significant figures‼️

Question 15

Significant figures: Zeros 0⃣

Answer 15

Leading➡️ NEVER SIGNIFICANT ‼️
Trailing➡️ only significant if there is a DECIMAL ➗
Trapped➡️ ALWAYS significant 🔝🚯 😍

Question 16

When adding or subtracting significant figures, your answers should always depend on what key principle?

Answer 16

The same number of decimals ➗ as the number of least amount of ❌💸 decimals ➗.
DONT FORGET TO ROUND

Question 17

When multiplying or dividing significant figures, you should always do what to determine the number of significant figures in your answer?

Answer 17

Look to see what is the least amount of significant figures and make that the same number of significant figures in your answer. In other words, your answer should have the same number of significant figures as the number with the least amounts ❌💸 of significant figures.

Question 18

What are two things significant figures require?

Answer 18

Rounding and on occasion scientific notation.

Question 19

Why the metric system?

Answer 19

1) simpler ➡️ based on tens
2) consistency ➡️ all countries except for three use the metric system. It makes talking about science a lost easier when everyone is talking in the same language.

Question 20

Recite the factor label method

Answer 20

1) write down the given quantity and put it over 1
2) determine what conversion factor you will use to turn the given label into the needed label
3) multiply the given quantities by the appropriate conversation factors to eliminate units you don’t want & leave the units you do.
4) round your answer to significant figures and write your units

Question 21

Explain what density is.

Answer 21

A ration of an objects mass to volume.

Usually measure in grams and milliliters

Question 22

What is the equation for density?

Answer 22

D=m/v

‼️ remember, density cuts your heart in half D + ❤️ = 💔 ❌❌❌ ‼️

Question 23

In your own words, define physical change

Answer 23

A substance is transformed, but the chemical composition is not changed.
Ex. An egg➡️ hard boiled egg